Osteoarthritis (OA) is a prevalent degenerative joint disease characterized by cartilage loss and accounts for a major source of pain and disability worldwide. However, effective strategies for cartilage repair are lacking, and patients with advanced OA usually need joint replacement. Better comprehending OA pathogenesis may lead to transformative therapeutics. Recently studies have reported that exosomes act as a new means of cell-to-cell communication by delivering multiple bioactive molecules to create a particular microenvironment that tunes cartilage behavior. Specifically, exosome cargos, such as noncoding RNAs (ncRNAs) and proteins, play a crucial role in OA progression by regulating the proliferation, apoptosis, autophagy, and inflammatory response of joint cells, rendering them promising candidates for OA monitoring and treatment. This review systematically summarizes the current insight regarding the biogenesis and function of exosomes and their potential as therapeutic tools targeting cell-to-cell communication in OA, suggesting new realms to improve OA management.
Apoptosis ; Cartilage/pathology* ; Cartilage, Articular/metabolism* ; Cell Communication ; Chondrocytes/metabolism* ; Exosomes/pathology* ; Humans ; Osteoarthritis/therapy*

The progressive destruction of condylar cartilage is a hallmark of the temporomandibular joint (TMJ) osteoarthritis (OA); however, its mechanism is incompletely understood. Here, we show that Kindlin-2, a key focal adhesion protein, is strongly detected in cells of mandibular condylar cartilage in mice. We find that genetic ablation of Kindlin-2 in aggrecan-expressing condylar chondrocytes induces multiple spontaneous osteoarthritic lesions, including progressive cartilage loss and deformation, surface fissures, and ectopic cartilage and bone formation in TMJ. Kindlin-2 loss significantly downregulates the expression of aggrecan, Col2a1 and Proteoglycan 4 (Prg4), all anabolic extracellular matrix proteins, and promotes catabolic metabolism in TMJ cartilage by inducing expression of Runx2 and Mmp13 in condylar chondrocytes. Kindlin-2 loss decreases TMJ chondrocyte proliferation in condylar cartilages. Furthermore, Kindlin-2 loss promotes the release of cytochrome c as well as caspase 3 activation, and accelerates chondrocyte apoptosis in vitro and TMJ. Collectively, these findings reveal a crucial role of Kindlin-2 in condylar chondrocytes to maintain TMJ homeostasis.
Aggrecans/metabolism* ; Animals ; Cartilage, Articular/metabolism* ; Chondrocytes/pathology* ; Cytoskeletal Proteins/metabolism* ; Mice ; Muscle Proteins/metabolism* ; Osteoarthritis/pathology* ; Temporomandibular Joint/pathology*

The changes of hyaline articular cartilage from rabbits after air exposure were evaluated. The knee joints were exposed to air for periods of thirty minutes to two hours. The animals were killed periodically, at three days, one week and three weeks postoperatively. After sacrifice, the cartilage was removed and prepared for study by light microscopy and electron microscopy. Exposure to room air for thirty minutes produced chondrocyte necrosis in the upper third of the cartilage, and exposure for 60 minutes or longer produced chondrocyte necrosis of the entire thickness of articular cartilage at three days after arthrotomy. But, three weeks after arthrotomy, we could not find any chondrocyte necrosis in any rabbits at varying periods of air exposure. There was no significant change in proteoglycan content between the aired and control cartilage. Clinical Relevance: Exposing cartilage to air can cause transient and reversible cartilage damage. If these changes are not reversible, the orthopedic surgeon should consider avoiding the prolonged exposure of articular cartilage to air, since complete matrix disintegration is known to occur months after chondrocyte necrosis.
*Air ; Animal ; Cartilage, Articular/metabolism/*pathology/ultrastructure ; Hyalin/*metabolism ; Microscopy, Electron ; Necrosis ; Rabbits ; Time Factors

OBJECTIVETo explore the effects of selenium and/or iodine deficiency on chondrocyte apoptosis in articular cartilage in rats.

METHODSForty-eight Sprague-Dawley rats were randomly divided into selenium deficiency group, iodine deficiency group, combined selenium and iodine deficiency group, and control group. Chondrocyte apoptosis was detected by terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) method, and Bcl-2 and Bax in articular cartilage were stained by immunohistochemistry in F3 generation of rats.

RESULTSIn articular cartilage, the positive rate of apoptotic chondrocytes stained by TUNEL in the upper and middle zones in selenium deficiency group, iodine deficiency group, and combined selenium and iodine deficiency group (all P < 0.05) were significantly higher than that in control group. The apoptotic chondrocytes were prominent in the middle zone. The positive percentage of chondrocytes apoptosis was not significantly different among these three groups (P > 0.05). Compared with the control group, the expressions of both Bcl-2 and Bax were significantly higher in the upper and middle zone in the selenium deficiency group, iodine deficiency group, and combined selenium and iodine deficiency group (all P < 0.05); however, the expressions of Bcl-2 and Bax were not significantly different among these three groups (P > 0.05).

CONCLUSIONSelenium and/or iodine deficiency may induce chondrocyte apoptosis.

Animals ; Apoptosis ; Cartilage, Articular ; metabolism ; pathology ; Chondrocytes ; metabolism ; pathology ; Female ; Iodine ; deficiency ; Male ; Rats ; Rats, Sprague-Dawley ; Selenium ; deficiency

Mitogen-activated protein kinases (MAPKs) signal is one of the important ways in eukaryotic cell,which adjusts and controls the structure and function of the cell. MAPKs in eukaryotes include p38, ERK, JNK and ERK5, etc. With the deepening research,we found that the activation of p38, ERK, JNK signal pathways were closely related with osteoarthritis (OA) cartilage injury. MAPKs are the key signaling systems involved in the production of matrix metalloproteinases and the regulation of cartilage cell proliferation, apoptosis and differentiation. Expecially the matrix metalloproteinases can accelerate the degradation of articular cartilage. So it has been the new spot in pathogenesis of osteoarthritis study.
Animals ; Cartilage, Articular ; pathology ; Humans ; MAP Kinase Signaling System ; Mitogen-Activated Protein Kinases ; metabolism ; Osteoarthritis ; etiology ; pathology

Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease is a disease of the elderly and extremely rare in young individuals. If young people develop CPPD crystal deposition disease, it may be associated with metabolic diseases such as hemochromatosis, hyperparathyroidism, hypophosphatasia, hypomagnesemia, Wilson's disease, hypothyroidism, gout, acromegaly, and X-linked hypophosphatemic rickets. Therefore, in young-onset polyarticular CPPD crystal deposition disease, investigation for predisposing metabolic conditions is warranted. We report a case of a young male patient with idiopathic CPPD crystal deposition disease, who did not have any evidences of metabolic diseases after thorough evaluations. As far as we know, this is the first report of a young male patient presented with idiopathic CPPD crystal deposition disease.
Adult ; Calcium Pyrophosphate/*metabolism ; Cartilage, Articular/metabolism/pathology ; Diagnosis, Differential ; Human ; Knee Joint/*pathology ; Male ; Metabolic Diseases/metabolism/pathology ; Shoulder Joint/pathology

OBJECTIVETo look into the character of the expression of collagen type II and transforming growth factor beta1 (TGF-beta1), basic fibroblast growth factor (bFGF) in the apical articular process cartilages of adolescent idiopathic scoliosis (AIS) and congenital scoliosis (CS) patients.

METHODSThe articular processes of 22 AIS and 18 CS were collected. The techniques of HE staining, immunohistochemistry and in situ hybridization were adopted in this research. By comparing the apical processes with the end processes, the convex processes with the concave processes, the AIS processes with CS processes, the pathological changes of the articular process cartilages of these patients and the distribution of collagen type II and TGF-beta1, bFGF in them were studied. The images of immunohistochemistry and in situ hybridization were input into the image analysis system and were analyzed semi-quantitatively. The SAS software (8.01) was adopted, and P < 0.05 was defined as the significant level.

RESULTSThe expression of collagen type II and TGF-beta1, bFGF in AIS was similar to CS: the concave sides of apexes were higher than the convex sides. The comparisons had statistical significance. There was no statistical significance between upper and lower end vertebrae in convex and concave sides, between convex and concave sides in upper and lower end vertebrae. The apical vertebrae were significantly higher than the ipsilateral sides of upper or lower end vertebrae for collagen type II. There was no statistical difference of the expression at the concave, convex, upper, lower end vertebrae between AIS and CS.

CONCLUSIONSThe cartilages of the apical processes show some signs of regression and hypoplasia in scoliosis. The concave side is more severe than the convex side. Increase of collagen type II and TGF-beta1, bFGF in the concave sides of apical processes in scoliosis may be the results of reconstruction of extracellular matrix and the compensation reactions which are caused by abnormal biomechanical forces such as compressive stresses. Compressive stress on the concave sides has more influences on the expression of collagen type II than tensile stress on the convex sides.

Adolescent ; Cartilage, Articular ; metabolism ; pathology ; Child ; Collagen Type II ; metabolism ; Fibroblast Growth Factor 2 ; metabolism ; Humans ; Scoliosis ; metabolism ; pathology ; Transforming Growth Factor beta1 ; metabolism

BACKGROUNDThe order and mechanism of pathological changes in acetabular dysplasia are still unclear. This study investigated cartilage changes in rabbit acetabular dysplasia models at different ages.

METHODSTwenty-seven 1-month-old New Zealand rabbits underwent cast immobilization of the left hind limb in knee extension. Serial acetabular dysplasia models were established by assessment of the acetabular index and Sharp's angle on radiographs. The thickness of the acetabular cartilage was measured under a microscope, and fibrosis was observed. Ultrastructural changes were investigated with scanning electron microscopy and transmission electron microscopy. The messenger RNA expression of collagen I and II, β1 integrin, and caspase-9 were measured by real-time fluorescence quantitative polymerase chain reaction.

RESULTSIn an immature group of rabbits, the acetabular index of the treated hip increased with animal growth. The cartilage on the brim of the left acetabulum was significantly thicker than that on the right side. The collagen fibrils on the surface of the cartilage became gross, and the chondrocytes in the enlargement layer underwent necrosis. In a mature group of rabbits, the left Sharp's angle increased in the rabbits with 6-week casting. The cartilage on the brim of the left acetabulum underwent fibrosis. The chondrocytes were weakly stained, and the number of lysosomes was much larger than normal. The messenger RNA expression of collagen I and II, β1 integrin, and caspase-9 in the cartilage differed significantly at different ages.

CONCLUSIONSIncreasing thickness followed by fibrosis may be the order of pathological cartilage changes in acetabular dysplasia, with changes in ultrastructure and collagen expression contributing to the process.

Acetabulum ; metabolism ; pathology ; ultrastructure ; Animals ; Cartilage, Articular ; metabolism ; pathology ; ultrastructure ; Female ; Fibrosis ; metabolism ; pathology ; Male ; Microscopy, Electron, Scanning ; Microscopy, Electron, Transmission ; Polymerase Chain Reaction ; Rabbits

OBJECTIVETo investigate the changes in the expressions of Fas-associated death domain protein (FADD) and cellular-FLICE inhibitory protein (c-FLIP) in the articular cartilage of patients with Kashin-Beck disease (KBD) and the role of these proteins in the pathogenesis of KBD.

METHODSThe cartilage samples were collected from patients with established diagnosis of KBD and osteoarthritis and from healthy control subjects undergoing amputation due to traffic accidents. The expressions of Fas-associated death domain protein (FADD) and cellular-FLICE inhibitory protein (c-FLIP) in the cartilage were detected by immunohistochemistry, and the positive chondrocytes were counted in different layers of the articular cartilage under microscope.

RESULTSThe positivity rates of FADD in the middle layer of articular cartilage from patients with KBD [(28.68∓2.19)%] and osteoarthritis [(35.40∓2.34)%] were significantly higher than that in normal cartilage [(10.51∓5.02)%, F=16.245, P=0.000], but the rates in the upper and deeper layers were comparable among the 3 groups (P=0.206-0.761). In KBD cartilage, FADD expression was the highest in the middle layer [(28.68∓5.38)%] followed by the deeper layer [(17.94∓8.38)%]. Compared with the healthy controls, KBD and osteoarthritis patients showed significantly higher FLIP expression in the upper layer of the cartilage (F=5.929, P=0.018) but similar expressions in middle and deeper layers.

CONCLUSIONSKBD patients have significant increased FADD expression in the middle layer but decreased FLIP expression in the upper layer of the cartilage, suggesting that the death receptor pathway and its regulators play important roles in the pathogenesis of KBD.

CASP8 and FADD-Like Apoptosis Regulating Protein ; metabolism ; Cartilage, Articular ; metabolism ; pathology ; Case-Control Studies ; Fas-Associated Death Domain Protein ; metabolism ; Humans ; Immunohistochemistry ; Kashin-Beck Disease ; metabolism ; pathology

OBJECTIVETo study the characteristics of cellular metabolism of mandibular condylar chondrocytes in repairing state of osteoarthrosis and investigate its role in the pathogenesis of the disease.

METHODSTemporomandibular joint osteoarthrosis model of rabbits was created by the partial resection of joint disc and confirmed with histological diagnosis. The chondrocytes were harvested from osteoarthritic condylar cartilage in the repairing state and cultured in vitro under the monolayer culture condition. The cellular expression of cartilaginous matrix protein, collagenase and growth factors between the osteoarthritic chondrocytes and the normal controls were measured with RT-PCR technique to outline the basic feature of the osteoarthritic cells.

RESULTSThe cultured cells were confirmed as chondrocytes with their ability of expression of collagen type II and Aggrecan. In the reactive repairing state of osteoarthrosis, the chondrocytes showed the imbalance of expression of ECM proteins, and increased expression of collagenase and endogenous growth factors such as IGF-1 and TGF-beta1.

CONCLUSIONSThis study found the active anabolism of the chondrocytes within the osteoarthritic condylar cartilage and the imbalance synthesis of cartilage matrix. These repairing attempts by the osteoarthritic chondrocytes may be impossible to restore the primary homeostasis within the condylar cartilage.

Animals ; Cartilage, Articular ; metabolism ; pathology ; Cells, Cultured ; Chondrocytes ; metabolism ; Extracellular Matrix ; genetics ; metabolism ; Male ; Mandibular Condyle ; metabolism ; pathology ; Osteoarthritis ; metabolism ; pathology ; RNA, Messenger ; genetics ; metabolism ; Rabbits ; Temporomandibular Joint Disc ; pathology ; Temporomandibular Joint Disorders ; metabolism ; pathology