Isolation and characterization of rabbit limbal niche cells

Limbal niche cells (LNCs) are one of the most important supporting cells for corneal epithelial stem cells (CES), however, research on LNCs has been mostly limited to humans and rats previously. To expand the research work into the rabbit animal model, one of the most often used animals in stem cell study, this study was carried out for the in vitro isolation and identification of rabbit LNCs. Rabbit LNCs were isolated by collagenase A digestion method and single cells were obtained, the cells were then seeded on 5% Matrigel-coated plastic surface and cultured in modified embryonic stem cell medium (MESCM). Three biological replicates of the isolating and characterization were recorded from New Zealand White rabbits aged from 2.5 months to 5 months. LNC markers (VIM/CD90/CD105/SCF/PDGFRβ) were analyzed using tyramide signal amplification (TSA) staining, immunohistochemical staining (IHC), western blotting (WB), and real-time reverse transcription polymerase chain reaction (qPCR). TSA staining suggested that VIM was highly expressed in rabbit limbus stroma, which was confirmed by WB, and P63α was expressed in the basal limbus epithelium. Pan-CK and CK12 were highly expressed in the central corneal epithelium but lightly expressed in the limbal epithelium. The WB result indicated that PDGFRβ and VIM expressions in rabbit-LNCs P4 were higher than in P1 and P7. In addition, rabbit corneal epithelium highly expressed Paired Box 6 (PAX6) and Epidermal growth factor-like domain 6(EGFL6). For the three repeat experiments, the cell expansion activity of rabbit-LNC was highest at P4. Rabbit-LNCs were passaged from P0 to P7, and the number of cell doublings (NCD) of P4 for the three repeat experiments was 2.816, 2.737, and 2.849. qPCR showed that high mRNA expression levels of VIM, CD90, CD105, SCF, and PDGFRβ in rabbit-LNCs P4. In conclusion, rabbit-LNCs could be successfully isolated by the collagenase A digestion method as used in human tissue. There were similar characteristics between rabbit and human LNCs (VIM+/CD90+/CD105+/SCF+/PAX6+/PDGFRβ+).