Because, I have been working on structure, functional characterization of CD34 and after that there were many reports indicating that CD34 negative cells are real stem cells & other important markers like AC133, Hoesct dye efflux methods are introduced for their identification. what, I have seen most clinicians are still in favour of transplant CD34 positive cell populations over other selection markers/ methods
Hello
If you mean Hematopoietic stem cells, yes the CD34+ is the best surfaces marker this is due to two reasons.
1- it is responsible for most of the hematopoietic activity in enriched cell population from marrow or mobilized peripheral blood appears . CD34 has therefore been considered to be the most critical marker for hematopoietic stem cells (HSCs). CD34 expression on primitive cells is down-regulated as they differentiate into mature cells. It is also found on clonogenic progenitors, however, and some lineage-committed cells. Although its precise function is still unknown, the pattern of expression of CD34 suggests that it plays a significant role in early hematopoiesis. The theory of CD34 being the most primitive HSC marker, however, has recently been challenged. Osawa et al. first demonstrated that murine HSCs could be CD34 negative. In addition, a low level of engraftment and hematopoietic capacity has been demonstrated in human CD34- cells. Transplantation studies also showed repopulation activity in a CD34- cell population in fetal sheep. Additionally, studies have shown that both murine and human CD34+ cells may be derived from CD34- cells. Collectively, these reports suggest the possibility that HSCs may be CD34+ or CD34- and that selection of cells expressing CD34 might result in exclusion of more primitive stem cells. Nevertheless, almost all clinical and experimental protocols including ex vivo culture, gene therapy, and HSC transplantation are currently designed for cell populations enriched for CD34+ cells.
2- was identified initially by the AC133 monoclonal Ab, which recognizes a CD34+ subset of human HSCs.29, 30 A CD133 isoform, AC133-2, has been recently cloned and identified as the original surface antigen recognized by the AC133 Ab.31 CD133 may provide an alternative to CD34 for HSC selection and ex vivo expansion. A CD133+ enriched subset can be expanded in a similar manner as a CD34+ enriched subset, retaining its multilineage capacity. Recent studies have offered evidence that CD133 expression is not limited to primitive blood cells, but defines unique cell populations in non-hematopoietic tissues as well. CD133+ progenitor cells from peripheral blood can be induced to differentiate into endothelial cells in vitro.33 In addition, human neural stem cells can be directly isolated by using an anti-CD133 Ab.
Best wishes
hello,
Following to Dr Saleh answer, we were capable of isolating CD34+ epithelial stem cells from some specific niches in the lungs. In vitro we were able to amplify and maintain them and were also capable to differciate them into specific cells
Article Bronchioloalveolar stem cells from the lamb lungs of can dif...
As per ICMR-DBT guidelines, in vitro techniques like isolation/culture using any specific markers with magnetic/Flourescence base could not be use for clinical purpose. In this regard, better you may use adult stem cell like autologous bone marrow mono nuclear cells for any disease. We should not cross the guidelines.
I think there is some misunderstanding: the question. i have been working on CD34 and recently a lot of literature is available showing number aphaeresis products/ AC133 etc. as an important cell surface marker for isolation of cells for clinical uses. That is used bu all the scientist. clinicians internally and even in INDIA. There were some controversies earlier about the expression level of CD34 on the most primitive stem cell population and people started saying that one might loose an important most primitive stem cell fraction when select CD34+ population only for all these purposes. But since then, i am seeing many reports are still claiming use of CD34+ population for showing stem cell in their research work and i wanted to know is there any shift in the isolation criteria in clinics also.
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