Quantitative estimation of cryopreservation viability in rat fetal hippocampal cells

Cryopreserved fetal tissue may be useful for neural grafting, but quantitation of yield is crucial for estimating cell transplant requirements. We have assessed cell survival and viability following dissociation, cryopreservation, and culture of rat fetal hippocampus to estimate cell yields at all stages of preparation. Hippocampal tissue from E17 fetal rats was dissected from the CNS and cryopreserved in toto after equilibration with 10% DMSO. Freshly dissociated tissue from contralateral hippocampi yielded a significantly greater number of cells per hippocampus than the cryopreserved tissue. Cell viability after dissociation and survival in culture was also significantly increased in the fresh hippocampi compared to that in the frozen group. Our results indicate that the overall cryopreservation cell yield at 24 h in culture is approximately 12% of the initial fresh tissue, taking these three factors into account. Though cryopreservation of fetal neural tissue for transplantation offers several practical advantages over immediate use, significant additional tissue may be required in comparison to fresh tissue to achieve a suitable quantity of live cells for grafting.