AKT/mTORC1/HIF-1α Effect Of Pathway On Subchondral Bone In The Progression Of Temporomandibular Joint Osteoarthritis

Objectives:Temporomandibular joint osteoarthritis(TMJ OA)is an organic disease of temporomandibular joint disorder(TMD),which is the degeneration of condylar cartilage and subchondral bone.Studies have shown that subchondral bone plays a significant role in OA as subchondral bone degenerates and remodels,aggravating OA.However,the etiology and pathogenesis of OA are still controversial.Previous studies on temporomandibular joint osteoarthritis were mostly carried out around the cartilage,and there were few studies on the subchondral bone.Studies have shown that the m TORC1 pathway plays an important role in the development of OA,and HIF-1α plays a negative feedback role in the development of OA.By inducing anterior crossbite in Sprague-Dawley(SD)rats,we established an animal TMJ OA model to explore the degeneration of subchondral bone in the progression of TMJ OA,the effect on osteoblast-osteoclasts,The effect of AKT/m TORC1/HIF-1α pathway on TMJ OA in rats,opening a new idea for the prevention and treatment of TMJ OA.Methods:80 6-week-old female Sprague-Dawley(SD)rats,40 of which were randomly selected to induce anterior cross-bite to establish experimental TMJ OA,were divided into experimental group(EXP)and experimental administration group(EXP+Rapa).There were 20 rats in each group;the remaining rats were randomly divided into control group(Con)and control administration group(Con+Rapa),with 20 rats in each group.Administration refers to inhibition of the m TORC1 pathway by local injection of Rapamycin(Rapa).The experimental administration group(EXP+Rapa)and the control administration group(Con+Rapa)were locally injected with 5m L/kg/d of rapamycin(Rapa,5m L/kg/d)in the temporomandibular joint area,1d/time;The experimental group(EXP)and the control group(Con)were locally injected with the same proportion of liquid,but did not contain Rapa,and the administration method and frequency were the same.At the 2nd,4th,6th,and 8th weeks of modeling,5 SD rats were randomly selected from each group to prepare specimens.The temporalis were observed by hematoxylin-eosin(HE),safranin O/fast green staining,and Micro-CT detection.Changes of mandibular condyle joint and subchondral bone,immunohistochemistry,RT-q PCR detection of osteoblast markers(ALP,RUNX2,Osteocalcin),osteoclast markers(OPG,RANK,RANKL),The expression of AKT1 and m TORC1 downstream factors 4E-BP1 and HIF-1α,and the effect of AKT/m TORC1/HIF-1α pathway on TMJ OA was analyzed.Results:1.After modeling,changes in the shape and structure of the condyle and joint degeneration were observed.With the passage of time,HE staining showed that the cell stratification and the disorderly arrangement of trabecular bone increased,the safranin O/fast green staining proteoglycan was gradually lost,and the chondrocytes were clustered and hypertrophied.2.The results of immunohistochemistry and RT-q PCR showed that the expression of osteoblast markers and osteoclast markers OPG increased in the experimental group compared with the control group at the same period,and there was no significant change in RANK and RANKL,AKT1,m TORC1 downstream factor 4E-BP1 expression increased,but the expression of HIF-1α decreased over time.3.Immunohistochemistry and RT-q PCR showed that compared with the experimental group in the same period,the expression of osteogenic markers and osteoclast marker OPG decreased in the experimental administration group,and there was no significant change in RANK and RANKL,and AKT1,m TORC1 downstream factor 4EBP1,HIF-1 α decreased expression.4.Micro-CT showed that compared with the control group,the joint density of the experimental group decreased,the shape of the condyle changed at 8 weeks,and bone resorption occurred.Compared with the three groups in the same period,the experimental administration group showed obvious bone degeneration changes.5.The expression of HIF-1α in the experimental group and the experimental administration group decreased with the passage of time,and the decrease in the experimental administration group was more obvious.Conclusion:The activation of the AKT/m TORC1/HIF-1α pathway in the experimental TMJ OA model promotes the proliferation of osteoblasts and is involved in the progression of TMJ OA.Local injection of rapamycin can inhibit the expression of m TORC1 signaling in the subchondral bone and inhibit the proliferation of osteoblasts,which may inhibit the proliferation of osteoclasts and aggravate the progression of TMJ OA.Therefore,it is believed that the AKT/m TORC1/HIF-1α pathway is involved in the joint degeneration of TMJ OA through the regulation of osteoblasts-osteoclasts in the subchondral bone,providing new ideas for the prevention and treatment of TMJ OA.