Isolation and characterization of multi-potent stem cells from human orbital fat tissues

Loss of corneal epithelial cells results in visual problems. Stem cells isolated from the limbal area of the ocular surface are able to replenish lost corneal epithelial cells. However, destruction of the healthy limbus tissue is inevitable. Theoretically, orbital fat should be an excellent source to isolate stem cells for regenerating ocular tissues as the orbital connective tissues share the same embryonic origin with the ocular proper in early organogenesis. The aim of this study is to isolate stem cells from the human orbital fat and to explore their differentiation potentials into epithelial cells. It was found that spindle-shaped, fibroblast-like cells with extensive proliferation potentials could be isolated from orbital fat tissues. These orbital fat-derived stem cells (OFSCs) possessed multi-lineage differentiation potential to become osteoblasts, chondrocytes, and adipocytes. Upon mix-culture with corneal epithelial cells, OFSCs changed their morphology to round, polygonal epithelial-like cells. Loss of CD105 expression and increased expression of epithelial cell markers, including epithelial-specific antigen and zonal occludin-1, were found upon mix-culture with corneal epithelial cells. Moreover, corneal epithelial differentiation was evidenced by expression of cytokeratin -19 and cytokeratin -3 after mix-culture with corneal epithelial cells, whereas human adipose-derived stem cells from subcutaneous fat were unable to differentiate into corneal epithelial cells under the same induction condition. We further found that direct contact with corneal epithelial cells was essential for OFSCs to commit to corneal epithelial cells. Taken together, orbital fat tissues are a novel source for multi-potent stem cells that possess the potential to differentiate into corneal epithelial lineage. OFSCs are therefore a potential candidate for cell therapy and tissue engineering of corneal epithelium.