Telomerase activity in human umbilical cord cell populations containing hematopoietic stem cells

by Murthy, Vidya.

Hematopoietic cell populations exhibiting detectable telomerase activity and elongated telomere lengths display strong engraftment survivability in humans during transplants. We investigated telomerase activity and telomere length in umbilical cord blood hematopoietic cell populations obtained from ViaCell Inc. at various intervals of a two-week ex vivo stem cell amplification process. Telomerase activity is increased with time in ViaCell’s amplification process, perhaps in response to the removal of differentiated cells and expansion of primitive hematopoietic stem cell populations in tissue culture media containing a mixture of growth factors. Two of ViaCell’s cell culture fractions were analyzed for telomere length using a TLA. Our results showed relatively long telomere lengths for day-0 and day-14 cord populations, and that despite an upregulation of telomerase activity in Day-14 samples, a loss of about 2 kb of telomeric DNA occurs. Our data are consistent with a model in which the increase in telomerase activity in day-14 ex vivo amplified cord blood hematopoietic cells relative to fresh cord is sufficient to reduce, but not prevent, telomere shortening caused by cell proliferation. Lastly, we investigated various culture conditions that could potentially upregulate telomerase activity in the Day-14 amplified cells. However none of the treatments tested altered telomerase activity. Our detection of increased telomerase activity and relatively long telomere lengths in ViaCell’s Day-14 ex vivo amplified cord blood stem cell fraction provides support for ViaCell’s Selective Clonogenic AmplificationTM indicating a high engraftment potential for these cells. ii