Downregulating of hsa-miR-143-3p induced by low fluid shear stress promotes chondrocyte proliferation and extracellular matrix secretion by promoting ERK5/KLF4 signal pathway

Objective: Low fluid shear stress (FSS, ≤2dyn/cm 2 ) can protect chondrocytes. Despite this, the function of miRNA in FSS-induced chondrocyte proliferation, maintenance of extracellular matrix stability and the potential molecular mechanism remains is still unknown. The intention of this research was to examine whether hsa-miR-143-3p played a defensive effect on chondrocytes after loading FSS and its related molecular mechanism. Materials and methods The level of hsa-miR-143-3p was examined by qRT-PCR. The expressions of ERK5, phosphorylated ERK5 and KLF4 were detected by Western blot. Double luciferase reporter gene assay was utilized to confirm the target gene of hsa-miR-143-3p. proliferation of cells was analyzed with CCK-8 method and EdU method. The ability of chondrocytes to secrete extracellular matrix was detected by type II collagen immunohistochemical staining and toluidine blue staining methods. Results When SW1353 cells were exposed to low FSS (1.8 dyn/cm 2 ,60 min), hsa-miR-143-3p was reduced. Then we confirmed the increase of hsa-miR-143-3p inhibited the proliferation of chondrocytes, the secretion of type II collagen and proteoglycan within extracellular matrix. Besides, FSS promoted extracellular matrix secretion and chondrocyte proliferation through down-regulating hsa-miR-143-3p. Double luciferase reporter gene assay revealed ERK5 was a direct target of hsa-miR-143-3p. QRT-PCR and Western blotting methods confirmed hsa-miR-143-3p targeted ERK5/KLF4 signal pathway to promote cell proliferation and maintain extracellular matrix stability. Conclusion This research shows the downregulation of hsa-miR-143-3p induced by low FSS promotes the proliferation of chondrocytes, the secretion of type II collagen and proteoglycan of cartilage by activating ERK5/KLF4 signal pathway. These findings may provide a new molecular mechanism for moderate mechanical stimulation to protect cartilage.