Low temperature tolerance of human embryonic stem cells

• Main Author: Boon Chin Heng, Kumar Jayaseelan Vinoth, Hua Liu, Manoor Prakash Hande, Tong Cao
• Format: Article
• Language: English
• Published: Ivyspring International Publisher 2006-01-01
• Series: International Journal of Medical Sciences
• Online Access: http://www.medsci.org/v03p0124.htm

<p>This study investigated the effects of exposing human embryonic stem cells (hESC) to 4^oC and 25^oC for extended durations of 24h and 48h respectively. Cell survivability after low temperature exposure was assessed through the MTT assay. The results showed that hESC survivability after exposure to 25^oC and 4^oC for 24h was 77.3 &#177; 4.8 % and 64.4 &#177; 4.4 % respectively (significantly different, P &#60; 0.05). The corresponding survival rates after 48h exposure to 25^oC and 4^oC was 71.0 &#177; 0.5 % and 69.0 &#177; 2.3 % respectively (not significantly different, P &#62; 0.05). Spontaneous differentiation of hESC after low temperature exposure was assessed by morphological observations under bright-field and phase-contrast microscopy, and by immunocytochemical staining for the pluripotency markers SSEA-3 and TRA-1-81. hESC colonies were assigned into 3 grades according to their degree of spontaneous differentiation: (1) Grade A which was completely or mostly undifferentiated, (2) Grade B which was partially differentiated, and (3) Grade C which was mostly differentiated. In all low temperature exposed groups, about 95% of colonies remain undifferentiated (Grade A), which was not significantly different (P &#62; 0.05) from the unexposed control group maintained at 37^oC. Additionally, normal karyotype was maintained in all low temperature-exposed groups, as assessed by fluorescence in situ hybridization (FISH) of metaphase spreads with telomere and centromere-specific PNA probes. Further analysis with m-FISH showed that chromosomal translocations were absent in all experimental groups. Hence, hESC possess relatively high-tolerance to extended durations of low temperature exposure, which could have useful implications for the salvage of hESC culture during infrequent occurrences of incubator break-down and power failure.</p>