Over-expression of CXCR4, a stemness enhancer, in human blastocysts by low level laser irradiation

The key role of chemokine receptor CXCR4 in the maintenance of stemness property of stem cells has been shown recently. The low level laser irradiation (LLLI) is being used currently in a wide variety of clinical cases as a therapeutic tool for wound healing, relieving pain and destroying tumor cells. The aim of this study was to evaluate the effect of LLLI mimicking low level laser therapy (LLLT) on the expression level of CXCR4 gene a few hours after irradiation on human blastocysts. After the development of human embryos to the first grade blastocyst stage, they were irradiated with a low power Ga-Al-As laser at a continuous wavelength of 650 nm and a power output of 30 mW. The total RNA of the irradiated blastocysts and control groups were isolated in groups of 1x2 J/cm2, 2x2 J/cm2, 1x4 J/cm2 and 2x4 J/cm2 LLLI. Specific Real-Time PCR primers were designed to amplify all the two CXCR4 isoforms yet identified. RNA amplifications were done for all the groups. We showed for the first time that LLLI makes the human blastocysts to increase the expression level of CXCR4 a few hours after irradiation. Moreover, it was shown that two irradiation doses with one day interval can cause a significant increase in CXCR4 expression level in human blastocysts. This study revealed that LLLI could be a proliferation motivator for embryonic cell divisions through enhanced over-expression of CXCR4 level.