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Very small embryonic like stem cells may not exist, say Stanford researchers

Very small embryonic like stem cells may not exist, say Stanford researchers

There’s a shake-up happening today in the world of stem cell research. Very small embryonic-like stem cells, or VSEL cells, have been proposed by some researchers as an alternative to human embryonic stem cells. Because they’re said to exist in the bone marrow of adult humans and mice, they could obviate the ethical issues surrounding the use of human embryos.

The research has sounded promising enough that a New York-based company, NeoStem, was awarded a grant from the National Institute of Dental and Craniofacial Research to investigate the use of the cells to stimulate bone growth after tooth extraction.

But in a study published today in Stem Cell Reports, Stanford stem cell scientist Irving Weissman, MD, casts doubt on the existence of the cells. From our release:

“It has become important to know to what extent and where these VSEL cells exist to understand how they may affect the field of stem cell research,” said Weissman, who directs Stanford’s Institute for Stem Cell Biology and Regenerative Medicine and the Ludwig Center for Cancer Stem Cell Research and Medicine at Stanford. “We tried as hard as we could to replicate the original published results using the methods described and were unable to detect these cells in either the bone marrow or the blood of laboratory mice.”

Although other groups have seemingly confirmed the existence of these cells as defined by size and the expression of key cell-surface molecules, Weissman’s study is the first to evaluate the biological potency of the cells.

An article in today’s Nature magazine summarizes the controversy surrounding the cells, and calls Weissman’s study a “major blow to the field.” Alison Abbott writes:

Led by Irving Weissman, a prominent stem-cell researcher at Stanford University in California, the study is the fourth to refute the cells’ existence — and the most thorough yet.

“Weissman’s evidence is a clincher — it is the end of the road for VSELs,” believes Rüdiger Alt, head of research at Vita 34, a private bank for umbilical cord blood in Leipzig, Germany, who last year published the first failure to replicate claims for the cells2.

Robin Smith, chief executive at Neostem, disagrees. She compares the attacks on VSELs to those suffered by Charles Darwin and Nicolaus Copernicus when they proposed their world-changing scientific theories.

It will likely take some time for the controversy to end. In the meantime, Weissman and his colleagues have concluded that “the existence of adult mouse VSELs in the bone marrow remains dubious.”

Previously: Stanford’s Irving Weissman on the (lost?) promise of stem cells

2 Responses to “ Very small embryonic like stem cells may not exist, say Stanford researchers ”

  1. Deepa Bhartiya Says:

    Dear Prof Weissman

    We read your paper with interest and thanks for citing our work- although it is apparent that you do not believe in our results.

    We have shown that VSELs are unknowingly discarded during volume reduction step while processing human bone marrow/cord blood. We also detected VSELs in ovary surface epithelium and in testicular smears. These cells do exist. They are pluripotent embryonic-like stem cells in adult body tissues and have the potential to unite adult and embryonic stem cell researchers. We define them as very small cells, spherical in shape, high nucleo-cytoplasmic ratio, slightly smaller than red blood cells in size with nuclear OCT-4, cell surface SSEA-4 and express many other pluripotent transcripts. They are relatively fewer in number and are invariably associated with large numbers of slightly larger stem cells with cytoplasmic OCT-4. Both the stem cells including VSELs and tissue specific progenitors exhibit dark Haematoxylin stained nuclei which does not easily get stained with DAPI. One needs to stain VSELs for almost 15-20 mins with DAPI suggesting presence of abundant euchromatin. We routinely see them in smears of ovary surface epithelium but are unable to detect them in ovarian sections. If you wish to see self-renewal property of VSELs, please refer to our recent paper (Patel et al, 2013).

    Since we found VSELs in human samples – we expected your findings in mice will support our work but they are in fact contradictory. We read carefully your methods and believe your research group lost the VSELs during initial processing. At one time, we also aspired to see more than 20-25 ovarian VSELs on a slide and I assigned this task to a graduate student in the lab. She would scrape surface epithelium of more than 50 sheep ovaries; we will see large number of VSELs initially but she lost them by the end of the day. This continued for almost a month – we doubted the very existence of VSELs in ovaries and then we realized that they do not settle easily on centrifugation, implying that she lost the VSELs during processing. Your methods (after lysis of mouse bone marrow) do not mention any speed for centrifugation – which is very crucial. We looked at the protocol of BD for processing bone marrow – mentions a speed of 600g – at this speed VSELs will not settle and may explain your doubting the very existence of VSELs in mouse bone marrow. Now we routinely enrich VSELs by magnetic sorting using SCA-1 antibody.

    We are convinced that these stem cells are best candidates for regenerative medicine. They are better that embryonic stem cells as they can be isolated from autologus source and do not form teratoma, better than adult stem cells as they in fact give rise to the adult stem cells and of course better than iPS cells (why to reprogram somatic cells to pluripotent state when pluripotent stem cells (VSELs) exist per se in adult body tissues).

    Seeing is believing. To conclude, we have observed VSELs under the microscope. We have no financial interests – neither own any company nor have patents to defend, I am a researcher and enjoy my work. At present I have 5 PhD students working on different aspects of VSELs biology in the lab and we can show you the VSELs in bone marrow, cord blood, ovary, testis and also Wharton’s jelly.

    Following are the highlights of our work:
    .VSELs are present in both adult mammalian ovary and testis
    .They are unknowingly discarded during volume reduction step of cord blood or bone marrow
    .Function of VSELs in adult ovary is modulated by FSH
    .We have shown how postnatal ovary undergoes neo-oogenesis and follicle assembly from VSELs (Bhartiya et al, 2012)
    .VSELs are shed off from the ovary surface when cortical tissue is cultured on cell inserts (Parte et al, 2013)
    .VSELs are relatively quiescent and resist oncotherapy (currently under review in both mice and human testes and mice ovaries). This work has huge translational potential
    .Cord blood VSELs exist, have been characterized in depth and have normal FISH signals confirming their diploid status (yet to be published)
    .Neonatal exposure of mice to estrogens (endocrine disruptors) alters VSELs function resulting in adult onset of diseases like polycystic ovarian disease, altered spermatogenesis, absent glands in uterus and signs of cancer initiation in uterus and prostate (currently under review).

    However we admit that it is very difficult to get our work published, get financial support with papers like yours in literature. Best will be to hold a symposium on VSELs in USA, we are willing to participate and can show you the VSELs under a microscope. May be ISSCR should take a lead in this direction. The basic truth is that all of us have a common goal to serve mankind through our research efforts.

    Dr Deepa Bhartiya
    Stem Cell Biology Department
    National Inst for Res in Reproductive Health
    JM Street, Mumbai, INDIA 400 012
    Tel No. +91 22 2419 2012
    Fax no. +91 22 2 413 9412
    deepa.bhartiya@yahoo.in; bhartiyad@nirrh.res.in

    References
    1.Follicle stimulating hormone modulates ovarian stem cells through alternately spliced receptor variant FSH-R3. Patel H, Bhartiya D, Parte S, Gunjal P, Vedulkar S, Bhatt M. J Ovarian Res. 2013 Jul 20;6(1):52. [Epub ahead of print]
    2.Stimulation of ovarian stem cells by follicle stimulating hormone and basic fibroblast growth factor during cortical tissue culture. Parte S, Bhartiya D, Manjramkar DD, Chauhan A, Joshi A.J Ovarian Res. 2013 Apr 1;6(1):20. doi: 10.1186/1757-2215-6-20.
    3.Gonadotropin treatment augments postnatal oogenesis and primordial follicle assembly in adult mouse ovaries? Bhartiya D, Sriraman K, Gunjal P, Modak H. J Ovarian Res. 2012 Nov 7;5(1):32. doi: 10.1186/1757-2215-5-32.
    4.Cellular origin of testis-derived pluripotent stem cells: a case for very small embryonic-like stem cells. Bhartiya D, Kasiviswananthan S, Shaikh A. Stem Cells Dev. 2012 Mar 20;21(5):670-4.
    5.Very small embryonic-like stem cells with maximum regenerative potential get discarded during cord blood banking and bone marrow processing for autologous stem cell therapy.Bhartiya D, Shaikh A, Nagvenkar P, Kasiviswanathan S, Pethe P, Pawani H, Mohanty S, Rao SG, Zaveri K, Hinduja I.
    Stem Cells Dev. 2012 Jan;21(1):1-6.
    6.Detection, characterization, and spontaneous differentiation in vitro of very small embryonic-like putative stem cells in adult mammalian ovary. Parte S, Bhartiya D, Telang J, Daithankar V, Salvi V, Zaveri K, Hinduja I. Stem Cells Dev. 2011 Aug;20(8):1451-64.
    7.Newer insights into premeiotic development of germ cells in adult human testis using Oct-4 as a stem cell marker. Bhartiya D, Kasiviswanathan S, Unni SK, Pethe P, Dhabalia JV, Patwardhan S, Tongaonkar HB. J Histochem Cytochem. 2010 Dec;58(12):1093-106.

  2. Morteza Abouzary Says:

    I am a PhD student in Tehran university and I have isolated VSEl stem cells form mice bone marrow,i used antibodies against cd45,cxcr4 and SSEA1 markers and sort these cells with FACS.

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