OBJECTIVE: To review clinical application and research progress of different types of intelligent responsive hydrogels in repairing articular cartilage injury. METHODS: The animal experiments and clinical studies of different types of intelligent responsive hydrogels for repairing articular cartilage injury were summarized by reviewing relevant literature at home and abroad. RESULTS: The intrinsic regenerative capacity of articular cartilage following injury is limited. Intelligent responsive hydrogels, including those that are temperature-sensitive, light-sensitive, enzyme-responsive, pH-sensitive, and other stimuli-responsive hydrogels, can undergo phase transitions in response to specific stimuli, thereby achieving optimal functionality. These hydrogels can fill the injured cartilage area, promote the proliferation and differentiation of chondrocytes, and expedite the repair of the damaged site. With advancements in cartilage tissue engineering materials research, intelligent responsive hydrogels offer a novel approach and promising potential for the treatment of cartilage injuries. CONCLUSION Intelligent responsive hydrogel is a kind of flexible, controllable, efficient, and stable polymer, which has similar structure and functional properties to articular cartilage, and has become one of the important biomaterials for cartilage repair. However, there is still a lack of unified treatment standards and simple and efficient preparation technology.
Hydrogels/therapeutic use* ; Cartilage, Articular/injuries* ; Tissue Engineering/methods* ; Humans ; Animals ; Chondrocytes/cytology* ; Biocompatible Materials/chemistry* ; Tissue Scaffolds/chemistry*

OBJECTIVE: To analyze the differences in the effects of different mechanical stimuli on cells, cytokines, and proteins in synovial fluid of osteoarthritis joints, and to elucidate the indirect mechanism by which mechanical signals remodel the synovial fluid microenvironment through tissue cells. METHODS: Systematically integrate recent literature, focusing on the regulatory effects of different mechanical stimuli on the physicochemical properties of synovial fluid. Analyze the dynamic process by which mechanical stimuli regulate secretory and metabolic activities through tissue cells, thereby altering the physicochemical properties of cytokines and proteins. RESULTS: Appropriate mechanical stimuli activate mechanical signals in chondrocytes, macrophages, and synovial cells, thereby influencing cellular metabolic activities, including inhibiting the release of pro-inflammatory factors and promoting the secretion of anti-inflammatory factors, and regulating the expression of matrix and inflammation-related proteins such as cartilage oligomeric matrix protein, peptidoglycan recognition protein 4, and matrix metalloproteinases. CONCLUSION Mechanical stimuli act on tissue cells, indirectly reshaping the synovial fluid microenvironment through metabolic activities, thereby regulating the pathological process of osteoarthritis.
Humans ; Osteoarthritis/physiopathology* ; Synovial Fluid/chemistry* ; Chondrocytes/metabolism* ; Cytokines/metabolism* ; Macrophages/metabolism* ; Stress, Mechanical ; Cartilage Oligomeric Matrix Protein/metabolism* ; Matrix Metalloproteinases/metabolism* ; Synovial Membrane/cytology*

OBJECTIVES: To explore the mechanism by which Tougu Xiaotong Capsule (TXC) promotes chondrogenic differentiation and cartilage repair in mice with osteoarthritis (OA). METHODS: Fifty 8-week-old male C57BL mice were randomly divided into normal control group, cartilage damage (induced by subchondral ring-shaped drilling) model group and TXC treatment groups at low, moderate and high doses (184, 368 and 736 mg/kg, respectively). Saline (in normal control and model groups) and TXC were administered after modeling by daily gavage for 6 consecutive weeks. The changes of cartilage damage in the mice were assessed by measuring thermal withdrawal latency (TWL) and mechanical withdrawal threshold (MWT) and using micro-CT, modified safranine O and fast green staining, HE staining, and qPCR. Primary cultures of mouse synovial mesenchymal stem cells (SMSCs) with lentivirus vector transfection for interfering CXCL12, TXC treatment, or both for 24 h were examined for chondrogenic differentiation using immunofluorescence staining, scratch assay, immunocytochemistry, and Western blotting. RESULTS: In mouse models with cartilage damage, TXC treatment at the moderate dose significantly alleviated joint pain, promoted cartilage repair, and upregulated the mRNA expression levels of CXCL12, GDF5, collagen II, aggrecan, Comp and Sox9 in the cartilage tissue. In primary mouse SMSCs, CXCL12 knockdown resulted in significant reduction of GDF5 protein expression, migration ability and Sox9 protein expression, and these changes were obviously reversed by TXC treatment. CONCLUSIONS TXC promotes chondrogenic differentiation of mouse SMSCs to promote repair of cartilage damage in mice by activating the CXCL12/GDF5 pathway.
Animals ; Drugs, Chinese Herbal/therapeutic use* ; Osteoarthritis/metabolism* ; Male ; Growth Differentiation Factor 5/metabolism* ; Mice, Inbred C57BL ; Mice ; Chemokine CXCL12/metabolism* ; Signal Transduction/drug effects* ; Cell Differentiation/drug effects* ; Cartilage, Articular/drug effects* ; Mesenchymal Stem Cells/cytology*

Due to the poor repair ability of cartilage tissue, regenerative medicine still faces great challenges in the repair of large articular cartilage defects. Quercetin is widely applied as a traditional Chinese medicine in tissue regeneration including liver, bone and skin tissues. However, the evidence for its effects and internal mechanisms for cartilage regeneration are limited. In the present study, the effects of quercetin on chondrocyte function were systematically evaluated by CCK8 assay, PCR assay, cartilaginous matrix staining assays, immunofluorescence assay, and western blotting. The results showed that quercetin significantly up-regulated the expression of chondrogenesis genes and stimulated the secretion of GAG (glycosaminoglycan) through activating the ERK, P38 and AKT signalling pathways in a dose-dependent manner. Furthermore, in vivo experiments revealed that quercetin-loaded silk protein scaffolds dramatically stimulated the formation of new cartilage-like tissue with higher histological scores in rat femoral cartilage defects. These data suggest that quercetin can effectively stimulate chondrogenesis in vitro and in vivo, demonstrating the potential application of quercetin in the regeneration of cartilage defects.
Animals ; Cartilage/cytology* ; Chondrocytes/drug effects* ; Chondrogenesis/drug effects* ; Extracellular Matrix/metabolism* ; Quercetin/pharmacology* ; Rats ; Signal Transduction/drug effects* ; Tissue Scaffolds

OBJECTIVE: To investigate the effect and mechanism of mechanical stress on cartilage repair in inflammatory environment. METHODS: The chondrogenic progenitor cells (CPCs) were isolated from the knee joint cartilage of patients with osteoarthritis (OA) undergoing total knee arthroplasty. The CPCs were cultured and expanded in a 3-D scaffold constructed with alginate. Intermittent hydrostatic pressure (IHP) was applied in a inflammatory environment induced by IL-1β, and Western blot was used to detect the expression of MAPK signaling pathway proteins. Cell proliferation was detected by CCK-8 method, and the expression of related genes like matrix metallo-proteinases 13 (MMP-13) and a disintegrins and metalloproteinase with thrombospondin motif 5 (ADAMTS-5) was detected by real-time RT-PCR. The anterior cruciate ligament of the rats was cut to construct the knee joint OA model, and the appropriate mechanical stress was constructed with external fixation to distract the knee joint in order to observe the repair of the cartilage and to explore its mechanism. RESULTS: Adding 0.01 ng/ml IL-1β in cell culture inhibited the proliferation of CPCs. After IHP application, the expression of MAPK pathway protein was decreased, the mRNA expression of MMP-13 and ADAMTS-5 was reduced. The inhibition of IL-1β on CPCs was counteracted by IHP. Four weeks after the anterior cruciate ligament resected, the articular cartilage degeneration was observed in rats. The Mankin score in the OA treatment (joint distraction) group was lower, and the cartilage repair was better than that of the control group (<0.01). Animal experiments found that the suitable mechanical stress reduced the expression of P-p38, MMP-13 and COLL-X, inhibited cartilage cells apoptosis and promoted the repair of OA cartilage. CONCLUSIONS Mechanical stress can promote the proliferation of CPCs, reduce the expression of matrix degrading enzymes, and promote the repair of OA cartilage by inhibiting MAPK signaling pathway.
Animals ; Anterior Cruciate Ligament ; pathology ; surgery ; Cartilage, Articular ; pathology ; Cells, Cultured ; Chondrocytes ; cytology ; Disease Models, Animal ; Gene Expression Profiling ; Humans ; Mitogen-Activated Protein Kinases ; genetics ; Osteoarthritis ; pathology ; Polymerase Chain Reaction ; Rats ; Signal Transduction ; genetics ; Stress, Mechanical

Cartilage tissue engineering, an effective way to repair cartilage defects, requires an ideal scaffold to promote the regeneration performance of stem cells. Cartilage extracellular matrix (CECM) can imitate the living environment of cartilage cells to the greatest extent. CECM not only exhibits good biocompatibility with chondrocytes and stem cells, which can meet the basic requirements of scaffolds, but also promotes chondrocytes to secrete matrix and induce stem cells to differentiate into chondrocytes; as such, this matrix is a better scaffold and has more advantages than existing ones. The promotion and induction effects could be related to various cartilage-related proteins inside. However, the practical application of this technique is hindered by problems, such as poor mechanical properties and insufficient cell penetration of CECM. Association with other materials can compensate for these inadequacies to a certain degree, and finding a combination mode with optimized performance is the application trend of CECM. This review focuses on research of CECM materials in cartilage tissue engineering.
Cartilage ; cytology ; Chondrocytes ; Extracellular Matrix ; Tissue Engineering ; Tissue Scaffolds

OBJECTIVETo investigate the effect of eletroacupuncture with close-to-bone needling treatment on expression of Sox9, vascular endothelial growth factor (VEGF) and type X collagen (ColX) in impaired cartilage of rabbits with knee osteoarthritis (KOA) and explore its possible mechanisms.

METHODSForty New Zealand rabbits were randomized equally into normal control group, KOA model group, eletroacupuncture with close-to-bone needling group (CN group), and normal thrust needing group (NTN group). In the latter 3 groups, KOA was induced by Hulth-Telhag treatment and evaluated with X-ray examination, and 6 weeks after the modeling, eletroacupuncture for 20 min was administered in CN and NTN groups at the acupoints "Zusanli", "Waixiyan", "Neixiyan", "Liangqiu" and "Yinlingquan" in the left knee joints once daily for 5 days as a treatment cycle. After 5 treatment cycles, the rabbits were examined for behavioral changes, cartilage morphology, and Mankin scores; The protein and mRNA expressions of S0x9, VEGF, and ColX were examined using Westen blotting, immunohistochemistry, and RT-PCR as appropriate.

RESULTSThe rabbits in the model, CN and NTN groups showed significant changes in behaviors and cartilage histomorphology after the modeling and after the treatments. HE staining showed that cartilage injury was repaired and tended to recovery in CN and NTN groups. The cartilage pathologies was severer in the model group than in the normal control, CN and NTN groups (P<0.01); Sox9 protein increased and VEGF mRNA level decreased in CN and NTN groups after treatment as compared with those in the model group (P<0.01).

CONCLUSIONEletroacupuncture with close-to-bone needling can effectively improve KOA in rabbits probably by enhancing Sox9 and reducing VEGF and ColX expressions in the cartilage to inhibit hypertrophic differentiation of the chondrocytes, maintain chondrogenic phenotype and repair cartilage cells.

Acupuncture Points ; Animals ; Cartilage, Articular ; metabolism ; pathology ; Cell Differentiation ; Chondrocytes ; cytology ; Chondrogenesis ; Collagen Type X ; metabolism ; Electroacupuncture ; Knee Joint ; physiopathology ; Osteoarthritis, Knee ; therapy ; Rabbits ; SOX9 Transcription Factor ; metabolism ; Vascular Endothelial Growth Factor A ; metabolism

PURPOSE: The purpose of this study was to investigate the effects of transplantation of an in vitro-generated, scaffold-free, tissue-engineered cartilage tissue analogue (CTA) using a suspension chondrocyte culture in a rabbit growth-arrest model. MATERIALS AND METHODS: We harvested cartilage cells from the articular cartilage of the joints of white rabbits and made a CTA using a suspension culture of 2x107 cells/mL. An animal growth plate defect model was made on the medial side of the proximal tibial growth plate of both tibias of 6-week-old New Zealand white rabbits (n=10). The allogenic CTA was then transplanted onto the right proximal tibial defect. As a control, no implantation was performed on the left-side defect. Plain radiographs and the medial proximal tibial angle were obtained at 1-week intervals for evaluation of bone bridge formation and the degree of angular deformity until postoperative week 6. We performed a histological evaluation using hematoxylin-eosin and Alcian blue staining at postoperative weeks 4 and 6. RESULTS: Radiologic study revealed a median medial proximal tibial angle of 59.0degrees in the control group and 80.0degrees in the CTA group at 6 weeks. In the control group, statistically significant angular deformities were seen 3 weeks after transplantation (p<0.05). On histological examination, the transplanted CTA was maintained in the CTA group at 4 and 6 weeks postoperative. Bone bridge formation was observed in the control group. CONCLUSION: In this study, CTA transplantation minimized deformity in the rabbit growth plate injury model, probably via the attenuation of bone bridge formation.
Animals ; *Bone Transplantation ; Cartilage/anatomy & histology ; Cell Culture Techniques ; Cells, Cultured ; Chondrocytes/*cytology/transplantation ; Growth Plate/anatomy & histology/*surgery ; *Mesenchymal Stem Cell Transplantation ; Rabbits ; Tibia/*surgery ; Tissue Engineering ; Transplantation, Autologous/methods ; Transplantation, Homologous

SRT1720, a new discovered drug, was reported to activate silent information regulator 1 (SIRT1) and inhibit the chondrocyte apoptosis. However, the underlying mechanism remains elusive. In the present study, the chondrocytes were extracted from the cartilage tissues of New Zealand white rabbits, cultured in the presence of sodium nitroprusside (SNP) (2.5 mmol/L) and divided into five groups: 1, 5, 10, and 20 μmol/L SRT1720 groups and blank control group (0 μmol/L SRT1720). MTT assay was used to detect the chondrocyte viability and proliferation, and DAPI staining and flow cytometry to measure the chondrocyte apoptosis. The expression levels of SIRT1, p53, NF-κB/p65, Bax, and peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) were detected by Western blotting and the expression levels of SIRT1, type II collagen, and aggrecan mRNA by RT-PCR. The results showed that in the SRT1720-treated groups, the nuclei of chondrocytes were morphologically intact and had uniform chromatin. In the blank control group, nuclear rupture into debris was observed in chondrocytes. With the SRT1720 concentration increasing, the chondrocyte viability increased, the apoptosis rate decreased, the protein expression levels of SIRT1 and PGC-1α and the mRNA expression levels of type II collagen and aggrecan increased ({ptP}<0.05), and the expression levels of p53, NF-κB and bax decreased (P<0.05). It was suggested that SRT1720 inhibits chondrocyte apoptosis by activating the expression of SIRT1 via p53/bax and NF-κB/PGC-1α pathways.
Aggrecans ; genetics ; metabolism ; Animals ; Apoptosis ; drug effects ; Cartilage, Articular ; cytology ; drug effects ; metabolism ; Cell Proliferation ; drug effects ; Cell Survival ; drug effects ; Chondrocytes ; cytology ; drug effects ; metabolism ; Chromatin ; chemistry ; drug effects ; metabolism ; Collagen Type II ; genetics ; metabolism ; Gene Expression Regulation ; Heterocyclic Compounds, 4 or More Rings ; pharmacology ; Nitroprusside ; toxicity ; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha ; genetics ; metabolism ; Primary Cell Culture ; Rabbits ; Signal Transduction ; drug effects ; genetics ; Sirtuin 1 ; genetics ; metabolism ; Transcription Factor RelA ; genetics ; metabolism ; Tumor Suppressor Protein p53 ; genetics ; metabolism ; bcl-2-Associated X Protein ; genetics ; metabolism

OBJECTIVETo establish a model of chondrocyte degeneration in vitro.

METHODSChondrocytes were isolated from articular cartilages of newly born SD rats by digestion with typeⅡ collagenase. The chondrocytes were cultured with H-DMEM medium containing 10%FBS, 50 ng/mL IL-1β+10%FBS, 2.5% rat serum and 5% rat serum, respectively; and the chondrocytes at passage one were used in the experiments. The morphology changes were investigated under phase contrast microscope after chondrocytes were treated with rat serum and IL-1β. Proliferation of chondrocytes was detected by MTT method. The protein expression levels of PCNA, typeⅡ collagen and MMP-13 were examined by Western blotting. The levels of ADAMTS5, MMP-9, Aggrecan and SOX-9 mRNA were detected by real-time PCR.

RESULTSThe cell morphology was changed from polygon to spindle in both rat serum groups and IL-1β group, and the proliferation of chondrocytes in these groups was much higher than that in control group. The results showed that the expression levels of typeⅡ collagen, Aggrecan and SOX-9 decreased while the expression levels of MMP-13, MMP-9 and ADMATS5 were up-regulated in rat serum and IL-1β-treated groups compared with control group.

CONCLUSIONThe results indicate that rat serum can induce chondrocyte degeneration and may be used for osteoarthritis model in vitro.

ADAM Proteins ; metabolism ; ADAMTS5 Protein ; Aggrecans ; metabolism ; Animals ; Cartilage, Articular ; cytology ; Cells, Cultured ; Chondrocytes ; pathology ; Collagen Type II ; metabolism ; Disease Models, Animal ; Interleukin-1beta ; pharmacology ; Matrix Metalloproteinase 13 ; metabolism ; Matrix Metalloproteinase 9 ; metabolism ; Osteoarthritis ; pathology ; Proliferating Cell Nuclear Antigen ; metabolism ; RNA, Messenger ; Rats ; Rats, Sprague-Dawley ; SOX9 Transcription Factor ; metabolism ; Serum ; Up-Regulation