Effect of Rho-associated kinase (ROCK) inhibitor Y-27632 on the post-thaw viability of cryopreserved human bone marrow-derived mesenchymal stem cells.

Human bone marrow-derived mesenchymal stem cells (MSC) have previously been reported to be susceptible to cryopreservation-induced apoptosis. A significant fraction of MSC lose their viability during freeze-thawing, which represent a major technical barrier in attaining adequate viable cell numbers for optimal efficacy in transplantation therapy. Recently, it was reported that a Rho-associated kinase (ROCK) inhibitor Y-27632 could enhance the post-thaw viability and physiological function of cryopreserved human embryonic stem cells (hESC). Hence, this study attempted to investigate whether Y-27632 can exert a similar beneficial effect on the post-thaw viability of cryopreserved MSC. A concentration range of 1-100 microM Y-27632 was supplemented in both the cryopreservation medium (10% (v/v) dimethyl sulfoxide), as well as the post-thaw culture medium. The supplementation of Y-27632 had no significant effect on the immediate post-thaw viability, as assessed by trypan blue exclusion. However, 24h after the frozen-thawed cell suspensions were re-plated on new cell culture dishes (with varying concentrations of Y-27632 within the post-thaw culture media); the MTT assay subsequently showed significant differences in the proportion of adherent viable cells over the concentration range of Y-27632 examined, with a peak at between 5 and 10 microM. At zero concentration of Y-27632, the proportion of viable adherent cells was 39.8+/-0.9%; and this value peaked at 48.5+/-1.7% with 5 microM Y-27632 and 48.4+/-1.8% with 10 microM Y-27632, prior to decreasing to 36.0+/-0.6% with 100 microM Y-27632. Additionally, it was observed that Y-27632 induced morphological changes in the frozen-thawed MSC. With increasing Y-27632 concentration, the cells displayed more extensive branching of cytoplasmic extensions that gave a 'web-like' appearance. This is consistent with previous reports of Y-27632 stimulating neuronal differentiation of MSC.