Abstract
Stem cells hold considerable promise for the treatment of a number of diseases, although availability of stem cells must be overcome before their therapeutic potential can be realized. Human bone marrow mesenchymal stem cell (hMSC) has multi-potency of osteogenic, chondrogenic and adipogenic differentiation. It has limited life span and the source of bone marrow is difficult to obtain. Therefore, we design a bicistronic retroviral plasmid construct for reversible immortalization by a combination of SV40 T antigen and hTERT (human telomerase reverse transcriptase) genes with Cre-loxP recombination system. An immortalized cell line of hMSC was failed to establish possibly due to the number of drug-resistant clones selected was not enough. Because genes carried by a retroviral vector integrate into the chromosome randomly so that it may interrupt the genomic structure to lose some functionality of genes. Previous studies have revealed that cell proliferation and cytokine secretion were increased by low level light irradiation. Here, the light emitting diodes (LED) was used to study the effect of light stimulation on cell proliferation and gene expression of hMSC. We found that the rate of hMSC proliferation and CFU-F (colony forming unit-fibroblast) were significantly improved when cells were stimulated by first day irradiation only or daily irradiation at total energy density of 1.5 J/cm2 and 2.5 J/cm2, respectively. Numbers of cell proliferation and CFU-F stimulated by daily light irradiation were significant higher than that by light irradiation on day 0 only. The gene expression of cytokines, extracellular matrix and cell cycle regulatory protein in hMSC were analyzed by RT-PCR. The results showed that no significant change was observed in flt3, GM-CSF and collagen type I expression after LED irradiation. We found that c-fos and cyclin D1 expression were slightly decreased 30 min after LED irradiation, and increased 1 hour after irradiation. 24 hours after light irradiation no effect on c-fos, cyclin D1, and c-myc was seen. There was no difference on cell cycle with or without LED irradiation. The study suggested that low level light stimulation could enhance replicative potential of hMSC. However, the mechanism of light stimulation on the regulation of hMSC proliferation remains unsolved.