Abstract 5631: Isolation of a Resident and Dynamic Oct4+ Stem Cell Population From Adult Skin
The transcription factor Oct3/4 is a critical regulator of pluripotency in embryonic stem cells and induced pluripotent stem (iPS) cells and iPS generation requires re-activation of endogenous Oct4 expression. Since Oct4 might be a critical regulator of somatic stem cell pluripotency we have employed a genetic, bona-fide reporter strategy to determine the temporo-spatial expression of Oct4 in adulte mice.
RESULTS: Postnatal Oct4 expression was determined in transgenic Oct4::eGFP reporter mice by flow cytometry, for hearts and skin the response to injury was also evaluated (n=9 –28). The fidelity of the Oct4-GFP reporter strain was confirmed by immunofluorescence confocal microscopy and by RT-PCR. No GFP+ cells were detected in bone marrow or spleen, nor in the atria or ventricles of the myocardium under baseline and post-ischemic conditions. Importantly, Oct4+ cells resided in skin, where levels increased postnatally over time until puberty and returned to low levels in the adult (Oct4+/500.000 cells: puberty 400±268; adult 53±23). Furthermore, the Oct4+ cell pool increased robustly after wound injury (289±156, n=9, p<0.05) even in remote skin areas. In situ analysis revealed the existence of GFP+ niches associated with distinct regions of hair follicle. Oct4+ cells after FACS-sorting revealed a phenotype of c-kit lo, sca-1 +, CXCR4 lo, alpha6 integrin lo, beta1 integrin -, and expressed by qRT low levels of Oct4, Sox2, Klf4, and high levels of c-myc, factors involved in iPS induction. The differentiation potential of Oct4+ skin cells was evaluated by transplanting dual reporter cells (GFP+; lacZ+) into nude mice following hindlimb ischemia and analysis of contribution to tissue lineages. 4 weeks after transplantation, LacZ+ cells contributed to muscle cells, adipose tissue and vascular structures.
CONCLUSION: Genetic reporter studies reveal no evidence for Oct4+ cells in bone marrow or heart but, unexpectedly, show persistence of resident Oct4+ stem cells in adult skin, which contribute to mesodermal cell lineage after transplantation. These findings suggest adult skin as an important source for regenerative cell therapy.