**Author details**

82 Blood Cell – An Overview of Studies in Hematology

since no cell lineage is expected to be aneuploid.

**11. Key points of the Chapter** 

cells in the bone marrow.

groups across the world.

blood, bone marrow and Wharton's jelly.

coming years will bring more answers to the potential of these cells.

The field of BMT also stands to greatly benefit once VSELs potential are realized. A review article by Takizawa et al [64] makes an interesting reading and that despite advances in the field, timely availability of HLA matched BM is still problematic for patients including those who require multiple transplantations. In this context, *in vitro* expansion of HSC is crucial but not yet achieved. It is still hoped that a single HSC may suffice to induce long-term multilineage engraftment. Notta et al [65] reported the possibility of CD49f as a specific marker to isolate HSC. In the chapter we are proposing that VSELs possibly give rise to HSC and may be better cell source to induce engraftment. Using cell surface markers to identify cell types always has associated issues since surface phenotype of a cell can change depending on the activation status of the precursor cells. Danova-Alt et al [66] recently concluded that UCB VSELs neither have embryonic nor adult stem cell-like phenotype, are not equivalent to mouse VSELs, have aneuploid karyotype and should not be regarded as a stem cell population. However, they have studied Lin-/CD45-/CD34+ cells and not Lin- /CD45-/CD133+ cells, which are the VSELs as described by Ratacjzak and group [38]. Further it remains to be confirmed whether the aneuploidies they report are a technical artefact,

VSELs could potentially be a real therapeutic alternative to the use of human ES cells since they do not form teratomas, are relatively quiescent and can be isolated from an autologous source. The fact that VSELs may differentiate *in vitro* into cells from all three germ layers makes these cells potential candidates in regenerative medicine. Finally, the mechanism by which VSELs could contribute to development of some malignancies could shed more light on origin of tumours. In conclusion it is of vital importance to evaluate if VSELs could be efficiently employed in the clinic. The work on VSELs is on the verge of development and in

 The trans-differentiation potential of the HSC or MSC from bone marrow is controversial and can be alternatively explained by the presence of pluripotent stem

 MAPC, MIAMI, VSELs, RS are possibly the same pluripotent stem cells, described differently by various investigators. All of these terminologies have disappeared over time in published literature except VSELs that are being widely studied by various

 VSELs are epiblast derived stem cells expressing pluripotent markers with high nucleocytoplasmic ratio and transcriptionally active chromatin. They have been isolated from various murine organs as well as from human organs including gonadal tissues, cord

VSELs (with nuclear OCT-4) possibly are the most primitive cell type in BM and

umbilical cord and give rise to HSC and MSC (with cytoplasmic OCT-4).

**10. Conclusions** 

Ambreen Shaikh and Deepa Bhartiya\*

*Stem Cell Biology Department, National Institute for Research in Reproductive Health (ICMR), Mumbai, India* 
