Mesenchymal Stem Cell-Laden In Situ-Forming Hydrogel for Preventing Corneal Stromal Opacity

PURPOSE

The aims of this study were to construct a mesenchymal stem cell (MSC)-laden in situ-forming hydrogel and study its effects on preventing corneal stromal opacity.

METHODS

The native gellan gum was modified by high temperature and pressure, and the rabbit bone marrow MSCs were encapsulated before adding Ca 2+ to initiate cross-linking. The effects of the hydrogel on 3D culture and gene expression of the rabbit bone marrow MSCs were observed in vitro. Then, the MSC-hydrogel was used to repair corneal stromal injury in New Zealand white rabbits within 28 days postoperation.

RESULTS

The short-chain gellan gum solution has a very low viscosity (<0.1 Pa·s) that is ideal for encapsulating cells. Moreover, mRNA expressions of 3D-cultured MSCs coding for corneal stromal components (decorin, lumican, and keratocan) were upregulated (by 127.8, 165.5, and 25.4 times, respectively) ( P < 0.05) on day 21 in vitro and were verified by Western blotting results. For the in vivo study, the corneal densitometry of the experimental group was (20.73 ± 1.85) grayscale units which was lower than the other groups ( P < 0.05). The MSC-hydrogel downregulated mRNA expression coding for fibrosis markers (α-smooth muscle actin, vimentin, collagen type 5-α1, and collagen type 1-α1) in the rabbit corneal stroma. Furthermore, some of the 5-ethynyl-2'-deoxyuridine (EdU)-labeled MSCs integrated into the upper corneal stroma and expressed keratocyte-specific antigens on day 28 postoperation.

CONCLUSIONS

The short-chain gellan gum allows MSCs to slowly release to the corneal stromal defect and prevent corneal stromal opacity. Some of the implanted MSCs can integrate into the corneal stroma and differentiate into keratocytes.

The Innovative Biomaterials and Technologies for Developing Corneal Endothelium Tissue Engineering Scaffolds: A Review and Prospect

Corneal transplantation is the only treatment for corneal endothelial blindness. However, there is an urgent need to find substitutes for corneal endothelium grafts due to the global shortage of donor corneas. An emerging research field focuses on the construction of scaffold-based corneal endothelium tissue engineering (CETE). Long-term success in CETE transplantation may be achieved by selecting the appropriate biomaterials as scaffolds of corneal endothelial cells and adding bioactive materials to promote cell activity. This article reviews the research progress of CETE biomaterials in the past 20 years, describes the key characteristics required for corneal endothelial scaffolds, and summarizes the types of materials that have been reported. Based on these, we list feasible improvement strategies for biomaterials innovation. In addition, we describe the improved techniques for the scaffolds' surface topography and drug delivery system. Some promising technologies for constructing CETE are proposed. However, some questions have not been answered yet, and clinical trials and industrialization should be carried out with caution.