Human keratocytes express the haematopoietic stem cell markers CD133 and CD34. This expression decreases with time in culture, with most but not all cells losing expression. On the basis of these markers, the corneal stroma shows a heterogeneous population of cells. Expression or down regulation of expression of these molecules could represent different stages of activation of these cells.
Oct‐4A (Octamer binding protein 4, isoform A) is a key component of the molecular circuitry which regulates stem cells self‐renewal and pluripotency. Very little is known about the mechanisms through which Oct‐4A responds to complex extracellular stimuli and regulates stemness. In our studies we noted that Oct‐4 was expressed both in nucleus and cytoplasm, implicating the presence of nuclear‐cytoplamatic translocation mechanisms. To further explore the functional network of Oct‐4A, in vitro and in vivo methods were used to search interacting proteins in human Dental Pulp Marrow Similar Cells (DPMSC) and NTera2, a human embryonal carcinoma (EC) stem cell line that shares many characteristics with human embryonic stem cells. Glutathione S‐transferase pull‐down and co‐immunoprecipitation assays identified Erk1/2 as a possible Oct‐4A interactor. One mechanism by which Erk1/2 kinases ensure their specificity of action is by interacting with their substrates through docking domains, enhancing also the efficiency of phosphorylation. Oct‐4A sequence analysis evidenced the presence of a D‐domain supporting our interaction hypothesis. Further studies are needed to better understand the mechanism.
Bone marrow derived stem cells (BMSCs) are able to generate many different cell types. Understanding biological significance and molecular mechanisms underlying adult stem cell trafficking seems crucial. Currently though, the real potential of BMSCs is not yet fully accepted and data reported after injection in uninjured animals are contradictory. This may be due to the use of total BMSCs, which may contain at variable rate and percentage different subpopulations with specific homing properties.We isolated from the BM of C57B1/6‐Tg(UBC‐GFP)30Scha/J adult mice, 4 different populations according to molecular markers or culture methods: CD105+, MSC, floaters (D. Trisler's method) and buffy coat. After extensive immunophenotyping and microarray analysis, they have been injected in the tail vein of C57B1/6 wildtype mice. Animals have been sacrificed 2 days later and different tissues harvested. In each tissue, the presence of GFP+ cells has been analyzed by PCR and immunohistochemistry. Here we present data indicating not only specific homing of the subpopulations in different tissues, but even preferential localization within each tissue.
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