[Factors influencing successful isolation of mesenchymal stem cells from human umbilical cord blood].

OBJECTIVE

Emerging evidences suggest that mesenchymal stem cells (MSCs) can be isolated from human umbilical cord blood (HUCB) and cultured in vitro, the same as the MSCs derived from bone marrow. However previous attempts to isolate MSCs from UCB showed a low rate of success (less than 30%). The present study was conducted to clarify the factors that influence the yields of MSCs from HUCB of different gestational age deliveries and to observe the bioactivity of MSCs derived from UCB.

METHODS

HUCB units were divided into three groups: gestational age (GA) 40 w group (n = 11); GA 36 w group (n = 6); GA 32 w or less than 32 w group (n = 5), cultured with optimal culture conditions. The relationship of the yields of MSCs derived from HUCB with several factors such as GA, the collected volume of HUCB and the mononuclear cells (MNCs) count of UCB, and the relationship among these factors were investigated. The bioactivity was observed by drawing the growth curve, calculating the population doubling, counting the fibroblast colony forming units (CFU-F) and detecting the surface antigen expression of MSCs by flow cytometry.

RESULTS

The success rate of generating MSCs cells was up to 54.5%. There were some correlations between the success rate and such factors as the MNCs count, the GA and the volume of UCB. The rate could be enhanced to 83.3% when the MNCs count was more than 1.25 x 10(8)/L. There was a negative correlation between the MNCs count in the same HUCB volume and the gestational age. The count of CFU-F varied with gestational age, the count of CFU-F was higher in smaller gestational age than the older. In the primary culture some cells displayed a fibroblast-like morphology and expressed MSCs-related antigens CD29, CD105, and the expression rate of these antigens were enhanced from 62.1% to 85.0% in one passage. The hematopoietic cells antigens CD34 and CD45 were less than 3% all the time.

CONCLUSIONS

The success rate could be increased when the MNCs count was more then 1.25 x 10(8)/L. There was a negative correlation between the MNCs count of the same UCB volume and the gestational age, the activity to form the CFU-F of UCB varied with gestational age; isolation of MSCs from UCB of pre-term deliveries may be relatively easier as compared to those from full term deliveries.