The aim of the present work was to determine proliferation capacity, immunophenotype and genome integrity of mesenchymal stromal cells (MSCs) from horse umbilical cord blood (UCB) at passage stage 5 and 10. Passage 4 cryopreserved UCB-MSCs from six unrelated donors were evaluated. Immunophenotypic analysis of UCB-MSC revealed a cell identity consistent with equine MSC phenotype by high expression of CD90, CD44, CD29, and very low expression of CD4, CD11a/18, CD73, and MHC class I and II antigens. Proliferative differences were noted among the UCB-MSC cultures. UCB-MSCs karyotype characteristics at passage 5 (eg, 2n = 64; XY, or XX) included 20% polyploidy and 62% aneuploidy. At passage 10, the proportion of polyploidy and aneuploidy was 21% and 82%, respectively, with the increase in aneuploidy being significant compared with passage 5. Furthermore, conventional GTG-banded karyotyping revealed several structural chromosome abnormalities at both passage 5 and 10. The clinical relevance of such chromosome instability is unknown, but determination of MSC cytogenetic status and monitoring of patient response to MSC therapies would help address this question.
Keywords: equine umbilical cord blood; genomic stability; long-term expansion; mesenchymal stromal cell; proliferation.