Improved cryopreservative medium suitable for the freeze-storage and transplantation of fetal neural tissues.

Techniques to maintain viable fetal neural tissue might be an important tool for a successful neural transplantation by giving enough time for preparation, storage, and transportation of donor tissue. In the present study, we examined the effect of freeze-storage (cryopreservation) for 7 days at liquid nitrogen temperature on the survivability of intraventricular rat fetal mesencephalic grafts (gestational day 15) when using 10% dimethyl sulfoxide (DMSO), 0.1% methylcellulose, or 10% DMSO with additional 0.1% methylcellulose (m-DMSO) as a cryoprotective agent. As a control group, the survivability of grafts transplanted immediately after dissection was examined. The volume of grafts treated with m-DMSO was 3 times as large as that of grafts treated with 10% DMSO alone. While the number of surviving neurons in 10% DMSO-treated transplants decreased down to 15% of the control value, there was no statistically significant difference in the number of surviving neurons between the m-DMSO treated group and control group. In the group treated with m-DMSO, there were a lot of well developed tyrosine hydroxylase positive neurons and fibers in the graft, and a few reactive astrocytes were observed only in the peripheral region of the grafts. In the group treated with 0.1% methylcellulose alone, no graft survival was observed in any of the animals. We conclude that the addition of methylcellulose to the commonly used cryoprotective agent (DMSO) is beneficial for the freeze-storage of fetal neural tissue.