Bachelor of Arts, University of California Berkeley (2006)
Doctor of Philosophy, University of California Berkeley (2013)
Cytoskeletal tension is an intracellular mechanism through which cells convert a mechanical signal into a biochemical response, including production of cytokines and activation of various signaling pathways.Adipose-derived stromal cells (ASCs) were allowed to spread into large cells by seeding them at a low-density (1,250 cells/cm(2)), which was observed to induce osteogenesis. Conversely, ASCs seeded at a high-density (25,000 cells/cm(2)) featured small cells that promoted adipogenesis. RhoA and actin filaments were altered by changes in cell size. Blocking actin polymerization by Cytochalasin D influenced cytoskeletal tension and differentiation of ASCs. To understand the potential regulatory mechanisms leading to actin cytoskeletal tension, cDNA microarray was performed on large and small ASCs. Connective tissue growth factor (CTGF) was identified as a major regulator of osteogenesis associated with RhoA mediated cytoskeletal tension. Subsequently, knock-down of CTGF by siRNA in ASCs inhibited this osteogenesis.We conclude that CTGF is important in the regulation of cytoskeletal tension mediated ASC osteogenic differentiation.
View details for DOI 10.1371/journal.pone.0011279
View details for Web of Science ID 000279135400023
View details for PubMedID 20585662
Cartilage is an avascular tissue, and chondrocytes in vivo experience a severely hypoxic environment. Using a defined in vitro model of early chondrogenesis, we attempted to enrich for cells with an enhanced ability for chondrogenic differentiation by pre-exposure of mouse adipose-derived adult stromal cells (ADASs) to a hypoxic (2% oxygen) environment. ADASs were subsequently expanded in 2% or 21% oxygen environments, resulting in 2 groups of cells, and then early chondrogenic differentiation was induced at 21% oxygen tension using a 3-dimensional micromass culture system. ADAS chondrogenesis was assessed using Alcian Blue staining for proteoglycans and quantification of sulfated glycosaminoglycans. Osteogenesis of the 2 cell groups was also studied. Two percent oxygen tension profoundly increased the proliferation of ADASs. ADASs expanded in 2% oxygen tension exhibited enhanced early chondrogenic differentiation and diminished osteogenesis, suggesting that the reduced oxygen environment may favor chondroprogenitors. Gene expression analysis suggested that matrix metalloproteinase synthesis was inhibited in cells expanded in 2% oxygen. Furthermore, re-oxygenation of the 2% oxygen-expanded ADASs before differentiation did not significantly affect early chondrogenesis. Thus, priming ADASs with 2% oxygen may have selected for chondrogenic progenitors with an enhanced ability to survive and differentiate. This study is relevant for the future application of cell-based therapies involving cartilage tissue regeneration.
View details for DOI 10.1089/ten.2007.0050
View details for Web of Science ID 000251788400018
View details for PubMedID 17916040
Cartilage is an avascular tissue with only a limited potential to heal and chondrocytes in vitro have poor proliferative capacity. Recently, adipose-derived stromal cells (ASC) have demonstrated a great potential for application to tissue engineering due to their ability to differentiate into cartilage, bone, and fat. In this study, we have utilized a high density three-dimensional (3D) micromass model system of early chondrogenesis with ASC. The material properties of these micromasses showed a significant increase in dynamic and static elastic modulus during the early chondrogenic differentiation process. These data suggest that the 3D micromass culture system represents an in vitro model of early chondrogenesis with dynamic cell signaling interactions associated with the mechanical properties of chondrocyte differentiation.
View details for DOI 10.1016/j.bbrc.2007.05.098
View details for Web of Science ID 000247494400020
View details for PubMedID 17543281