ABSTRACT
BACKGROUND: Bandage internal fixation (defined as the interphalangeal insertion of “8”-shaped bandage for elastic external fixation) produces a suitable mechanical environment for bone healing after minimally invasive treatment of hallux valgus. Stress stimulation is essential for bone healing after osteotomy, but the mechanism is still unclear OBJECTIVE: To study the regulatory mechanism of mechanical stress on fibroblasts-derived exosomes. METHODS: The medial bone tissue of the first metatarsal bone obtained in the surgery for hallux valgus was taken as a specimen. The fibroblasts were passaged in vitro via direct tissue adherent culture. The loading system provided a cell strain simulating external fixation using “8”-shaped bandage for the pressure-loading culture of hallux valgus fibroblasts, and then exosomes were extracted. Size distribution, morphology and markers of exosomes were detected by electron microscopy, nanoparticle tracking analysis and western blot assay. The study protocol was approved by the Ethics Committee of Wangjing Hospital of China Academy of Chinese Medical Sciences with approval No. 2013-03-21 on March 21, 2013. RESULTS AND CONCLUSION: Static stretching (15%) could promote the secretion of exosomes from fibroblasts. The expression of CD9 and CD81 was detected in the fibroblasts-derived exosomes of the control group and the experimental group. Range of exosome particle size distribution was consistent in the two groups of exosomes, and 15% static stretching increased the concentration of exosomes. This indicates that 15% static stretching helps fibroblasts secrete growth factors, which in turn contribute to osteoblast osteogenesis.