Optimising antiresorptive therapies in postmenopausal women: why do we need to give due consideration to the degree of suppression?

Profiling and targeting connective tissue remodeling in autoimmunity - A novel paradigm for diagnosing and treating chronic diseases

Connective tissue (ConT) remodeling is an essential process in tissue regeneration, where a balanced replacement of old tissue by new tissue occurs. This balance is disturbed in chronic diseases, often autoimmune diseases, usually resulting in the buld up of fibrosis and a gradual loss of organ function. During progression of liver, lung, skin, heart, joint, skeletal and kidney diseasesboth ConT formation and degradation are elevated, which is tightly linked to immune cell activation and a loss of specific cell types and extracellular matrix (ECM) structures that are required for normal organ function. Here, we address the balance of key general and organ specific components of the ECM during homeostasis and in disease, with a focus on collagens, which are emerging as both structural and signaling molecules harbouring neoepitopes and autoantigens that are released during ConT remodeling. Specific collagen molecular signatures of ConT remodeling are linked to disease activity and stage, and to prognosis across different organs. These signatures accompany and further drive disease progression, and often become detectable before clinical disease manifestation (illness). Recent advances allow to quantify and define the nature of ConT remodeling via blood-based assays that measure the levels of well-defined collagen fragments, reflecting different facets of ConT formation and degradation, and associated immunological processes. These novel serum assays are becoming important tools of precision medicine, to detect various chronic and autoimmune diseases before their clinical manifestation, and to non-invasively monitor the efficacy of a broad range of pharmacological interventions.

Medication-Related Osteonecrosis of the Jaws

Medication-related osteonecrosis of the jaw is an oral complication in cancer patients being treated with either antiresorptive or antiangiogenic drugs. The first reports of MRONJ were published in 2003. Hundreds of manuscripts have been published in the medical and dental literature describing the complication, clinical and radiographic signs and symptoms, possible pathophysiology, and management. Despite this extensive literature, the pathobiological mechanisms by which medication-related osteonecrosis of the jaw develops have not yet been fully delineated. The aim of this manuscript is to present current knowledge about the complication ragarding to the definition, known risk factors, and clinical management recommendations. Based on this current state of the science, we also propose research directions that have potential to enhance the management of future oncology patients who are receiving these agents.

Cathepsin K Localizes to Equine Bone In Vivo and Inhibits Bone Marrow Stem and Progenitor Cells Differentiation In Vitro

Selective inhibition of Cathepsin K (CatK) has a promising therapeutic potential for diseases associated with bone loss and osseous inflammation, such as osteoarthritis, periodontitis, and osteoporosis. In horses, stress-related bone injuries are common and accompanied by bone pain and inflammation resulting in excessive bone resorption and periostitis. VEL-0230 is a highly selective inhibitor of CatK that significantly decreased bone resorption and increased bone formation biomarkers. The goal of this study was to demonstrate the presence of CatK in equine bone and a simultaneous influence on the bone marrow cellular components including function and differentiation. Our objectives were: 1) to investigate the tissue localization of CatK protein in equine bone using immunohistochemistry, and 2) to determine the effect of CatK inhibition on osteoclastogenic, chondrogenic and osteogenic differentiation potential of equine stem and progenitor cells in vitro using histochemical staining and differentiation-related gene expression analyses. Bone biopsies, harvested from the tuber coxae and proximal phalanx of six healthy horses, were processed for immunostaining against CatK. Sternal bone marrow aspirates were cultured in 0, 1, 10, or 100 μM of VEL-0230 and subsequent staining scoring and gene expression analyses performed. All cells morphologically characterized as osteoclasts and moderate number of active bone lining osteoblasts stained positive for CatK. Histochemical staining and gene expression analyses revealed a significant increase in the osteoclastogenic, chondrogenic and osteogenic differentiation potential of equine bone marrow cells, which was VEL-0230-concentration dependent for the latter two. These results suggested that CatK inhibition may have anabolic effects on bone and cartilage regeneration that may be explained as a feedback response to CatK depletion. In conclusion, the use of CatK inhibition to reduce inflammation and associated bone resorption in equine osseous disorders may offer advantages to other therapeutics that would require further study.

Serological biomarkers detect active joint destruction and inflammation in patients with haemophilic arthropathy

INTRODUCTION

Progressive arthropathy caused by recurrent joint bleeds is a severe complication in haemophilia.

AIM

We investigated whether biomarkers of cartilage and bone degradation, and inflammation were altered in haemophilia patients and whether these biomarkers could identify haemophilia patients with arthropathy.

METHODS

Serum from 35 haemophilia patients with varying degrees of arthropathy and 43 age- and gender-matched control subjects were analysed. Biomarkers of cartilage degradation (C2M, COMP, CTX-II, ADAMTS5), cartilage formation (PRO-C2), bone formation (PINP), bone resorption (CTX-I) and inflammation (hsCRP, CRPM) were measured by ELISA. Arthropathy was assessed by radiological evaluation (Pettersson score) and physical examination (Gilbert score).

RESULTS

In patients with haemophilia, cartilage degradation, measured by C2M, CTX-II and COMP, was increased by 25% (P < 0.05) compared with control subjects. Levels of the cartilage degradation enzyme, ADAMTS5, were 10% lower in haemophilia patients (P < 0.05). Bone formation (PINP) was reduced by 25% (P < 0.05) in haemophilia patients, whereas bone resorption (CTX-I) was increased by 30% (P < 0.001). Acute inflammation (hsCRP) was increased by 50% (P < 0.01), whereas chronic inflammation (CRPM) was decreased by 25% (P < 0.0001). The hsCRP/CRPM ratio was 60% higher (P < 0.001) in haemophilia patients relative to control subjects. A biomarker panel combining C2M, CRPM, and ADAMTS5 could distinguish haemophilia patients from control subjects with 85.3% accuracy (P < 0.0001). We found no strong correlation between biomarkers and radiological and physical examination of the joint.

CONCLUSION

Biomarkers detect increased cartilage and bone degradation, and altered inflammatory activity in haemophilia patients with arthropathy. These biomarkers could potentially be used to identify patients with progressing joint disease.

Early changes in blood-based joint tissue destruction biomarkers are predictive of response to tocilizumab in the LITHE study

Background

Rheumatoid arthritis (RA) is characterized by gradual joint destruction. Tocilizumab (TCZ) significantly suppresses symptoms, however not all patients are protected from joint damage. We investigated whether early measurement of specific biomarkers could predict early joint protection response to tocilizumab.

Method

Serum biomarkers (CRPM, VICM, C1M, C2M, C3M (MMP-degraded CRP, vimentin type I, II and III collagen), CTX-I/OC (bone turnover), and CRP) were measured in 740 RA patients (the LITHE study) treated with Placebo, or 4 or 8 mg/kg TCZ. Early responders were those with ≥20 % improvement in SJC or TJC by week 16. The biomarkers' predictability of response was investigated by AUROC and classification regression tree analysis.

Results

The best biomarker predictability for identification of TCZ responders were; baseline CTX-I/OC (AUC 0.66, p = 0.0005) and changes in C1M (AUC 0.67, p = 0.0072), C2M (AUC 0.72, p = 0.0002), C3M (AUC 0.63, p = 0.018) and the combination of biomarkers (AUC 0.81, p = 0.0025). Patients with high bone turnover (CTX-I/OC) and low C2M were 6.8-fold (p = 0.003) more likely to have an early response to TCZ.

Conclusion

This enhanced pharmacodynamic (PD) response enabled identification of early responders with a superior TCZ clinical benefit. This biomarker model may assist in the identification of TCZ responsive RA patients and thus potentially benefit individual patients.

Trial registration

Clinicaltrials.gov: NCT00106535. JAN 2005

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0913-x) contains supplementary material, which is available to authorized users.

An Evaluative History of Bisphosphonate Drugs: Dual Physiologic Effects of Pyrophosphate as Inspiration for a Novel Pharmaceutical Class

The documented history of the development of the bisphosphonate drugs is reviewed in sufficient detail to permit independent evaluation of the consistency of the conclusions reached from the available data. The evidence developed during the early interval of these studies 1960-1975 was sufficient to establish that pyrophosphate shares the subsequently established dual bisphosphonate characteristics of bone resorption inhibition and prevention of tissue mineralization.

Scalable solution-phase synthesis of the biologically active cyclodepsipeptide destruxin E, a potent negative regulator of osteoclast morphology

The scalable solution-phase synthesis of the cyclodepsipeptide destruxin E (1) has been achieved. Diastereoselective dihydroxylation of the terminal alkene in a 2-alkoxy-4-pentenoic amide, 7, was successfully accomplished utilizing (DHQD)2PHAL as the chiral ligand, and it was found that the use of the l-proline moiety in the substrate as a chiral auxiliary was essential for the induction of high diastereoselectivity to afford the key compound 4 on a gram scale. MNBA-mediated macrolactonization of 3 was also performed without formation of the dimerized product even under higher-dilution conditions, and it is noteworthy that the internal hydrogen bonds and s-cis configuration of the amide bond between N-methylalanine and N-methylvaline in the cyclization precursor 3 would assist in the macrolactonization to provide the macrolactone 2 without forming a dimerized product. Finally, epoxide formation in the side chain afforded destruxin E (1) on a gram scale in high purity (>98%).

PTH replacement therapy of hypoparathyroidism

Hypoparathyroidism is characterized by hypocalcemia with inappropriately low parathyroid hormone (PTH) levels. Bone turnover is abnormally low and bone mineral density (BMD) is typically increased. Plasma calcium levels can be normalized by treatment with calcium supplements and vitamin D analogs, but bone turnover remains low and patients complain of a reduced quality of life (QoL). During recent years, a number of studies have shown that PTH replacement therapy (PTH-RT) may maintain calcium levels within the normal range, while the need for calcium and vitamin D supplements is reduced. In the initial response to subcutaneous PTH injections once or twice daily, bone turnover is overstimulated. BMD increases in cancellous bone, but decreases in cortical bone due to an increased porosity. Microcomputed tomography scans and histomorphometric studies on bone biopsies have shown changes similar to the well-known bone anabolic effects of PTH treatment in osteoporosis rather than a normalization of bone remodeling balancing the anabolic and catabolic effects of PTH. Most recently, continuous PTH delivery by pump was shown to increase the levels of bone markers into the normal range (without overstimulation of bone turnover) and with a normalization of renal calcium excretion. As PTH has a short plasma half-life, these findings indicate that exposure to PTH once or twice daily is not sufficient to reestablish a calcium homeostasis and bone metabolism that resembles normal physiology. Further studies should assess the effects of continuous PTH exposure by pump delivery (or multiple daily injections) on BMD and bone histology, as well as the effects of PTH-RT on indices of QoL.

Distribution of serum βCTX in a population-based study of postmenopausal women taking into account different anti-osteoporotic therapies (the FRODOS Cohort)

This cross-sectional study evaluated the distribution of serum cross-linked C-telopeptides of collagen type I (βCTXs) in postmenopausal women, the characteristics of bone remodeling, and the factors influencing this bone marker, especially the use of anti-osteoporotic drugs. Women (n = 4,175) aged 59-70 years randomly selected from the community were invited to participate, measuring βCTXs and lumbar and femoral bone mineral density at recruitment. Risk factors for osteoporosis and the use of anti-osteoporotic treatment were collected with a structured questionnaire. We evaluated the percentage of women with increased (βCTXs >0.620 ng/mL) and decreased bone turnover (βCTXs <0.100 ng/mL) and those reaching the so-called treatment target (values of βCTXs within the lower half of the reference range for healthy young premenopausal women). Two thousand nine hundred sixty-eight women (70 %) participated (2,405 non-treated and 563 treated). Increased and decreased bone turnover was observed in 16.4 and 1.8 %, respectively, of non-treated women with significant differences compared with treated women (9.7 and 14.2 %, respectively, p < 0.001); 28 % of non-treated osteoporotic individuals had increased bone turnover versus 14 % of osteopenic participants and 8.8 % of women with normal bone density (p < 0.001). Women receiving bisphosphonates presented the highest percentages of decreased bone turnover (27 %) and βCTXs (43 %) within the treatment target. Increased bone turnover is observed in 16.4 % of non-treated postmenopausal women and is more frequent in individuals with osteoporosis, whereas decreased bone turnover is unusual. Most participants taking bisphosphonates had values within the treatment target, but nearly one quarter had decreased bone turnover.

Recommendations on the management of fragility fracture risk in women younger than 70 years

The risk for fragility fracture represents a problem of enormous magnitude. It is estimated that only a small fraction of women with this risk take the benefit of preventive measures. The relationship between estrogen and bone mass is well known as they are the other factors related to the risk for fracture. There are precise diagnostic methods, including a tool to diagnose the risk for fracture. Yet there continues to be an under-diagnosis, with the unrecoverable delay in instituting preventive measures. Women under the age of 70 years, being much more numerous than those older, and having risk factors, are a group in which it is essential to avoid that first fragility fracture. Today it is usual not to differentiate between the treatment and the prevention of osteoporosis since the common aim is to prevent fragility fractures. Included in this are women with osteoporosis or with low bone mass and increased risk for fracture, for whom risk factors play a primary role. There is clearly controversy over the type of treatment and its duration, especially given the possible adverse effects of long-term use. This justifies the concept of sequential treatment, even more so in women under the age of 70, since they presumably will need treatment for many years. Bone metabolism is age-dependent. In postmenopausal women under 70 years of age, the increase in bone resorption is clearly predominant, related to a sharp drop in estrogens. Thus a logical treatment is the prevention of fragility fractures by hormone replacement therapy (HRT) and, in asymptomatic women, selective estradiol receptor modulators (SERMs). Afterwards, there is a period of greater resorption, albeit less intense but continuous, when one could utilise anti-resorptive treatments such as bisphosphonates or denosumab or a dual agent like strontium ranelate. Bone formation treatment, such as parathyroid hormone (PTH), in women under 70 years will be uncommon. That is because it should be used in cases where the formation is greatly diminished and there is a high risk for fracture, something found in much older women.

IL-6 receptor inhibition positively modulates bone balance in rheumatoid arthritis patients with an inadequate response to anti-tumor necrosis factor therapy: biochemical marker analysis of bone metabolism in the tocilizumab RADIATE study (NCT00106522)

OBJECTIVE

To evaluate changes in biochemical markers of bone metabolism in response to tocilizumab in patients with anti-tumor necrosis factor-refractory rheumatoid arthritis (RA).

METHODS

RADIATE was a randomized, double-blind, placebo-controlled, parallel-group phase 3 trial. C-reactive protein, osteocalcin (OC), C-terminal telopeptides of type-I collagen (C-terminal telopeptides of type-1 collagen (CTX-I) and type-I collagen degradation product), and matrix metalloproteinase-3 (MMP-3) serum levels were analyzed from 299 RA patients. Patients were randomly assigned to either tocilizumab (4 or 8 mg/kg) or placebo intravenously every 4 weeks, along with concomitant stable methotrexate (10 to 25 mg weekly) in all treatment arms. The change in biochemical markers CTX-I and OC in combination was evaluated as a measure of net bone balance, a reflection of the change in equilibrium between resorption and formation.

RESULTS

Both tocilizumab doses decreased C-reactive protein levels and significantly inhibited cathepsin K-mediated bone resorption in RADIATE subjects, as measured by a decrease in CTX-I. There was a significant overall improvement in net bone balance at week 16 as measured by a decrease in the CTX-I:OC ratio (-25%, P < 0.01). Furthermore, a significant reduction in MMP-3 (43%, P < 0.001) and type-I collagen degradation product levels (18%, P < 0.001) were observed following treatment, both consistent with decreased MMP-mediated type-I collagen catabolism in joint tissue.

CONCLUSIONS

In anti-tumor necrosis factor-refractory patients, tocilizumab significantly reduced the levels of biochemical markers of cathepsin K-mediated bone resorption and MMP-mediated tissue degradation and remodeling. These observations suggest that tocilizumab has a positive effect on bone balance, which could in part explain the retardation of progressive structural damage observed with tocilizumab. Clinical trial registry number: NCT00106522.

Oral salmon calcitonin--pharmacology in osteoporosis

IMPORTANCE OF THE FIELD

Osteoporosis is a slow progressive disease with develops over decades, and where intervention is needed for an extended number of years. This highlights the need for safe intervention possibilities, which have sustained beneficial effects post-treatment.

AREAS COVERED IN THIS REVIEW

Articles on salmon calcitonin appearing on Pubmed from 1960 until today, with focus on a newly developed oral formulation showing increased exposure and efficacy compared with nasal formulation is reviewed. The second half focuses on long-term phenomena, such as bone quality and resolution effects. The final part discusses potential additional benefits of salmon calcitonin.

WHAT THE READER WILL GAIN

Insight into the clinical development of an orally formulated peptide, as well as a detailed understanding of why this approach could revive salmon calcitonin as a treatment for osteoporosis.

TAKE HOME MESSAGE

The oral formulation of salmon calcitonin provides additional benefits and increased efficacy on bone based on Phase I and II clinical trials data, as compared with the nasal formulation. Hence, the results on the ongoing Phase III fracture trial are awaited with great interest.

Is bone quality associated with collagen age?

The World Health Organization defines osteoporosis as a systemic disease characterized by decreased bone tissue mass and microarchitectural deterioration, resulting in increased fracture risk. Since this statement, a significant amount of data has been generated showing that these two factors do not cover all risks for fracture. Other independent clinical factors, such as age, as well as aspects related to qualitative changes in bone tissue, are believed to play an important role. The term "bone quality" encompasses a variety of parameters, including the extent of mineralization, the number and distribution of microfractures, the extent of osteocyte apoptosis, and changes in collagen properties. The major mechanism controlling these qualitative factors is bone remodeling, which is tightly regulated by the osteoclast/osteoblast activity. We focus on the relationship between bone remodeling and changes in collagen properties, especially the extent of one posttranslational modification. In vivo, measurements of the ratio between native and isomerized C-telopeptides of type I collagen provides an index of bone matrix age. Current preclinical and clinical studies suggests that this urinary ratio provides information about bone strength and fracture risk independent of bone mineral density and that it responds differently according to the type of therapy regulating bone turnover.

Clodronic acid formulations available in Europe and their use in osteoporosis: a review

Clodronic acid (Cl(2)-MBP [dichloromethylene bisphosphonic acid], clodronate) is a halogenated non-nitrogen-containing bisphosphonate with antiresorptive efficacy in a variety of diseases associated with excessive bone resorption. The drug is believed to inhibit bone resorption through induction of osteoclast apoptosis, but appears also to possess anti-inflammatory and analgesic properties that contrast with the acute-phase and inflammatory effects seen with nitrogen-containing bisphosphonates. Clodronic acid has been shown to be effective in the maintenance or improvement of bone mineral density when given orally, intramuscularly or intravenously in patients with osteoporosis. Use of the drug is also associated with reductions in fracture risk. The intramuscular formulation, which is given at a dose of 100 mg weekly or biweekly, is at least as effective as daily oral therapy and appears more effective than intermittent intravenous treatment. Intramuscular clodronic acid in particular has also been associated with improvements in back pain. The drug is well tolerated, with no deleterious effects on bone mineralization, and use of parenteral therapy eliminates the risk of gastrointestinal adverse effects that may be seen in patients receiving bisphosphonate therapy.

Investigation of the diurnal variation in bone resorption for optimal drug delivery and efficacy in osteoporosis with oral calcitonin

Background

Bone resorption displays marked diurnal variation. Reversible inhibition of bone resorption may result in best possible efficacy when bone resorption peaks. The aim of the study was to assess the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of 0.8 mg of oral salmon calcitonin (sCT) and the effect of timing of drug intake.

Methods

The study was a randomized, double-blind, double-dummy, placebo-controlled, phase I study to assess the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of 0.8 mg of oral sCT in healthy postmenopausal women. Totally 81 subjects were included, aimed at investigation of a morning dose given at 8:00 (n = 42), a pre-dinner dose given at 17:00 (n = 20), and an evening dose given at 22:00 (n = 19). Plasma sCT concentrations and bone resorption (C-terminal-telopeptide of collagen type I (CTX-I)) was assessed.

Results

Morning and pre-dinner dosing led to comparable concentration of sCT of 45 pg/ml, whereas there was a tendency towards lower Cmax for the evening dosing having a mean of 24 pg/ml. The maximum difference from placebo was observed 1 to 3 hours post-dose with a 40 to 50% suppression consequent to morning dose, and about 75% suppression after pre-dinner and evening dose, due to the increase bone resorption as a result of circadian variation.

Conclusion

The study suggests that orally administered 0.8 mg of salmon calcitonin was effective in suppression of serum CTX irrespective of time of dosing. The pre-dinner dosing resulted in optimum efficacy response corresponding to an overall suppression of bone resorption by 25%.

Trial registration

NCT00411125

Theoretical implications of the biomechanical fracture threshold

Because of the dichotomous nature of a bone fracture, when Phi, the ratio of the applied impact force to the bone strength, is greater than a critical value--the biomechanical fracture threshold--fracture should occur. We sought to elucidate the conceptual implications of this biomechanical fracture threshold with application to hip fracture. We used data from the PaTH study, a 2-yr clinical trial in postmenopausal women treated with alendronate, PTH, or their combination. Outcomes included the force applied to the hip in a sideways fall as estimated from subject height and weight; femoral strength as determined by QCT-based finite element analysis; the load-to-strength ratio Phi; and total hip areal BMD from DXA. Results indicated that those with "very low" femoral strength (<2000 N) invariably had load-to-strength ratio Phi values well above the theoretical biomechanical fracture threshold (Phi = 1), but those with "moderately low" femoral strength (2000-4000 N) displayed Phi values both above and below the theoretical biomechanical fracture threshold. This finding implies that the risk of a hip fracture can be high in those with only moderately low BMD because femoral strength can be low relative to fall impact forces. The observed weak correlation between areal BMD and the load-to-strength ratio Phi (r2 = 0.14) suggests that consideration of the biomechanical fracture threshold may improve fracture risk assessment, particularly for those in the osteopenic range. Regarding treatment effects, only those subjects having load-to-strength ratio Phi values within a relatively narrow "transition zone" of +/- 20% of the assumed biomechanical fracture threshold at baseline were predicted to change fracture status during the trial. In theory, outcomes of fracture trials may be dominated by the responses of those within the "transition zone" at baseline, and treatment benefits in terms of fracture efficacy may depend the patient's baseline status with respect to the biomechanical fracture threshold. We conclude that consideration of the theoretical implications of the biomechanical fracture threshold may lead to new insights and advances in the assessment and treatment of osteoporosis.

Calcitonin: a drug of the past or for the future? Physiologic inhibition of bone resorption while sustaining osteoclast numbers improves bone quality

Postmenopausal osteoporosis results from a continuous imbalance between bone resorption and bone formation, favoring bone resorption. An increasing number of treatments for osteoporosis are in development and on the market. A range of differences and similarities are found between these treatment options, and these need to be carefully evaluated before the initiation of treatment. This article summarizes data from in vitro and animal studies, as well as clinical trials, on the effect of calcitonin on bone turnover. Calcitonin was found to exert its antiresorptive effects via directly reducing osteoclastic resorption, and thus leads to an increase in bone mineral density and bone strength. Furthermore, calcitonin appears to mainly target the most active osteoclasts, and in contrast to most other antiresorptive agents it does not reduce the number of osteoclasts. Finally, in humans, while attenuating resorption, calcitonin treatment does not interfere markedly with bone formation, in contrast to other currently available antiresorptive agents. Thus, we speculate that calcitonin treatment will lead to a continuously positive bone balance in contrast with other antiresorptive agents currently on the market and thereby, in a physiologic manner, result in improved bone quality. Calcitonin is currently only available in injectable and nasal formulations. An oral formulation may, however, improve patient acceptance and compliance. Currently, several different routes are being pursued to identify an optimal oral formulation, of which the technology based on 5-CNAC is the most advanced. There are promising clinical data available for this formulation from both osteoarthritis and osteoporosis clinical trials, although the antifracture efficacy is not yet known.

Should subchondral bone turnover be targeted when treating osteoarthritis?

OBJECTIVE

Osteoarthritis (OA) is the most common form of arthritic disease, and it is a major cause of disability and impaired quality of life in the elderly. OA is a complex disease of the entire joint, including bone and cartilage, thereby presenting alternative approaches for treatment. This review summarizes emerging observations from cell biology to preliminary clinical trials, describing interactions between the bone and cartilage components. We speculate whether a treatment for OA would be possible without targeting the bone compartment?

METHODS

Peer-reviewed articles found using pre-defined search criteria and published in the PubMed database until June 2007 are summarized. In addition, abstracts from the OsteoArthritis Research Society International (OARSI) conferences in the time period 2000-2007 were included.

RESULTS

Bone and cartilage health seem to be tightly associated. Ample evidence is found for bone changes during progression of OA, including, but not limited to, increased turnover in the subchondral bone, thinning of the trabecular structure, osteophytes, bone marrow lesions and sclerosis of the subchondral plate. In addition, a range of investigations has described secondary positive effects on cartilage health when bone resorption was suppressed, or deterioration of the cartilage when resorption is increased.

CONCLUSION

An optimal treatment for OA might include targeting both the bone and cartilage compartments. Hence, as several cell systems are to be targeted in a safe manner, limited options seem possible.