Bio

Honors & Awards


  • 1st Place, Joseph Lister Award for New Investigators, American Association for Dental Research (AADR) (2018)
  • 2nd Place, Joseph Lister Award for New Investigators, International Association for Dental Research (IADR) (2018)
  • 1st Place NSRG Dentsply Sirona Restorative Competition Basic Science Category, AADR National Student Research Group (2017)
  • James English Research Award for Ph.D. Students, University at Buffalo (2015)
  • Graduate Student Association Conference Funding, University at Buffalo (2014-2015)
  • Mark Diamond Research Fund award, University at Buffalo (2014-2015)
  • Excellence in Post-Graduate Research Award, University at Buffalo (2014)
  • Young Investigator Award, American society for bone and mineral research (ASBMR) (2014)
  • Excellent Graduate Student, Simcere Pharmaceutical Corporation R&D Center (2008)

Professional Education


  • Bachelor of Science, China Pharmaceutical University (2007)
  • Master of Science, China Pharmaceutical University (2009)
  • Doctor of Philosophy, S.U.N.Y. State University at Buffalo (2015)

Stanford Advisors


Publications

All Publications


  • Improving intraoperative storage conditions for autologous bone grafts: an experimental investigation in mice. Journal of tissue engineering and regenerative medicine Sun, Q., Li, Z., Liu, B., Yuan, X., Guo, S., Helms, J. 2019

    Abstract

    Autologous bone grafts constitute the second most transplanted tissue in medicine today. The viability, and consequently the osteogenic capacity, of an autograft is directly impacted by the interval between harvest and transplantation, but how the temperature and the solution in which the graft is held intraoperatively affect viability is not clear. Using a syngeneic mouse model and in vivo bone-forming assays, these variables were tested for their effects on programmed cell death, osteoprogenitor cell proliferation, and ultimately the ability of the autograft to produce new bone in an ectopic site. Based on these results, the intraoperative treatment with a WNT protein therapeutic was tested for its effects on the viability and osteogenic capacity of an autograft. Viability, programmed cell death, mitotic activity, osteogenic protein expression, and bone-forming capacity were assessed. Experimental results demonstrated that the osteogenic capacity of an autograft is significantly improved by intraoperative storage in L-WNT3A at physiological temperature.

    View details for DOI 10.1002/term.2970

    View details for PubMedID 31617958

  • Wnt-Responsive Stem Cell Fates in the Oral Mucosa. iScience Yuan, X., Xu, Q., Zhang, X., Van Brunt, L. A., Ticha, P., Helms, J. A. 2019; 21: 84?94

    Abstract

    Epithelia of the oral cavity exhibit variations in morphologies and turnover rates. Are these differences related to environment or to region-specific stem cell populations? A lineage-tracing strategy allowed visualization of Wnt-responsive cells, and their progeny, in the hard and soft palates. In both anatomic locations, Wnt-responsive basal cells self-renewed and gave rise to supra-basal cells. Palatal injuries triggered an enlargement of this population, and their descendants were responsible for wound re-epithelialization. Compared with the hard palate, soft palate stem cells exhibited an earlier, more robust burst in proliferation, culminating in significantly faster repair. Thereafter, excess Wnt-responsive basal cells were removed, and stem cell numbers were restored back to homeostatic level. Thus, we uncovered a stem cell population in oral mucosa, and its relative abundance is correlate with the rate of oral wound healing. Besides the activation during injury, an endogenous mechanism exists to constrain the stem cell pool after repair.

    View details for DOI 10.1016/j.isci.2019.10.016

    View details for PubMedID 31655258

  • A Correlation between Wnt/Beta-catenin Signaling and the Rate of Dentin Secretion. Journal of endodontics Zhao, Y., Yuan, X., Bellido, T., Helms, J. A. 2019

    Abstract

    INTRODUCTION: Odontoblasts produce dentin throughout life and in response to trauma. The purpose of this study was to identify the roles of endogenous Wnt signaling in regulating the rate of dentin accumulation.METHODS: Histology, immunohistochemistry, vital dye labeling, and histomorphometric assays were used to quantify the rate of dentin accumulation as a function of age. Two strains of Wnt reporter mice were used to identify and follow the distribution and number of Wnt-responsive odontoblasts as a function of age. To show a causal relationship between dentin secretion and Wnt signaling, dentin accumulation was monitored in a strain of mice in which Wnt signaling was aberrantly elevated.RESULTS: Dentin deposition occurs throughout life, but the rate of accumulation slows with age. This decline in dentin secretion correlates with a decrease in endogenous Wnt signaling. In a genetically modified strain of mice, instead of tubular dentin, aberrantly elevated Wnt signaling resulted in accumulation of reparative dentin or osteodentin secreted from predontoblasts.CONCLUSIONS: Wnt signaling regulates dentin secretion by odontoblasts, and the formation of reparative or osteodentin is the direct consequence of elevated Wnt signaling. These preclinical data have therapeutic implications for the development of a biologically based pulp capping medicant.

    View details for DOI 10.1016/j.joen.2019.07.014

    View details for PubMedID 31522810

  • Osteoporotic Changes in the Periodontium Impair Alveolar Bone Healing. Journal of dental research Arioka, M., Zhang, X., Li, Z., Tulu, U. S., Liu, Y., Wang, L., Yuan, X., Helms, J. A. 2019: 22034518818456

    Abstract

    Osteoporosis is associated with decreased bone density and increased bone fragility, but how this disease affects alveolar bone healing is not clear. The objective of this study was to determine the extent to which osteoporosis affects the jaw skeleton and then to evaluate possible mechanisms whereby an osteoporotic phenotype might affect the rate of alveolar bone healing following tooth extraction. Using an ovariectomized mouse model coupled with micro-computed tomographic imaging, histologic, molecular, and cellular assays, we first demonstrated that the appendicular and jaw skeletons both develop osteoporotic phenotypes. Next, we demonstrated that osteoporotic mice exhibit atrophy of the periodontal ligament (PDL) and that this atrophy was accompanied by a reduction in the pool of osteoprogenitor cells in the PDL. The paucity of PDL-derived osteoprogenitor cells in osteoporotic mice was associated with significantly slower extraction socket healing. Collectively, these analyses demonstrate that the jaw skeleton is susceptible to the untoward effects of osteoporosis that manifest as thinner, more porous alveolar bone, PDL thinning, and slower bone repair. These findings have potential clinical significance for older osteopenic patients undergoing reconstructive procedures.

    View details for PubMedID 30626268

  • Molecular Basis for Periodontal Ligament Adaptation to In Vivo Loading. Journal of dental research Zhang, X., Yuan, X., Xu, Q., Arioka, M., Van Brunt, L. A., Shi, Y., Brunski, J., Helms, J. A. 2019: 22034518817305

    Abstract

    A soft food diet leads to changes in the periodontal ligament (PDL). These changes, which have been recognized for more than a century, are ascribed to alterations in mechanical loading. While these adaptive responses have been well characterized, the molecular, cellular, and mechanical mechanisms underlying the changes have not. Here, we implicate Wnt signaling in the pathoetiology of PDL responses to underloading. We show that Wnt-responsive cells and their progeny in the PDL space exhibit a burst in proliferation in response to mastication. If an animal is fed a soft diet from the time of weaning, then this burst in Wnt-responsive cell proliferation is quelled; as a consequence, both the PDL and the surrounding alveolar bone undergo atrophy. Returning these animals to a hard food diet restores the Wnt signaling in PDL. These data provide, for the first time, a molecular mechanism underlying the adaptive response of the PDL to loading.

    View details for PubMedID 30612508

  • IFT80 is required for stem cell proliferation, differentiation, and odontoblast polarization during tooth development. Cell death & disease Yuan, X., Cao, X., Yang, S. 2019; 10 (2): 63

    Abstract

    Primary cilia and intraflagellar transport (IFT) proteins control a wide variety of processes during tissue development and homeostasis. However, their role in regulation of stem cell properties during tooth development remains elusive. Here, we revealed that dental pulp stem cells (DPSCs) express IFT80, which is required for maintaining DPSC properties. Mice with deletion of IFT80 in odontoblast lineage show impaired molar root development and delayed incisor eruption through reduced DPSC proliferation and differentiation, and disrupted odontoblast polarization. Impaired odontoblast differentiation resulted from disrupted hedgehog (Hh) signaling pathways. Decreased DPSC proliferation is associated with impaired fibroblast growth factor 2 (FGF2) signaling caused by loss of IFT80, leading to the disruption of FGF2-FGFR1-PI3K-AKT signaling in IFT80-deficient DPSCs. The results provide the first evidence that IFT80 controls tooth development through influencing cell proliferation, differentiation, and polarization, and Hh and FGF/AKT signaling pathways, demonstrating that IFT proteins are likely to be the new therapeutic targets for tooth and other tissue repair and regeneration.

    View details for DOI 10.1038/s41419-018-0951-9

    View details for PubMedID 30683845

    View details for PubMedCentralID PMC6347632

  • Aberrantly elevated Wnt signaling is responsible for cementum overgrowth and dental ankylosis. Bone Wu, Y., Yuan, X., Perez, K. C., Hyman, S., Wang, L., Pellegrini, G., Salmon, B., Bellido, T., Helms, J. A. 2018

    Abstract

    Vertebrate teeth are attached to the jawbones using a variety of methods but in mammals, a fibrous connection is the norm. This fibrous periodontal ligament (PDL) allows teeth to move in the jawbones in response to natural eruptive forces, mastication, and orthodontic tooth movement. In some disease states the PDL either calcifies or is replaced by a mineralized tissue and the result is ankylosis, where the tooth is fused to the alveolar bone. To understand how the PDL maintains this fibrous state we examined a strain of mice in which tooth movement is arrested. DabetacatOt mice express a stabilized form of beta-catenin in DMP1-positive alveolar bone osteocytes and cementocytes, which results in elevated Wnt signaling throughout the periodontium. As a consequence, there is an accrual of massive amounts of cellular cementum and alveolar bone, the PDL itself calcifies and teeth become ankylosed. These data suggest that to maintain its fibrous nature, Wnt signaling must normally be repressed in the PDL space.

    View details for DOI 10.1016/j.bone.2018.10.023

    View details for PubMedID 30408613

  • Antimicrobial Peptide Combined with BMP2-Modified Mesenchymal Stem Cells Promotes Calvarial Repair in an Osteolytic Model. Molecular therapy : the journal of the American Society of Gene Therapy Liu, Z., Yuan, X., Liu, M., Fernandes, G., Zhang, Y., Yang, S., Ionita, C. N., Yang, S. 2018; 26 (1): 199?207

    Abstract

    Repair and regeneration of inflammation-induced bone loss remains a clinical challenge. LL37, an antimicrobial peptide, plays critical roles in cell migration, cytokine production, apoptosis, and angiogenesis. Migration of stem cells to the affected site and promotion of vascularization are essential for tissue engineering therapy, including bone regeneration. However, it is largely unknown whether LL37 affects mesenchymal stem cell (MSC) behavior and bone morphogenetic protein 2 (BMP2)-mediated bone repair during the bone pathologic remodeling process. By performing in vitro and in vivo studies with MSCs and a lipopolysaccharide (LPS)-induced mouse calvarial osteolytic bone defect model, we found that LL37 significantly promotes cell differentiation, migration, and proliferation in both unmodified MSCs and BMP2 gene-modified MSCs. Additionally, LL37 inhibited LPS-induced osteoclast formation and bacterial activity in vitro. Furthermore, the combination of LL37 and BMP2 markedly promoted MSC-mediated angiogenesis and bone repair and regeneration in LPS-induced osteolytic defects in mouse calvaria. These findings demonstrate for the first time that LL37 can be a potential candidate drug for promoting osteogenesis and for inhibiting bacterial growth and osteoclastogenesis, and that the combination of BMP2 and LL37 is ideal for MSC-mediated bone regeneration, especially for inflammation-induced bone loss.

    View details for DOI 10.1016/j.ymthe.2017.09.011

    View details for PubMedID 28988712

  • Biomechanics of Immediate Postextraction Implant Osseointegration. Journal of dental research Yuan, X., Pei, X., Zhao, Y., Li, Z., Chen, C. H., Tulu, U. S., Liu, B., Van Brunt, L. A., Brunski, J. B., Helms, J. A. 2018: 22034518765757

    Abstract

    The aim of this study was to gain insights into the biology and mechanics of immediate postextraction implant osseointegration. To mimic clinical practice, murine first molar extraction was followed by osteotomy site preparation, specifically in the palatal root socket. The osteotomy was positioned such that it removed periodontal ligament (PDL) only on the palatal aspect of the socket, leaving the buccal aspect undisturbed. This strategy created 2 distinct peri-implant environments: on the palatal aspect, the implant was in direct contact with bone, while on the buccal aspect, a PDL-filled gap existed between the implant and bone. Finite element modeling showed high strains on the palatal aspect, where bone was compressed by the implant. Osteocyte death and bone resorption predominated on the palatal aspect, leading to the loss of peri-implant bone. On the buccal aspect, where finite element modeling revealed low strains, there was minimal osteocyte death and robust peri-implant bone formation. Initially, the buccal aspect was filled with PDL remnants, which we found directly provided Wnt-responsive cells that were responsible for new bone formation and osseointegration. On the palatal aspect, which was devoid of PDL and Wnt-responsive cells, adding exogenous liposomal WNT3A created an osteogenic environment for rapid peri-implant bone formation. Thus, we conclude that low strain and high Wnt signaling favor osseointegration of immediate postextraction implants. The PDL harbors Wnt-responsive cells that are inherently osteogenic, and if the PDL tissue is healthy, it is reasonable to preserve this tissue during immediate implant placement.

    View details for DOI 10.1177/0022034518765757

    View details for PubMedID 29608868

  • Wnt-Responsive Odontoblasts Secrete New Dentin after Superficial Tooth Injury. Journal of dental research Zhao, Y., Yuan, X., Liu, B., Tulu, U. S., Helms, J. A. 2018: 22034518763151

    Abstract

    The objective of our experiments was to identify new therapeutic strategies to stimulate dentin formation in an adult tooth. To address this objective, we evaluated dentin production in 2 acute trauma models: one involving a pulp exposure and the other involving a superficial dentin injury. Molecular, cellular, and histologic analyses revealed that in response to a severe injury, where the pulp is exposed to the oral cavity, cell death is rampant and the repair response initiates from surviving pulp cells and, to a lesser extent, surviving odontoblasts. When an injury is superficial, as in the case of a dentin injury model, then disturbances are largely confined to pulp tissue immediately underneath the damaged dentin tubules. We found that the pulp remained vital and innervated; primary odontoblasts upregulated HIF1?; and the rate of mineralization was significantly increased. A tamoxifen-inducible Axin2CreERT2/+; R26RmTmG/+reporter strain was then used to demonstrate that a population of long-lived Wnt-responsive odontoblasts, which secreted dentin throughout the life of the animal, were responsible for depositing new dentin in response to a superficial injury. Amplifying Wnt signaling in the pulp stimulates dentin secretion, and in the dentin injury model, we show that a liposomal formulation of human WNT3A protein passes through dentinal tubules and is capable of upregulating Wnt signaling in the pulp. These data provide strong proof of concept for a therapeutic pulp-capping material to stimulate Wnt signaling in odontoblasts and thus improve the pulp repair response.

    View details for DOI 10.1177/0022034518763151

    View details for PubMedID 29566345

  • A Wnt-Responsive PDL Population Effectuates Extraction Socket Healing. Journal of dental research Yuan, X., Pei, X., Zhao, Y., Tulu, U. S., Liu, B., Helms, J. A. 2018: 22034518755719

    Abstract

    Stem cells residing in the periodontal ligament (PDL) support the homeostasis of the periodontium, but their in vivo identity, source(s), and function(s) remain poorly understood. Here, using a lineage-tracing mouse strain, we identified a quiescent Wnt-responsive population in the PDL that became activated in response to tooth extraction. The Wnt-responsive population expanded by proliferation, then migrated from the PDL remnants that remained attached to bundle bone, into the socket. Once there, the Wnt-responsive progeny upregulated osteogenic protein expression, differentiated into osteoblasts, and generated the new bone that healed the socket. Using a liposomal WNT3A protein therapeutic, we showed that a single application at the time of extraction was sufficient to accelerate extraction socket healing 2-fold. Collectively, these data identify a new stem cell population in the intact periodontium that is directly responsible for alveolar bone healing after tooth removal.

    View details for PubMedID 29420105

  • Wnt signals control development of the periodontium. Yuan, X., Wu, Y., Zhao, Y., Perez, K., Pellegrini, G., Condon, K., McAndrews, K., Cregor, M., Bellido, T., Helms, J. WILEY. 2017: S131?S132
  • Intraflagellar transport protein is required for stem cell maintenance through regulating and coupling of FGF and Hh signaling. Yuan, X., Cao, X., Yang, S. WILEY. 2017: S175
  • The combination of nano-calcium sulfate/platelet rich plasma gel scaffold with BMP2 gene-modified mesenchymal stem cells promotes bone regeneration in rat critical-sized calvarial defects. Stem cell research & therapy Liu, Z., Yuan, X., Fernandes, G., Dziak, R., Ionita, C. N., Li, C., Wang, C., Yang, S. 2017; 8 (1): 122-?

    Abstract

    Mesenchymal stem cells (MSCs) can be differentiated into an osteoblastic lineage in the presence of growth factors (GFs). Platelet-rich plasma (PRP), which can be easily isolated from whole blood, contains a large amount of GFs, and, therefore, promotes bone growth and regeneration. The main goal of this work was to develop and investigate the effect of a new sandwich-like bone scaffold which combines a nano-calcium sulfate (nCS) disc along with PRP fibrin gel (nCS/PRP) with BMP2-modified MSCs on bone repair and regeneration in rat critical-sized calvarial defects.We evaluated the cytotoxicity, osteogenic differentiation and mineralization effect of PRP extract on BMP2-modified MSCs and constructed a sandwich-like nCS/PRP scaffold (mimicking the nano-calcium matrix of bone and carrying multi GFs in the PRP) containing BMP2-modified MSCs. The capacity of this multifunctional bone regeneration system in promoting bone repair was assessed in vivo in a rat critical-sized (8 mm) calvarial bone defect model.We developed an optimized nCS/PRP sandwich-like scaffold. Scanning electron microscopy (SEM) results showed that nCS/PRP are polyporous with an average pore diameter of 70-80 ?m and the cells can survive in the nCS/PRP scaffold. PRP extract dramatically stimulated proliferation and differentiation of BMP2-modified MSCs in vitro. Our in vivo results showed that the combination of BMP2-modified MSCs and nCS/PRP scaffold dramatically increased new bone regeneration compared with the groups without PRP and/or BMP2.nCS/PRP scaffolds containing BMP2-modified MSCs successfully promotes bone regeneration in critical-sized bone defects. This system could ultimately enable clinicians to better reconstruct the craniofacial bone and avoid donor site morbidity for critical-sized bone defects.

    View details for DOI 10.1186/s13287-017-0574-6

    View details for PubMedID 28545565

    View details for PubMedCentralID PMC5445399

  • Contribution of the PDL to Osteotomy Repair and Implant Osseointegration. Journal of dental research Pei, X., Wang, L., Chen, C., Yuan, X., Wan, Q., Helms, J. A. 2017: 22034517707513-?

    Abstract

    Our objective was to clarify the fate of the periodontal ligament (PDL) retained in the socket after tooth extraction, then determine if this tissue contributed to the osseointegration of "immediate" implants placed in these fresh extraction sockets. Mice underwent maxillary first molar extraction, the residual PDL was removed by an osteotomy, and titanium implants were placed. The osteotomy was created in such a way that the palatal surface was devoid of PDL remnants while the buccal, mesial, and distal surfaces retained PDL fibers. At multiple time points after surgery, tissues were analyzed using a battery of molecular, cellular, and histomorphometrical assays. We found that PDL remnants mineralized and directly contributed to new bone formation in the extraction site. Compared with regions of an extraction site where the PDL was removed by osteotomy, regions that retained PDL fibers had produced significantly more new bone. Around immediate implants, the retained PDL remnants directly contributed to new bone formation and osseointegration. Thus, we conclude that PDL remnants are inherently osteogenic, and if the tissue is healthy, it is reasonable to conclude that curetting out an extraction socket prior to immediate implant placement should be avoided. This recommendation aligns with contemporary trends toward minimally invasive surgical manipulations of the extraction socket prior to immediate implant placement.

    View details for DOI 10.1177/0022034517707513

    View details for PubMedID 28481696

    View details for PubMedCentralID PMC5502960

  • Combination of bone marrow mesenchymal stem cells sheet and platelet rich plasma for posterolateral lumbar fusion. Oncotarget Liu, Z., Zhu, Y., Ge, R., Zhu, J., He, X., Yuan, X., Liu, X. 2017; 8 (37): 62298?311

    Abstract

    Bone tissue engineering provides a substitute for bone transplantation in spinal fusion. This study examined if combined bone marrow-derived mesenchymal stem cells (BMSCs) sheet with platelet-rich plasma (PRP) could promote bone regeneration in a rabbit posterolateral spinal fusion model. BMSCs was isolated and confirmed by Flow cytometric analysis and immunofluorescence staining. The morphology of BMSCs was examined by Hematoxylin and Eosin staining, scanning and transmission electron microscopy. BMSCs were cultured in induction medium or control medium. The osteogenic ability of BMSCs was investigated by various histochemical staining, immunofluorescence staining and qRT-PCR analysis. The BMSCs/PRP was constructed by encapsulating the PRP block with BMSCs sheet. Twenty-four adult rabbits were randomly divided into four groups based on the implanted biomaterials: BMSCs/PRP, BMSCs, iliac crest autograft, and control group. Manual palpation and digital radiography analysis showed that the fusion rate was 100%, 0, 83.3%, and 0 in these 4 groups, respectively. Formation of continuous bone masses in BMSCs/PRP group was confirmed by computed tomography scanning and 3D-reconstruction. These studies demonstrated that BSMCs/PRP significantly accelerated bone regeneration in the rabbit posterolateral spinal fusion model.

    View details for DOI 10.18632/oncotarget.19749

    View details for PubMedID 28977946

    View details for PubMedCentralID PMC5617506

  • Combination of Controlled Release Platelet-Rich Plasma Alginate Beads and Bone Morphogenetic Protein-2 Genetically Modified Mesenchymal Stem Cells for Bone Regeneration. Journal of periodontology Fernandes, G., Wang, C., Yuan, X., Liu, Z., Dziak, R., Yang, S. 2016; 87 (4): 470-480

    Abstract

    Platelet-rich plasma (PRP) consists of platelet-derived growth factor and transforming growth factor-? that increase proliferation of mesenchymal stem cells (MSCs), whereas bone morphogenetic protein-2 (BMP2) promotes osteogenic differentiation of MSCs. However, the high degradation rate of fibrin leads to the dissociation of cytokines even before the process of bone regeneration begins. To the best of the authors' knowledge, this is the first study to examine the combined effect of sustained release of PRP from alginate beads on BMP2-modified MSC osteogenic differentiation in vitro and sustained release of PRP alone on a fracture defect model ex vivo as well as its effect on calvarial suture closure.After optimizing the alginate concentration for microspheres, the combined osteogenic and mineralization effect of PRP and BMP2 on MSCs was studied. Self-setting alginate hydrogel carrying PRP was tested on a femur defect model ex vivo. The effect of PRP at day 15 on the closure of the embryonic mouse calvaria sutures ex vivo was also studied.Increase of PRP concentration promoted proliferation of MSCs, and 2.5% to 10% of PRP gradually increased alkaline phosphatase (ALP) activity in the cells in a dose-dependent manner. Sustained release of PRP and BMP2 demonstrated significantly higher ALP and mineralization activity (P <0.05). Radiographs of alginate hydrogel with PRP-treated bone demonstrated nearly complete healing of the fracture, and histologic sections of the embryonic calvaria revealed that PRP leads to suture fusion.Sustained release of PRP along with BMP2-modified MSCs can significantly promote bone regeneration.

    View details for DOI 10.1902/jop.2016.150487

    View details for PubMedID 26745613

  • Hybrid Biomaterial with Conjugated Growth factors and Mesenchymal Stem Cells for Ectopic Bone Formation. Tissue engineering. Part A Yuan, X., Smith, R. J., Guan, H., Ionita, C. N., Khobragade, P., Dziak, R., Liu, Z., Pang, M., Wang, C., Guan, G., Andreadis, S. T., Yang, S. 2016

    Abstract

    Bone is a highly vascularized tissue and efficient bone regeneration requires neovascularization, especially for critical size bone defects. We developed a novel hybrid biomaterial comprising of calcium sulfate (nCS) nanoparticles and fibrin hydrogel to deliver mesenchymal stem cells (MSCs) and angiogenic factors VEGF and FGF9 in order to promote neovascularization and bone formation. MSC and growth factor(s) loaded scaffolds were implanted subcutaneously into mice to examine their angiogenic and osteogenic potential. Micro CT, alkaline phosphatase activity assay and histological analysis were used to evaluate bone formation, while immunohistochemistry was employed to assess neovessel formation. The presence of fibrin preserved the nCS scaffold structure and promoted de novo bone formation. In addition, the presence of BMP2-expressing MSC in nCS and fibrin hydrogels improved bone regeneration significantly. While FGF9 alone had no significant effect, the combination FGF9 and VEGF conjugated in fibrin enhanced neovascularization and bone formation more than 4-fold as compared to nCS with MSC. Overall, our results suggested that the combination of nCS (to support bone formation) with a fibrin-based VEGF/FGF9 release system (support vascular formation) is an innovative and effective strategy that significantly enhanced ectopic bone formation in vivo.

    View details for DOI 10.1089/ten.TEA.2016.0052

    View details for PubMedID 27269204

  • Ciliary IFT80 balances canonical versus non-canonical hedgehog signalling for osteoblast differentiation. Nature communications Yuan, X., Cao, J., He, X., Serra, R., Qu, J., Cao, X., Yang, S. 2016; 7: 11024-?

    Abstract

    Intraflagellar transport proteins (IFT) are required for hedgehog (Hh) signalling transduction that is essential for bone development, however, how IFT proteins regulate Hh signalling in osteoblasts (OBs) remains unclear. Here we show that deletion of ciliary IFT80 in OB precursor cells (OPC) in mice results in growth retardation and markedly decreased bone mass with impaired OB differentiation. Loss of IFT80 blocks canonical Hh-Gli signalling via disrupting Smo ciliary localization, but elevates non-canonical Hh-G?i-RhoA-stress fibre signalling by increasing Smo and G?i binding. Inhibition of RhoA and ROCK activity partially restores osteogenic differentiation of IFT80-deficient OPCs by inhibiting non-canonical Hh-RhoA-Cofilin/MLC2 signalling. Cytochalasin D, an actin destabilizer, dramatically restores OB differentiation of IFT80-deficient OPCs by disrupting actin stress fibres and promoting cilia formation and Hh-Gli signalling. These findings reveal that IFT80 is required for OB differentiation by balancing between canonical Hh-Gli and non-canonical Hh-G?i-RhoA pathways and highlight IFT80 as a therapeutic target for craniofacial and skeletal abnormalities.

    View details for DOI 10.1038/ncomms11024

    View details for PubMedID 26996322

  • Primary Cilia and Intraflagellar Transport Proteins in Bone and Cartilage. Journal of dental research Yuan, X., Yang, S. 2016

    Abstract

    Primary cilia, present on most mammalian cells, function as a sensor to sense the environment change and transduce signaling. Loss of primary cilia causes a group of human pleiotropic syndromes called Ciliopathies. Some of the ciliopathies display skeletal dysplasias, implying the important role of primary cilia in skeletal development and homeostasis. Emerging evidence has shown that loss or malfunction of primary cilia or ciliary proteins in bone and cartilage is associated with developmental and function defects. Intraflagellar transport (IFT) proteins are essential for cilia formation and/or function. In this review, we discuss the role of primary cilia and IFT proteins in the development of bone and cartilage, as well as the differentiation and mechanotransduction of mesenchymal stem cells, osteoblasts, osteocytes, and chondrocytes. We also include the role of primary cilia in tooth development and highlight the current advance of primary cilia and IFT proteins in the pathogenesis of cartilage diseases, including osteoarthritis, osteosarcoma, and chondrosarcoma.

    View details for DOI 10.1177/0022034516652383

    View details for PubMedID 27250654

  • Regulators of G protein signaling 12 promotes osteoclastogenesis in bone remodeling and pathological bone loss CELL DEATH AND DIFFERENTIATION Yuan, X., Cao, J., Liu, T., Li, Y., Scannapieco, F., He, X., Oursler, M. J., Zhang, X., Vacher, J., Li, C., Olson, D., Yang, S. 2015; 22 (12): 2046-2057

    Abstract

    Regulators of G protein signaling (Rgs) have pivotal roles in controlling various cellular processes, such as cell differentiation. How Rgs proteins regulate osteoclast (OC) differentiation, function and bone homeostasis is poorly understood. It was previously demonstrated that Rgs12, the largest protein in the Rgs family, is predominantly expressed in OCs and regulates OC differentiation in vitro. To further understand the role and mechanism of Rgs12 in OC differentiation and bone diseases in vivo, we created OC-targeted Rgs12 knockout mice by using inducible Mx1-Cre and CD11b-Cre. Deletion of Rgs12 in hematopoietic cells or specifically in OC precursors resulted in increased bone mass with decreased OC numbers. Loss of Rgs12 impaired OC differentiation and function with impaired Ca(2+) oscillations and reduced nuclear factor of activated T cells (NFAT) 2 expression. The introduction of wild-type osteoblasts did not rescue the defective osteoclastogenesis. Ectopic expression of NFAT2 rescued defective OC differentiation in CD11b;Rgs12(fl/fl) cells and promoted normal OC differentiation. Moreover, deletion of Rgs12 significantly inhibited pathological osteoclastogenesis and bone destruction in Rgs12-deficient mice that were subjected to ovariectomy and lipodysaccharide for bone loss. Thus our findings demonstrate that Rgs12 is an important regulator in OC differentiation and function and identify Rgs12 as a potential therapeutic target for osteoporosis and inflammation-induced bone loss.

    View details for DOI 10.1038/cdd.2015.45

    View details for Web of Science ID 000364849400014

    View details for PubMedID 25909889

  • Deletion of IFT80 Impairs Epiphyseal and Articular Cartilage Formation Due to Disruption of Chondrocyte Differentiation PLOS ONE Yuan, X., Yang, S. 2015; 10 (6)

    Abstract

    Intraflagellar transport proteins (IFT) play important roles in cilia formation and organ development. Partial loss of IFT80 function leads Jeune asphyxiating thoracic dystrophy (JATD) or short-rib polydactyly (SRP) syndrome type III, displaying narrow thoracic cavity and multiple cartilage anomalies. However, it is unknown how IFT80 regulates cartilage formation. To define the role and mechanism of IFT80 in chondrocyte function and cartilage formation, we generated a Col2?1; IFT80f/f mouse model by crossing IFT80f/f mice with inducible Col2?1-CreER mice, and deleted IFT80 in chondrocyte lineage by injection of tamoxifen into the mice in embryonic or postnatal stage. Loss of IFT80 in the embryonic stage resulted in short limbs at birth. Histological studies showed that IFT80-deficient mice have shortened cartilage with marked changes in cellular morphology and organization in the resting, proliferative, pre-hypertrophic, and hypertrophic zones. Moreover, deletion of IFT80 in the postnatal stage led to mouse stunted growth with shortened growth plate but thickened articular cartilage. Defects of ciliogenesis were found in the cartilage of IFT80-deficient mice and primary IFT80-deficient chondrocytes. Further study showed that chondrogenic differentiation was significantly inhibited in IFT80-deficient mice due to reduced hedgehog (Hh) signaling and increased Wnt signaling activities. These findings demonstrate that loss of IFT80 blocks chondrocyte differentiation by disruption of ciliogenesis and alteration of Hh and Wnt signaling transduction, which in turn alters epiphyseal and articular cartilage formation.

    View details for DOI 10.1371/journal.pone.0130618

    View details for Web of Science ID 000356835800085

    View details for PubMedID 26098911

  • Endostar attenuates melanoma tumor growth via its interruption of b-FGF mediated angiogenesis CANCER LETTERS Xiao, L., Yang, S., Hao, J., Yuan, X., Luo, W., Jiang, L., Hu, Y., Fu, Z., Zhang, Y., Zou, C. 2015; 359 (1): 148-154

    Abstract

    To develop optimal therapeutics is one of the hotspots in both clinical and basic melanoma studies. Previous studies indicate that fibroblast growth factors (b-FGF/FGF-2), an angiogenesis inducer beyond VEGF, might be a potential drug target in melanoma. As a novel anti-angiogenesis peptide drug, Endostar has shown promising therapeutic efficacy in non-small cell lung cancer. However, the effect of Endostar on b-FGF-induced angiogenesis in melanoma is unraveled. To this end, both in vivo and in vitro experiments were conducted and it was found that treatment of Endostar could inhibit tumor growth, which was accompanied by decreased micro-vessel density and serum b-FGF levels in a mouse melanoma model. In addition, treatment with Endostar in blood vessel endothelial cells could reduce their proliferation, cell migration and tube formation capacity in a dosage-dependent manner. Moreover, treatment of Endostar could also attenuate b-FGF-activated phosphorylation of p38 and ERK1/2 in HUVECs. These findings indicate that Endostar might exert its anti-tumor effect via suppressing b-FGF-induced angiogenesis and b-FGF-activated MAPK signaling pathway, suggesting that Endostar might be a potential choice for clinical melanoma treatment.

    View details for DOI 10.1016/j.canlet.2015.01.012

    View details for Web of Science ID 000350181700015

    View details for PubMedID 25597785

  • Cilia/Ift protein and motor-related bone diseases and mouse models FRONTIERS IN BIOSCIENCE-LANDMARK Yuan, X., Yang, S. 2015; 20: 515-555

    Abstract

    Primary cilia are essential cellular organelles projecting from the cell surface to sense and transduce developmental signaling. They are tiny but have complicated structures containing microtubule (MT)-based internal structures (the axoneme) and mother centriole formed basal body. Intraflagellar transport (Ift) operated by Ift proteins and motors are indispensable for cilia formation and function. Mutations in Ift proteins or Ift motors cause various human diseases, some of which have severe bone defects. Over the last few decades, major advances have occurred in understanding the roles of these proteins and cilia in bone development and remodeling by examining cilia/Ift protein-related human diseases and establishing mouse transgenic models. In this review, we describe current advances in the understanding of the cilia/Ift structure and function. We further summarize cilia/Ift-related human diseases and current mouse models with an emphasis on bone-related phenotypes, cilia morphology, and signaling pathways.

    View details for DOI 10.2741/4323

    View details for Web of Science ID 000354353700008

    View details for PubMedID 25553465

  • Function and regulation of primary cilia and intraflagellar transport proteins in the skeleton MARROW Yuan, X., Serra, R. A., Yang, S. 2015; 1335: 78-99

    Abstract

    Primary cilia are microtubule-based organelles that project from the cell surface to enable transduction of various developmental signaling pathways. The process of intraflagellar transport (IFT) is crucial for the building and maintenance of primary cilia. Ciliary dysfunction has been found in a range of disorders called ciliopathies, some of which display severe skeletal dysplasias. In recent years, interest has grown in uncovering the function of primary cilia/IFT proteins in bone development, mechanotransduction, and cellular regulation. We summarize recent advances in understanding the function of cilia and IFT proteins in the regulation of cell differentiation in osteoblasts, osteocytes, chondrocytes, and mesenchymal stem cells (MSCs). We also discuss the mechanosensory function of cilia and IFT proteins in bone cells, cilia orientation, and other functions of cilia in chondrocytes.

    View details for DOI 10.1111/nyas.12463

    View details for Web of Science ID 000348920600007

    View details for PubMedID 24961486

  • Deletion of IFT20 in early stage T lymphocyte differentiation inhibits the development of collagen-induced arthritis BONE RESEARCH Yuan, X., Garrett-Sinha, L. A., Sarkar, D., Yang, S. 2014; 2

    Abstract

    IFT20 is the smallest member of the intraflagellar transport protein (IFT) complex B. It is involved in cilia formation. Studies of IFT20 have been confined to ciliated cells. Recently, IFT20 was found to be also expressed in non-ciliated T cells and have functions in immune synapse formation and signaling in vitro. However, how IFT20 regulates T-cell development and activation in vivo is still unknown. We deleted the IFT20 gene in early and later stages of T-cell development by crossing IFT20(flox/flox) (IFT20(f/f) ) mice with Lck-Cre and CD4-Cre transgenic mice, and investigated the role of IFT20 in T-cell maturation and in the development of T cell-mediated collagen-induced arthritis (CIA). We found that both Lck-Cre/IFT20(f/f) and CD4-Cre/IFT20(f/f) mice were indistinguishable from their wild-type littermates in body size, as well as in the morphology and weight of the spleen and thymus. However, the number of CD4- and CD8-positive cells was significantly lower in thymus and spleen in Lck-Cre/IFT20(f/f) mice. Meanwhile, the incidence and severity of CIA symptoms were significantly decreased, and inflammation in the paw was significantly inhibited in Lck-Cre/IFT20(f/f) mice compared to Lck-Cre/IFT20(+/+) littermates. Deletion IFT20 in more mature T cells of CD4-Cre/IFT20(f/f) mice had only mild effects on the development of T cells and CIA. The expression of IL-1?, IL-6 and TGF-?1 were significantly downregulated in the paw of Lck-Cre/IFT20(f/f) mice, but just slight decreased in CD4-Cre/IFT20(f/f) mice. These results demonstrate that deletion of IFT20 in the early stage of T-cell development inhibited CIA development through regulating T-cell development and the expression of critical cytokines.

    View details for DOI 10.1038/boneres.2014.38

    View details for Web of Science ID 000344999700001

    View details for PubMedID 26097753

  • Enhanced Healing of Rat Calvarial Defects with MSCs Loaded on BMP-2 Releasing Chitosan/Alginate/Hydroxyapatite Scaffolds PLOS ONE He, X., Liu, Y., Yuan, X., Lu, L. 2014; 9 (8)

    Abstract

    In this study, we designed a chitosan/alginate/hydroxyapatite scaffold as a carrier for recombinant BMP-2 (CAH/B2), and evaluated the release kinetics of BMP-2. We evaluated the effect of the CAH/B2 scaffold on the viability and differentiation of bone marrow mesenchymal stem cells (MSCs) by scanning electron microscopy, MTS, ALP assay, alizarin-red staining and qRT-PCR. Moreover, MSCs were seeded on scaffolds and used in a 8 mm rat calvarial defect model. New bone formation was assessed by radiology, hematoxylin and eosin staining 12 weeks postoperatively. We found the release kinetics of BMP-2 from the CAH/B2 scaffold were delayed compared with those from collagen gel, which is widely used for BMP-2 delivery. The BMP-2 released from the scaffold increased MSC differentiation and did not show any cytotoxicity. MSCs exhibited greater ALP activity as well as stronger calcium mineral deposition, and the bone-related markers Col1?, osteopontin, and osteocalcin were upregulated. Analysis of in vivo bone formation showed that the CAH/B2 scaffold induced more bone formation than other groups. This study demonstrates that CAH/B2 scaffolds might be useful for delivering osteogenic BMP-2 protein and present a promising bone regeneration strategy.

    View details for DOI 10.1371/journal.pone.0104061

    View details for Web of Science ID 000339819800122

    View details for PubMedID 25084008

  • Role of regulator of G protein signaling proteins in bone FRONTIERS IN BIOSCIENCE-LANDMARK Keinan, D., Yang, S., Cohen, R. E., Yuan, X., Liu, T., Li, Y. 2014; 19: 634-648

    Abstract

    Regulators of G protein signaling (RGS) proteins are a family with more than 30 proteins that all contain an RGS domain. In the past decade, increasing evidence has indicated that RGS proteins play crucial roles in the regulation of G protein coupling receptors (GPCR), G proteins, and calcium signaling during cell proliferation, migration, and differentiation in a variety of tissues. In bone, those proteins modulate bone development and remodeling by influencing various signaling pathways such as GPCR-G protein signaling, Wnt, calcium oscillations and PTH. This review summarizes the recent advances in the understanding of the regulation of RGS gene expression, as well as the functions and mechanisms of RGS proteins, especially in regulating GPCR-G protein signaling, Wnt signaling, calcium oscillations signaling and PTH signaling during bone development and remodeling. This review also highlights the regulation of different RGS proteins in osteoblasts, chondrocytes and osteoclasts. The knowledge from the recent advances of RGS study summarized in the review would provide the insights into new therapies for bone diseases.

    View details for DOI 10.2741/4232

    View details for Web of Science ID 000330029200004

    View details for PubMedID 24389209

  • BMP2 Genetically Engineered MSCs and EPCs Promote Vascularized Bone Regeneration in Rat Critical-Sized Calvarial Bone Defects PLOS ONE He, X., Dziak, R., Yuan, X., Mao, K., Genco, R., Swihart, M., Sarkar, D., Li, C., Wang, C., Lu, L., Andreadis, S., Yang, S. 2013; 8 (4)

    Abstract

    Current clinical therapies for critical-sized bone defects (CSBDs) remain far from ideal. Previous studies have demonstrated that engineering bone tissue using mesenchymal stem cells (MSCs) is feasible. However, this approach is not effective for CSBDs due to inadequate vascularization. In our previous study, we have developed an injectable and porous nano calcium sulfate/alginate (nCS/A) scaffold and demonstrated that nCS/A composition is biocompatible and has proper biodegradability for bone regeneration. Here, we hypothesized that the combination of an injectable and porous nCS/A with bone morphogenetic protein 2 (BMP2) gene-modified MSCs and endothelial progenitor cells (EPCs) could significantly enhance vascularized bone regeneration. Our results demonstrated that delivery of MSCs and EPCs with the injectable nCS/A scaffold did not affect cell viability. Moreover, co-culture of BMP2 gene-modified MSCs and EPCs dramatically increased osteoblast differentiation of MSCs and endothelial differentiation of EPCs in vitro. We further tested the multifunctional bone reconstruction system consisting of an injectable and porous nCS/A scaffold (mimicking the nano-calcium matrix of bone) and BMP2 genetically-engineered MSCs and EPCs in a rat critical-sized (8 mm) caviarial bone defect model. Our in vivo results showed that, compared to the groups of nCS/A, nCS/A+MSCs, nCS/A+MSCs+EPCs and nCS/A+BMP2 gene-modified MSCs, the combination of BMP2 gene -modified MSCs and EPCs in nCS/A dramatically increased the new bone and vascular formation. These results demonstrated that EPCs increase new vascular growth, and that BMP2 gene modification for MSCs and EPCs dramatically promotes bone regeneration. This system could ultimately enable clinicians to better reconstruct the craniofacial bone and avoid donor site morbidity for CSBDs.

    View details for DOI 10.1371/journal.pone.0060473

    View details for Web of Science ID 000317717300124

    View details for PubMedID 23565253

  • IFT80 is essential for chondrocyte differentiation by regulating Hedgehog and Wnt signaling pathways EXPERIMENTAL CELL RESEARCH Wang, C., Yuan, X., Yang, S. 2013; 319 (5): 623-632

    Abstract

    Partial mutation of intraflagellar transport 80 (IFT80) in humans causes Jeune asphyxiating thoracic dystrophy (JATD) and short-rib polydactyly (SRP) syndrome type III. These diseases are autosomal recessive chondrodysplasias that share clinical similarities, including shortened long bones and constricted thoracic cage. However, the role and mechanism of IFT80 in the regulation of chondrocyte differentiation and function remain largely unknown. We hypothesize that IFT80 is required for the formation and function of cilia and plays a critical role in chondrogenic differentiation by regulating Hedgehog (Hh) and Wingless (Wnt) signaling pathways. To test this hypothesis, we first analyzed the IFT80 expression pattern and found that IFT80 was predominantly expressed in growth plate chondrocytes and during chondrogenic differentiation. Silencing IFT80 impaired cilia formation and chondrogenic differentiation in mouse bone marrow derived stromal cells (BMSCs), and decreased the expression of chondrocyte marker genes--collagen II and aggrecan. Additionally, silencing IFT80 down-regulated Hh signaling activity whereas up-regulated Wnt signaling activity. The overexpression of Gli2 in IFT80-silenced cells promoted chondrogenesis and recovered the chondrogenic deficiency from IFT80 silencing. Overall, our results demonstrate that IFT80 is essential for chondrocyte differentiation by regulating the Hh and Wnt signaling pathways.

    View details for DOI 10.1016/j.yexcr.2012.12.028

    View details for Web of Science ID 000315615900005

    View details for PubMedID 23333501

  • Mx1-Cre mediated Rgs12 conditional knockout mice exhibit increased bone mass phenotype GENESIS Yang, S., Li, Y., Liu, T., He, X., Yuan, X., Li, C., Cao, J., Kim, Y. 2013; 51 (3): 201-209

    Abstract

    Regulators of G-protein Signaling (Rgs) proteins are the members of a multigene family of GTPase-accelerating proteins (GAP) for the Galpha subunit of heterotrimeric G-proteins. Rgs proteins play critical roles in the regulation of G protein couple receptor (GPCR) signaling in normal physiology and human diseases such as cancer, heart diseases, and inflammation. Rgs12 is the largest protein of the Rgs protein family. Some in vitro studies have demonstrated that Rgs12 plays a critical role in regulating cell differentiation and migration; however its function and mechanism in vivo is largely unknown. Here, we generated a floxed Rgs12 allele (Rgs12(flox/flox) ) in which the exon 2, containing both PDZ and PTB_PID domains of Rgs12, was flanked with two loxp sites. By using the inducible Mx1-cre and Poly I:C system to specifically delete Rgs12 at postnatal 10 days in interferon-responsive cells including monocyte and macrophage cells, we found that Rgs12 mutant mice had growth retardation with the phenotype of increased bone mass. We further found that deletion of Rgs12 reduced osteoclast numbers and had no significant effect on osteoblast formation. Thus, Rgs12(flox/flox) conditional mice provide a valuable tool for in vivo analysis of Rgs12 function and mechanism through time- and cell-specific deletion of Rgs12.

    View details for DOI 10.1002/dvg.22373

    View details for Web of Science ID 000316229500006

    View details for PubMedID 23349096

  • N-terminal modification increases the stability of the recombinant human endostatin in vitro BIOTECHNOLOGY AND APPLIED BIOCHEMISTRY Jiang, L., Zou, C., Yuan, X., Luo, W., Wen, Y., Chen, Y. 2009; 54: 113-120

    Abstract

    Endostar, approved for the treatment of non-small-cell lung cancer by the State Food and Drug Administration in China, is a derivative of human endostatin that is modified with an additional metal-chelating sequence (MGGSHHHHH) at the N-terminus. This modification contributes to an additional zinc-binding site in the endostatin sequence. In the present study, zinc-binding and zinc-free endostar were compared to further characterize their biochemical and structural properties. Thermally induced denaturation was determined by monitoring changes in fluorescence emission spectra. The data indicated that zinc binding significantly increased the transition temperature of endostar and contributed to a reversible change in protein conformation after recooling. Proteolysis assays demonstrated that the modified protein binding with zinc ions can stabilize the N-terminus and the C-terminus of endostar when treated with trypsin, chymotrypsin and carboxypeptidase A and B. Western-blot analyses using anti-His6 antibody confirmed that the major cleaved fragments of endostar were in the N-terminus when treated with trypsin and chymotrypsin. In the proliferation assay with human umbilical-vein endothelial cells, the zinc-binding and zinc-free endostar samples with extra zinc-binding sites displayed similar inhibiting activities.

    View details for DOI 10.1042/BA20090063

    View details for Web of Science ID 000270769000005

    View details for PubMedID 19527221

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