Cryptochrome 1 Promotes Low-Level Laser Irradiation-Induced Bone Marrow Mesenchymal Stem Cells Proliferation and Differentiation

Mesenchymal stem cells (MSCs) are able to differentiate into diverse types of specialized cells, playing a critical role in cell-based therapy in various medical fields. Cryptochrome 1 (Cry1) is a key clock gene of circadian rhythms, which control nearly all biological processes. The present study aims to investigate the effect of Cry1 on low-level laser irradiation (LLLI)-induced bone marrow MSCs (BMSCs) proliferation and differentiation. Our results showed that BMSCs responded to LLLI treatment (660 nm, 10 mW) in a dose- and time-dependent manner. High cell growth and proliferation were observed when cells were irradiated with a dose of 1.0 J/cm(2) after 72 h. LLLI increased Cry1 protein expression, which was paralleled with the proliferation of BMSCs induced by LLLI. Overexpression of Cry1 potentiated LLLI-induced cell growth and proliferation, accompanied by enhanced Cyclin D1, c-myc and bcl-2 expressions. In contrast, Cry1 deficiency significantly suppressed cell viability, proliferation and the above cell cycle regulators expressions. Moreover, LLLI-induced BMSCs osteogenic differentiation was augmented by Cry1 upregulation, but was inhibited after knockdown of Cry1. Mechanistically, Cry1 overexpression further increased ERK phosphorylation and RhoA activity under LLLI treatment, concomitantly with inhibition of cAMP level and PKA signaling However, inverse results were obtained in cells lacking of Cry1 These findings demonstrate that Cry increases the sensitivity of BMSCs to LLLI, indicating that forced Cry1 expression may be a novel approach for improving MSCs-based therapy in clinic.