Stimulating progress in regenerative medicine: improving the cloning and recovery of cryopreserved human pluripotent stem cells with ROCK inhibitors.

Until recently, culturing human pluripotent stem cells was hampered by three prominent technical problems: a high degree of unwanted cellular stress when the cells are passaged, unacceptably low cloning efficiency and poor recovery of cryopreserved stocks. This review discusses recent developments that address these problems. A major focus of the review is the use of p160 Rho-associated coiled-coil kinase inhibitors for improving both the cloning efficiency and the recovery of cryopreserved human embryonic stem cells and human induced pluripotent stem cells. An underlying theme of this review is that the three problems have a common cause: separation of human pluripotent stem cells from one another increases cellular stress, which greatly decreases their viability unless special steps are taken.