Recovery of cellular activity in cryopreserved human foetal brain tissue

Since long-term cryopreservation can cause losses in neural tissue viability and function a prerequisite would be the ability to monitor and promote functional recovery in donor tissue intended for neural transplantation. Rapid assessment of cryopreserved tissue's functional status prior to grafting is presently difficult in a clinical setting. A convenient indicator of functional status may be the level of DNA synthesis activity taking place in the tissue. Using immunocytochemical detection of incorporated bromodeox-yuridine we have quantified and compared DNA synthesis activity (expressed as proliferative capacity (PC)) in human foetal mesencephalic, striatal, cortical and cerebellar tissue before and after a 275-376 day storage in liquid nitrogen. There was a post-storage reduction in viability of 48-73% and in PC of 26-59%; the higher the PC before storage the greater the reduction after. Incubation of cryopreserved tissue with fetal calf serum resulted in 2-4-fold higher PC levels than serum-untreated controls and reached 80% of fresh tissue levels in mesencephalic cells after 3-4 h incubation. Assuming that quantification of proliferative activity is a practical indicator of the tissue's functional status, these findings suggest that treatment of the tissue with serum can largely restore the lost function caused by cryopreservation.