The Protective Effects of Parathyroid Hormone (1-34) on Cartilage and Subchondral Bone Through Down-Regulating JAK2/STAT3 and WNT5A/ROR2 in a Collagenase-Induced Osteoarthritis Mouse Model.

OBJECTIVE: To assess the effects of PTH (1-34) on bone and cartilage metabolism in a collagenase-induced mouse model of osteoarthritis (OA) and examine whether PTH (1-34) affects the expression of JAK2/STAT3 and WNT5A/ROR2 in this process. METHODS: Eighteen 12-week-old male C57Bl/6 mice were randomly assigned into three groups as follows: sham group (Group A), the collagenase + saline injection group (Group B), and the collagenase + PTH (1-34) treatment group (Group C). Collagenase was injected (intra-articular) into the knee joint of Group B and C. The PTH (1-34)-treatment was started at 6 weeks after the operation and lasted for 6 weeks. Cartilage pathology was evaluated by gross visual, histological, and immunohistochemical assessments. Subchondral bone was evaluated by microcomputed tomography (micro-CT) and immunohistochemical analyses. RESULTS: The OARSI macroscopic and microscopic scores of Group B were higher than those of Group A (P = 0.026; P = 0.002, respectively). Group C showed statistically significant differences in macroscopic and microscopic scores from Group B (P = 0.041; P = 0.008, respectively). The results showed that the Col-II and AGG expression levels in the cartilage tissue were significantly lower in Group B than Group A (P < 0.001; P = 0.008, respectively). The Col-II and AGG expression levels were significantly higher in Group C than Group B (P = 0.009; P = 0.014, respectively). MMP-13, ADAMTS-4, Caspase-3, P53, and Bax expression levels were significantly higher in Group B than the Group A (P < 0.001; P < 0.001; P = 0.04; P < 0.001; P = 0.005, respectively); however, the cartilage tissue in Group C showed significantly less ADAMTS-4, MMP-13, Caspase-3, P53, and Bax expression than Group B (P < 0.001, P < 0.001, P = 0.044; P = 0.002; P = 0.005, respectively). Over-expressed JAK2/STAT3 and WNT5A/ROR2 were observed in both cartilage and subchondral bone in this model; however, these changes were prevented by PTH (1-34) treatment. These parameters (bone mineral density, bone volume ratio, trabecular bone pattern factor, and structure model index) of micro-CT indicated subchondral bone loss and architecture changes in Group B, but improvements in these parameters in Group C. CONCLUSIONS: PTH (1-34) exhibits protective effects on both cartilage and subchondral bone in a collagenase-induced OA mouse model, and it may be involved in down-regulating the expression of JAK2/STAT3 and WNT5A/ROR2.

Denosumab alleviates intervertebral disc degeneration adjacent to lumbar fusion by inhibiting endplate osteochondral remodeling and vertebral osteoporosis in ovariectomized rats.

BACKGROUND: Although adjacent segmental intervertebral disc degeneration (ASDD) is one of the most common complications after lumbar fusion, its exact mechanism remains unclear. As an antibody to RANKL, denosumab (Dmab) effectively reduces bone resorption and stimulates bone formation, which can increase bone mineral density (BMD) and improve osteoporosis. However, it has not been confirmed whether Dmab has a reversing or retarding effect on ASDD. METHODS: Three-month-old female Sprague-Dawley rats that underwent L4-L5 posterolateral lumbar fusion (PLF) with spinous-process wire fixation 4 weeks after bilateral ovariectomy (OVX) surgery were given Dmab 4 weeks after PLF surgery (OVX+PLF+Dmab group). In addition, the following control groups were defined: Sham, OVX, PLF, and OVX+PLF (n=12 each). Next, manual palpation and X-ray were used to evaluate the state of lumbar fusion. The bone microstructure in the lumbar vertebra and endplate as well as the disc height index (DHI) of L5/6 was evaluated by microcomputed tomography (µCT). The characteristic alterations of ASDD were identified via Safranin-O green staining. Osteoclasts were detected using tartrate-resistant acid phosphatase (TRAP) staining, and the biomechanical properties of vertebrae were evaluated. Aggrecan (Agg), metalloproteinase-13 (MMP-13), and a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4) expression in the intervertebral disc were detected by immunohistochemistry and real-time polymerase chain reaction (RT-PCR) analysis. In addition, the expression of CD24 and Sox-9 was assessed by immunohistochemistry. RESULTS: Manual palpation showed clear evidence of the fused segment's immobility. Compared to the OVX+PLF group, more new bone formation was observed by X-ray examination in the OVX+PLF+Dmab group. Dmab significantly alleviated ASDD by retaining disc height index (DHI), decreasing endplate porosity, and increasing vertebral biomechanical properties and BMD. TRAP staining results showed a significantly decreased number of active osteoclasts after Dmab treatment, especially in subchondral bone and cartilaginous endplates. Moreover, the protein and mRNA expression results in discs (IVDs) showed that Dmab not only inhibited matrix degradation by decreasing MMP-13 and ADAMTS-4 but also promoted matrix synthesis by increasing Agg. Dmab maintained the number of notochord cells by increasing CD24 but reducing Sox-9. CONCLUSIONS: These results suggest that Dmab may be a novel therapeutic target for ASDD treatment.

Raloxifene inhibits the overexpression of TGF-ß1 in cartilage and regulates the metabolism of subchondral bone in rats with osteoporotic osteoarthritis.

Overexpression of transforming growth factor-beta 1 (TGF-ß1) and subchondral bone remodelling play key roles in osteoarthritis (OA). Raloxifene (RAL) reduces the serum level of TGF-ß1 in postmenopausal women. However, the effect of RAL on TGF-ß1 expression in articular cartilage is still unclear. Therefore, we aimed to investigate the protective effect of RAL on osteoporotic osteoarthritis via affecting TGF-ß1 expression in cartilage and the metabolism of subchondral bone. Osteoporotic osteoarthritis was induced by a combination of anterior cruciate transection (ACLT) and ovariectomy (OVX). Rats were divided into five groups (n = 12): The sham group, the ACLT group, the OVX group, the ACLT + OVX group, and the RAL group (ACLT + OVX + RAL, 6.25 mg/kg/day for 12 weeks). Assessment was performed by histomorphology, microcomputed tomography (micro-CT) scan, immunohistochemistry, and tartrate-resistant acid phosphatase (TRAP) staining. We found that severe cartilage degeneration was shown in the ACLT + OVX group. The histomorphological scores, the levels of TGF-ß1, and its related catabolic enzymes and osteoclasts numbers in the ACLT + OVX group were higher than those in other groups (p < 0.05). Furthermore, structure model index (SMI) and trabecular spacing (Tb.Sp) were decreased (p < 0.05), while bone mineral density (BMD), bone volume fraction (BV/TV), and trabecular number (Tb.N) were increased by RAL compared with the ACLT + OVX group (p < 0.05). Our findings demonstrated that RAL in clinical doses retards the development of osteoporotic osteoarthritis by inhibiting the overexpression of TGF-ß1 in cartilage and regulating the metabolism of subchondral bone. These results provide support for RAL in the expansion of clinical indication for prevention and treatment in postmenopausal osteoarthritis.

Parathyroid hormone (1-34) ameliorates cartilage degeneration and subchondral bone deterioration in collagenase-induced osteoarthritis model in mice.

AIMS: Parathyroid hormone (PTH) (1-34) exhibits potential in preventing degeneration in both cartilage and subchondral bone in osteoarthritis (OA) development. We assessed the effects of PTH (1-34) at different concentrations on bone and cartilage metabolism in a collagenase-induced mouse model of OA and examined whether PTH (1-34) affects the JAK2/STAT3 signalling pathway in this process. METHODS: Collagenase-induced OA was established in C57Bl/6 mice. Therapy with PTH (1-34) (10 µg/kg/day or 40 µg/kg/day) was initiated immediately after surgery and continued for six weeks. Cartilage pathology was evaluated by gross visual, histology, and immunohistochemical assessments. Cell apoptosis was analyzed by TUNEL staining. Microcomputed tomography (micro-CT) was used to evaluate the bone mass and the microarchitecture in subchondral bone. RESULTS: Enhanced matrix catabolism, increased apoptosis of chondrocytes in cartilage, and overexpressed JAK2/STAT3 and p-JAK2/p-STAT3 were observed in cartilage in this model. All of these changes were prevented by PTH (1-34) treatment, with no significant difference between the low-dose and high-dose groups. Micro-CT analysis indicated that bone mineral density (BMD), bone volume/trabecular volume (BV/TV), and trabecular thickness (Tb.Th) levels were significantly lower in the OA group than those in the Sham, PTH 10 µg, and PTH 40 µg groups, but these parameters were significantly higher in the PTH 40 µg group than in the PTH 10 µg group. CONCLUSION: Intermittent administration of PTH (1-34) exhibits protective effects on both cartilage and subchondral bone in a dose-dependent manner on the latter in a collagenase-induced OA mouse model, which may be involved in regulating the JAK2/STAT3 signalling pathway.Cite this article: Bone Joint Res 2020;9(10):675-688.