The Effect Of Peripheral Sensory And Motor Nerves On Early Stage Of Osteoarthritis In Mice

Part ⅠThe effect of peripheral sensory nerve on early osteoarthritis in miceObjective:To investigate the effect of peripheral sensory nerve on early osteoarthritis in mice.Methods:50 male adult C57BL/6 mice(8 weeks old)were selected.Firstly,10 of 50 mice were randomly divided into the normal group and the capsaicin injection group,5 mice per group.One week after capsaicin injection,the right knee joints of each group were collected for immunofluorescence staining.Then,the remaining 40 mice were randomly divided into 4 groups:normal group(control group),normal saline injection+osteoarthritis induction group(vehicle+DMM group),capsaicin injection+osteoarthritis induction group(capsaicin+DMM group)and capsaicin injection+sham group(capsaicin+sham group),10 mice per group.Subcutaneous injection of capsaicin or normal saline for three consecutive days was conducted one week before osteoarthritis induction.The right knee joints of each group were collected 4 weeks after osteoarthritis induction,and micro-CT scanning,histological staining and RT-PCR examination were performed respectively.Results:Immunofluorescence staining showed that the number of CGRP positive sensory nerve fibers in the tibial subchondral bone and the diaphysis of capsaicin injection group was significantly lower than that in the normal group(P<0.001).Micro-CT analysis indicated that the BV/TV value in capsaicin+DMM group was significantly lower than that in vehicle+DMM group(P<0.001).Histological staining showed that the OARSI score of capsaicin+DMM group was lower than that of vehicle+DMM group(P=0.003).In addition,there were more empty osteocyte lacunae in the subchondral bone in capsaicin+DMM group than that in vehicle+DMM group.RT-PCR analysis indicated that compared with vehicle+DMM group,the expression of pro-inflammatory factors(IL-1α,IL-1β,IL-6 and TNF-α)in capsaicin+DMM group increased,and the expression of anti-inflammatory neuropeptide somatostatin decreased.Conclusion:Capsaicin-induced sensory denervation accelerated OA progression at early stage in mice.To put it another way,sensory nerve protects from OA progression at early stage in mice.Part Ⅱ The effect of peripheral motor nerve on early osteoarthritis in miceObjective:To investigate the effect of peripheral motor nerve on early osteoarthritis in mice.Methods:48 male adult C57BL/6 mice(8 weeks old)were randomly divided into the normal group(control group),osteoarthritis induction group(DMM group),tibial nerve combined with common peroneal nerve transection+osteoarthritis induction group(T+P+DMM group),and tibial nerve combined with common peroneal nerve transection+sham group(T+P+sham group),12 mice per group.Tibial nerve combined with common peroneal nerve transection was performed one week before the osteoarthritis induction.Half of the mice in each group were sacrificed 4 weeks after osteoarthritis induction,and the remaining half were sacrificed 8 weeks after osteoarthritis induction.The right knee joints of each group were collected for micro-CT scanning,histological staining,immunohistochemistry,footprint analysis and muscle atrophy detection,respectively.Results:Micro-CT scanning revealed that 4 weeks and 8 weeks after osteoarthritis induction,the BV/TV value in the T+P+DMM group was lower than that in DMM group(P<0.001).BV/TV value in T+P+DMM group was not significantly different from those in T+P+sham group(P>0.05).The BV/TV value in T+P+DMM group and T+P+sham group was increased significantly in 8 weeks compared with that in 4 weeks(P<0.001),respectively.Histological staining indicated that the OARS I score in the T+P+DMM group was lower than that in the DMM group at 4 and 8 weeks after osteoarthritis induction(P<0.001).OARSI score in the T+P+DMM group was higher than that in the T+P+DMM group at 8 weeks after osteoarthritis induction than that at 4 weeks after osteoarthritis induction(P<0.001).Immunohistochemical staining showed that compared with the DMM group,collagen II content on the cartilage surface increased and collagen I content decreased in the T+P+DMM group at 4 weeks and 8 weeks after osteoarthritis induction.Compared with the control group,collagen II content on the cartilage surface decreased and collagen I content increased in the T+P+sham group at 4 weeks and 8 weeks.Footprint analysis showed that compared with the DMM group,the right hind stride length,hindfoot base width and hindlimb stance in T+P+DMM group at 4 weeks and 8 weeks after osteoarthritis induction were decreased significantly(P<0.05).The muscle atrophy analysis indicated that compared with the DMM group,the wet weight of the right tibial anterior muscle and the calf triceps muscle in the T+P+DMM group decreased at 4 weeks and 8 weeks after osteoarthritis induction.Conclusion:Reduction of mechanical loading in knee joint induced by peripheral motor nerve transection leads to bone loss of subchondral bone and reduction thickness of articular cartilage layer,which was suggested that the appropriate joint mechanical loading play an important role in maintaining the homeostasis of articular cartilage and subchondral bone.