Alendronate protects against articular cartilage erosion by inhibiting subchondral bone loss in ovariectomized rats

Osteoporosis (OP) and osteoarthritis (OA) are major health problems in the increasing elderly population, particularly in postmenopausal women, but their relationship remains unclear. The present study investigated whether alendronate (ALN), a potent inhibitor of bone resorption, could protect articular cartilage from degeneration in a combined animal model of OP and OA induced by ovariectomy (OVX). Seventy-eight seven-month-old female Sprague–Dawley rats were assigned into five experimental groups: (1) sham-operated with vehicle treatment, (2) sham-operated with ALN treatment, (3) OVX with vehicle treatment, (4) ALN treatment starting at OVX, and (5) ALN treatment starting at eight weeks after OVX. Histological and micro-CT analyses, together with urine collagen degradation markers, indicated that early ALN treatment completely prevented both subchondral bone loss and cartilage surface erosion induced by OVX. Although late ALN treatment also inhibited subchondral bone loss and significantly reduced cartilage erosion in the OVX rats, these tissues did not completely recover even after 10-weeks of ALN treatment. Quantitative RT-PCR analyses showed that the protective effect of ALN correlated with increased ratio of OPG/RANKL in both subchondral bone and cartilage. Moreover, whereas OVX caused upregulation of expression of matrix metalloproteinases MMP-13 and MMP-9 in the articular cartilage and chondrocytes in the interface between the articular cartilage and subchondral bone, respectively, early ALN treatment blocked whereas late ALN treatment attenuated the upregulation of these catabolic enzymes in the corresponding tissues. Together, these data indicate that the subchondral bone loss plays an important role in OA pathogenesis in the combined OP and OA model and suggest that treatment timing is an important factor for the effectiveness of anti-resorptive drug therapy of combined OP and OA.     

Changes in articular cartilage and subchondral bone histomorphometry in osteoarthritic knee joints in humans

In this study, we have examined the correlation between the histological and histochemical changes of articular cartilage and bone parameters of the underlying subchondral bone. The aim was to elucidate patterns of bone parameter changes within different depths of subchondral bone in the joints with macroscopically normal cartilage and in joints with osteoarthritis (OA). Ten tibial plateaus were taken from patients during total knee replacement surgery due to severe OA. They were compared with 10 sets of tibial condyles obtained from autopsy subjects with no history of bone or joint disease. The cylindrical cartilage-bone samples were taken out from the anterior, posterior, external, and internal areas of the condyles for cartilage assessment (Mankin score) and subchondral bone histomorphometry. Four histomorphometric parameters were measured: bone volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.S). Our study showed that subchondral bone from the OA group had significantly higher bone volume (54.1 +/- 10.6%) than control group (37.8 +/- 8.1%) (P < 0.01). In addition, trabecular parameters from the OA subchondral bone showed a smaller number of sparsely distributed and thicker trabecules than in control group (P < 0.05). Medial and lateral condyle from the control group did not differ significantly, while medial condyle from OA group showed a high increase of bone volume (62.8 +/- 13.3) and consecutively different trabecular parameters when compared with the lateral condyle from the same group. Also, it was shown that there are regional differences (anterior, posterior, internal, and external) in bone parameters between both condyles within both, control and OA groups. Comparison of bone parameters from three different stage of articular cartilage degeneration (Mankin score) showed that higher degree of cartilage degeneration is followed by significant changes in subchondral bone architecture. Furthermore, we have found that progression of cartilage degeneration leads to changes in bone parameters which affected deeper levels of subchondral bone. According to these results, it can be suggested that changes in histomorphometric parameters of subchondral bone are secondary to cartilage damage and proceed deeper into subchondral bone with increasing cartilage degeneration.     

Three-dimensional visualization and pathologic characteristics of cartilage and subchondral bone changes in the lumbar facet joint of an ovariectomized mouse model

Background Context

Low back pain (LBP) is more prevalent among postmenopausal women than men. Ovariectomy (OVX) is an established animal model that mimics the estrogen deficiency of postmenopausal women. Little is known about the three-dimensional (3D) morphologic properties of cartilage and subchondral bone changes in the lumbar facet joint (LFJ) of an OVX mouse model.

Effects of estrogen replacement therapy on bone turnover in subchondral bone and epiphyseal metaphyseal cancellous bone of ovariectomized cynomolgus monkeys.

ERT decreases the severity of OA in OVX cynomolgus monkeys. We show that bone formation is greater in subchondral bone compared with epiphyseal/metaphyseal cancellous bone of the proximal tibia in these animals and that ERT decreases bone formation in both sites. ERT may decrease the risk of OA by decreasing bone formation in the SC bone. INTRODUCTION: Estrogen replacement therapy (ERT) decreases the risk of osteoporosis and osteoarthritis (OA) in postmenopausal women and has been shown to have direct effects on cells of the bone and cartilage. The effects of ERT have been studied extensively in cancellous bone, but subchondral (SC) bone directly beneath the articular cartilage has not been specifically evaluated. MATERIALS AND METHODS: Adult feral female cynomolgus monkeys were bilaterally ovariectomized (OVX) to simulate menopause; treated with ERT, soy phytoestrogens (SPE), or no hormones (OVX control group) for 3 years; and labeled with calcein before necropsy. At necropsy, the proximal tibias of 20 randomly selected animals from each treatment group were embedded in bioplastic and sectioned. Areas and labels were measured in a carefully defined region of the SC bone and epiphyseal/metaphyseal cancellous (EMC) bone, and derived dynamic and static indices were compared between the SC and EMC bone and among the three treatment groups. Student's t-tests and ANOVA were used to compare the data. RESULTS AND CONCLUSIONS: In both the SC and EMC bone, most of the values for the dynamic indices were highest in the OVX control group, intermediate in the SPE group, and lowest in the ERT group. The mineralizing surface, double-labeled surface, and bone formation rate (surface referent) were significantly higher in the SC bone compared with the EMC bone in the OVX control group. The trabecular bone volume was higher in the SPE-treated group compared with the OVX control group. In conclusion, the bone turnover indices were higher in the SC bone compared with the EMC bone, and ERT decreased these indices in both sites. In addition, SPE was protective against loss of bone volume.     

Alterations in mineral composition observed in osteoarthritic joints of cynomolgus monkeys

Osteoarthritis (OA) is a prevalent joint disease that affects more than 40 million Americans and is characterized by degeneration of the articular cartilage and thickening of the underlying subchondral bone. Although subchondral bone thickening has been implicated in articular cartilage degeneration, very little is known about the composition of subchondral bone in OA. In the present study, infrared microspectroscopy (IRMS) was used to determine the chemical composition of the calcified cartilage-subchondral bone plate in a monkey model of OA. Specifically, the levels of mineralization (mineral/protein ratio), carbonate accumulation (carbonate/protein ratio), crystallinity, and collagen structure were determined as a function of animal age and OA severity. OA severity was assessed using a grading scheme that included scores or measurements for several histomorphometric parameters including articular cartilage fibrillation or clefting, subchondral bone thickness, and numbers of tidemarks and chondrocyte clones. Individual scores and measurements were summarized using principal components (factor) analysis. Results demonstrated that the level of mineralization and carbonate content increased as a function of animal age. In addition, bone mineralization level increased as subchondral bone thickness increased. Dramatic increases in the mineralization level and carbonate accumulation were also observed as a function of the number of tidemarks. The presence of multiple tidemarks indicates the occurrence of one or more additional phases of cartilage calcification, suggesting that the observed compositional changes are due to cartilage mineralization. Our results support a reactivation of endochondral ossification that occurs with age, which is more pronounced in OA. No relationships were observed between mineral crystallinity and collagen cross-linking as a function of age or OA severity. In summary, compositional analysis of the mineralized plate beneath the articular cartilage in OA is characterized by thickened, overmineralized calcified cartilage or subchondral bone, which likely puts added mechanical stress on the joint, contributing to the progression of OA.     

Association between subchondral bone structure and osteoarthritis histopathological grade

Despite increasing evidence that subchondral bone contributes to osteoarthritis (OA) pathogenesis, little is known about local changes in bone structure compared to cartilage degeneration. This study linked structural adaptation of subchondral bone with histological OA grade. Twenty‐five osteochondral samples of macroscopically different degeneration were prepared from tibiae of 14 patients. Samples were scanned with micro‐computed tomography (μCT) and both conventional structural parameters and novel 3D parameters based on local patterns were analyzed from the subchondral plate and trabecular bone. Subsequently, samples were processed for histology and evaluated for OARSI grade. Each bone parameter and OARSI grade was compared to assess structural adaptation of bone with OA severity. In addition, thicknesses of cartilage, calcified cartilage, and subchondral plate were analyzed from histological sections and compared with subchondral bone plate thickness from μCT. With increasing OARSI grade, the subchondral plate became thicker along with decreased specific bone surface, while there was no change in tissue mineral density. Histological analysis showed that subchondral plate thickness from μCT also includes calcified cartilage. Entropy of local patterns increased with OA severity, reflecting higher tissue heterogeneity. In the trabecular compartment, bone volume fraction and both trabecular thickness and number increased with OARSI grade while trabecular separation and structure model index decreased. Also, elevation of local patterns became longitudinal in the subchondral plate and axial transverse in trabecular bone with increasing OARSI grade. This study demonstrates the possibility of radiological assessment of OA severity by structural analysis of bone. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. J Orthop Res 35:785–792, 2017.

     

膝关节原发性骨关节炎软骨和软骨下骨病理改变的定量研究

目的观察膝关节原发性骨关节炎(osteoarthritis,OA)胫骨平台软骨和软骨下骨病理改变特点,对比内、外侧平台软骨和软骨下骨结构参数,探讨钙化层和软骨下骨在OA发病机制中的作用。方法取2009年10月-2011年5月行人工全膝关节置换术治疗的30例30膝原发性OA患者自愿捐赠的新鲜胫骨平台标本进行实验。其中男11例,女19例;年龄55～78岁,平均65.1岁。病程10～25年,平均16.6年;患膝内翻畸形1～23°,平均9.3°。大体观察胫骨平台后在内、外侧中央负重区取材,常规制备脱钙石蜡切片,行HE和番红O/固绿染色,观察关节软骨退变特点,参照Mankin评分标准评分并分期;观察钙化层及软骨下骨病理改变。应用Image Pro Plus 6.0图像分析软件测量软骨和软骨下骨结构参数,包括软骨全层(total articular cartilage,TAC)厚度、钙化层(articular calcified cartilage,ACC)厚度、ACC/TAC比值、软骨下骨板(subchondral bone plate,SCP)厚度以及骨小梁体积分数(trabecular bone volume,BV/TV)。结果大体观察内侧平台软骨退变较外侧严重,内侧平台软骨Mankin评分为(12.4±1.1)分,显著高于外侧平台的(8.3±1.6)分(t=12.173,P=0.000)。根据Mankin评分结果在60个标本中,14个为OA早期,可见软骨浅表层裂隙、潮线复制和软骨下骨增厚;19个为OA中期,可见软骨深层裂隙、多发软骨下骨吸收陷窝和明显增厚的软骨下骨;27个为OA晚期,可见软骨全层缺失、软骨内化骨和"象牙化"软骨下骨。软骨和软骨下骨结构参数测定示:内侧平台TAC厚度显著低于外侧平台,ACC/TAC比值、BV/TV及SCP厚度显著高于外侧平台,差异均有统计学意义(P<0.05)。内、外侧平台ACC厚度比较,差异无统计学意义(P>0.05)。结论钙化层和软骨下骨可能在OA发生与进展中发挥了重要作用。     

In vivo effect of two different pulsed electromagnetic field frequencies on osteoarthritis

Osteoarthritis (OA) is a joint pathology characterized by fibrillation, reduced cartilage thickness and subchondral bone sclerosis. There is evidence that pulsed electromagnetic fields (PEMFs) counteract OA progression, but the effect of two different PEMF frequencies has not yet been shown. The aim of this study was to test the effectiveness of PEMFs at two different frequencies (37 and 75 Hz) in a late OA stage in 21‐month‐old Guinea pigs. After 3 months of 6 h/day PEMF stimulation, histological and histomorphometric analyses of the knees were performed. At both frequencies, PEMFs significantly reduced histological cartilage score, fibrillation index (FI), subchondral bone thickness (SBT) and trabecular number (Tb.N) and increased trabecular thickness (Tb.Th) and separation (Tb.Sp) in comparison to the not treated SHAM group. However, PEMFs at 75 Hz produced significantly more beneficial effects on the histological score and FI than 37 Hz PEMFs. At 75 Hz, PEMFs counteracted cartilage thinning as demonstrated by a significantly higher cartilage thickness values than either those of the SHAM or 37 Hz PEMF‐treated groups. Although in severe OA both PEMF frequencies were able to limit its progression, 75 Hz PEMF stimulation achieved the better results. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:677–685, 2014.     

伊班膦酸钠对大鼠膝骨关节炎关节软骨及软骨下骨的影响

目的观察伊班膦酸钠对大鼠膝骨关节炎关节软骨及软骨下骨的影响,并从MAPKs信号通路探讨其作用机制。方法将30只3月龄SD雄性大鼠随机分成3组(每组10只)。假手术组、前交叉韧带切断术组(ACLT组)、前交叉韧带切断术+伊班膦酸钠治疗组(治疗组)。其中ACLT组及治疗组均行ACLT术(膝关节前交叉韧带切断术)处理。术后1w,治疗组予以腹腔注射伊班膦酸钠10μg/kg,1 w 1次,共12 w;ACLT组腹腔注射生理盐水,剂量参照伊班膦酸钠,1w 1次,共12 w。12 w后处死动物,对关节软骨行Mankin评分、软骨下骨显微CT及骨组织定量分析、以及对MAPKs信号通路和MMP-13 mRNA表达水平进行分析。结果 1ACLT组的骨体积分数(BV/TV)、骨小梁数量(Tb.N)显著低于假手术组(P0.05、P0.05),骨小梁厚度(Tb.Th)两组之间差异无明显统计学意义、而骨小梁间隔(Tb.Sp)显著高于假手术组(P0.01);治疗组骨体积分数(BV/TV)、骨小梁数量(Tb.N)明显高于ACLT组(P0.05、P0.05),骨小梁厚度(Tb.Th)两组之间差异无明显统计学意义,而骨小梁间隔(Tb.Sp)显著低于ACLT组(P0.05)。2ACLT组的Mankin评分明显高于假手术组(P0.01);治疗组的Mankin评分明显低于ACLT组(P0.05)。3ACLT组中MAPKs信号通路(C-JUN、ERK1及P38)和MMP-13水平明显高于假手术组(P0.01、P0.01、P0.01、P0.01);治疗组的MAPKs信号通路(C-JUN、ERK1及P38)和MMP-13水平明显低于ACLT组(P0.01、P0.01、P0.01、P0.01)。结论伊班膦酸钠可能通过调控MAPKs信号通路的机制缓解大鼠膝骨关节炎关节软骨退变,并且抑制软骨下骨的骨质疏松。     

Similarities and discrepancies in subchondral bone structure in two differently induced canine models of osteoarthritis

In osteoarthritis (OA), cartilage degradation is accompanied by subchondral bone changes. The pathogenesis and physiology of bone changes in OA are still unclear. The changes in subchondral bone architecture and cartilage damage were compared in differently induced experimental models of OA. Experimental OA was induced bilaterally by anterior cruciate ligament transection (ACLT) or by cartilage trauma (Groove model); bilateral sham surgery served as control. Lysylpyridinoline (LP, bone resorption) and C‐telopeptide of type II collagen (CTX‐II, cartilage breakdown) were measured over time. At 20 weeks after surgery, the subchondral cortical plate and trabecular bone of the tibia were analyzed by micro–computed tomography (µCT) and cartilage degeneration was analyzed histologically and biochemically. In both models, cartilage degeneration and cortical subchondral plate thinning were present. CTX‐II levels were elevated over time in both models. Subchondral trabecular bone changes were observed only in the ACLT model, not in the Groove model. Correspondingly, LP levels were elevated over time in the ACLT model and not in the Groove model. Interestingly, the trabecular bone changes in the ACLT model were extended to the metaphyseal area. The early decrease in plate thickness, present in both models, as was cartilage damage, suggests that plate thinning is a phenomenon that is intrinsic to the process of OA independent of the cause/induction of OA. On the other hand, trabecular changes in subchondral and metaphyseal bone are not part of a common pathway of OA development and may be induced biomechanically in the destabilized and less loaded ACLT joint. © 2010 American Society for Bone and Mineral Research     

Subchondral bone fragility with meniscal tear accelerates and parathyroid hormone decelerates articular cartilage degeneration in rat osteoarthritis model

The aims of this study were to investigate the influence of subchondral bone fragility (SBF) on the progression of the knee osteoarthritis by using a novel rat model, and to examine the preventive effect of parathyroid hormone (PTH) on cartilage degeneration. First, 40 rats were assigned to the following four groups: Sham, SBF, Medial meniscal tear (MMT), and MMT + SBF groups. In SBF and MMT + SBF groups, we induced SBF by microdrilling the subchondral bone. Second, 10 additional rats were randomly assigned to the following two groups: MMT + SBF + saline and MMT + SBF + PTH groups. Osteoarthritic changes in the articular cartilage and subchondral bone were evaluated using safranin‐O/fast green staining, matrix metalloproteinase‐13 (MMP‐13), and type X collagen immunohistochemistry, toluidine blue staining, and micro‐CT scanning. The combination of SBF and meniscal tear increased the number of mast cells in the subchondral bone, and led to the abnormal subchondral bone microarchitecture, such as abnormally decreased trabecular number and increased trabecular thickness, compared with meniscal tear alone. Moreover, SBF with meniscal tear enhanced articular cartilage degeneration and increased the expression of MMP‐13 and type X collagen, compared with meniscal tear alone. The administration of PTH decreased the number of mast cells in the subchondral bone and improved the microstructural parameters of the subchondral bone, and delayed the progression of articular cartilage degeneration. These results suggest that SBF is one of the factors underlying the osteoarthritis development, especially in knees with traumatic osteoarthritis, and that the administration of PTH is a potential therapeutic treatment for preventing OA progression. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1959–1968, 2018.

     

The inhibition of subchondral bone resorption in the early phase of experimental dog osteoarthritis by licofelone is associated with a reduction in the synthesis of MMP-13 and cathepsin K

OBJECTIVE: To evaluate the morphological changes that take place in the subchondral bone and calcified cartilage zone in the experimental anterior cruciate ligament (ACL) dog model of osteoarthritis (OA) and analyze concomitant changes in the level of MMP-13 and cathepsin K, as well as examine the therapeutic effects of licofelone, a lipoxygenase (LO)/cyclooxygenase (COX) inhibitor, on these morphological and biochemical changes. METHODS: Experimental group 1 underwent sectioning of the ACL of the right knee with no active treatment (placebo group). Experimental groups 2 and 3 underwent sectioning of the ACL of the right knee and were administered therapeutic concentrations of licofelone (2.5 or 5.0 mg/kg/day p.o., respectively) for 8 weeks, beginning the day following surgery. Group 4 consisted of untreated dogs used as normal control. Specimens of subchondral bone including the calcified cartilage were selected from lesional and non-lesional areas of OA tibial plateaus. Specimens were processed for static morphometric analysis and immunohistochemical analysis for MMP-13 and cathepsin K. RESULTS: As indicated by a reduction in bone surface and trabecular thickness, a significant loss of subchondral bone occurred in OA dogs. These changes were associated with an increased level of MMP-13 synthesis by bone cells and an increase in the osteoclast population that stained strongly positive for cathepsin K and MMP-13. Changes were much more pronounced in the specimens taken from the lesional areas. Treatment with licofelone decreased, in a dose-dependent manner, the OA bone morphological changes at the same time it reduced the level of MMP-13 in bone cells and the number of cathepsin K and MMP-13 positive osteoclasts. CONCLUSIONS: Increased bone loss and bone resorption is associated with the development of OA cartilage lesions. Licofelone treatment was found to prevent the morphological and biochemical changes seen in early experimental OA effectively. These findings may help explain the mechanisms by which this drug could exert its possible effect on the development of OA.     

Ultrastructural immunolocalization of bone sialoprotein in guinea-pig osteoarthritis

In diarthrodial joints, bone and cartilage are structurally and functionally inseparable as shown in osteoarthritis (OA), where subchondral bone changes are integral in the disease process. By ultrastructural immunohistochemistry using polyclonal antibodies against guinea-pig bone sialoprotein (BSP), we investigated the distribution of this matrix protein at the osteocartilaginous interface in Hartley guinea-pig knees at different stages of primary osteoarthritis. Between 6 and 12 months they developed moderate osteoarthritic changes predominantly in the medial condyle, progressing to severe OA at 30 months. In all age groups BSP labeling was concentrated to the osteocartilaginous interface at a 1 μm narrow zone at the interface. In the medial osteoarthritic condyle, BSP was increased as compared with the lateral nonosteoarthritic condyle, but only at 30 months, when cartilage fibrillation correlated to BSP. Our observations suggest that altered BSP abundance may be a potential bone marker for late stage OA, while early events in bone cannot be monitored. BSP is expressed early in osteogenesis and may have a role in biological mineralization and growth. Since a sharp zone of intense BSP labeling remains at a remarkably constant level throughout life in guinea-pigs, BSP may have an important structural and/or regulating role at the interface. The protein may act as an anchor of calcified articular cartilage to subchondral bone or by regulating mineralization at the osteocartilaginous interface.     

LMP-1 Retroviral Gene Therapy Influences Osteoblast Differentiation and Fracture Repair: A Preliminary Study

Bisphosphonates are antiresorptive drugs commonly used to treat osteoporosis. It is not clear, however, what the influence of the time point of treatment is. Recently developed in vivo micro-computed tomographic (CT) scanners offer the possibility to study such effects on bone microstructure in rats. The aim of this study was to determine the influence of early and late zoledronic acid treatment on bone in ovariectomized rats, using in vivo micro-CT. Twenty-nine female Wistar rats were divided into the following groups: ovariectomy (OVX, n = 5), OVX and zoledronic acid (ZOL) at week 0 (n = 8), OVX and ZOL at week 8 (n = 7), and sham (n = 9). CT scans were made of the proximal tibia at weeks 0, 2, 4, 8, 12, and 16; and bone structural parameters were determined in the metaphysis. Two fluorescent labels were administered to calculate dynamic histomorphometric parameters. At week 16, all groups were significantly different from each other in bone volume fraction (BV/TV), connectivity density, and trabecular number (Tb.N), except for the early ZOL and control groups which were not significantly different for any structural parameter. After ZOL treatment at week 8, BV/TV, structure model index, Tb.N, and trabecular thickness significantly improved in the late ZOL group. The OVX and ZOL groups showed, respectively, higher and lower bone formation rates than the control group. Early ZOL treatment inhibited all bone microstructural changes seen after OVX. Late ZOL treatment significantly improved bone microstructure, although the structure did not recover to original levels. Early ZOL treatment resulted in a significantly better microstructure than late treatment. However, late treatment was still significantly better than no treatment.     

Subchondral bone micro-architectural alterations in osteoarthritis: a synchrotron micro-computed tomography study

OBJECTIVES: We evaluated the three-dimensional (3D) micro-architecture of subchondral trabecular (Tb) bone in osteoarthritis (OA). Due to high signal-to-noise ratio and high resolution, micro-computed tomography (micro-CT) by synchrotron radiation is considered as the gold standard for bone micro-architecture imaging. DESIGN: Subchondral bone were extracted from femoral heads in OA cases in areas without cartilage (OAc-; n=6) and in adjacent areas with cartilage (OAc+; n=6) and compared to eight subchondral bone cores from osteoporosis cases (OP). The voxel size of images was 10.13 microm. We measured the bone volume fraction (BV/TV) and morphological parameters: Tb thickness (TbTh), Tb spacing (TbSp), Tb number (TbN), and bone surface/bone volume (BS/BV). The degree of anisotropy (DA), the connectivity by the Euler number and the degree of mineralization (DM) were equally assessed. RESULTS: BV/TV and morphological parameters showed significant differences between OAc- and OP samples (P<0.01 except TbTh: P<0.05) and between OAc- and OAc+ (0.05相似文献   

Characterization of articular cartilage and subchondral bone changes in the rat anterior cruciate ligament transection and meniscectomized models of osteoarthritis

Osteoarthritis (OA) is a chronic joint disease characterized by cartilage destruction, subchondral bone sclerosis, and osteophyte formation. Subchondral bone stiffness has been proposed to initiate and/or contribute to cartilage deterioration in OA. The purpose of this study was to characterize subchondral bone remodeling, cartilage damage, and osteophytosis during the disease progression in two models of surgically induced OA. Rat knee joints were subjected either to anterior cruciate ligament transection (ACLT) alone or in combination with resection of medial menisci (ACLT + MMx). Histopathological changes in the surgical joints were compared with sham at 1, 2, 4, 6, and 10 weeks post-surgery. Using a modified Mankin scoring system, we demonstrate that articular cartilage damage occurs within 2 weeks post-surgery in both surgical models. Detectable cartilage surface damage and proteoglycan loss were observed as early as 1 week post-surgery. These were followed by the increases in vascular invasion into cartilage, in loss of chondrocyte number and in cell clustering. Histomorphometric analysis revealed subchondral bone loss in both models within 2 weeks post-surgery followed by significant increases in subchondral bone volume relative to sham up to 10 weeks post-surgery. Incidence of osteophyte formation was optimally observed in ACLT joints at 10 weeks and in ACLT + MMx joints at 6 weeks post-surgery. In summary, the two surgically induced rat OA models share many characteristics seen in human and other animal models of OA, including progressive articular cartilage degradation, subchondral bone sclerosis, and osteophyte formation. Moreover, increased subchondral bone resorption is associated with early development of cartilage lesions, which precedes significant cartilage thinning and subchondral bone sclerosis. Together, these findings support a role for bone remodeling in OA pathogenesis and suggest that these rat models are suitable for evaluating bone resorption inhibitors as potential disease-modifying pharmaco-therapies.     

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.     

Elevated cross-talk between subchondral bone and cartilage in osteoarthritic joints

Osteoarthritis (OA) is a degenerative joint disease and one of the leading causes of disability in the United States and across the world. As a disease of the whole joint, OA exhibits a complicated etiology with risk factors including, but not limited to, ageing, altered joint loading, and injury. Subchondral bone is hypothesized to be involved in OA development. However, direct evidence supporting this is lacking. We previously detected measurable transport of solute across the mineralized calcified cartilage in normal joints, suggesting a potential cross-talk between subchondral bone and cartilage. Whether this cross-talk exists in OA has not been established yet. Using two models that induced OA by either ageing or surgery (destabilization of medial meniscus, DMM), we tested the hypothesis that increased cross-talk occurs in OA. We quantified the diffusivity of sodium fluorescein (mol. wt. 376Da), a marker of small-sized signaling molecules, within calcified joint matrix using our newly developed fluorescence loss induced by photobleaching (FLIP) method. Tracer diffusivity was found to be 0.30±0.17 and 0.33±0.20μm(2)/s within the calcified cartilage and 0.12±0.04 and 0.07±0.03μm(2)/s across the osteochondral interface in the aged (20-24-month-old, n=4) and DMM OA joints (5-month-old, n=5), respectively, which were comparable to the control values for the contralateral non-operated joints in the DMM mice (0.48±0.13 and 0.12±0.06μm(2)/s). Although we did not detect significant changes in tissue matrix permeability in OA joints, we found i) an increased number of vessels invading the calcified cartilage (and sometimes approaching the tidemark) in the aged (+100%) and DMM (+50%) joints relative to the normal age controls; and ii) a 60% thinning of the subchondral bone and calcified cartilage layers in the aged joints (with no significant changes detected in the DMM joints). These results suggested that the capacity for cross-talk between subchondral bone and articular cartilage could be elevated in OA. Further studies are needed to identify the direction of the cross-talk, the signaling molecules involved, and to test whether subchondral bone initiates OA development and could serve as a pharmaceutical target for OA treatment. This article is part of a Special Issue entitled "Osteoarthritis".     

Progressive cell‐mediated changes in articular cartilage and bone in mice are initiated by a single session of controlled cyclic compressive loading

We previously showed that repetitive cyclic loading of the mouse knee joint causes changes that recapitulate the features of osteoarthritis (OA) in humans. By applying a single loading session, we characterized the temporal progression of the structural and compositional changes in subchondral bone and articular cartilage. We applied loading during a single 5‐minute session to the left tibia of adult (26‐week‐old) C57Bl/6 male mice at a peak load of 9.0N for 1,200 cycles. Knee joints were collected at times 0, 1, and 2 weeks after loading. The changes in articular cartilage and subchondral bone were analyzed by histology, immunohistochemistry (caspase‐3 and cathepsin K), and microcomputed tomography. At time 0, no change was evident in chondrocyte viability or cartilage or subchondral bone integrity. However, cartilage pathology demonstrated by localized thinning and proteoglycan loss occurred at 1 and 2 weeks after the single session of loading. Transient cancellous bone loss was evident at 1 week, associated with increased osteoclast number. Bone loss was reversed to control levels at 2 weeks. We observed formation of fibrous and cartilaginous tissues at the joint margins at 1 and 2 weeks. Our findings demonstrate that a single session of noninvasive loading leads to the development of OA—like morphological and cellular alterations in articular cartilage and subchondral bone. The loss in subchondral trabecular bone mass and thickness returns to control levels at 2 weeks, whereas the cartilage thinning and proteoglycan loss persist. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1941–1949, 2016.     

髋关节骨性关节炎组织学计量与炎性因子表达

目的 探讨骨性关节炎各组织成分中细胞冈子、金属基质蛋白酶等炎性物质表达水平与疾病的关系.方法 获取行OA组关节置换及创伤性股骨颈骨折组患者手术时的软骨、滑膜组织和软骨下骨,苏木素-伊红(HE)染色行软骨下骨组织形态计量分析,应用放射免疫测定肿瘤坏死因子(TNF)-α与门细胞介素(IL)-1β,以酶联免疫吸附试验(ELISA)测金属基质蛋白酶(MMP)-9蛋白表达水平,并将两组结果进行t检验,软骨下骨组织计量值与细胞因子水平进行相关分析.结果 OA组较非OA对照组软骨下骨骨形成增加,骨质硬化骨小梁数目增加并错乱;滑膜组织中MMP-9表达是调;软骨组织中MMP-9及IL-1 β较对照组提高;而在软骨下骨,MMP-9、TNF-α及IL-β均有增高,并且与软骨下骨组织学改变相关联.结论 证实了OA促炎症条件的病理学基础,并且炎性改变与软骨硬化及关节软骨退变相关.