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Low efficiency of somatic cell reprogramming and heterogeneity among human induced pluripotent stem cells (hiPSCs) demand extensive characterization of isolated clones before their use in downstream applications. By monitoring human fibroblasts undergoing reprogramming for their morphological changes and expression of fibroblast (CD13), pluripotency markers (SSEA-4 and TRA-1-60) and a retrovirally expressed red fluorescent protein (RV-RFP), we compared the efficiency of these features to identify bona fide hiPSC colonies. The co-expression kinetics of fibroblast and pluripotency markers in the cells being reprogrammed and the emerging colonies revealed the heterogeneity within SSEA-4+ and TRA-1-60+ cells, and the inadequacy of these commonly used pluripotency markers for the identification of bona fide hiPSC colonies. The characteristic morphological changes in the emerging hiPSC colonies derived from fibroblasts expressing RV-RFP showed a good correlation between hiPSC morphology acquisition and silencing of RV-RFP and facilitated the easy identification of hiPSCs. The kinetics of retroviral silencing and pluripotency marker expression in emerging colonies suggested that combining both these markers could demarcate the stages of reprogramming with better precision than with pluripotency markers alone. Our results clearly demonstrate that the pluripotency markers that are routinely analyzed for the characterization of established iPSC colonies are not suitable for the isolation of pluripotent cells in the early stages of reprogramming, and silencing of retrovirally expressed reporter genes helps in the identification of colonies that have attained a pluripotent state and the morphology of human embryonic stem cells (hESCs).

Aim of the present study was in vitro expansion and characterization of caprine wharton's jelly derived mesenchymal stem cells (cWJ-MSCs) to investigate their tissue healing potential in xenogenic animal model. Plastic adherent fibroblastoid cell populations with distinctive homogeneous morphology were isolated from caprine Wharton's jelly explants. These Wharton's jelly derived cells were found positive for the surface markers CD-73, STRO-1 and CD-105, whereas they were negative for hematopoetic stem cell marker CD-34. In vitro cultured cWJ-MSCs also showed differentiation properties into osteogenic, adipogenic and chondrogenic lineages as demonstrated by von Kossa, Oil Red-O and Alcian blue staining respectively, which was further confirmed and quantified by flow cytometric analysis. Furthermore, these well characterized cWJ-MSCs were evaluated for the wound-healing potential in full-thickness skin wounds in rabbit model for 28 days. Caprine WJ- MSCs treated skin wounds showed significantly (P < 0.05) higher percentage of wound contraction especially at the 21(st) day post transplantation when compared to PBS treated control group animals. Further, we observed better healing potential of cWJ-MSCs in terms of histo-morphological evaluation, epithelialisation and collagenization with matured vascularization stage by day 28 as compared to control. In conclusion, cWJ- MSCs provide an alternative inexhaustible source of mesenchymal stem cells and also unravel new perspectives pertaining to the therapeutic use of these cells in different species.

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