Abstract
Purpose: :
To isolate and further characterize the niche cells from the human limbal niche.
Methods: :
The Vim+ stromal cells subjacent to limbal basal epithelial progenitor cells were isolated with collagenase and serially cultured on coated Matrigel in ESCM with bFGF and LIF. Their ability of differentiating into angiofenic progenitors was assessed by marker expression and differentiation into vascular endothelial cells and support of the vascular network formed by human umbilical vein endothelial cells (HUVEC). Their ability of supporting limbal epithelial progenitor cells was tested in coculturing to generate sphere growth in 3D Matrigel.
Results: :
The Vim+ limbal stromal cells could be isolated and expanded for at least 25 population doublings by keeping them in contact with the basement membrane mimicked by Matrigel. When immediately seeded in 3D Matrigel in ESCM, these stromal mesenchymal cells were mitotically quiescent and did not express any markers indicative of angiogenesis progenitors. However, when serially cultured on coated Matrigel in ESCM with bFGF and LIF, they turned into spindle cells that expressed pericyte markers. Upon being reseeded in 3D Matrigel, the expanded spindle cells turned into angiogenesis progenitor cells able to differentiate into both vascular endothelial cells that expressed CD34, CD31, Flk-1, and vWF, as well as pericytes that expressed NG2, alpha-SMA, and PDGFR-beta. Although both expanded angiogenesis progenitors and HUVEC could join single limbal epithelial progenitors to form spheres with upregulation of p63-alpha, CK15 and C/EBP-delta, the former, but not the latter, could suppress expression of CK12 keratin in the limbal progenitors/SCs.
Conclusions: :
These findings suggest that limbal niche cells cultured continuously on the basement membrane can differentiate into angiogenesis progenitors that may prevent differentiation of limbal epithelial progenitors/SCs.
Keywords: cornea: basic science • cornea: epithelium