Recent Publications

Abstract

Corneal transplantation is the primary treatment for corneal blindness, affecting millions globally. However, challenges like donor scarcity and surgical complications remain. Recently, in situ-forming corneal stroma substitutes have emerged, offering potential solutions to these limitations. These substitutes enable liquid-to-hydrogel formation in situ, eliminating sutures and reducing complications. Here we performed a direct, side-by-side comparison of a composite hyaluronan-collagen (HA-Col) hydrogel crosslinked by either photochemistry or bio-orthogonal chemistry to ascertain the impact of reaction specificity on corneal wound healing. Testing in rodent and rabbit models suggests that composite HA-Col gels crosslinked by bio-orthogonal chemistry results in more rapid and optically favorable wound healing compared to the same composition crosslinked by photochemistry as well as bio-orthogonally crosslinked collagen alone. These findings underscore biochemical parameters that may be important to the success of crosslinked, in situ-forming hydrogels as an alternative to corneal transplantation, with the potential for expanded access to treatment and improved outcomes.

View details for DOI 10.1038/s41536-024-00385-9

View details for PubMedID 39905045

View details for PubMedCentralID 3872837

Abstract

Electrospun gelatin nanofibers coated with hyaluronic acid (GelNF-HA) were synthesized as a scaffold for delivering human corneal mesenchymal stromal cells (C-MSCs) directly to deep corneal injuries. Aligned GelNFs were produced by electrospinning, crosslinked using vapor of glutaraldehyde, coated with HA, and crosslinked with EDC/NHS. The GelNF-HA was characterized by SEM, mechanical, and optical properties. It was then investigated as a substrate for C-MSC proliferation and migration in vitro and in a rabbit cornea culture model. The expression of α-smooth muscle actin (α-SMA) was determined in the ex vivo model. SEM showed that the GelNF-HA scaffold was composed of aligned GelNFs with 75 % of the fibers oriented against the same angle. It exhibited a Young's modulus of 1.66 ± 0.59 MPa and approximately 93 % transmittance of visible light. The GelNF-HA membranes supported C-MSC proliferation in vitro. In a scratch migration assay, it facilitated complete wound closure after 48 h in culture. C-MSC-laden GelNF-HA scaffolds supported corneal wound healing in an ex vivo model as well, expressing a lower percentage of stromal α-SMA compared to both the no-treatment keratectomy-only and C-MSC groups (p < 0.05). The C-MSC-supportive GelNF-HA scaffolds hold therapeutic potential for stromal regeneration in the treatment of deep corneal defects.

View details for DOI 10.1016/j.ijpharm.2024.125009

View details for PubMedID 39613275

Abstract

In situ-forming hydrogels are an attractive option for corneal regeneration, and the delivery of growth factors from such constructs have the potential to improve re-epithelialization and stromal remodeling. However, challenges persist in controlling the release of therapeutic molecules from hydrogels. Here, an in situ-forming bio-orthogonally crosslinked hydrogel containing growth factors tethered via photocleavable linkages (PC-HACol hydrogel) was developed to accelerate corneal regeneration. Epidermal growth factor (EGF) was conjugated to the hydrogel backbone through photo-cleavable (PC) spacer arms and was released when exposed to mild intensity ultraviolet (UV) light (2-5mW/cm2, 365nm). The PC-HACol hydrogel rapidly gelled within a few minutes when applied to corneal defects, with excellent transparency and biocompatibility. After subsequent exposure to UV irradiation, the hydrogel promoted the proliferation and migration of corneal epithelial cells in vitro. The rate of re-epithelialization was positively correlated to the frequency of irradiation, verified through ex vivo rabbit cornea organ culture studies. In an in vivo rat corneal wound healing study, the PC-HACol hydrogel exposed to UV light significantly promoted re-epithelialization, the remodeling of stromal layers, and exhibited significant anti-scarring effects, with minimal alpha-SMA and robust ALDH3A1 expression. Normal differentiation of the regenerated epithelia after healing was evaluated by expression of the corneal epithelial biomarker, CK12. The remodeled cornea exhibited full recovery of corneal thickness and layer number without hyperplasia of the epithelium.

View details for DOI 10.1016/j.bioactmat.2024.05.045

View details for PubMedID 39022184

Abstract

Purpose: To report a case of Light Adjustable Lens (LAL, RxSight, Aliso Viejo, CA) implantation in a patient with bilateral 50-cut radial keratotomy (RK) and discuss related preoperative, intraoperative, and postoperative considerations.Methods: A 78-year-old patient with history of bilateral 50-cut RK underwent phacoemulsification with implantation of LALs in both eyes one month apart. Although LAL technology was not approved specifically for addressing limitations in intraocular lens calculation post-RK due to corneal topography irregularity, the patient opted for this lens due to its ability to make post-operative adjustments to its refractive power. At postoperative month one following the second eye surgery, YAG capsulotomy was performed in both eyes. At postoperative month two following the second eye surgery, the patient began LAL adjustments spaced 1-2 weeks apart for a total of 2 LAL adjustments and 2 lock-in sessions.Results: Our patient achieved a final refraction of -0.25 +0.25 * 110 with an UDVA of 20/20-2 in the right eye and -0.25 +0.50 * 135 with an UDVA 20/25-1 in the left eye.Conclusions: The LAL may be a promising option for patients undergoing cataract surgery after RK, although further studies are needed to understand long-term changes in eyes with RK and the inability of LAL to address all aspects of corneal aberration.

View details for DOI 10.1097/coa.0000000000000045

View details for PubMedID 39513024

Abstract

Corneal defects can lead to stromal scarring and vision loss, which is currently only treatable with a cadaveric corneal transplant. Although in situ-forming hydrogels have been shown to foster regeneration of the cornea in the setting of stromal defects, the cross-linking, biomechanical, and compositional parameters that optimize healing have not yet been established. This, Corneal defects are also almost universally inflamed, and their rapid closure without fibrosis are critical to preserving vision. Here, an in situ forming, bioorthogonally cross-linked, nanocluster (NC)-reinforced collagen and hyaluronic acid hydrogel (NCColHA hydrogel) with enhanced structural integrity and both pro-regenerative and anti-inflammatory effects was developed and tested within a corneal defect model in vivo. The NCs serve as bioorthogonal nanocross-linkers, providing higher cross-linking density than polymer-based alternatives. The NCs also serve as delivery vehicles for prednisolone (PRD) and the hepatocyte growth factor (HGF). NCColHA hydrogels rapidly gel within a few minutes upon administration and exhibit robust rheological properties, excellent transparency, and negligible swelling/deswelling behavior. The hydrogel's biocompatibility and capacity to support cell growth were assessed using primary human corneal epithelial cells. Re-epithelialization on the NCColHA hydrogel was clearly observed in rabbit eyes, both ex vivo and in vivo, with expression of normal epithelial biomarkers, including CD44, CK12, CK14, α-SMA, Tuj-1, and ZO-1, and stratified, multilayered morphology. The applied hydrogel maintained its structural integrity for at least 14 days and remodeled into a transparent stroma by 56 days.

View details for DOI 10.1021/acsnano.4c02345

View details for PubMedID 39106436

Abstract

This study explores the impact of electrostatic interactions and hydrogen bonding on tear film stability, a crucial factor for ocular surface health. While mucosal and meibomian layers have been extensively studied, the role of electrolytes in the aqueous phase remains unclear. Dry eye syndrome, characterized by insufficient tear quantity or quality, is associated with hyperosmolality, making electrolyte composition an important factor that might impact tear stability. Using a model buffer solution on a silica glass dome, we simulated physiologically relevant tear film conditions. Sodium chloride alone induced premature dewetting through salt crystal nucleation. In contrast, trace amounts of solutes with hydroxyl groups (sodium phosphate dibasic, potassium phosphate monobasic, and glucose) exhibited intriguing phenomena: quasi-stable films, solutal Marangoni-driven fluid influx increasing film thickness, and viscous fingering due to Saffman-Taylor instability. These observations are rationalized by the association of salt solutions with increased surface tension and the propensity of hydroxyl-group-containing solutes to engage in significant hydrogen bonding, altering local viscosity. This creates a viscosity contrast between the bulk buffer solution and the film region. Moreover, these solutes shield the glass dome, counteracting sodium chloride crystallization. These insights not only advance our understanding of tear film mechanics but also pave the way for predictive diagnostics in dry eye syndrome, offering a robust platform for personalized medical interventions based on individual tear film composition.

View details for DOI 10.1073/pnas.2407501121

View details for PubMedID 39042697

Abstract

The corneal endothelium, comprising densely packed corneal endothelial cells (CECs) adhering to Descemet's membrane (DM), plays a critical role in maintaining corneal transparency by regulating water and ion movement. CECs have limited regenerative capacity within the body, and globally, there is a shortage of donor corneas to replace damaged corneal endothelia. The development of a carrier for cultured CECs may address this worldwide clinical need. In this study we successfully manufactured a gelatin nanofiber membrane (gelNF membrane) using electrospinning, followed by crosslinking with glutaraldehyde (GA). The fabricated gelNF membrane exhibited approximately 80% transparency compared with glass and maintained a thickness of 20 m. The gelNF membrane demonstrated desirable permeability and degradability for a Descemet's membrane analog. Importantly, CECs cultured on the gelNF membrane at high densities showed no cytotoxic effects, and the expression of key CEC functional biomarkers was verified. To assess the potential of this gelNF membrane as a carrier for cultured CEC transplantation, we used it to conduct Descemet's membrane endothelial keratoplasty (DMEK) on rabbit eyes. The outcomes suggest this gelNF membrane holds promise as a suitable carrier for cultured CEC transplantation, offering advantages in terms of transparency, permeability, and sufficient mechanical properties required for successful transplantation.

View details for DOI 10.3390/bioengineering11010054

View details for PubMedID 38247931

Abstract

Microextrusion-based 3D bioprinting into support baths has emerged as a promising technique to pattern soft biomaterials into complex, macroscopic structures. We hypothesized that interactions between inks and support baths, which are often composed of granular microgels, could be modulated to control the microscopic structure within these macroscopic-printed constructs. Using printed collagen bioinks crosslinked either through physical self-assembly or bioorthogonal covalent chemistry, we demonstrate that microscopic porosity is introduced into collagen inks printed into microgel support baths but not bulk gel support baths. The overall porosity is governed by the ratio between the ink's shear viscosity and the microgel support bath's zero-shear viscosity. By adjusting the flow rate during extrusion, the ink's shear viscosity was modulated, thus controlling the extent of microscopic porosity independent of the ink composition. For covalently crosslinked collagen, printing into support baths comprised of gelatin microgels (15-50 µm) resulted in large pores (∼40 µm) that allowed human corneal mesenchymal stromal cells to readily spread, while control samples of cast collagen or collagen printed in non-granular support baths did not allow cell spreading. Taken together, these data demonstrate a new method to impart controlled microscale porosity into 3D printed hydrogels using granular microgel support baths. This article is protected by copyright. All rights reserved.

View details for DOI 10.1002/adhm.202303325

View details for PubMedID 38134346