Bisphosphonates for osteoarthritis prevention: "Holy Grail" or not?

Effect of intra-articular injection of a hyaluronic acid-alendronate conjugate on post-traumatic osteoarthritis induced by destabilization of the medial meniscus in rats

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by pain and cartilage damage. Intra-articular (i.a) viscosupplementation with hyaluronic acid (HA) is frequently used for the management of OA. Preclinical studies have reported that bisphosphonates (BPs) may have a therapeutic potential to slow down or reverse the progression of OA. Among these, alendronate (ALN) has demonstrated chondroprotective effects in both in vitro and vivo experiments. This study evaluated the effects of a novel alendronate-hyaluronic acid (ALN-HA) conjugate on an OA in vivo model induced by medial meniscus destabilization (DMM). DMM surgery was performed on the knees of Sprague Dawley rats that received, after four weeks, one intra-articular (i.a.) injection of: (1) ALN-HA; (2) HA; (3) sodium chloride (NaCl). Sham-operated rats were used as control. Allodynia was assessed by Von Frey test. Joint degeneration was evaluated eight weeks after treatment by micro-computed tomography (micro-CT), histology, and immunohistochemistry. Collagen cross-linked C-telopeptides (CTX-I and CTX-II) serum levels were determined by ELISA. Paw withdrawal threshold increased in ALN-HA group when compared to rats treated with NaCl or HA. Micro-CT did not show differences between ALN-HA, HA and NaCl groups. ALN-HA injection produced significant improvements in articular cartilage degeneration showing an OARSI score lower than those of HA and NaCl, and reduced matrix metalloproteinase (MMP)-13, MMP-3, interleukin-6, vascular endothelial growth factor and Caspase-3 expression. CTX-I was reduced after ALN-HA treatment when compared to NaCl. Our results indicate that i.a. use of ALN after conjugation with HA limits OA development and progression in the rat DMM model, and may lead to the development of novel therapeutic strategies in OA management.

Advancing drug delivery to articular cartilage: From single to multiple strategies

Articular cartilage (AC) injuries often lead to cartilage degeneration and may ultimately result in osteoarthritis (OA) due to the limited self-repair ability. To date, numerous intra-articular delivery systems carrying various therapeutic agents have been developed to improve therapeutic localization and retention, optimize controlled drug release profiles and target different pathological processes. Due to the complex and multifactorial characteristics of cartilage injury pathology and heterogeneity of the cartilage structure deposited within a dense matrix, delivery systems loaded with a single therapeutic agent are hindered from reaching multiple targets in a spatiotemporal matched manner and thus fail to mimic the natural processes of biosynthesis, compromising the goal of full cartilage regeneration. Emerging evidence highlights the importance of sequential delivery strategies targeting multiple pathological processes. In this review, we first summarize the current status and progress achieved in single-drug delivery strategies for the treatment of AC diseases. Subsequently, we focus mainly on advances in multiple drug delivery applications, including sequential release formulations targeting various pathological processes, synergistic targeting of the same pathological process, the spatial distribution in multiple tissues, and heterogeneous regeneration. We hope that this review will inspire the rational design of intra-articular drug delivery systems (DDSs) in the future.

Mice Lacking Wnt9a or Wnt4 Are Prone to Develop Spontaneous Osteoarthritis With Age and Display Alteration in Either the Trabecular or Cortical Bone Compartment

Osteoarthritis (OA) is a common degenerative disease of the joint, with a complex multifactorial not yet fully understood etiology. Over the past years, the Wnt signaling pathway has been implicated in osteoarthritis. In a recent genomewide association study (GWAS), the chromosomal location on chromosome 1, linked to the Wnt3a-Wnt9a gene locus, was identified as the most significant locus associated with a thumb osteoarthritis endophenotype. Previously, it was shown that WNT9a is involved in maintaining synovial cell identity in the elbow joint during embryogenesis. Here, we report that the conditional loss of Wnt9a in the Prx1-Cre expressing limb mesenchyme or Prg4-CreER expressing cells predispositions the mice to develop spontaneous OA-like changes with age. In addition, the trabecular bone volume is altered in these mice. Similarly, mice with a conditional loss of Wnt4 in the limb mesenchyme are also more prone to develop spontaneously OA-like joint alterations with age. These mice display additional alterations in their cortical bone. The combined loss of Wnt9a and Wnt4 increased the likelihood of the mice developing osteoarthritis-like changes and enhanced disease severity in the affected mice. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Platelet-Rich Plasma Combined with Alendronate Reduces Pain and Inflammation in Induced Osteoarthritis in Rats by Inhibiting the Nuclear Factor-Kappa B Signaling Pathway

Purpose

Osteoarthritis (OA) is one of the common degenerative diseases of the joint in the world. This study was designed to explore the effect of platelet-rich plasma (PRP) combined with alendronate (ALN) on OA.

Methods

We induced OA model by anterior cruciate ligament transection (ACLT) method in rats and treating chondrocytes by IL-1β in vitro. PRP and/or ALN were used to treat induced rats and chondrocytes. Hematoxylin and eosin (H&E) and Safranin O staining were used to observe the structures of cartilage. The mRNA expression of Collagen II, MMP-13, and inflammatory factors (IL-18, IL-1β, and TNF-α) in the cartilage and chondrocytes of rats was determined by qRT-PCR. The expression of NF-κB pathway-related proteins (p-p65, p65, IκBα, and p-IκBα) in the cartilage and chondrocytes of rats was determined by Western blot. The proliferation of chondrocytes was detected by MTT assay.

Results

Treatment with PRP, ALN, or PRP combined with ALN decreased the degree of cartilage destruction, the mRNA expression of MMP-13 and inflammatory factors (IL-18, IL-1β, and TNF-α), and the protein expression of p-IκBα/IκBα and p-p65/p65, increased Collagen II expression, and the threshold of tender and thermal pain in OA rats. Meanwhile, ALN, PRP, or ALN combined with PRP reversed the inhibiting effect of phorbol myristate acetate (PMA, an NF-κB agonist) on cell proliferation and cartilage matrix metabolism. Among them, the effects of ALN combined with PRP were most obvious.

Conclusion

PRP combined with ALN delayed OA progression by inhibiting the NF-κB signaling pathway.

Longitudinal Effects of Acute Anterior Cruciate Ligament Tears on Peri-Articular Bone in Human Knees Within the First Year of Injury

Anterior cruciate ligament (ACL) tears are common sports-related knee injuries that increase the risk of developing post-traumatic osteoarthritis. ACL tears are rarely an isolated injury but are often associated with traumatic bone marrow lesions (BMLs). While early loss of bone mass following the ACL injury has been previously described, to date, microarchitectural information has not been reported due to the limited resolution of clinical imaging systems. In this study, we provide the first evidence of detailed bone mass and microarchitectural changes in the first 10 months following an acute ACL tear, and localized to traumatic BMLs. Fifteen participants with an acute unilateral ACL tear were assessed at four-time points using dual-energy X-ray absorptiometry and high-resolution peripheral quantitative computed tomography, and traumatic BMLs were identified with magnetic resonance imaging. Loss of bone mass was localized to the injured knee (-4.6% to -15.8%, depending on bone and depth) and was accelerated immediately following the injury before suggesting a recovery phase. This loss of bone was accelerated even greater in traumatic BMLs (-18.2% to -20.6%, depending on bone). Bone loss was accompanied by microstructural degeneration of trabecular bone. For example, in the lateral femur of the injured knee, the subchondral bone plate decreased in thickness (-9.0%). This study confirmed loss of bone mass in the months following ACL tears and described the underlying bone microstructural changes. The presented bone changes were accelerated in regions of traumatic BMLs. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2325-2336, 2019.

Efficacy of bisphosphonates in specific knee osteoarthritis subpopulations: protocol for an OA Trial Bank systematic review and individual patient data meta-analysis

INTRODUCTION

Randomised clinical trials to date investigating the efficacy of bisphosphonates in knee osteoarthritis (OA) have found divergent results, with a recent meta-analysis finding no superiority of these drugs over placebo. Whether particular patient subgroups are more likely to benefit from this therapy than others is still unclear. We aim to investigate the effects of bisphosphonates compared with a control group (placebo, no treatment, another active treatment) on clinical and structural outcomes in specific knee OA subpopulations with possible distinct rates of subchondral bone turnover.

METHODS AND ANALYSIS

Medline, Embase, Scopus, Web of Sciences and Cochrane Central Register of Controlled Trials will be searched from inception to February 2018. Randomised clinical trials will be eligible if they reported at least one potential treatment effect modifier at baseline: gender, menopausal status, age, body mass index, radiographic stage, knee pain severity, presence of bone marrow lesions, levels of biochemical markers of bone turnover (serum and/or urinary) and systemic bone mineral density status. Authors of original trials will be contacted to obtain individual patient data from each study. Risk of bias will be assessed using the Cochrane Collaboration's tool. The primary outcomes will include pain and radiographic joint space width loss. Studies using other MRI-based assessment of disease progression will also be eligible. Outcomes will be grouped into short-term (≤3 months), intermediate-term (>3 months; ≤12 months) and long-term (>12 months). Regression models will be used, adding an interaction term for each subgroup of interest to determine possible subgroup effects. There was no source of funding for this study.

ETHICS AND DISSEMINATION

Dissemination of our findings is planned to occur through conference presentations, publication in peer-reviewed journals and social media. No formal ethics approval is generally required as no new data collection will be undertaken.

PROSPERO REGISTRATION NUMBER

CRD42018093327.

Modulation of cartilage's response to injury: Can chondrocyte apoptosis be reversed?

Osteoarthritis is characterized by a chronic, progressive and irreversible degradation of the articular cartilage associated with joint inflammation and a reparative bone response. More than 100 million people are affected by this condition worldwide with significant health and welfare costs. Our available treatment options in osteoarthritis are extremely limited. Chondral or osteochondral grafts have shown some promising results but joint replacement surgery is by far the most common therapeutic approach. The difficulty lies on the limited regeneration capacity of the articular cartilage, poor blood supply and the paucity of resident progenitor stem cells. In addition, our poor understanding of the molecular signalling pathways involved in the senescence and apoptosis of chondrocytes is a major factor restricting further progress in the area. This review focuses on molecules and approaches that can be implemented to delay or even rescue chondrocyte apoptosis. Ways of modulating the physiologic response to trauma preventing chondrocyte death are proposed. The use of several cytokines, growth factors and advances made in altering several of the degenerative genetic pathways involved in chondrocyte apoptosis and degradation are also presented. The suggested approaches can help clinicians to improve cartilage tissue regeneration.

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.

Dynamic Alterations in Microarchitecture, Mineralization and Mechanical Property of Subchondral Bone in Rat Medial Meniscal Tear Model of Osteoarthritis

Background:

The properties of subchondral bone influence the integrity of articular cartilage in the pathogenesis of osteoarthritis (OA). However, the characteristics of subchondral bone alterations remain unresolved. The present study aimed to observe the dynamic alterations in the microarchitecture, mineralization, and mechanical properties of subchondral bone during the progression of OA.

Methods:

A medial meniscal tear (MMT) operation was performed in 128 adult Sprague Dawley rats to induce OA. At 2, 4, 8, and 12 weeks following the MMT operation, cartilage degeneration was evaluated using toluidine blue O staining, whereas changes in the microarchitecture indices and tissue mineral density (TMD), mineral-to-collagen ratio, and intrinsic mechanical properties of subchondral bone plates (BPs) and trabecular bones (Tbs) were measured using micro-computed tomography scanning, confocal Raman microspectroscopy and nanoindentation testing, respectively.

Results:

Cartilage degeneration occurred and worsened progressively from 2 to 12 weeks after OA induction. Microarchitecture analysis revealed that the subchondral bone shifted from bone resorption early (reduced trabecular BV/TV, trabecular number, connectivity density and trabecular thickness [Tb.Th], and increased trabecular spacing (Tb.Sp) at 2 and 4 weeks) to bone accretion late (increased BV/TV, Tb.Th and thickness of subchondral bone plate, and reduced Tb.Sp at 8 and 12 weeks). The TMD of both the BP and Tb displayed no significant changes at 2 and 4 weeks but decreased at 8 and 12 weeks. The mineral-to-collagen ratio showed a significant decrease from 4 weeks for the Tb and from 8 weeks for the BP after OA induction. Both the elastic modulus and hardness of the Tb showed a significant decrease from 4 weeks after OA induction. The BP showed a significant decrease in its elastic modulus from 8 weeks and its hardness from 4 weeks.

Conclusion:

The microarchitecture, mineralization and mechanical properties of subchondral bone changed in a time-dependent manner as OA progressed.

Emerging drugs for the treatment of knee osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is the most prevailing form of joint disease, with symptoms affecting 10 - 12% of the adult population with a projection of a 50% increase in prevalence in the next two decades. The disease characteristics are defined by articular cartilage damage, low-grade synovial inflammation and hypertrophic bone changes, leading to pain and functional deterioration. To date, available pain treatments are limited in their efficacy and have associated toxicities. No structural disease modification agents have been approved by regulatory agencies for this indication.

AREAS COVERED

We reviewed drugs in Phase II - III for OA pain and joint structure modification. Different aspects of structure modification are divided into targets of inflammatory pathway, cartilage catabolism and anabolism, and subchondral bone remodeling.

EXPERT OPINION

Further insight into the pathophysiology of the disease will allow for development of novel target classes focusing on the link between symptomatology and structural changes. Given the complexity of OA, one single therapy is unlikely to be universally and uniformly effective. Promising therapies are under development, but there are obstacles in the translation of treatment from preclinical models and trial designs need to be cognizant of the complex reasons for previous trial failures.

Inhibited osteoclastic bone resorption through alendronate treatment in rats reduces severe osteoarthritis progression

Osteoarthritis (OA) is a non-rheumatoid joint disease characterized by progressive degeneration of extra-cellular cartilage matrix (ECM), enhanced subchondral bone remodeling, osteophyte formation and synovial thickening. Alendronate (ALN) is a potent inhibitor of osteoclastic bone resorption and results in reduced bone remodeling. This study investigated the effects of pre-emptive use of ALN on OA related osteoclastic subchondral bone resorption in an in vivo rat model for severe OA. Using multi-modality imaging we measured effects of ALN treatment within cartilage and synovium. Severe osteoarthritis was induced in left rat knees using papain injections in combination with a moderate running protocol. Twenty rats were treated with subcutaneous ALN injections and compared to twenty untreated controls. Animals were longitudinally monitored for 12weeks with in vivo μCT to measure subchondral bone changes and SPECT/CT to determine synovial macrophage activation using a folate-based radiotracer. Articular cartilage was analyzed at 6 and 12weeks with ex vivo contrast enhanced μCT and histology to measure sulfated-glycosaminoglycan (sGAG) content and cartilage thickness. ALN treatment successfully inhibited subchondral bone remodeling. As a result we found less subchondral plate porosity and reduced osteophytosis. ALN treatment did not reduce subchondral sclerosis. However, after the OA induction phase, ALN treatment protected cartilage ECM from degradation and reduced synovial macrophage activation. Surprisingly, ALN treatment also improved sGAG content of tibia cartilage in healthy joints. Our data was consistent with the hypothesis that osteoclastic bone resorption might play an important role in OA and may be a driving force for progression of the disease. However, our study suggest that this effect might not solely be effects on osteoclastic activity, since ALN treatment also influenced macrophage functioning. Additionally, ALN treatment and physical activity exercised a positive effect in healthy control joints, which increased cartilage sGAG content. More research on this topic might lead to novel insights as to improve cartilage quality.

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

OBJECTIVE

Bisphosphonates are considered potential disease modifying osteoarthritis (OA) agents. The present study investigated the efficacy of pre-emptive, early, and delayed alendronate (ALN) treatment initiation on subchondral trabecular bone and cartilage in low-dose monosodium iodoacetate (MIA)-induced knee OA in rats.

METHODS

Male rats received pre-emptive (n = 12, day 0-end of week 2), early (n = 12, end of week 2-end of week 6), or delayed (n = 12, end of week 6-end of week 10) ALN treatment (30 μg/kg/week). Pre-emptive ALN-treated rats were scanned using in vivo micro-computed tomography (micro-CT) after 2 weeks and then sacrificed, early ALN-treated rats were scanned after 2 and 6 weeks and sacrificed, and the delayed ALN-treated rats were scanned after 2, 6, and 10 weeks of OA induction and sacrificed. After sacrifice, bone histomorphometry and histology of the tibia and biomarker analyses were undertaken. Changes in hind limb weight-bearing were assessed from day -1 until day 14.

RESULTS

MIA-induced pathological features similar to progressive human OA in the cartilage and subchondral bone. Pre-emptive ALN treatment preserved subchondral trabecular bone microarchitecture, prevented bone loss, decreased bone turnover and joint discomfort. Pre-emptive ALN treatment had moderate effects on cartilage degradation. Early and delayed ALN treatments prevented loss of trabeculae and decreased bone turnover, but had no significant effect on cartilage degradation.

CONCLUSION

ALN prevented increased bone turnover and preserved the structural integrity of subchondral bone in experimental OA. The time point of treatment initiation is crucial for treating OA. Treating both the subchondral bone and cartilage in OA would be clinically more beneficial.

Osteoarthritis and osteoporosis: what is the overlap?

Osteoarthritis (OA) and osteoporosis (OP) are highly prevalent health problems, associated with considerable morbidity. In the past, attention was focused on a supposed inverse relationship between OA and OP, since both disorders usually affect the elderly, but were regarded to rarely coexist in a single person. However, recent studies have revealed several factors which contribute to the pathogenesis of both disorders. These insights might contribute to the development of shared new treatment options in the near future. Increased subchondral bone loss is a characteristic feature of OP and the early stage of OA, and this finding is the rationale for studies on the effect of anti-osteoporotic drugs in OA. In addition, inflammation and unfavourable body composition have been recognized as contributing factors for both disorders. Underweight is a risk factor for OP, while obesity stimulates the development of OA, by mechanical overloading of weight-bearing joints but also by supposed unfavourable effects of adipokines.

Impact of treatments for osteoporosis on cartilage biomarkers in humans

The rationale to target bone for treating osteoarthritis (OA) relies on the known cross-talk between subchondral bone and cartilage and the demonstration that subchondral bone resorption occurs at an early stage in the development of OA. Therefore, the possible OA disease-modifying effects of bone antiresorptive agents are of interest. This paper aims to review the published data on the effect of estrogens, selective estrogen receptor modulators, calcitonin, strontium ranelate, and bisphosphonates on cartilage biomarkers levels used as surrogate endpoints in clinical trials. Except for findings for tibolone, most observations indicated that these antiresorptive therapies decreased the urinary levels of CTX-II, a biomarker of type II collagen degradation. These data, which should be cautiously interpreted, suggest that these drugs might favorably affect cartilage homeostasis.

Pharmacodynamics of bisphosphonates in arthritis

Inflammatory arthritis is a group of autoimmune diseases characterized by chronic inflammation of the joints. Rheumatoid arthritis, the most common form of arthritis, is associated with local joint destruction and systemic bone loss. Osteoclasts, the only cells of the body able to resorbe bone, are key players in these two types of bone loss. Bisphosphonates are analogs of pyrophosphate that inhibit osteoclast action and bone resorption. They are indicated in pathology associated with excess resorption. Besides their effect on bone they also exhibit extra-osseous properties, acting on tumor cells, inflammation and angiogenesis. As a result, they have been trialed in the context of arthritis. It is now clear that they do not have any significant direct effect on disease activity or pain. If their indication in the prevention of glucocorticoid-induced osteoporosis is clear, any beneficial effects on bone erosions are still controversial but interesting preliminary results warrant further investigations.

Bone remodelling in osteoarthritis

The classical view of the pathogenesis of osteoarthritis (OA) is that subchondral sclerosis is associated with, and perhaps causes, age-related joint degeneration. Recent observations have demonstrated that OA is associated with early loss of bone owing to increased bone remodelling, followed by slow turnover leading to densification of the subchondral plate and complete loss of cartilage. Subchondral densification is a late event in OA that involves only the subchondral plate and calcified cartilage; the subchondral cancellous bone beneath the subchondral plate may remain osteopenic. In experimental models, inducing subchondral sclerosis without allowing the prior stage of increased bone remodelling to occur does not lead to progressive OA. Therefore, both early-stage increased remodelling and bone loss, and the late-stage slow remodelling and subchondral densification are important components of the pathogenetic process that leads to OA. The apparent paradoxical observations that OA is associated with both increased remodelling and osteopenia, as well as decreased remodelling and sclerosis, are consistent with the spatial and temporal separation of these processes during joint degeneration. This Review provides an overview of current knowledge on OA and discusses the role of subchondral bone in the initiation and progression of OA. A hypothetical model of OA pathogenesis is proposed.

Clinical significance of bone changes in osteoarthritis

Osteoarthritis (OA), the most common form of arthritis, is now understood to involve all joint tissues, with active anabolic and catabolic processes. Knee OA in particular is considered to be a largely mechanically-driven disease. As bone adapts to loads by remodeling to meet its mechanical demands, bone alterations likely play an important role in OA development. Subchondral bone changes in bone turnover, mineralization, and volume result in altered apparent and material density of bone that may adversely affect the joint's biomechanical environment. Subchondral bone alterations such as bone marrow lesions (BMLs) and subchondral bone attrition (SBA) both tend to occur more frequently in the more loaded knee compartments, and are associated with cartilage loss in the same region. Recently, MRI-based 3D bone shape has been shown to track concurrently with and predict OA onset.The contributions of structural abnormalities to the clinical manifestations of knee OA are becoming better understood as well. While a structure-symptom discordance in knee OA is thought to exist, such observations do not take into account all potential factors that can contribute to between-person differences in the pain experience. Using novel methodology, pain fluctuation has been associated with changes in BMLs, synovitis and effusion. SBA has also been associated with knee pain, but the relationship of osteophytes to pain has been conflicting.Understanding the pathophysiologic sequences and consequences of OA pathology will guide rational therapeutic targeting. Importantly, rational treatment targets require understanding what structures contribute to pain as pain is the reason patients seek medical care.

Efficacy of zoledronic acid in treatment of teoarthritis is dependent on the disease progression stage in rat medial meniscal tear model

AIM

To investigate whether the stage of osteoarthritis (OA) progression influenced the efficacy of the third-generation bisphosphonate zoledronic acid in a rat medial meniscal tear model.

METHODS

Medial meniscal tear (MMT) was surgically induced in adult male Sprague Dawley rats. Zoledronic acid (ZOL, 100 μg/kg, sc, twice a week) was administered starting immediately, early (from 4 weeks) or late (from 8 weeks) after OA induction. The degeneration of articular cartilage was evaluated with toluidine blue O staining. Subchondral bone remodeling was evaluated with X-ray micro-CT scanning. Joint pain was measured with respect to weight-bearing asymmetry. Calcitonin gene-related peptide (CGRP) expression in dorsal root ganglia (DRGs) was examined using immunofluorescence analysis. The afferent neurons in DRGs innervating the joint were identified by retrograde labeling with fluorogold.

RESULTS

Progressive cartilage loss was observed during 12 weeks after OA induction. Subchondral bone remodeling manifested as increased bone resorption at early stage (4 weeks), but as increased bone accretion at advanced stages (8 weeks). Immediately and early ZOL administration significantly improved subchondral microstructural parameters, attenuated cartilage degeneration, reduced weight-bearing asymmetry and CGRP expression, whereas the late ZOL administration had no significant effects.

CONCLUSION

The stage of OA progression influences the efficacy of ZOL in treating joint degeneration and pain. To obtain the maximum efficacy, bisphosphonate treatment should be initiated in rat with early stages of OA pathogenesis.

Methodologic issues in clinical trials for prevention or risk reduction in osteoarthritis

The design and execution of prevention trials for OA have methodological issues that are distinct from trials designed to impact prevalent disease. Disease definitions and their precise and sensitive measurement, identification of high-risk populations, the nature of the intervention (pharmaceutical, nutraceutical, behavioral) and its potential pleiotropic impacts on other organ systems are critical to consider. Because prevention trials may be prolonged, close attention to concomitant life changes and co-morbidities, adherence and participant retention in the trial is of primary importance, as is recognition of the potential for "preventive misconception" and "behavioral disinhibition" to affect the ability of the trial to show an effect of the intervention under study. None of these potential pitfalls precludes a successful and scientifically rigorous process and outcome. As technology improves the means to measure and predict the OA process and its clinical consequences, it will be increasingly possible to screen individuals for high-risk phenotypes, combining clinical factors with information from imaging, genetic, metabolic and other biomarkers and to impact this high-risk condition to avoid or delay OA both structurally and symptomatically.

Inhibition of osteoclasts prevents cartilage loss and pain in a rat model of degenerative joint disease

OBJECTIVE

To investigate the relationship between efficacy of a bisphosphonate, pain and extent of joint damage in the monosodium iodoacetate (MIA) model of painful degenerative joint disease.

METHODS

Zoledronate treatment was initiated prior to and at various times following model induction, including late time points representing advanced disease. Radiographic and histological structural parameters were correlated with pain as measured by weight bearing.

RESULTS

Intraarticular (IA) MIA resulted in a progressive loss of bone mineral density (BMD) and chondrocytes, thinning of cartilage, loss of proteoglycan, resorption of calcified cartilage and subchondral bone, as well as pain. This was completely prevented by pre-emptive chronic zoledronate treatment with joint sections being histologically indistinguishable from saline-injected controls. When initiation of treatment was delayed efficacy was reduced. In animals with advanced joint degeneration, treatment partially restored BMD and had a significant, but limited, effect on pain. We confirmed these radiographic and behavioral findings in the medial meniscal tear model. To understand the mechanism-of-action of zoledronate we investigated an early time point 4 days post-model induction when chondrocytes were histologically viable, with minor loss of proteoglycan and generalized synovitis. Osteoclast-mediated resorption of the calcified cartilage was observed and was prevented by two doses of zoledronate.

CONCLUSION

Subchondral bone remodeling plays an important role in nociception and the pathobiology of the MIA model with osteoclasts being implicated in both bone and cartilage resorption. Inhibition of osteoclastic activity when initiated early leads to improved efficacy.

In early OA, thinning of the subchondral plate is directly related to cartilage damage: results from a canine ACLT-meniscectomy model

OBJECTIVE

The pathogenesis of osteoarthritis (OA) includes cartilage degeneration, synovial inflammation, and bone changes. Slowly, the sequence and inter-relationship of these features is becoming clearer. Early models of OA suggest thinning of the subchondral plate in addition to trabecular bone changes. In the present study subchondral bone changes were studied in the canine anterior cruciate ligament transection (ACLT)-meniscectomy model. This model is characterized by intra-joint variability with respect to cartilage damage (predominantly medial) and loading (lateral unloading due to a shifted axis).

METHODS

In 13 Labrador dogs, OA was induced by transection of the anterior cruciate ligament and removal of the medial meniscus. Twelve weeks later, cartilage integrity was evaluated histologically using the modified Mankin score (0-11), and proteoglycan content was determined by Alcian Blue assay. Bone architecture of the tibia was quantified by micro-CT.

RESULTS

Cartilage damage was severe in the medial compartment (Mankin score +3.5, glycosaminoglycan (GAG) content -28%) and mild in the lateral compartment (Mankin score +1.6, GAG content -15%). Thinning and porosity of the subchondral plate were only present on the medial side (-21%, +87%, respectively). Interestingly, changes in trabecular bone structure did almost not occur in the medial compartment (volume fraction -7%) but were clear in the lateral compartment (-20%).

CONCLUSION

Thinning of the subchondral plate is a localized phenomenon related to cartilage degeneration while trabecular bone changes are related to mechanical (un)loading. The different mechanisms responsible for bone changes in OA should be taken in account when designing and interpreting studies interfering with bone turnover in the treatment of OA.

Effects of risedronate on osteoarthritis of the knee

The purpose of the present study was to discuss the effects of risedronate on osteoarthritis (OA) of the knee by reviewing the existing literature. The literature was searched with PubMed, with respect to prospective, double-blind, randomized placebo-controlled trials (RCTs), using the following search terms: risedronate, knee, and osteoarthritis. Two RCTs met the criteria. A RCT (n = 231) showed that risedronate treatment (15 mg/day) for 1 year improved symptoms. A larger RCT (n = 1,896) showed that risedronate treatment (5 mg/day, 15 mg/day, 35 mg/week, and 50 mg/week) for 2 years did not improve signs or symptoms, nor did it alter radiological progression. However, a subanalysis study (n = 477) revealed that patients with marked cartilage loss preserved the structural integrity of subchondral bone by risedronate treatment (15 mg/day and 50 mg/week). Another subanalysis study (n = 1,885) revealed that C-terminal crosslinking telopeptide of type II collagen (CTX-II) decreased with risedronate treatment in a dose-dependent manner, and levels reached after 6 months were associated with radiological progression at 2 years. The results of these RCTs show that risedronate reduces the marker of cartilage degradation (CTX-II), which could contribute to attenuation of radiological progression of OA by preserving the structural integrity of subchondral bone. The review of the literature suggests that higher doses of risedronate (15 mg/day) strongly reduces the marker of cartilage degradation (CTX-II), which could contribute to attenuation of radiological progression of OA by preserving the structural integrity of subchondral bone.

Alendronate inhibits VEGF expression in growth plate chondrocytes by acting on the mevalonate pathway

Bisphosphonates decrease chondrocyte turnover at the growth plate and impact bone growth. Likewise vascular endothelial growth factor (VEGF) plays an important role in endochondral bone elongation by influencing chondrocyte turnover at the growth plate. To investigate whether the action of bisphosphonate on the growth plate works through VEGF, VEGF protein expression and isoform transcription in endochondral chondrocytes isolated from growing mice and treated with a clinically used bisphosphonate, alendronate, were assessed. Alendronate at 10µM and 100µM concentrations decreased secreted VEGF protein expression but not cell associated protein. Bisphosphonates are known to inhibit the mevalonate intracellular signaling pathway used by VEGF. Addition of the mevalonate pathway intermediates farnesol (FOH) and geranylgeraniol (GGOH) interacted with the low concentration of alendronate to further decrease secreted VEGF protein whereas FOH partially restored VEGF protein secretion when combined with the high alendronate. Similar to the protein data, the addition of alendronate decreased VEGF mRNA isoforms. VEGF mRNA levels were rescued by the GGOH mevalonate pathway intermediate at the low alendronate dose whereas neither intermediate consistently restored the VEGF mRNA levels at the high alendronate dose. Thus, the bisphophonate alendronate impairs growth plate chondrocyte turnover by down-regulating the secreted forms of VEGF mRNA and protein by inhibiting the mevalonate pathway.