CD34 positive stem cells recovered from cord blood remain viable after six months of cryoprotective storage process

Abstract

Cord blood can be used as an alternative source for bone marrow transplantation and its use is developing into a new field of treatment for patients presenting with haematological disorders, immunological defects and specific genetic diseases; including haemoglobinopathies. The aim was to assess the viability of frozen cord blood as a source of HSC which may be suitable for transplantation. Blood specimens were obtained from umbilical cords of 30 consenting mothers and dispensed into 5 cryovials with glycerine for freezing at -20°C; while quantitative assay was carried out on a fresh citrated sample by immunophenotyping using CD34 as marker of HSC. Partec Cyflow cube 6 was used to measure viable cells after labelling the cells with specific fluorochrome/antibody obtained from Sysmex Partec. A repeat quantification was carried out at one month interval for 5 consecutive months and results generated were analysed using T- independent test. The mean ± standard error of mean (SEM) for the 6 consecutive counts were 20,798±2750, 19849±2691, 19223±2637, 18363±2582, 17052±2583 and 16184±2423. The p values obtained when the cryoprotected samples were compared to the baseline were 0.806, 0.681, 0.521, 0.325 and 0.213; reflecting that subsequent counts were insignificantly different from the baseline count. Thus, it is a safe alternative in resource-poor setting to store stem cells in a cryoprotective agent and freeze at -20°C for up to 6 months, without significant depreciation in viability. This alternative should be explored and further researches should be conducted with possibility of extending the number of months. Key words: CD34+ cells, immunophenotyping, stem cells, cryopreservation.