Abstract
Adult stem cells are characterised by longer telomeres compared to mature cells from the same tissue. In this study, candidate CD146 (+) umbilical cord (UC) mesenchymal stem cells (MSCs) were purified by cell sorting from UC tissue digests and their telomere lengths were measured in comparison to donor-matched CD146-negative fraction. UC tissue fragments were enzymatically treated with collagenase and the cells were used for cell sorting, colony-forming fibroblast (CFU-F) assay or for long-term MSC cultivation. Telomere lengths were measured by qPCR in both culture-expanded MSCs and candidate native UC MSCs. Immunohistochemistry was undertaken to study the topography of CD146 (+) cells. Culture-expanded UC MSCs had a stable expression of CD73, CD90 and CD105, whereas CD146 declined in later passages which correlated with the shortening of telomeres in the same cultures. In three out of four donors, telomeres in candidate native UC MSCs (CD45 (-)CD235α (-)CD31 (-)CD146 (+)) were longer compared to donor-matched CD146 (-) population (CD45 (-)CD235α (-)CD31 (-)CD146 (-)). The frequency of CD45 (-)CD235α (-)CD31 (-)CD146 (+) cells measured by flow cytometry was ~1000-fold above that of donor-matched CFU-Fs (means 10.4% and 0.01%, respectively). CD146 (+) cells were also abundant in situ having a broad topography including high levels of positivity in muscle areas in addition to vessels.
Highlights
Perinatal mesenchymal stem cell (MSC) sources are attracting increasing attention as an alternative to ‘gold standard’ bone marrow (BM) mesenchymal stem cells (MSCs)
Molecular profile of culture-expanded umbilical cord (UC) MSCs compared to fibroblasts We initially aimed to confirm the validity of CD146 as a candidate marker of UC MSCs using cultures established following standard MSC protocols[2]
We studied the expression of 45 MSC- and fibroblast-related transcripts by TLDA in these cultures and compared their expression levels to those of negative control skin fibroblasts
Summary
Perinatal mesenchymal stem cell (MSC) sources are attracting increasing attention as an alternative to ‘gold standard’ bone marrow (BM) MSCs. The potency of standard culture-expanded UC MSCs, especially towards osteoblasts, chondrocytes and adipocytes, is lower compared to BM MSCs2,3. This can be explained by the fact that conventional UC MSC cultures arise from diverse clonal populations that possess varying degrees of self-renewal leading to mixed cultures that gradually lose their MSC properties[4]. The therapeutic advantages of minimally-expanded UC MSCs would include a better preservation of their native functionality as well as rapid manufacture and reduced cost[2]. No agreement yet exists on the native phenotype of UC MSCs5–7, which is an essential pre-requisite for their isolation and minimal expansion
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