Systemic sclerosis (SSc) is an autoimmune disorder characterized by vascular damage, excessive fibrosis and abnormal T cells immune-regulation. CD146 is an adhesion molecule essentially expressed in the vascular system, but also on TH17 lymphocytes. In view of the recently described role of CD146 in SSc, we hypothesized an involvement of CD146 positive TH17 cells in this disease. Compared to healthy controls, we showed that both soluble form of CD146 (sCD146), and IL17A levels were increased in patients with SSc with a positive correlation between both factors. A significant increase in TH17 cells attested by an increase of RORγT, IL17A mRNA and CD4+ IL17A+ cell was observed in patients with SSc. Interestingly, the percentage of TH17 cells expressing CD146 was higher in patients with SSc and inversely correlated with pulmonary fibrosis. In vitro experiments showed an augmentation of the percentage of TH17 cells expressing CD146 after cell treatment with sCD146, suggesting that, in patients the increase of this sub-population could be the consequence of the sCD146 increase in serum. In conclusion, TH17 cells expressing CD146 could represent a new component of the adaptive immune response, opening the way for the generation of new tools for the management of SSc.

While muscle and bone adaptations to deconditioning have been widely described, few studies have focused on the tendon enthesis. Our study examined the effects of mechanical loading on the structure and mechanical properties of the Achilles tendon enthesis. We assessed the fibrocartilage surface area, the organization of collagen, the expression of collagen II, the presence of osteoclasts, and the tensile properties of the mouse enthesis both after 14 days of hindlimb suspension (HU) and after a subsequent 6 days of reloading. Although soleus atrophy was severe after HU, calcified fibrocartilage (CFc) was a little affected.In contrast, we observed a decrease in non-calcified fibrocartilage (UFc) surface area, collagen fiber disorganization, modification of morphological characteristics of the fibrocartilage cells, and altered collagen II distribution. Compared to the control group, restoring normal loads increased both UFc surface area and expression of collagen II, and led to a crimp pattern in collagen. Reloading induced an increase in CFc surface area, probably due to the mineralization front advancing toward the tendon. Functionally, unloading resulted in decreased enthesis stiffness and a shift in site of failure from the osteochondral interface to the bone, whereas 6 days of reloading restored the original elastic properties and site of failure. In the context of spaceflight, our results suggest that care must be taken when performing countermeasure exercises both during missions and during the return to Earth.