Effect Of Feeding High-fat Diet On Bone Cartilage In Rabbits With Osteoarthritis Induced By Papain

Osteoarthritis(OA)is a disease characterized by inflammation and hyperplasia of articular cartilage.It is also one of the important factors that cause clinical lameness of livestock.Long term pain will lead to the decline of livestock productivity or even early elimination.Obesity is considered to be the main risk factor for chronic diseases,of which Osteoarthritis is a disease with a high incidence rate among obese animals.This experiment explored the effects of long-term high-fat diet on cartilage damage and subchondral bone remodeling in rabbits with Osteoarthritis by observing the changes of cartilage and subchondral bone structure,serum inflammation and bone metabolism indicators in Japanese long ear rabbits and rabbit OA models induced by Papain,It is of great significance to understand the influence mechanism between obesity and Osteoarthritis.Experimental method: 36 Japanese long ear rabbits were randomly divided into 4 groups:control group,arthritis group,high-fat diet group,high-fat diet+arthritis group,with 9 rabbits in each group.After one week of adaptive feeding,the knee joint cavity of arthritis group and high-fat diet+arthritis group was injected with Papain to create a model.Each rabbit was injected with 0.3m L of 4% Papain physiological saline solution into the joint cavity,once every three days,three times in total.After operation,the injection side of the animals was observed,If there is obvious swelling and dysfunction of flexion and extension,it is considered as successful modeling,and the experimental animals are fed in the same environment after surgery.The high-fat feed group and the high-fat feed+arthritis group were fed with high-fat feed,while the control group and high-fat feed group were injected with an equal volume of physiological saline.After successful modeling,X-ray films of the right knee joint were taken every two weeks to observe the morphological changes of the knee joint.The severity of OA was evaluated by observing clinical manifestations and X-ray examination.Three rabbits in each group were randomly killed at weeks 4,8,and 12,and serum,femur,and tibia samples were collected.Micro-CT was used to measure BMD,BV/TV,Tb.Th,Tb.N,Tb.SP and SMI bone parameters.ELISA method for detecting IL-1β,IL-6,TNF-α,MMP13,OC and CTX-Ⅰ in serum,macroscopic observation and scoring of tibia and femoral plateau in each group,and HE staining,safranine O fixation green staining,and Mankin scoring;Western blot for detecting the expression of MMP-3,IL-1β and TNF-α in cartilage.Experimental results: Compared with group C,X-ray and Micro CT in OA inflammatory group showed that the joint space was narrowed,the articular surface was rough,the subchondral bone plate was thickened,the bone Trabecular meshwork was sparse,and the bone trabecular density was reduced,which showed that the bone trabecular arrangement was obviously disordered and uneven;The HFD+OA group showed that with time increasing,the joint damage was serious,the joint surface was rough,the joint space was obviously narrow,there was obvious osteophyte formation,the joint surface was rough,there was obvious osteophyte formation,the joint space was narrowed,the cartilage thickness was reduced,the articular cartilage was seriously damaged,the subchondral bone Trabecular meshwork was sparse,and the visible bone trabeculae were disorderly and unevenly arranged,and there were widening,fusion,loss,stripping and other phenomena,the epiphyseal plate was seriously damaged,and the tide line was uneven,The severity of HFD+OA group was higher than that of OA group.The HE staining results showed that compared with Group C,the surface of cartilage in the OA group was uneven,with cracks and severe cartilage damage.There were many cell clusters formed,and chondrocytes were hypertrophic and severely lost;At 4 W in the HFD group,there was no significant lesion or proliferation of chondrocytes,but the surface of the cartilage was not smooth.At 8 W and 12 W,there were cell clusters formed,cell arrangement changed,the cartilage layer became thinner,and the number of chondrocytes gradually decreased;In the HFD+OA group,there were obvious cracks on the surface of the cartilage,severe damage,thinning of the cartilage layer,increased vacuolization of chondrocytes,severe loss of chondrocytes,and the formation of a large number of cell clusters.The results of safranine O solid green staining showed that compared with group C,the cartilage surface of OA group was rough,severely damaged,with cracks appearing,blurred cell morphology,thinning of the cartilage layer,cell hypertrophy and vacuolization,and loss and clustering of chondrocytes;The surface damage of cartilage in the HFD group was relatively mild,with edema on the surface.Over time,the cartilage layer became thinner,the number of chondrocytes decreased,and cell clusters formed;In the HFD+OA group,the surface of the cartilage was eroded and severely damaged,with a significant thinning of the cartilage layer,severe loss of chondrocytes,and clusters of vacuoles.At 12 W,the red staining almost disappeared,and the cartilage matrix was severely damaged.IL-1β,IL-6,TNF-α,MMP-13,OC and CTX-Ⅰ in serum of OA group and the protein expression MMP-3,IL-1β and TNF-α in cartilage increased,and compared with the control group,the serum IL-1β,IL-6 and TNF-α levels in the HFD group increased,content of MMP-13,OC,CTX-Ⅰ and the protein express of ionintrachondral MMP-3,IL-6,and TNF-α increased.IL-1β,IL-6,TNF-α,content of MMP-13,OC,CTX-Ⅰ in serum of HFD+OA group and the protein expression of intrachondral MMP-3,IL-1β and TNF-α was significantly increased and significantly higher than that of the OA group.Based on this: the experiment draws the following conclusions:(1)Feeding high-fat diet can increase the serum inflammatory factor IL-1β,IL-6,TNF-α,MMP-13 and the protein expression MMP-3,IL-1β and TNF-α in cartilage increased in the rabbit OA model induced by Papain,by promoting the release of inflammatory factors,promotes matrix degradation,exacerbates cartilage damage,and promotes the development of OA;(2)Feeding high-fat diet can lead to significant deterioration of subchondral bone microstructure,severe destruction of bone trabecular meshwork,increase the level of OC,a bone metabolism marker,and CTX-I,a Bone resorption marker in serum,and destroy the stability of joint microenvironment and bone metabolism balance,thus aggravating the cartilage damage and abnormal remodeling of subchondral bone in rabbits.