Pre-emptive, early, and delayed alendronate treatment in a rat model of knee osteoarthritis: effect on subchondral trabecular bone microarchitecture and cartilage degradation of the tibia, bone/cartilage turnover, and joint discomfort

Differential effects of alendronate on chondrocytes, cartilage matrix and subchondral bone structure in surgically induced osteoarthritis in mice

Bisphosphonates (BP) are considered a treatment option for osteoarthritis (OA) due to reduction of OA-induced microtrauma in the bone marrow, stabilization of subchondral bone (SB) layer and pain reduction. The effects of high-dose alendronate (ALN) treatment on SB and articular cartilage after destabilization of the medial meniscus (DMM) or Sham surgery of male C57Bl/6J mice were analyzed. We performed serum analysis; histology and immunohistochemistry to assess the severity of OA and a possible pain symptomatology. Subsequently, the ratio of bone volume to total volume (BV/TV), epiphyseal trabecular morphology and the bone mineral density (BMD) was analyzed by nanoCT. Serum analysis revealed a reduction of ADAMTS5 level. The histological evaluation displayed no protective effect of ALN-treatment on cartilage erosion. NanoCT-analysis of the medial epiphysis revealed an increase of BV/TV in ALN-treated mice. Only the DMM group had significantly higher SB volume accompanied by decreased subchondral bone surface. Furthermore Nano-CT analysis revealed an increase in trabecular density and number, a decreased BMD and reduced osteophyte formation in the ALN mice. ALN treatment affected bone micro-architecture by reducing osteophytosis with simultaneous increasing subchondral bone plate thickness, trabecular thickness and BMD. Accordingly, ALN cannot be considered as a potential treatment strategy in general, however in a subgroup of patients with high bone turnover in an early-stage of OA, ALN might be an option when applied during a restricted time frame.

A RANKL-UCHL1-sCD13 negative feedback loop limits osteoclastogenesis in subchondral bone to prevent osteoarthritis progression

Abnormal subchondral bone remodeling plays a pivotal role in the progression of osteoarthritis (OA). Here, we analyzed subchondral bone samples from OA patients and observed a significant upregulation of ubiquitin carboxy-terminal hydrolase L1 (UCHL1) specifically in subchondral bone osteoclasts. Notably, we found a strong correlation between UCHL1 expression and osteoclast activity in the subchondral bone during OA progression in both human and murine models. Conditional UCHL1 deletion in osteoclast precursors exacerbated OA progression, while its overexpression, mediated by adeno-associated virus 9, alleviated this process in male mice. Mechanistically, RANKL stimulates UCHL1 expression in osteoclast precursors, subsequently stabilizing CD13, augmenting soluble CD13 (sCD13) release, and triggering an autocrine inhibitory effect on the MAPK pathway, thereby suppressing osteoclast formation. These findings unveil a previously unidentified negative feedback loop, RANKL-UCHL1-sCD13, that modulates osteoclast formation and presents a potential therapeutic target for OA.

The BMP7-Derived Peptide p[63-82] Reduces Cartilage Degeneration in the Rat ACLT-pMMx Model for Posttraumatic Osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is characterized by articular cartilage erosion, pathological subchondral bone changes, and signs of synovial inflammation and pain. We previously identified p[63-82], a bone morphogenetic protein 7 (BMP7)-derived bioactive peptide that attenuates structural cartilage degeneration in the rat medial meniscal tear-model for posttraumatic OA. This study aimed to evaluate the cartilage erosion-attenuating activity of p[63-82] in a different preclinical model for OA (anterior cruciate ligament transection-partial medial meniscectomy [anterior cruciate ligament transection (ACLT)-pMMx]). The disease-modifying action of the p[63-82] was followed-up in this model for 5 and 10 weeks.

DESIGN

Skeletally mature male Lewis rats underwent ACLT-pMMx surgery. Rats received weekly intra-articular injections with either saline or 500 ng p[63-82]. Five and 10 weeks postsurgery, rats were sacrificed, and subchondral bone characteristics were determined using microcomputed tomography (µCT). Histopathological evaluation of cartilage degradation and Osteoarthritis Research Society International (OARSI)-scoring was performed following Safranin-O/Fast Green staining. Pain-related behavior was measured by incapacitance testing and footprint analysis.

RESULTS

Histopathological evaluation at 5 and 10 weeks postsurgery showed reduced cartilage degeneration and a significantly reduced OARSI score, whereas no significant changes in subchondral bone characteristics were found in the p[63-82]-treated rats compared to the saline-treated rats. ACLT-pMMx-induced imbalance of static weightbearing capacity in the p[63-82] group was significantly improved compared to the saline-treated rats at weeks 5 postsurgery. Footprint analysis scores in the p[63-82]-treated rats demonstrated improvement at week 10 postsurgery.

CONCLUSIONS

Weekly intra-articular injections of p[63-82] in the rat ACLT-pMMx posttraumatic OA model resulted in reduced degenerative cartilage changes and induced functional improvement in static weightbearing capacity during follow-up.

The effects of alendronate on the suppression of bone resorption and the promotion of cartilage formation in the human mosaicplasty donor site: A randomized, double-blind, placebo-controlled prospective study

BACKGROUND

We previously reported that early alendronate administration accelerated bone formation and improved the quality of repaired cartilage in the donor site in rabbits. To investigate whether alendronate administration has effects in humans similar to those observed in rabbits.

METHODS

The study cohort included 35 patients over the age of 12-years old who underwent mosaicplasty without osteoporotic therapy from March 2011 to October 2012. The donor sites were medial or lateral in the patellofemoral joint. Placebo (P) or Bonalon containing 35 mg of alendronate (A) was administered orally every week for 8 weeks. The cohort comprised 15 male and 20 female, including 14 right and 21 left knees. The mean age at the time of surgery was 57.1 years. Bone formation was examined using computer tomography and lateral knee radiography, and cartilage formation was examined using magnetic resonance imaging (MRI), second-look assessment, and intraoperative acoustic evaluation. The clinical outcomes were assessed using the Japanese Orthopaedic Association knee score and visual analog scale (VAS). Bone and cartilage formation in the donor site and clinical outcomes were assessed at 3, 6, and 12 months after mosaicplasty.

RESULTS

The ratio of TRAP-5b in group A was significantly smaller than that in group P at 2 and 8 weeks after mosaicplasty. The extent of bone formation in the donor sites in group A was significantly greater than that in group P at 3 and 6 months after mosaicplasty. Cartilage formation did not differ significantly between the two groups as determined by MRI, macroscopic assessment, and intraoperative acoustic evaluation. Clinical outcomes did not differ significantly between the two groups, and no negative clinical outcomes were observed.

CONCLUSION

Early alendronate administration accelerated bone formation but not cartilage formation in the mosaicplasty donor site in humans.

Emodin Attenuates the ECM Degradation and Oxidative Stress of Chondrocytes through the Nrf2/NQO1/HO-1 Pathway to Ameliorate Rat Osteoarthritis

Osteoarthritis (OA) substantially reduces the quality of life of the elderly. OA therapy remains a challenge since no treatment options for its causes are so far available. Over recent years, researchers have speculated that emodin may represent a potential treatment strategy for OA. However, it remains unclear whether the mechanism of action of emodin is associated with the inhibition of OA-induced oxidative stress. In the present study, the potential antioxidant mechanism of action of emodin and its protective properties against the development of OA were investigated both in vitro and in vivo. In vitro, emodin inhibited the production of reactive oxygen species (ROS) in chondrocytes induced by hydrogen peroxide (H2O2) and reduced the expression of matrix metalloproteinase (MMP)3 and MMP13 in a concentration-dependent manner. It was found that emodin upregulated the Nrf2/NQO1/HO-1 pathway, thereby attenuating the effects of oxidative stress caused by OA. In a rat model of posttraumatic OA induced by anterior cruciate ligament transection (ACLT), emodin reduced the extent of joint swelling. Emodin attenuated oxidative damage in the cartilage by upregulating superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) activity, reducing malondialdehyde (MDA) concentration and inhibiting the expression of the extracellular matrix (ECM) degradation biomarkers cartilage oligomeric matrix protein (COMP), and C-terminal telopeptide of type I collagen (CTX-I) and type II collagen (CTX-II), thereby reducing cartilage damage. In summary, the present study indicates that emodin reduces ECM degradation and oxidative stress in chondrocytes via the Nrf2/NQO1/HO-1 pathway, thereby ameliorating OA in rats.

Does Bisphosphonate Increase the Sclerosis of Tibial Subchondral Bone in the Progression of Knee Osteoarthritis-A Propensity Score Matching Cohort Study Based on Osteoarthritis Initiative

Bisphosphonate has great potential in KOA therapy, but whether the anti-resorption mechanism of bisphosphonate aggravates sclerosis of subchondral bone remains unclear. We found that bisphosphonate use did not increase sclerosis of subchondral bone in established KOA, perhaps resolving some concerns about bisphosphonate in patients with KOA. Introduction: Most studies have focused on the protective effect of bisphosphonate on early knee osteoarthritis (KOA) through its anti-resorption mechanism in osteoclasts. However, late KOA has a decreased rate of resorption, which is the opposite of early KOA. The risk of subchondral bone sclerosis in late KOA after using bisphosphonate has not been investigated using morphometry. Methods: Forty-five patients who had ever used bisphosphonate (or 33 patients with current use) were matched with controls through propensity matching methods, including age, body mass index (BMI), sex, health status (12-Item Short Form Survey physical health score), physical activity level (Physical Activity Scale for the Elderly score), vitamin D use, and calcium use. At the baseline and 12-month (or 18-month) follow-up, bone mineral density (BMD) of the tibia and hip was measured by dual-energy X-ray absorptiometry (DXA), and medial tibial subchondral bone morphometry: bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) were calculated based on 3-T trabecular MRI. Data were obtained from the Bone Ancillary Study in the Osteoarthritis Initiative (OAI) project. Results: The yearly percentage change in hip BMD of the current bisphosphonate-use group was significantly greater than that of the non-bisphosphonate-use group (0.7% vs. -1%, P = 0.02). The other outcomes (BV/TV, Tb.N, Tb.Sp, Tb.Th, tibia medial BMD, and tibia lateral BMD) between the two groups presented no significant difference. The non-bisphosphonate-use group experienced a significant increase in Tb.Th [2%, 95% CI = (1%, 4%), P = 0.01], while the bisphosphonate-use group presented no significant change [1%, 95% CI = (-2%, 4%), P = 0.54]. Conclusions: Bisphosphonate use did not increase sclerosis of subchondral bone in established KOA. Bisphosphonate might have a stage-dependent effect on subchondral bone in KOA initiation and progression.

Low bone mass resulting from impaired estrogen signaling in bone increases severity of load-induced osteoarthritis in female mice

OBJECTIVE

Reduced subchondral bone mass and increased remodeling are associated with early stage OA. However, the direct effect of low subchondral bone mass on the risk and severity of OA development is unclear. We sought to determine the role of low bone mass resulting from a bone-specific loss of estrogen signaling in load-induced OA development using female osteoblast-specific estrogen receptor-alpha knockout (pOC-ERαKO) mice.

METHODS

Osteoarthritis was induced by cyclic mechanical loading applied to the left tibia of 26-week-old female pOC-ERαKO and littermate control mice at peak loads of 6.5N, 7N, or 9N for 2 weeks. Cartilage damage and thickness, osteophyte development, and joint capsule fibrosis were assessed from histological sections. Subchondral bone morphology was analyzed by microCT. The correlation between OA severity and intrinsic bone parameters was determined.

RESULTS

The loss of ERα in bone resulted in an osteopenic subchondral bone phenotype, but did not directly affect cartilage health. Following two weeks of cyclic tibial loading to induce OA pathology, pOC-ERαKO mice developed more severe cartilage damage, larger osteophytes, and greater joint capsule fibrosis compared to littermate controls. Intrinsic bone parameters negatively correlated with measures of OA severity in loaded limbs.

CONCLUSIONS

Subchondral bone osteopenia resulting from bone-specific loss of estrogen signaling was associated with increased severity of load-induced OA pathology, suggesting that reduced subchondral bone mass directly exacerbates load-induced OA development. Bone-specific changes associated with estrogen loss may contribute to the increased incidence of OA in post-menopausal women.

Early inhibition of subchondral bone remodeling slows load-induced posttraumatic osteoarthritis development in mice

Posttraumatic osteoarthritis (PTOA) is associated with abnormal and increased subchondral bone remodeling. Inhibiting altered remodeling immediately following joint damage can slow PTOA progression. Clinically, however, inhibiting remodeling when significant joint damage is already present has minimal effects in slowing further disease progression. We sought to determine the treatment window following PTOA initiation in which inhibiting remodeling can attenuate progression of joint damage. We hypothesized that the most effective treatment would be to inhibit remodeling immediately after PTOA initiation. We used an animal model in which a single bout of mechanical loading was applied to the left tibia of 26-week-old male C57Bl/6 mice at a peak load of 9 N to initiate load-induced PTOA development. Following loading, we inhibited bone remodeling using daily alendronate (ALN) treatment administered either immediately or with 1 or 2 weeks' delay up to 3 or 6 weeks post-loading. A vehicle (VEH) treatment group controlled for daily injections. Cartilage and subchondral bone morphology and osteophyte development were analyzed and compared among treatment groups. Inhibiting remodeling using ALN immediately after load-induced PTOA initiation reduced cartilage degeneration, slowed osteophyte formation, and preserved subchondral bone volume compared to VEH treatment. Delaying the inhibition of bone remodeling at 1 or 2 weeks similarly attenuated cartilage degeneration at 6 weeks, but did not slow the development of osteoarthritis (OA)-related changes in the subchondral bone, including osteophyte formation and subchondral bone erosions. Immediate inhibition of subchondral bone remodeling was most effective in slowing PTOA progression across the entire joint, indicating that abnormal bone remodeling within the first week following PTOA initiation played a critical role in subsequent cartilage damage, subchondral bone changes, and overall joint degeneration. These results highlight the potential of anti-resorptive drugs as preemptive therapies for limiting PTOA development after joint injury, rather than as disease-modifying therapies after joint damage is established. © 2021 American Society for Bone and Mineral Research (ASBMR).

Interleukin 4 promotes anti-inflammatory macrophages that clear cartilage debris and inhibits osteoclast development to protect against osteoarthritis

OBJECTIVE

Osteoarthritis (OA), the leading cause of joint failure, is characterized by breakdown of articular cartilage and remodeling of subchondral bone in synovial joints. Despite the high prevalence and debilitating effects of OA, no disease-modifying drugs exist. Increasing evidence, including genetic variants of the interleukin 4 (IL-4) and IL-4 receptor genes, implicates a role for IL-4 in OA, however, the mechanism underlying IL-4 function in OA remains unknown. Here, we investigated the role of IL-4 in OA pathogenesis.

METHODS

Il4-, myeloid-specific-Il4ra-, and Stat6-deficient and control mice were subjected to destabilization of the medial meniscus to induce OA. Macrophages, osteoclasts, and synovial explants were stimulated with IL-4 in vitro, and their function and expression profiles characterized.

RESULTS

Mice lacking IL-4, IL-4Ra in myeloid cells, or STAT6 developed exacerbated cartilage damage and osteophyte formation relative to WT controls. In vitro analyses revealed that IL-4 downregulates osteoarthritis-associated genes, enhances macrophage phagocytosis of cartilage debris, and inhibits osteoclast differentiation and activation via the type I receptor.

CONCLUSION

Our findings demonstrate that IL-4 protects against osteoarthritis in a myeloid and STAT6-dependent manner. Further, IL-4 can promote an immunomodulatory microenvironment in which joint-resident macrophages polarize towards an M2 phenotype and efficiently clear pro-inflammatory debris, and osteoclasts maintain a homeostatic level of activity in subchondral bone. These findings support a role for IL-4 modulation of myeloid cell types in maintenance of joint health and identify a pathway that could provide therapeutic benefit for osteoarthritis.

Histomorphometric Quantitative Evaluation of Long-Term Risedronate Use in a Knee Osteoarthritis Rabbit Model

Osteoarthritis (OA) treatment is a major orthopedic challenge given that there is no ideal drug capable to reverse or stop the progression of the OA. In that regard, bisphosphonates have been proposed as potential disease-modifying drugs due to their possible chondroprotective effect related to obtaining a greater subchondral bone quality. However, their effectiveness in OA is still controversial and additionally, there is little evidence focused on their long-term effect in preclinical studies. The aim of this study was to evaluate the risedronate quantitative effect on articular and subchondral periarticular bone by histomorphometry, in an experimental rabbit model in an advanced stage of OA. Twenty-four adult New Zealand rabbits were included in the study. OA was surgically induced in one randomly chosen knee, using the contralateral as healthy control. Animals were divided into three groups (n = 8): placebo control group, sham surgery group and risedronate-treated group. After 24 weeks of treatment, cartilage and subchondral femorotibial pathology was evaluated by micro-computed tomography (micro-CT) and undecalcified histology. The research results demonstrated that the experimental animal model induced osteoarthritic changes in the operated joints, showing an increased cartilage thickness and fibrillation associated with underlying subchondral bone thinning and decreased trabecular bone quality. These changes were especially highlighted in the medial tibial compartments as a possible response to surgical instability. Regarding the trabecular analysis, significant correlations were found between 2D histomorphometry and 3D imaging micro-CT for the trabecular bone volume, trabecular separation, and the trabecular number. However, these associations were not strongly correlated, obtaining more precise measurements in the micro-CT analysis. Concerning the long-term risedronate treatment, it did not seem to have the capacity to reduce the osteoarthritic hypertrophic cartilage response and failed to diminish the superficial cartilage damage or prevent the trabecular bone loss. This study provides novel information about the quantitative effect of long-term risedronate use on synovial joint tissues.

Subchondral bone microenvironment in osteoarthritis and pain

Osteoarthritis comprises several joint disorders characterized by articular cartilage degeneration and persistent pain, causing disability and economic burden. The incidence of osteoarthritis is rapidly increasing worldwide due to aging and obesity trends. Basic and clinical research on osteoarthritis has been carried out for decades, but many questions remain unanswered. The exact role of subchondral bone during the initiation and progression osteoarthritis remains unclear. Accumulating evidence shows that subchondral bone lesions, including bone marrow edema and angiogenesis, develop earlier than cartilage degeneration. Clinical interventions targeting subchondral bone have shown therapeutic potential, while others targeting cartilage have yielded disappointing results. Abnormal subchondral bone remodeling, angiogenesis and sensory nerve innervation contribute directly or indirectly to cartilage destruction and pain. This review is about bone-cartilage crosstalk, the subchondral microenvironment and the critical role of both in osteoarthritis progression. It also provides an update on the pathogenesis of and interventions for osteoarthritis and future research targeting subchondral bone.

Bisphosphonates as disease-modifying drugs in osteoarthritis preclinical studies: a systematic review from 2000 to 2020

Bisphosphonates have been proposed as possible disease-modifying drugs in osteoarthritis. However, the evidence of their efficacy is poor and their outcomes presented a great heterogeneity. Therefore, the aim of this study is to systematically review the main effects of bisphosphonate use on synovial joint tissues and biochemical markers in preclinical studies over the past two decades (2000-2020). Three databases (Pubmed, Scopus, and Web of Science) were searched, and after screening, twenty-six studies with five different types of bisphosphonates were included in the review. The animal model selected, the type of bisphosphonate used, the therapy duration, and the main effects of individual drugs on synovial tissues were evaluated. Additionally, the quality and risk of bias assessments were performed using the Animals in Research Reporting In Vivo Experiments guidelines and the Systematic Review Centre for Laboratory animal Experimentation tool. Studies showed high variability in experimental designs. Consequently, the comparison of the findings in order to draw specific conclusions about the effectiveness of the drugs is complicated. However, the results of this systematic review suggested that bisphosphonates seemed to reduce the osteoarthritic changes in a dose-dependent manner showing better chondroprotective effects at high doses. Besides, a time-dependent efficacy was also detected in terms of cartilage status. One can conclude that the disease stage of the time-point of treatment initiation may constitute a key factor in the antiresorptive drug efficacy. Generally, we noted that bisphosphonate administration seemed to show positive subchondral bone conservation and fewer biomarker alterations. However, they did not appear to suppress the osteophyte development and their chondroprotective effect is highly variable among the studies. Bisphosphonates appeared to show a positive anti-inflammatory effect on the synovial membrane. However, only a few included publications were focused on their investigation. Regarding the therapy duration, there is a significant lack of evidence on evaluating their effectiveness in preclinical long-term studies and further experimental studies may be needed to examine the pharmacological response in these circumstances. This systematic review might help to clarify the efficacy of bisphosphonates and their function as disease-modifying treatments in osteoarthritis.

Emerging pharmaceutical therapies for osteoarthritis

The prevalence of osteoarthritis (OA) and the burden associated with the disease are steadily increasing worldwide, representing a major public health challenge for the coming decades. The lack of specific treatments for OA has led to it being recognized as a serious disease that has an unmet medical need. Advances in the understanding of OA pathophysiology have enabled the identification of a variety of potential therapeutic targets involved in the structural progression of OA, some of which are promising and under clinical investigation in randomized controlled trials. Emerging therapies include those targeting matrix-degrading proteases or senescent chondrocytes, promoting cartilage repair or limiting bone remodelling, local low-grade inflammation or Wnt signalling. In addition to these potentially disease-modifying OA drugs (DMOADs), several targets are being explored for the treatment of OA-related pain, such as nerve growth factor inhibitors. The results of these studies are expected to considerably reshape the landscape of OA management over the next few years. This Review describes the pathophysiological processes targeted by emerging therapies for OA, along with relevant clinical data and discussion of the main challenges for the further development of these therapies, to provide context for the latest advances in the field of pharmaceutical therapies for OA.

Refining surgical models of osteoarthritis in mice and rats alters pain phenotype but not joint pathology

The relationship between osteoarthritis (OA) structural change and pain is complex. Surgical models of OA in rodents are often rapid in onset, limiting mechanistic utility and translational validity. We aimed to investigate the effect of refining surgical small rodent models of OA on both joint pathology and pain behaviour. Adult male C57BL/6 mice (n = 76, 10-11 weeks of age at time of surgery) underwent either traditional (transection of the medial meniscotibial ligament [MMTL]) or modified (MMTL left intact, transection of the coronary ligaments) DMM surgery, or sham surgery. Adult male Sprague Dawley rats (n = 76, weight 175-199g) underwent either modified meniscal transection (MMNX) surgery (transection of the medial meniscus whilst the medial collateral ligament is left intact) or sham surgery. Pain behaviours (weight bearing asymmetry [in mice and rats] and paw withdrawal thresholds [in rats]) were measured pre-surgery and weekly up to 16 weeks post-surgery. Post-mortem knee joints were scored for cartilage damage, synovitis, and osteophyte size. There was a significant increase in weight bearing asymmetry from 13 weeks following traditional, but not modified, DMM surgery when compared to sham operated mice. Both traditional and modified DMM surgery led to similar joint pathology. There was significant pain behaviour from 6 weeks following MMNX model compared to sham operated control rats. Synovitis was significant 4 weeks after MMNX surgery, whereas significant chondropathy was first evident 8 weeks post-surgery, compared to sham controls. Pain behaviour is not always present despite significant changes in medial tibial plateau cartilage damage and synovitis, reflecting the heterogeneity seen in human OA. The development of a slowly progressing surgical model of OA pain in the rat suggests that synovitis precedes pain behaviour and that chondropathy is evident later, providing the foundations for future mechanistic studies into the disease.

Topographic modeling of early human osteoarthritis in sheep

Articular cartilage damage occurring during early osteoarthritis (OA) is a key event marking the development of the disease. Here, we modeled early human OA by gathering detailed spatiotemporal data from surgically induced knee OA development in sheep. We identified a specific topographical pattern of osteochondral changes instructed by a defined meniscal injury, showing that both cartilage and subchondral bone degeneration are initiated from the region adjacent to the damage. Alterations of the subarticular spongiosa arising locally and progressing globally disturbed the correlations of cartilage with subchondral bone seen at homeostasis and were indicative of disease progression. We validated our quantitative findings against human OA, showing a similar pattern of early OA correlating with regions of meniscal loss and an analogous late critical disturbance within the entire osteochondral unit. This translational model system can be used to elucidate mechanisms of OA development and provides a roadmap for investigating regenerative therapies.

Pharmacology of bisphosphonates in pain

The treatment of pain, in particular, chronic pain, remains a clinical challenge. This is particularly true for pain associated with severe or rare conditions, such as bone cancer pain, vulvodynia, or complex regional pain syndrome. Over the recent years, there is an increasing interest in the potential of bisphosphonates in the treatment of pain, although there are few papers describing antinociceptive and anti-hypersensitizing effects of bisphosphonates in various animal models of pain. There is also increasing evidence for clinical efficacy of bisphosphonates in chronic pain states, although the number of well-controlled studies is still limited. However, the mechanisms underlying the analgesic effects of bisphosphonates are still largely elusive. This review provides an overview of preclinical and clinical studies of bisphosphonates in pain and discusses various pharmacological mechanisms that have been postulated to explain their analgesic effects. LINKED ARTICLES: This article is part of a themed issue on The molecular pharmacology of bone and cancer-related bone diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.9/issuetoc.

A novel device to measure static hindlimb weight-bearing forces in pronograde rodents

BACKGROUND

Joint pain is composed of both spontaneous and movement-induced pain. In animal models, static bodyweight distribution is a surrogate for spontaneous joint pain. However, there are no commercially-available instruments that measure static bodyweight distribution in normal, pronograde rodents.

NEW METHOD

We designed a Static Horizontal Incapacitance Meter (SHIM) to measure bodyweight distribution in pronograde standing rodents. We assessed the device for feasibility, repeatability, and sensitivity to quantify hindlimb bodyweight distribution. Mice and rats with unilateral inflammatory pain induced by subcutaneous injections of capsaicin or Complete Freund's Adjuvant (CFA) into the plantar surface of the left hind paw were used to measure static weight-bearing. The ability to attenuate inflammatory pain-associated weight-bearing asymmetry was tested by administering a non-steroidal anti-inflammatory drug, meloxicam.

RESULTS

The SHIM's ability to detect significant reductions in limb loading on the injected hindlimb in mice and rats was validated using both acute and sub-chronic pain models. Treatment with meloxicam partially reversed CFA-induced effects.

COMPARISON WITH EXISTING METHODS

In contrast with assays that measure kinetic or static weight-bearing forces (e.g., walking, or standing at a 45 ° incline), the SHIM allows evaluation of weight-bearing in rodents that are standing at rest in their normal pronograde position.

CONCLUSIONS

The SHIM successfully detected: (a) asymmetric weight-bearing in acute and sub-chronic pain models; and (b) the analgesic effects of meloxicam. This study provides a novel tool to objectively evaluate limb use dysfunction in rodents.

The Effects of Annatto Tocotrienol Supplementation on Cartilage and Subchondral Bone in an Animal Model of Osteoarthritis Induced by Monosodium Iodoacetate

Osteoarthritis is a degenerative joint disease which primarily affects the articular cartilage and subchondral bones. Since there is an underlying localized inflammatory component in the pathogenesis of osteoarthritis, compounds like tocotrienol with anti-inflammatory properties may be able to retard its progression. This study aimed to determine the effects of oral tocotrienol supplementation on the articular cartilage and subchondral bone in a rat model of osteoarthritis induced by monosodium iodoacetate (MIA). Thirty male Sprague-Dawley rats (three-month-old) were randomized into five groups. Four groups were induced with osteoarthritis (single injection of MIA at week 0) and another served as the sham group. Three of the four groups with osteoarthritis were supplemented with annatto tocotrienol at 50, 100 and 150 mg/kg/day orally for five weeks. At week 5, all rats were sacrificed, and their tibial-femoral joints were harvested for analysis. The results indicated that the groups which received annatto tocotrienol at 100 and 150 mg/kg/day had lower histological scores and cartilage remodeling markers. Annatto tocotrienol at 150 mg/kg/day significantly lowered the osteocalcin levels and osteoclast surface of subchondral bone. In conclusion, annatto tocotrienol may potentially retard the progression of osteoarthritis. Future studies to confirm its mechanism of joint protection should be performed.

Effects of electromagnetic fields on osteoarthritis

Osteoarthritis (OA), characterized by joint malfunction and chronic disability, is the most common form of arthritis. The pathogenesis of OA is unclear, yet studies have shown that it is due to an imbalance between the synthesis and decomposition of chondrocytes, cell matrices and subchondral bone, which leads to the degeneration of articular cartilage. Currently, there are many therapies that can be used to treat OA, including the use of pulsed electromagnetic fields (PEMFs). PEMFs stimulate proliferation of chondrocytes and exert a protective effect on the catabolic environment. Furthermore, this technique is beneficial for subchondral trabecular bone microarchitecture and the prevention of subchondral bone loss, ultimately blocking the progression of OA. However, it is still unknown whether PEMFs could be used to treat OA in the clinic. Furthermore, the deeper signaling pathways underlying the mechanism by which PEMFs influence OA remain unclear.

Protective Effect of Alendronate on Lumbar Facet Degeneration in Ovariectomized Rats

Background

Facet joint degeneration (FJD) is a potential source of lower back pain, and estrogen deficiency can accelerate FJD. The present study aimed to investigate the effects of alendronate (ALN) on FJD induced by ovariectomy (OVX) in rats.

Material/Methods

Thirty female Sprague-Dawley rats underwent either bilateral OVX (n=20) or sham surgery (n=10). The OVX rats subsequently received either subcutaneous ALN (70 μg/kg/week) or vehicle for 12 weeks. Subchondral bone mass and microarchitecture were evaluated by micro-computed tomography. Cartilage degradation was evaluated by toluidine blue staining and histological scoring.

Results

Compared with the Sham group, the OVX group had significantly decreased bone mineral density, bone volume/trabecular volume, and trabecular thickness, significantly increased trabecular separation in subchondral bone, and significantly higher histological score for cartilage degeneration, particularly loss of cartilage thickness. ALN treatment significantly reversed the changes in subchondral bone, preserved cartilage thickness, and reduced the histological score. Immunohistochemical analyses showed significantly decreased expression of ADAMTS-4, MMP-13, and caspase-3 in the OVX+ALN group compared with the OVX group.

Conclusions

Treatment with ALN suppressed bone loss, subchondral bone architecture deterioration, and cartilage degeneration in OVX rats, which can be explained by roles of ALN in preservation of subchondral bone mass and microarchitecture, and counteraction of catabolism and chondrocyte apoptosis in cartilage.

Antioxidative nanofullerol inhibits macrophage activation and development of osteoarthritis in rats

Background: There is emerging evidence which suggests that cellular ROS including nitric oxide (NO) are important mediators for inflammation and osteoarthritis (OA). Water-soluble polyhydroxylated fullerene C60 (fullerol) nanoparticle has been demonstrated to have an outstanding ability to scavenge ROS.

Purpose: The objective of this study is to assess the effects of fullerol on inflammation and OA by in vitro and in vivo studies.

Methods: For in vitro experiments, primary mouse peritoneal macrophages and a macrophage cell line RAW264.7 were stimulated to inflammatory phenotypes by lipopolysaccharide (LPS) in the presence of fullerol. For the animal study, OA model was created by intra-articular injection of monoiodoacetate into the knee joints of rats and fullerol was intravenously injected immediately after OA induction.

Results: NO production and pro-inflammatory gene expression induced by LPS was significantly diminished by fullerol in both macrophage cell types. Meanwhile, fullerol could remarkably reduce phosphorylation of p38 mitogen-activated protein kinase, and protein level of transcription factors nuclear factor-kappaB and forkhead box transcription factor 1 within the nucleus. The animal study delineated that systematic administration of fullerol prevented OA, inhibiting inflammation of synovial membranes and the damage toward the cartilage chondrocytes in the OA joints.

Conclusion: Antioxidative fullerol may have a potential therapeutic application for OA.

Penalized-Likelihood Reconstruction With High-Fidelity Measurement Models for High-Resolution Cone-Beam Imaging

We present a novel reconstruction algorithm based on a general cone-beam CT forward model, which is capable of incorporating the blur and noise correlations that are exhibited in flat-panel CBCT measurement data. Specifically, the proposed model may include scintillator blur, focal-spot blur, and noise correlations due to light spread in the scintillator. The proposed algorithm (GPL-BC) uses a Gaussian Penalized-Likelihood objective function, which incorporates models of blur and correlated noise. In a simulation study, GPL-BC was able to achieve lower bias as compared with deblurring followed by FDK as well as a model-based reconstruction method without integration of measurement blur. In the same study, GPL-BC was able to achieve better line-pair reconstructions (in terms of segmented-image accuracy) as compared with deblurring followed by FDK, a model-based method without blur, and a model-based method with blur but not noise correlations. A prototype extremities quantitative cone-beam CT test-bench was used to image a physical sample of human trabecular bone. These data were used to compare reconstructions using the proposed method and model-based methods without blur and/or correlation to a registered CT image of the same bone sample. The GPL-BC reconstructions resulted in more accurate trabecular bone segmentation. Multiple trabecular bone metrics, including trabecular thickness (Tb.Th.) were computed for each reconstruction approach as well as the CT volume. The GPL-BC reconstruction provided the most accurate Tb.Th. measurement, 0.255 mm, as compared with the CT derived value of 0.193 mm, followed by the GPL-B reconstruction, the GPL-I reconstruction, and then the FDK reconstruction (0.271 mm, 0.309 mm, and 0.335 mm, respectively).

Are bisphosphonates efficacious in knee osteoarthritis? A meta-analysis of randomized controlled trials

OBJECTIVE

To clarify the effects of bisphosphonates in knee osteoarthritis (OA) using an up-to-date meta-analysis of randomized controlled trials (RCTs).

DESIGN

The protocol is registered in PROSPERO (CRD42017073449). We searched MEDLINE, EMBASE, Google Scholar, Web of Science, and Cochrane Database from inception until August 2017. We included only RCTs comparing any bisphosphonates vs placebo in knee OA patients and reporting validated pain and function scales, radiographic progression, and adverse events (AEs) outcomes. We excluded studies using active comparators or concomitant medications besides non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen. We calculated standardized mean differences (SMDs) to account for variation in outcome scales. Random effects meta-analyses were performed.

RESULTS

We included seven RCTs (3013 patients, 69% female); most patients (N = 2767) received oral risedronate. No pain or function outcomes, regardless of dose, route, time point or measuring instrument, revealed statistically significant results (end of trial pain SMD = -0.16 [95% confidence interval (CI): -0.34, 0.02]). Similarly, we found no statistically significant effect on radiographic progression (risk ratio = 0.98 [95% CI: 0.77, 1.26]). One small RCT in patients with bone marrow lesions (BMLs) suggested a reduction in BML size at 6 months. Bisphosphonates displayed good tolerability, with no statistically significant differences in AE outcomes vs placebo.

CONCLUSIONS

Contrary to prior reviews, our analysis showed that bisphosphonates neither provide symptomatic relief nor defer radiographic progression in knee OA. However, these agents may still be beneficial in certain subsets of patients who display high rates of subchondral bone turnover. Future studies should be directed at defining such OA subsets and investigating the effects of bisphosphonates in those patients.

A rat model of knee osteoarthritis suitable for electroacupuncture study

Acupuncture is widely used for knee osteoarthritis (KOA) treatment in clinical practice. In the present study, we aimed to set a standard KOA animal model for electroacupuncture (EA) study and provide an acupuncture recipe for further KOA studies. Rats intra-articularly administered monosodium iodoacetate (MIA, 0.3, 1 or 3 mg respectively, n=12 each) were evaluated for pain-like behavior: paw withdrawal mechanical threshold, weight bearing deficit, and joint pathological changes (OARSI score) until 28 days after injury. Then by using the suitable dose (1 mg MIA), therapeutic effects of EA treatment (bilateral ST36 and ST35 acupoints, 2/10 Hz, 30 min/d, 6d/w, 2w) were evaluated in 3 groups (n=16 each): Early-on EA, Mid-term EA and Delayed EA, in which EA was started on day 1, day 7 or day 14 after MIA injection. Both 1 mg and 3 mg MIA induced significant joint damage and persistent pain behavior. But animals accepted 3 mg MIA rapidly developed cartilage and bone damage within 14 days. Early-on EA treatment provided significant pain relief and joint structure preservation in KOA rats. Mid-term EA treatment only reduced pain, while delayed EA treatment resulted in no effects in both aspects. 1 mg of MIA produces steady pain behavior and progressive joint damage, which was suitable for EA treatment evaluation. Early-on EA treatment provided both joint protection and pain reduction, while Mid-term EA could only be used for studying EA-induced analgesia in KOA.

Contrast enhanced μCT imaging of early articular changes in a pre-clinical model of osteoarthritis

OBJECTIVE

The objective of this study was to characterize early osteoarthritis (OA) development in cartilage and bone tissues in the rat medial meniscus transection (MMT) model using non-destructive equilibrium partitioning of an ionic contrast agent micro-computed tomography (EPIC-μCT) imaging. Cartilage fibrillation, one of the first physiological developments in OA, was quantified in the rat tibial plateau as three-dimensional (3D) cartilage surface roughness using a custom surface-rendering algorithm.

METHODS

Male Lewis rats underwent MMT or sham-operation in the left leg. At 1- and 3-weeks post-surgery, the animals (n = 7-8 per group) were euthanized and the left legs were scanned using EPIC-μCT imaging to quantify cartilage and bone parameters. In addition, a custom algorithm was developed to measure the roughness of 3D surfaces. This algorithm was validated and used to quantify cartilage surface roughness changes as a function of time post-surgery.

RESULTS

MMT surgery resulted in significantly greater cartilage damage and subchondral bone sclerosis with the damage increasing in both severity and area from 1- to 3-weeks post-surgery. Analysis of rendered 3D surfaces could accurately distinguish early changes in joints developing OA, detecting significant increases of 45% and 124% in surface roughness at 1- and 3-weeks post-surgery respectively.

CONCLUSION

Disease progression in the MMT model progresses sequentially through changes in the cartilage articular surface, extracellular matrix composition, and then osteophyte mineralization and subchondral bone sclerosis. Cartilage surface roughness is a quantitative, early indicator of degenerative joint disease in small animal OA models and can potentially be used to evaluate therapeutic strategies.

Quantitative evaluation of subchondral bone microarchitecture in knee osteoarthritis using 3T MRI

Background

Osteoarthritis (OA) is now increasingly recognized as being related to the whole joint instead of the cartilage alone. In particular, the importance of subchondral bone in OA pathogenesis has drawn a lot of interest. The aim of this study is to investigate subchondral bone microstructural features in two femoral condyles of human knee osteoarthritis.

Methods

Eighty subjects were enrolled in our study and divided into three groups: without OA (group 0), mild OA (group 1), and severe OA (group 2). Sagittal 3D Balanced Fast Field Echo (3D–FFE) images were obtained by 3T MRI to quantify trabecular bone structure, and sagittal FatSat 3D Fast Field Echo (3D–FFE) images were acquired to assess cartilage thickness. Trabecular bone parameters, including bone volume fraction (BVF), erosion index (EI) and the trabecular plate-to-rod ratio (SCR), and trabecular thickness were evaluated using digital topological analysis. Subchondral bone and cartilage parameters between different groups and different locations were compared, and their correlations were analyzed.

Results

Within two femoral condyles, subchondral bone structure was deteriorated in mild OA, showing a lower BVF (−0.011 to −0.014 P < 0.001), a higher EI (0.346 to 0.310 P < 0.001), a lower SCR (−0.581 to −0.542 P < 0.001)) and lower trabecular thickness (−6.588 to −4.759 P < 0.05). In severe OA, BVF was further decreased, but EI, SCR and trabecular thickness showed no significant difference than mild OA(P > 0.05). Moreover, there was a lower BVF, SCR and higher EI in the medial femoral condyle in each group. Interestingly, cartilage attrition mainly occurred in the medial femoral condyle. Medial cartilage thickness was not only positively correlated with the ipsilateral femoral BVF (r = 0.321 P = 0.004) but also with the opposite femoral BVF (r = 0.270 P = 0.015).

Conclusions

Our results indicated that deterioration in the trabecular bone structure in both femoral condyles could more sensitively reveal early OA, and BVF could be a better biomarker to evaluate OA severity.

Quantitative histological grading methods to assess subchondral bone and synovium changes subsequent to medial meniscus transection in the rat

AIM OF THE STUDY

The importance of the medial meniscus to knee health is demonstrated by studies which show meniscus injuries significantly increase the likelihood of developing osteoarthritis (OA), and knee OA can be modeled in rodents using simulated meniscus injuries. Traditionally, histological assessments of OA in these models have focused on damage to the articular cartilage; however, OA is now viewed as a disease of the entire joint as an organ system. The aim of this study was to develop quantitative histological measures of bone and synovial changes in a rat medial meniscus injury model of knee OA.

MATERIALS AND METHODS

To initiate OA, a medial meniscus transection (MMT) and a medial collateral ligament transection (MCLT) were performed in 32 male Lewis rats (MMT group). MCLT alone served as the sham procedure in 32 additional rats (MCLT sham group). At weeks 1, 2, 4, and 6 post-surgery, histological assessment of subchondral bone and synovium was performed (n = 8 per group per time point).

RESULTS

Trabecular bone area and the ossification width at the osteochondral interface increased in both the MMT and MCLT groups. Subintimal synovial cell morphology also changed in MMT and MCLT groups relative to naïve animals.

CONCLUSIONS

OA affects the joint as an organ system, and quantifying changes throughout an entire joint can improve our understanding of the relationship between joint destruction and painful OA symptoms following meniscus injury.

Measuring and realizing the translational significance of preclinical in vivo studies of painful osteoarthritis

In this communication, we discuss some key issues surrounding the translation of preclinical efficacy studies in models of painful osteoarthritis (OA) to the clinical arena. We highlight potential pitfalls which could negatively impact successful translation. These include lack of alignment between a model + endpoint and the intended clinical population, employing testing strategies in animals that are not appropriate for the targeted human population such as pre-emptive treatment and lastly, underestimating the magnitude of the efficacy signal in animals that may be needed to see an effect in the clinical population. Through careful analysis, we highlight the importance of each pitfall by providing relevant examples that will hopefully improve future chances of optimizing translation in the area of OA pain research. We advocate advancing publications directed at comparing methods, outcomes and conclusions between preclinical and clinical studies, regardless of whether the findings are positive or negative, are important for improving the potential for a desired successful translation from the bench to bedside.

Osteoarthritis of the hip joint in elderly patients is most commonly atrophic, with low parameters of acetabular dysplasia and possible involvement of osteoporosis

As elderly patients with hip osteoarthritis aged, acetabular dysplasia parameters decreased (Sharp's angle, acetabular roof obliquity angle, and acetabular head index) and the incidence of the atrophic type increased. Vertebral body fracture was more frequent in the atrophic type, suggesting the involvement of osteoporosis at the onset of hip osteoarthritis.

INTRODUCTION

Osteoarthritis (OA) is associated with increased bone formation at a local site. However, excessive bone resorption has also been found to occur in the early stages of OA. Osteoporosis may be involved in the onset of OA in elderly patients. We conducted a cross-sectional radiographic study of patients with hip OA and examined the association between age and factors of acetabular dysplasia (Sharp's angle, acetabular roof obliquity angle, and acetabular head index) as well as the osteoblastic response to determine the potential involvement of osteoporosis.

METHODS

This study included 366 patients (58 men, 308 women) who had undergone total hip arthroplasty for the diagnosis of hip OA. We measured the parameters of acetabular dysplasia using preoperative frontal X-ray images and evaluated each patient according to Bombelli classification of OA (hypertrophic, normotrophic, or atrophic type).

RESULTS

As the patients aged, the parameters of acetabular dysplasia decreased. The incidence of the atrophic type of OA was significantly higher in older patients. Vertebral body fractures were more frequent in the atrophic type than in the other types. Additionally, the index of acetabular dysplasia was lower in the atrophic type. By contrast, the hypertrophic type was present in relatively younger patients and was associated with an increased index of acetabular dysplasia.

CONCLUSION

In elderly patients with hip OA, the parameters of acetabular dysplasia decreased and the incidence of the atrophic type increased as the patients aged. The frequency of vertebral body fracture was high in patients with the atrophic type, suggesting the involvement of osteoporosis in the onset of hip OA.

Automated selection of bone texture regions on hand radiographs: Data from the Osteoarthritis Initiative

Manual selection of finger trabecular bone texture regions on hand X-ray images is time-consuming, tedious, and observer-dependent. Therefore, we developed an automated method for the region selection. The method selects square trabecular bone regions of interest above and below the second to fifth distal and proximal interphalangeal joints. Two regions are selected per joint (16 regions per hand). The method consists of four integral parts: (1) segmentation of a radiograph into hand and background, (2) identification of finger regions, (3) localization of center points of heads of distal phalanges and the distal interphalangeal, proximal interphalangeal, and metacarpophalangeal joints, and (4) placement of the regions of interest under and above the distal and proximal interphalangeal joints. A gold standard was constructed from regions selected by two observers on 40 hand X-ray images taken from Osteoarthritis Initiative cohort. Datasets of 520 images were generated from the 40 images to study the effects of hand and finger positioning. The accuracy in regions selection and the agreement in calculating five directional fractal parameters were evaluated against the gold standard. The accuracy, agreement, and effects of hand and finger positioning were measured using similarity index (0 for no overlap and 1 for entire overlap) and interclass correlation coefficient as appropriate. A high accuracy in selecting regions (similarity index ≥ 0.79) and a good agreement in fractal parameters (interclass correlation coefficient ≥ 0.58) were achieved. Hand and finger positioning did not affect considerably the region selection (similarity index ≥ 0.70). These results indicate that the method developed selects bone regions on hand X-ray images with accuracy sufficient for fractal analyses of bone texture.

Effects of bisphosphonates on mandibular condyle of ovariectomized osteoporotic rats using micro-ct and histomorphometric analysis

OBJECTIVE

To evaluate microarchitectural changes in condylar cartilage and associated subchondral bone after bisphosphonates treatment using an ovariectomized (OVX) osteoporosis rat model.

METHODS

Thirty six-month-old female Sprague-Dawley rats were randomly divided into sham, OVX, and risedronate (RIS)-treated groups. Both OVX and RIS groups received bilateral ovariectomy. OVX group was treated subcutaneously with saline, whereas RIS group received risedronate treatment (2.4 μg/kg) subcutaneously for 3 months. At the end of 3 months, animals were sacrificed and the entire condyles were harvested for micro-CT and histological analyses. Immunohistochemistry (IHC) was performed to assess the expression of type I/II collagen protein by semiquantitative imaging analysis.

RESULTS

Micro-CT analysis showed OVX group had significant condylar subchondral bone loss compared to sham as shown by significant decrease in bone volume fraction (P = 0.028), trabecular thickness (P = 0.041), and significant increase in trabecular spacing (P = 0.003). In RIS group, partial inhibition of OVX-induced bone loss was detected. HE staining showed proliferative layer of condylar cartilage reduced, while hypertrophic chondrocyte layer increased significantly in RIS group compared to sham and OVX groups. IHC showed reduced expression of Col I in both the OVX and RIS groups, whereas expression of Col II was reduced in the OVX group but increased in the RIS group.

CONCLUSION

Our findings suggest that systemic bisphosphonate treatment influences the structure and ossification of condylar cartilage and it has a dual action on condyle in a postmenopausal osteoporosis rat model which raises the concerns for the potential side effects of BPs on condyle to elder patients.

Kartogenin treatment prevented joint degeneration in a rodent model of osteoarthritis: A pilot study

Osteoarthritis (OA) is a major degenerative joint disease characterized by progressive loss of articular cartilage, synovitis, subchondral bone changes, and osteophyte formation. Currently there is no treatment for OA except temporary pain relief and end-stage joint replacement surgery. We performed a pilot study to determine the effect of kartogenin (KGN, a small molecule) on both cartilage and subchondral bone in a rat model of OA using multimodal imaging techniques. OA was induced in rats (OA and KGN treatment group) by anterior cruciate ligament transection (ACLT) surgery in the right knee joint. Sham surgery was performed on the right knee joint of control group rats. KGN group rats received weekly intra-articular injection of 125 μM KGN 1 week after surgery until week 12. All rats underwent in vivo magnetic resonance imaging (MRI) at 3, 6, and 12 weeks after surgery. Quantitative MR relaxation measures (T_1ρ and T₂ ) were determined to evaluate changes in articular cartilage. Cartilage and bone turnover markers (COMP and CTX-I) were determined at baseline, 3, 6, and 12 weeks. Animals were sacrificed at week 12 and the knee joints were removed for micro-computed tomography (micro-CT) and histology. KGN treatment significantly lowered the T_1ρ and T₂ relaxation times indicating decreased cartilage degradation. KGN treatment significantly decreased COMP and CTX-I levels indicating decreased cartilage and bone turnover rate. KGN treatment also prevented subchondral bone changes in the ACLT rat model of OA. Thus, kartogenin is a potential drug to prevent joint deterioration in post-traumatic OA. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1780-1789, 2016.

Subchondral bone sclerosis and cancellous bone loss following OA induction depend on the underlying bone phenotype

OBJECTIVES

Osteoarthritis (OA) is increasingly considered a disease of the whole joint, yet the interplay between the articular cartilage and the subchondral bone remains obscure. We here set out to investigate the impact of bone mass on the progression of surgically induced knee OA in the mouse.

METHODS

OA was induced in the right knees of female C57BL/6 (low bone mass) and STR/ort (high bone mass) mice via anterior cruciate ligament transection and destabilization of the medial meniscus. At 36 weeks of age, left and right knee joints were histologically compared for cartilage degeneration and via microCT analysis for subchondral bone plate thickness. In addition, femora were analyzed for bone mass at diaphysis and distal meta- and epiphysis.

RESULTS

The severity of cartilage deterioration did not differ under high and low bone mass conditions. However, the extent of bone sclerosis differed and was proportional to the baseline subchondral bone plate thickness. Moreover, the cancellous bone loss following OA progression was inversely related to the bone mass: high bone mass restricted the loss to the epiphysis, whereas low bone mass allowed for a more widespread loss extending into the metaphysis.

CONCLUSIONS

Our results suggest that cartilage degeneration is independent of the underlying bone mass. In contrast, subchondral bone remodeling associated with OA progression seem to correlate with the initial bone mass and suggest an enhanced crosstalk between the deteriorating cartilage and the subchondral bone under low bone mass conditions.

Osteoclasts are recruited to the subchondral bone in naturally occurring post-traumatic equine carpal osteoarthritis and may contribute to cartilage degradation

The role of osteoclasts in osteochondral degeneration in osteoarthritis (OA) has rarely been investigated in spontaneous disease or animal models of OA.

OBJECTIVE

The objectives of the current study were to investigate osteoclast density and location in post-traumatic OA (PTOA) and control specimens from racehorses.

METHOD

Cores were harvested from a site in the equine third carpal bone, that undergoes repetitive, high intensity loading. Histological and immunohistochemical (Cathepsin K and Receptor-activator of Nuclear Factor kappa-β ligand (RANKL)) stained sections were scored (global and subregional) and the osteoclast density calculated. The cartilage histological scores were compared with osteoclast density and RANKL scores.

RESULTS

There was a greater density of osteoclasts in PTOA samples and they were preferentially located in the subchondral bone plate. RANKL scores positively correlated to the scores of cartilage degeneration and the osteoclast density. The relationship between hyaline articular cartilage RANKL score and osteoclast density was stronger than that of the subchondral bone RANKL score suggesting that cartilage RANKL may have a role in recruiting osteoclasts. The RANKL score in the articular calcified cartilage correlated with the number of microcracks also suggesting that osteoclasts recruited by RANKL may contribute to calcified cartilage degeneration in PTOA.

CONCLUSION

Our results support the hypothesis that osteoclasts are recruited during the progression of spontaneous equine carpal PTOA by cartilage RANKL, contributing to calcified cartilage microcracks and focal subchondral bone loss.

Effect of antiresorptive and anabolic bone therapy on development of osteoarthritis in a posttraumatic rat model of OA

Introduction

Osteoarthritis (OA) is a leading cause of disability, but despite the high unmet clinical need and extensive research seeking dependable therapeutic interventions, no proven disease-modifying treatment for OA is currently available. Due to the close interaction and interplay between the articular cartilage and the subchondral bone plate, it has been hypothesized that antiresorptive drugs can also reduce cartilage degradation, inhibit excessive turnover of the subchondral bone plate, prevent osteophyte formation, and/or that bone anabolic drugs might also stimulate cartilage synthesis by chondrocytes and preserve cartilage integrity. The benefit of intensive zoledronate (Zol) and parathyroid hormone (PTH) therapy for bone and cartilage metabolism was evaluated in a rat model of OA.

Methods

Medial meniscectomy (MM) was used to induce OA in male Lewis rats. Therapy with Zol and human PTH was initiated immediately after surgery. A dynamic weight-bearing (DWB) system was deployed to evaluate the weight-bearing capacity of the front and hind legs. At the end of the 10-week study, the rats were euthanized and the cartilage pathology was evaluated by contrast (Hexabrix)-enhanced μCT imaging and traditional histology. Bone tissue was evaluated at the tibial metaphysis and epiphysis, including the subchondral bone. Histological techniques and dynamic histomorphometry were used to evaluate cartilage morphology and bone mineralization.

Results

The results of this study highlight the complex changes in bone metabolism in different bone compartments influenced by local factors, including inflammation, pain and mechanical loads. Surgery caused severe and extensive deterioration of the articular cartilage at the medial tibial plateau, as evidenced by contrast-enhanced μCT and histology. The study results showed the negative impact of MM surgery on the weight-bearing capacity of the operated limb, which was not corrected by treatment. Although both Zol and PTH improved subchondral bone mass and Zol reduced serum CTX-II level, both treatments failed to prevent or correct cartilage deterioration, osteophyte formation and mechanical incapacity.

Conclusions

The various methods utilized in this study showed that aggressive treatment with Zol and PTH did not have the capacity to prevent or correct the deterioration of the hyaline cartilage, thickening of the subchondral bone plate, osteophyte formation or the mechanical incapacity of the osteoarthritic knee.

On the predictive utility of animal models of osteoarthritis

Animal models of osteoarthritis are extensively used for investigating disease pathways and for preclinical testing of novel therapies. Their predictive utility, however, has often been questioned, mainly because preclinical efficacy of novel therapeutics is poorly translated in clinical trials. In the current narrative review, we consider the preclinical models that were used to support undertaking clinical trials for disease-modifying osteoarthritis drugs, and compare outcomes between clinical and preclinical studies. We discuss this in light of the 1999 Food and Drug Administration draft guidelines for industry for use in the development of drugs, devices, and biological products intended for the treatment of osteoarthritis, which raised five considerations on the usefulness of osteoarthritis models. We systematically discuss what has been learnt regarding these five points since 1999, with emphasis on replicating distinct risk factors and subtypes of human osteoarthritis, and on comprehensive evaluation of the disease in animals, including pathology of all joint tissues, biomarker analysis, and assessment of pain and joint function. Finally, we discuss lessons learnt and propose some recommendations for how the evidence from preclinical research might be strengthened with a view to improving success in clinical translation.

7T MRI detects deterioration in subchondral bone microarchitecture in subjects with mild knee osteoarthritis as compared with healthy controls

PURPOSE

To determine how subchondral bone microarchitecture is altered in patients with mild knee osteoarthritis.

MATERIALS AND METHODS

This study had Institutional Review Board approval. We recruited 24 subjects with mild radiographic knee osteoarthritis and 16 healthy controls. The distal femur was scanned at 7T using a high-resolution 3D FLASH sequence. We applied digital topological analysis to assess bone volume fraction, markers of trabecular number (skeleton density), trabecular network osteoclastic resorption (erosion index), plate-like structure (surface), rod-like structure (curve), and plate-to-rod ratio (surface-curve ratio). We used two-tailed t-tests to compare differences between osteoarthritis subjects and controls.

RESULTS

7T magnetic resonance imaging (MRI) detected deterioration in subchondral bone microarchitecture in both medial and lateral femoral condyles in osteoarthritis subjects as compared with controls. This was manifested by lower bone volume fraction (-1.03% to -5.43%, P < 0.04), higher erosion index (+8.49 to +22.76%, P < 0.04), lower surface number (-2.31% to -9.63%, P < 0.007), higher curve number (+6.85% to +16.93%, P < 0.03), and lower plate-to-rod ratio (-7.92% to -21.71%, P < 0.05).

CONCLUSION

The results provide further support for the concept that poor subchondral bone quality is associated with osteoarthritis and may serve as a potential therapeutic target for osteoarthritis interventions. J. Magn. Reson. Imaging 2015;41:1311-1317. © 2014 Wiley Periodicals, Inc.

Effect of alendronate on post-traumatic osteoarthritis induced by anterior cruciate ligament rupture in mice

Introduction

Previous studies in animal models of osteoarthritis suggest that alendronate (ALN) has antiresorptive and chondroprotective effects, and can reduce osteophyte formation. However, these studies used non-physiologic injury methods, and did not investigate early time points during which bone is rapidly remodeled prior to cartilage degeneration. The current study utilized a non-invasive model of knee injury in mice to investigate the effect of ALN treatment on subchondral bone changes, articular cartilage degeneration, and osteophyte formation following injury.

Methods

Non-invasive knee injury via tibial compression overload or sham injury was performed on a total of 90 mice. Mice were treated with twice weekly subcutaneous injections of low-dose ALN (40 μg/kg/dose), high-dose ALN (1,000 μg/kg/dose), or vehicle, starting immediately after injury until sacrifice at 7, 14 or 56 days. Trabecular bone of the femoral epiphysis, subchondral cortical bone, and osteophyte volume were quantified using micro-computed tomography (μCT). Whole-joint histology was performed at all time points to analyze articular cartilage and joint degeneration. Blood was collected at sacrifice, and serum was analyzed for biomarkers of bone formation and resorption.

Results

μCT analysis revealed significant loss of trabecular bone from the femoral epiphysis 7 and 14 days post-injury, which was effectively prevented by high-dose ALN treatment. High-dose ALN treatment was also able to reduce subchondral bone thickening 56 days post-injury, and was able to partially preserve articular cartilage 14 days post-injury. However, ALN treatment was not able to reduce osteophyte formation at 56 days post-injury, nor was it able to prevent articular cartilage and joint degeneration at this time point. Analysis of serum biomarkers revealed an increase in bone resorption at 7 and 14 days post-injury, with no change in bone formation at any time points.

Conclusions

High-dose ALN treatment was able to prevent early trabecular bone loss and cartilage degeneration following non-invasive knee injury, but was not able to mitigate long-term joint degeneration. These data contribute to understanding the effect of bisphosphonates on the development of osteoarthritis, and may support the use of anti-resorptive drugs to prevent joint degeneration following injury, although further investigation is warranted.

Chondroprotective effect of high-dose zoledronic acid: An experimental study in a rabbit model of osteoarthritis

To address the need to impact the subchondral bone-articular cartilage interaction for the treatment of degenerative osteoarthritis (OA), bisphosphonates may be used as a means to inhibit the subchondral bone resorption. The purpose of the present study is to evaluate the chondroprotective effect of zoledronic acid (ZOL) in a model of OA. Eighteen adult male rabbits underwent an anterior cruciate ligament transection and were separated into two groups: ZOL group (n=10) received 0.6 mg/kg intravenous injection of ZOL on day 1, 15, and 29 and placebo group (n=8) received saline. The animals were euthanized at 8 weeks. Macroscopically, the ZOL group had significantly milder ulcerations, cartilage softening and fibrillation compared to the placebo group. Microscopically, morphology of the articular cartilage was better in the ZOL treated group compared with the placebo group, without complete disorganization in any section of the ZOL group. Furthermore, the chondrocytes in the ZOL treated group were mainly cloning, indicating cartilage repairing and regeneration process, while in the placebo group hypocellularity predominated. Additionally, subchondral necrosis was evident in some specimens of the placebo group. Zoledronic acid, in a high-dose regimen, proved to be chondroprotective in a well-established animal model of OA.

Parathyroid hormone (1-34) prevents cartilage degradation and preserves subchondral bone micro-architecture in guinea pigs with spontaneous osteoarthritis

OBJECTIVE

To assess whether parathyroid hormone (PTH) (1-34) could improve the micro-structure of subchondral bone, and retard cartilage degradation in a naturally occurring Osteoarthritis (OA) model.

DESIGN

Forty-eight 1-month-old guinea pigs were divided into two groups: 32 were treated by normal saline (NS) and sacrificed at 1, 3, 6 and 9 months of age; the other 16 received PTH (1-34) from 3 months, and were sacrificed at 6 and 9 months. Masson staining and the Osteoarthritis Research Society International (OARSI) grade scores were used to assess cartilage degradation. Immunohistochemistry analyses of type-II collagen, matrix metalloproteinases-13 (MMP-13) and sclerostin (SOST) in the cartilage, osteoprotegerin (OPG) and receptor activator of nuclear factor-kB ligand (RANKL) and PTH receptor (PTH1R) in the cartilage and subchondral bone were performed. Subchondral bone micro-architecture was assessed by micro-computed tomography (micro-CT).

RESULTS

Histological analyses revealed OA occurred at 3 months of age and was more severe with increasing age, and PTH (1-34) reduced the OARSI scores at 6 and 9 months of age. Micro-CT analysis indicated that PTH (1-34) treatment increased the bone volume ratio and bone mineral density (BMD), while retarding the subchondral trabecular bone micro-architectural changes from rod-like to plate-like. Immunohistochemical staining demonstrated that PTH (1-34) treatment increased type-II collagen expression and decreased SOST and MMP-13 expression in the cartilage, while elevating the PTH1R, OPG/RANKL expression ratio in the cartilage and subchondral trabecular bone when compared with the control groups.

CONCLUSIONS

PTH (1-34) can prevent cartilage damage progression and retard the deterioration of subchondral trabecular bone in guinea pigs.

Age dependent changes in cartilage matrix, subchondral bone mass, and estradiol levels in blood serum, in naturally occurring osteoarthritis in Guinea pigs

The Dunkin Hartley (DH) guinea pig is a widely used naturally occurring osteoarthritis model. The aim of this study was to provide detailed evidence of age-related changes in articular cartilage, subchondral bone mineral density, and estradiol levels. We studied the female Dunkin Hartley guinea pigs at 1, 3, 6, 9, and 12 months of age (eight animals in each group). Histological analysis were used to identify degenerative cartilage and electron microscopy was performed to further observe the ultrastructure. Estradiol expression levels in serum were assessed, and matrix metalloproteinase 3 and glycosaminoglycan expression in cartilage was performed by immunohistochemistry. Bone mineral density of the tibia subchondral bone was measured using dual X-ray absorptiometry. Histological analysis showed that the degeneration of articular cartilage grew more severe with increasing age starting at 3 months, coupled with the loss of normal cells and an increase in degenerated cells. Serum estradiol levels increased with age from 1 to 6 months and thereafter remained stable from 6 to 12 months. Matrix metalloproteinase 3 expression in cartilage increased with age, but no significant difference was found in glycosaminoglycan expression between 1- and 3-month old animals. The bone mineral density of the tibia subchondral bone increased with age before reaching a stable value at 9 months of age. Age-related articular cartilage degeneration occurred in Dunkin Hartley guinea pigs beginning at 3 months of age, while no directly positive or negative correlation between osteoarthritis progression and estradiol serum level or subchondral bone mineral density was discovered.

Bone-cartilage interface crosstalk in osteoarthritis: potential pathways and future therapeutic strategies

Currently, osteoarthritis (OA) is considered a disease of the entire joint, which is not simply a process of wear and tear but rather abnormal remodelling and joint failure of an organ. The bone-cartilage interface is therefore a functioning synergistic unit, with a close physical association between subchondral bone and cartilage suggesting the existence of biochemical and molecular crosstalk across the OA interface. The crosstalk at the bone-cartilage interface may be elevated in OA in vivo and in vitro. Increased vascularisation and formation of microcracks associated with abnormal bone remodelling in joints during OA facilitate molecular transport from cartilage to bone and vice versa. Recent reports suggest that several critical signalling pathways and biological factors are key regulators and activate cellular and molecular processes in crosstalk among joint compartments. Therapeutic interventions including angiogenesis inhibitors, agonists/antagonists of molecules and drugs targeting bone remodelling are potential candidates for this interaction. This review summarised the premise for the presence of crosstalk in bone-cartilage interface as well as the current knowledge of the major signalling pathways and molecular interactions that regulate OA progression. A better understanding of crosstalk in bone-cartilage interface may lead to development of more effective strategies for treating OA patients.