Mid-term and long-term simulated microgravity causes calcification of common carotid artery in rat

Objective　To explore the effects of mid-term (4 weeks) and long-term (8 weeks) simulated microgravity on calcification of the common carotid artery in the rat. Methods　Hindlimb-unweighted (HU) rat model was used to simulate the effects of weightlessness on the cardiovascular system. Seventy-five male SD rats were randomized into the control group, 4-week HU group (HU4w), and 8-week HU group (HU8w). After the common carotid arteries were separated, the quantification of calcium content and the alizarin red staining were used to detect the calcium salt deposition in the common carotid arteries. The alkaline phosphatase (ALP) activity of common carotid arteries was measured. Western blot analysis and the real-time polymerase chain reaction (RT-PCR) were performed to measure the protein and mRNA levels of Runx2, Msx2, BMP2, osteocalcin, and SM22α. Results　Compared with the control group, the calcium content and the calcium salt deposition were increased, meanwhile, the ALP activity was enhanced in the common carotid arteries of 4-week and 8-week HU rats. Besides, the protein and mRNA levels of Runx2, Msx2, BMP2, osteocalcin were increased, while those of SM22α were decreased in the common carotid arteries of 4-week and 8-week HU rats (P<0.05 or P<0.01). Interestingly, there was no statistically significant difference of above tests between the HU4w and HU8w groups. Conclusion　Mid- and long-term simulated microgravity induced the osteogenic transdifferentiation of smooth muscle cells and calcification in the common carotid artery of rats, while the degree of calcification did not change significantly with the prolonged period of simulated microgravity. DOI: 10.11855/j.issn.0577-7402.2021.01.01