In vivo reactivation of a quiescent cell population located in the ocular ciliary body of adult mammals.
Rare quiescent cells with stem cell characteristics have been isolated from the ocular ciliary body (CB) of adult mammals. In vitro, adult retinal stem cells were reported to generate sphere colonies containing multipotent retinal progenitor cells. Whether proliferation of this stem cell population can be stimulated in vivo in order to generate new retinal cells is an important issue. Herein we report on the in vivo reactivation of a quiescent cell population present in the CB upon growth factors (GF) stimulation. GF stimulation resulted in the re-acquisition of embryonic characteristics (Nestin) and expression of the cell cycle entry markers CyclinD1 and Ki67 by a subset of CB epithelial cells. This inductive effect was not observed in the neural retina. GF-activated CB epithelial cells co-express the retinal progenitor homeodomain transcription factors Pax6 and Chx10. Serial GF injections led to do novo proliferation of clusters of cells in the CB, in a dose-dependent manner, as revealed by bromodeoxyuridine (BrdU) incorporation. Analysis of cells' BrdU content within individual clusters suggests a mode of cell division that is predominantly asymmetric. Cell proliferation was not induced by CB or retinal damage, as indicated by the absence of TUNEL-labeled cells. Newly produced cells did not migrate into the retina nor did they differentiate into retinal neurons. This study demonstrates that proliferation of a quiescent cell population with retinal stem/progenitor cell characteristics can be reactivated in vivo upon GF injections and suggests that, in adult mammals, the CB is a non-permissive environment for cell migration and neurogenesis.
Maisonneuve-Rosemont Hospital, 5415 Boulevard de l'Assomption, Montreal, PQ, Canada H1T 2M4.
Mohamed
M
Abdouh
Gilbert
G
Bernier
D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002453:Cell Cycle / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002924:Ciliary Body / Q000166:cytology*; D019938:Cyclin D1 / Q000032:analysis; D004847:Epithelial Cells / Q000502:physiology; D005136:Eye Proteins / Q000032:analysis*; D006133:Growth Substances / Q000008:administration & dosage / Q000502:physiology*; D018398:Homeodomain Proteins / Q000032:analysis; D007150:Immunohistochemistry / Q000379:methods; D020287:In Situ Nick-End Labeling / Q000379:methods; D007267:Injections; D007381:Intermediate Filament Proteins / Q000032:analysis; D007498:Iris / Q000166:cytology; D019394:Ki-67 Antigen / Q000032:analysis; D009419:Nerve Tissue Proteins / Q000032:analysis; D064231:Nestin; D009474:Neurons / Q000502:physiology; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D012097:Repressor Proteins / Q000032:analysis; D012160:Retina / Q000166:cytology; D013234:Stem Cells / Q000502:physiology*; D014157:Transcription Factors / Q000032:analysis
D015415:Biomarkers; D005136:Eye Proteins; D006133:Growth Substances; D018398:Homeodomain Proteins; D007381:Intermediate Filament Proteins; D019394:Ki-67 Antigen; D009419:Nerve Tissue Proteins; C577485:Nes protein, mouse; C577486:Nes protein, rat; D064231:Nestin; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; C000605733:Pax6 protein, rat; D012097:Repressor Proteins; D014157:Transcription Factors; C088975:Vsx2 protein, mouse; D019938:Cyclin D1