Effect of posterior root amputation on rabbit knee joint cartilage and proprioception

Objective:To Observe the characteristics of changes in the cartilage of the rabbit's knee joint after spinal nerve transection,as well as the influence of proprioceptors and proprioceptive pathways,and explore the relationship between proprioception disorder and knee osteoarthritis.Methods:According to the principle of random allocation,20 New Zealand white rabbits were divided into groups,9 in the control group and 11 in the model group.In the model group,the posterior roots of the L5-L6 spinal nerve were cut off using the posterior root cutting method,while the control group only cut the skin and paraspinal muscles.8 weeks after the operation,the modified Tarlov scoring standard was used to evaluate the behavioral differences between the two groups of rabbits,and electrophysiology-SEPs(Somatosensory Evoked Potentials)and EMG(Surface Electromyography)were used to evaluate proprioception and muscle contraction.After the test was completed,it was unified They were sacrificed and performed HE staining.Mankin's score was used to evaluate the pathological conditions of the knee articular cartilage in the two groups.The anterior cruciate ligament(ACL)of the right knee was taken and the Bielschowsky nerve staining method was used to observe the number of proprioceptors in the two groups.Results:8 weeks after the operation,the hind limbs of the model group showed a light stroke posture,and the motor function basically returned to normal.Compared with the control group,there was no significant difference in behavioral changes(P>0.05);the model group rabbits SEPs and EMG were compared with the control group Compared with the prolonged incubation period,the amplitude decreased,and the difference was statistically significant(P<0.05).The rabbit articular cartilage surface of the model group was rough or even disappeared,and the cell arrangement was disordered.The Mankin's score was significantly higher than that of the control group(P<0.01),and cartilage damage was more severe.Compared with the control group,the number of proprioceptors in the model group was significantly reduced,the morphology changed,and the ligament tissue was loose and constricted.The difference was statistically significant(P<0.01);the rabbit chondrocytes in the model group were over-apopted and the rate of apoptosis It was significantly higher than the control group(P<0.01).Conclusion:The transection of the spinal nerve can lead to loss of proprioception,excessive apoptosis of chondrocytes,degeneration of articular cartilage,and promotion of the occurrence and development of knee osteoarthritis.

Umbilical cord as a mesenchymal stem cell source for treating joint pathologies

Articular cartilage disorders and injuries often result in life-long chronic pain and compromised quality of life.Regrettably,the regeneration of articular cartilage is a continuing challenge for biomedical research.One of the most promising therapeutic approaches is cellbased tissue engineering,which provides a healthy population of cells to the injured site but requires differentiated chondrocytes from an uninjured site.The use of healthy chondrocytes has been found to have limitations.A promising alternative cell population is mesenchymal stem cells(MSCs),known to possess excellent proliferation potential and proven capability for differentiation into chondrocytes.The“immunosuppressive”property of human MSCs makes them an important candidate for allogeneic cell therapy.The use of allogeneic MSCs to repair large defects may prove to be an alternative to current autologous and allogeneic tissue-grafting procedures.An allogeneic cell-based approach would enable MSCs to be isolated from any donor,expanded and cryopreserved in allogeneic MSC banks,providing a readily available source of progenitors for cell replacement therapy.These possibilities have spawned the current exponential growth in stem cell research in pharmaceutical and biotechnology communities.Our objective in this review is to summarize the knowledge about MSCs from umbilical cord stroma and focus mainly on their applications for joint pathologies.

Initial effects of inflammation-related cytokines and signaling pathways on the pathogenesis of post-traumatic osteoarthritis

The main pathological change in post-traumatic osteoarthritis （PTOA） is cartilage degeneration, which is closely related to inflammation and oxidative stress. Inflammation can cause degeneration of articular cartilage. Cartilage degeneration can also stimulate the progression of inflammation. It has been found that inflammatory cytokines can participate in the pathological process of cartilage degeneration through multiple signaling pathways, mainly mitogen-activated protein kinase, nuclear transcription factor kappa B, and Wnt-p-catenin signal transduction pathways. This review aimed at exploring the relationship between PTOA and inflammation-related cytokines by introducing the role of proinflammatory cytokines in chondrocyte destruction and extracellular matrix degradation.

Effects of SIRT1 Gene Knock-Out via Activation of SREBP2 Protein-Mediated PI3K/AKT Signaling on Osteoarthritis in Mice

This study investigated the effects of SIRT1 gene knock-out on osteoarthritis in mice, and the possible roles of SREBP2 protein and the PI3K/AKT signaling pathway in the effects. Mice were randomly divided into a normal group and a SIRT1 gene knock-out group（6 mice in each group）. In these groups, one side of the knee anterior cruciate ligament was traversed, and the ipsilateral medial meniscus was cut to establish an osteoarthritis model of knee joint. The countralateral synovial bursa was cut out, serving as controls. The knee joint specimens were then divided into four groups： SIRT1^（＋/＋） control group（group A, n=6）; SIRT1^（＋/＋） osteoarthritis group（group B, n=6）; SIRT1^（–/–） control group（group C, n=6）; SIRT1^（–/–） osteoarthritis group（group D, n=6）. HE staining, Masson staining, Safranin O-Fast Green staining and Van Gieson staining were used to observe the morphological changes in the articular cartilage of the knee. Immunohistochemical staining was employed to detect the expression of SIRT1, SREBP2, VEGF, AKT, HMGCR and type Ⅱ collagen proteins. SA-β-gal staining was utilized to evaluate chondrocyte aging. The results showed clear knee joint cartilage destruction and degeneration in the SIRT1^（–/–） osteoarthritis group. The tidal line was twisted and displaced anteriorly. Type Ⅱ collagen was destroyed and distributed unevenly. Compared with the SIRT1^（＋/＋） osteoarthritis group and SIRT1^（–/–） control group, SIRT1 protein expression was not obviously changed in the SIRT1^（–/–） osteoarthritis group（P〉0.05）, while the expression levels of the SREBP2, VEGF and HMGCR proteins were significantly increased（P〈0.05） and the levels of AKT and type Ⅱ collagen proteins were significantly decreased（P〈0.05）. SIRT1 gene knock-out may aggravate cartilage degeneration in osteoarthritis by activating the SREBP2 protein-mediated PI3K/AKT signalling pathway, suggesting that SIRT1 gene may play a protective role against osteoarthritis.

Osteopontin(OPN)alleviates the progression of osteoarthritis by promoting the anabolism of chondrocytes

Osteoarthritis(OA)is a chronic debilitating joint disease,characterized by degen-eration of the cartilage and loss of the cartilage matrix,and it is clinically manifested as joint pain.Osteopontin(OPN)is a glycoprotein that is abnormally expressed in the bone and carti-lage tissues and plays a vital role in various pathological processes such as the osteoarthritic inflammatory response and endochondral ossification.The focus of our study is to investigate the therapeutic potential and specific role of OPN in OA.Using morphological comparisons,we found that the cartilage was severely worn-out and there was a significant loss of the cartilage matrix in OA.OPN,CD44,and hyaluronic acid(HA)synthase 1(HAS1)were highly expressed,and the anabolism of HA was significantly higher in the OA chondrocytes than in the control chondrocytes.Additionally,we treated the OA chondrocytes with small interfering RNA(siRNA)targeting OPN,recombinant human OPN(rhOPN),and a combination of rhOPN and anti-CD44 antibodies.Furthermore,in vivo experiments were performed in mice.We found that OPN up-regulated the expression of downstream HAS1 and increased the anabolism of HA through CD44 protein expression in OA mice compared with those in control mice.Moreover,intra-articular injection of OPN in mice with OA significantly inhibited OA progression.In summary,OPN ini-tiates an intracellular cascade via CD44 which results in an anabolic increase in HA levels,thereby inhibiting OA progression.Therefore,OPN is a promising therapeutic agent in precision treatment of OA.

Osteopontin inhibits osteoarthritis progression via the OPN/CD44/PI3K signal axis

Chondrocyte degeneration and extracellular matrix component loss are the primary causes of osteoarthritis(OA).OA can be treated by inhibiting chondrocyte degeneration and increasing extracellular matrix component secretion.Osteopontin(OPN),a multifunctional protein,has gained immense attention with regard to its involvement in OA.This study aimed to explore the therapeutic value and mechanism of action of OPN in OA treatment.Results of the histomorphological analysis revealed a worn-off OA cartilage tissue surface,cartilage matrix layer deterioration,and calcium salt deposition.Compared to that in normal chondrocytes,in OA chondrocytes,the OPN,CD44,and PI3K protein and mRNA expression was upregulated.Further,siOPN,rhOPN,and rhOPN plus LS-C179404 interfered with OA chondrocytes.As verified in mice,OPN directly inhibited the expression level of PI3K in OA chondrocytes by binding with CD44.Morphological analysis of the knee joints demonstrated that OPN effectively inhibited OA progression via the OPN/CD44/PI3K signal axis.In conclusion,OPN activates intracellular PI3K signaling molecules by binding to CD44 on the cell surface to cause downstream cascading effects,thereby delaying chondrocyte degeneration and reducing cartilage matrix component loss;therefore,OPN is a potential therapeutic agent for OA.