Astaxanthin ameliorates cartilage damage in experimental osteoarthritis

Abstract

Purpose. Astaxanthin is a red-pigment carotenoid found in certain marine animals and plants. Astaxanthin has been shown to inhibit matrix metalloproteinases (MMPs) expression in vitro. However, the effect of astaxanthin on cartilage is still unclear. The aim of this study was to investigate the effects of astaxanthin on cartilage in experimental osteoarthritis (OA).

Methods. New Zealand rabbits underwent anterior cruciate ligament transection to induce OA in right knee. Rabbits received intra-articular injection containing 0.3 ml of vehicle (dimethyl sulfoxide) or astaxanthin (50 μM). Injection was started on the day of operation, and the injection were performed once weekly for six consecutive weeks. Then, rabbits were sacrificed and the right knees were harvested for study.

Results. Cartilage degradation was reduced by astaxanthin, as assessed by morphological and histological examination. Astaxanthin inhibited the gene expression of MMP-1, MMP-3, and MMP-13 in cartilage as compared with the vehicle group.

Conclusions. The results suggest that astaxanthin may be considered as pharmaceutical agent in OA treatment.     

Trichostatin A inhibits expression of cathepsins in experimental osteoarthritis

The aim of this study was to investigate the effects of trichostatin A (TSA) on expression of cathepsins in cartilage in experimental osteoarthritis (OA). OA was induced in 18 rabbits by bilateral anterior cruciate ligament transection (ACLT). Four weeks after surgery, rabbits received intra-articular injection with TSA dissolved in the dimethylsulphoxide (DMSO) in the right knees and DMSO in the left knees once a week for 5 weeks. Rabbits were killed 7 days after the last injection. The knee joints were assessed by morphological and histological examination. Messenger RNA expression of cathepsins K, B, L, S and cystatin C was studied by real-time PCR. TSA inhibited the expression of cathepsins K, B, L, S and cystatin C accompanied with the less degradation in cartilage. The results suggest that TSA exhibits protective effects against cartilage degradation in rabbits with OA and the effects may be associated with the inhibition of cathepsins.     

壳聚糖膝关节腔内注射疗法对兔骨关节炎关节软骨的影响

目的观察关节内注射羧甲基壳聚糖(CMCTS)对兔骨关节炎(OA)关节软骨退变及软骨基质金属蛋白酶(MMP)-1,-3mRNA表达的影响。方法24只大耳白兔行单侧膝关节前交叉韧带切断术,术后5周将动物随机分为3组,A组关节内注射2%CMCTS0.3ml,每2周1次;B组关节内注射1%透明质酸钠(HA)0.3ml,每周1次;C组关节内不注射药物。术后11周处死动物,观察各组股骨内髁关节软骨的大体变化,采用反转录-聚合酶链反应(RT-PCR)方法检测股骨内髁退变软骨中MMP-1和MMP-3的mRNA表达。结果CMCTS和HA注射组软骨退变程度较不用药组明显减轻,CMCTS注射组软骨MMP-1、MMP-3的mRNA表达明显低于HA注射组和不用药组。HA注射组软骨MMP-1和MMP-3的mRNA表达与不用药组比较,差异没有显著性意义。结论CMCTS能够明显抑制OA软骨MMP-1和MMP-3的mRNA表达,明显减轻软骨退变的程度,CMCTS对早期OA软骨有修复保护作用。     

Effect of dehydroepiandrosterone on cartilage and synovium of knee joints with osteoarthritis in rabbits

The aim of this study was to investigate the effects of intra-articular injection of dehydroepiandrosterone (DHEA) on cartilage and synovium of knee joints with osteoarthritis (OA) in rabbits and the underlying mechanism. Forty rabbits underwent unilateral anterior cruciate ligament transaction and were divided into two groups. Rabbits were injected with 100 μmol/l DHEA dissolved in the dimethylsulphoxide (DMSO) in the knee joints 5 weeks after transaction, once a week for 5 weeks. Rabbits injected with DMSO under the same condition were served as a control. All rabbits were killed 1 week after the last injection. The knee joints were evaluated by gross morphology, histology, and gene expression analysis. Gross morphologic inspection and histological evaluation showed that the DHEA group appeared less damage in cartilage and synovium as compared with the control. Gene expression analysis revealed that the mRNA expression of matrix metalloproteinase-3 (MMP-3) in cartilage and synovium decreased significantly in the DHEA group and that of tissue inhibitor of metalloproteinase-1 (TIMP-1) increased. No significant difference of interleukin-1 beta (IL-1β) mRNA expression was found in the cartilage between two groups while the mRNA expression of IL-1β in the synovium was largely suppressed in the DHEA group. The study suggests that DHEA plays a protective role against cartilage degradation and synovium inflammation in rabbits with OA. This role may be achieved through the regulation of the MMP-3, TIMP-1, and IL-1β gene expression in the cartilage and synovium.     

Ultrasonographic assessment of pes anserinus tendon and pes anserinus tendinitis bursitis syndrome in patients with knee osteoarthritis

Abstract

Objective. The aim of this study was to assess the ultrasonographic (US) findings of pes anserinus tendon and bursa in patients with knee osteoarthritis (OA) with or without clinical pes anserinus tendinitis bursitis syndrome (PATBS).

Methods. A total of 157 female patients with the diagnosis of knee OA on both knees (314 knees), and 30 age, and body mass index- matched healthy female controls without knee pain (60 knees), were included in the study. PATBS was clinically diagnosed. US evaluation parameters were the measurement of the thickness of pes anserinus tendon insertion region (PA) and examination of the morphologic intratendinous PA tissue characteristics and pes anserinus bursitis (PAB). Radiographic knee osteoarthritis graded I-IV according to Kellgren and Lawrence (KL) for each knee was recorded. Pain and functional status were assessed by the Visual Analog Scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

Results. There were 183 PATBS (58.3%) clinical diagnoses among the 314 knees with OA. The mean thickness of PA in the patients with knee OA graded 1,2,3,4 with/without PATBS was significantly greater than the controls (p = 0.001). The mean thickness of PA in knees with OA KL graded 3 and 4 with/without PATBS, was greater than knees with OA KL graded 1 and 2 with/without PATBS (p < 0,05) (except knee OA KL graded 2 with PATBS versus knee OA KL graded 4 without PATBS).The knee OA KL graded 1,2,3,4 with PATBS had significantly more PAB and less loss of normal fibrillar echotexture of PA compared to controls and knees with OA KL graded 1,2,3,4 without PATBS (p < 0.05). The VAS scores of knees with OA KL graded 3, 4 with PATBS were significantly greater than those of knees with OA KL graded 3,4 without PATBS (p < 0.05). PA thickness was significantly associated with the KL grade (r: 0.336, p:0.001) and PATBS (r: 0.371, p < 0.001).

Conclusion. It is concluded that the mean thickness of PA in knees with OA with/without PATBS was significantly greater than the controls. The mean thickness of PA in knees with OA, KL graded 3 and 4 with/without PATBS, was greater than in knees with OA KL graded 1 and 2 with/without PATBS. The knee OA with PATBS had significantly more PAB, less loss of normal fibrillar echotexture of PA, and higher VAS scores compared to the knees with OA without PATBS. US can serve as a useful diagnostic tool for detection of PATBS in knee OA.     

Technology insight: adult mesenchymal stem cells for osteoarthritis therapy

Despite the high prevalence and morbidity of osteoarthritis (OA), an effective treatment for this disease is currently lacking. Restoration of the diseased articular cartilage in patients with OA is, therefore, a challenge of considerable appeal to researchers and clinicians. Techniques that cause multipotent adult mesenchymal stem cells (MSCs) to differentiate into cells of the chondrogenic lineage have led to a variety of experimental strategies to investigate whether MSCs instead of chondrocytes can be used for the regeneration and maintenance of articular cartilage. MSC-based strategies should provide practical advantages for the patient with OA. These strategies include use of MSCs as progenitor cells to engineer cartilage implants that can be used to repair chondral and osteochondral lesions, or as trophic producers of bioactive factors to initiate endogenous regenerative activities in the OA joint. Targeted gene therapy might further enhance these activities of MSCs. Delivery of MSCs might be attained by direct intra-articular injection or by graft of engineered constructs derived from cell-seeded scaffolds; this latter approach could provide a three-dimensional construct with mechanical properties that are congruous with the weight-bearing function of the joint. Promising experimental and clinical data are beginning to emerge in support of the use of MSCs for regenerative applications.     

Characterization of human synovial fluid cells of 26 patients with osteoarthritis knee for cartilage repair therapy

Aim: To investigate the possibility of chondrogenic differentiation and cartilage repair of synovial fluid cells of osteoarthritis (OA) knee. Methods: Synovial fluids from 26 patients with OA knee were aspirated from each knee joint and cultured in vitro. The morphology of cultured synovial fluid cells, cell proliferation rate, the phenotype, and chondrogenic differentiation were analyzed in in vitro. Also, human autologous synovial fluid cells were transplanted to OA cartilage, and the cells were traced in ex vivo. Results: In 19 of 26 materials, the cells proliferated satisfactorily. The cell proliferation in six materials was very slow and one material contaminated. Culture‐expanded synovial fluid cells had a fibroblastic morphology and the phenotype was negative for CD10, CD14, and CD45, and positive for CD13, CD44, and CD105. Pellet culture of synovial fluid cells showed chondrogenic differentiation. In the ex vivo study, autologous transplanted synovial fluid cells were observed in repaired or enhanced regenerative cartilage areas and showed a tendency to infiltrate the original degenerative cartilage of OA. Conclusions: This study proved the possibility of chondrogenic differentiation of synovial fluid cells of OA knee joints despite the pathologic environment within a diseased joint. Synovial fluid cells were actually heterogeneous cells but they showed chondrogenic differentiation, similar to that of bone marrow‐derived mesenchymal progenitor cells (BMMPCs). The Ex vivo study suggested that synovial fluid cells had a tendency to adhere to OA degenerative cartilage in humans.     

The potential of intra-articular injection of chondrogenic-induced bone marrow stem cells to retard the progression of osteoarthritis in a sheep model

In recent years, the use of bone marrow mesenchymal stem cell (BMSC) implantation has provided an alternative treatment for osteoarthritis. The objective of this study is to determine whether or not an intra-articular injection of a single dose of autologous chondrogenic induced BMSC could retard the progressive destruction of cartilage in a surgically induced osteoarthritis in sheep. Sheep BMSCs were isolated and divided into two groups. One group was cultured in chondrogenic media containing (Ham's F12:DMEM, 1:1) FD+1% FBS+5 ng/ml TGFβ3+50 ng/ml IGF-1 (CM), and the other group was cultured in the basal media, FD+10% FBS (BM). The procedure for surgically induced osteoarthritis was performed on the donor sheep 6 weeks prior to intra-articular injection into the knee joint of a single dose of BMSC from either group, suspended in 5 ml FD at density of 2 million cells/ml. The control groups were injected with basal media, without cells. Six weeks after injection, gross evidence of retardation of cartilage destruction was seen in the osteoarthritic knee joints treated with CM as well as BM. No significant ICRS (International Cartilage Repair Society) scoring was detected between the two groups with cells. However macroscopically, meniscus repair was observed in the knee joint treated with CM. Severe osteoarthritis and meniscal injury was observed in the control group. Interestingly, histologically the CM group demonstrated good cartilage histoarchitecture, thickness and quality, comparable to normal knee joint cartilage. As a conclusion, intra-articular injection of a single dose of BMSC either chondrogenically induced or not, could retard the progression of osteoarthritis (OA) in a sheep model, but the induced cells indicated better results especially in meniscus regeneration.     

Rates of change and sensitivity to change in cartilage morphology in healthy knees and in knees with mild, moderate, and end-stage radiographic osteoarthritis: results from 831 participants from the Osteoarthritis Initiative

Objective

To study the longitudinal rate of (and sensitivity to) change of knee cartilage thickness across defined stages of radiographic osteoarthritis (OA), specifically healthy knees and knees with end‐stage radiographic OA.

Methods

One knee of 831 Osteoarthritis Initiative participants was examined: 112 healthy knees, without radiographic OA or risk factors for knee OA, and 719 radiographic OA knees (310 calculated Kellgren/Lawrence [K/L] grade 2, 300 calculated K/L grade 3, and 109 calculated K/L grade 4). Subregional change in thickness was assessed after segmentation of weight‐bearing femorotibial cartilage at baseline and 1 year from coronal magnetic resonance imaging (MRI). Regional and ordered values (OVs) of change were compared by baseline radiographic OA status.

Results

Healthy knees displayed small changes in plates and subregions (±0.7%; standardized response mean [SRM] ±0.15), with OVs being symmetrically distributed close to zero. In calculated K/L grade 2 knees, changes in cartilage thickness were small (<1%; minimal SRM ?0.22) and not significantly different from healthy knees. Knees with calculated K/L grade 3 showed substantial loss of cartilage thickness (up to ?2.5%; minimal SRM ?0.35), with OV1 changes being significantly (P < 0.05) greater than those in healthy knees. Calculated K/L grade 4 knees displayed the largest rate of loss across radiographic OA grades (up to ?3.9%; minimal SRM ?0.51), with OV1 changes also significantly (P < 0.05) greater than in healthy knees.

Conclusion

MRI‐based cartilage thickness showed high rates of loss in knees with moderate and end‐stage radiographic OA, and small rates (indistinguishable from healthy knees) in mild radiographic OA. From the perspective of sensitivity to change, end‐stage radiographic OA knees need not be excluded from longitudinal studies using MRI cartilage morphology as an end point.

     

玻璃酸钠对老年膝关节炎患者本体感觉的影响

目的 研究关节内注射玻璃酸钠后对老年膝骨关节炎患者膝关节本体感觉的影响.方法 共53例老年患者入选该研究.受试者被随机分为治疗组(35例)和安慰剂组(18例).治疗组患者行双侧膝关节玻璃酸钠(阿尔治)关节内注射,安慰剂组则予双侧膝关节注射生理盐水.测量膝关节本体感觉,西方安大略和麦克马斯特大学(WOMAC)骨关节炎指数评分表用于评估膝关节疼痛和功能改善情况.结果 共50例患者100个膝关节进行了评估,平均绝对角误差值在第4次注射后1周,治疗组明显低于安慰剂组,分别为(1.8±0.9)分和(2.9±1.1)分(t=2.42,P=0.02);治疗组WOMAC积分在注射玻璃酸钠1周后开始明显下降,治疗组和安慰剂组WOMAC积分分别为(8.7±3.1)分和(11.5±4.0)分(t=0.73,P＜0.05).结论 老年膝骨关节炎患者关节内注射玻璃酸钠可短时间改善膝关节本体感觉及疼痛.

Abstract：

Objective To investigate the short-term effects of intra-articular injection of hyaluronan on proprioception of the knee in gerontal patients with osteoarthritis (OA). Methods The 53 gerontal patients were included in this study. The study included treatment group (n=35) and the placebo group (n=18). Hyaluronan was intra-articularly injected into both knees of the subjects in treatment group, whereas physiological saline was intra-articularly injected in the placebo group. Proprioception test was performed, and Western Ontario and McMaster Universities(WOMAC) scales were used to evaluate pain and physical function. Results Statistical analysis was performed on 100 knees of 50 patients who completed the trial. Compared with the placebo group,the average absolute angular error (AAAE) value in the treatment group was detected to be statistically lower one week after the 4th injection (1.8±0.9 vs.2.9±1.1,t=2.42,P=0.02),and WOMAC was lower in the treatment group after one week (8.7±3.1 vs.11.5±4.0, t=0.73,P＜0.05). Conclusions Intra-articular injection of hyaluronan in gerontal patients with knee OA leads to a short-term increase in proprioception, and significant improvement in the functional conditions of patients.     

A case report of ultrasound-guided knee nerve pulse radiofrequency combined with platelet-rich plasma in the treatment of knee osteoarthritis

Rationable:Knee osteoarthritis (KOA) is a disease characterized by noninflammatory degenerative changes of articular cartilage. The main clinical manifestations are joint pain and stiffness. Pulsed radiofrequency (PRF) is thought to treat pain by destroying nerve tissue and changing the physical characteristics of nerve tissue membrane.Patient concerns:The patients presents with joint pain and tenderness. Touching around the knee joint will induce pain and joint stiffness when the hand is pressed hard.Interventions:Four patients with knee osteoarthritis underwent pulsed radiofrequency thermocoagulation in the knee joint cavity under ultrasound guidance and injected 2 mL of 10 mg/mL platelet-rich plasma into the joint cavity once a week for a total of 4 times. Record the patient''s Visual Analogue Scale (VAS) score and the degree of knee movement limitation before treatment, 1, 3, and 6 months after treatment.Diagnoses:Four patients with knee osteoarthritis.Outcomes:After treatment, the patient''s VAS score improved, and the knee joint mobility function recovered well. Ultrasound-guided knee nerve pulse radiofrequency combined with intra-articular injection of platelet-rich plasma can effectively improve the knee joint function and reduce the pain of the patient. The clinical effect is significant, and it is worthy of clinical application.     

Analysis of the chondrogenic potential of human synovial stem cells according to harvest site and culture parameters in knees with medial compartment osteoarthritis

OBJECTIVE: Synovial mesenchymal stem cells (MSCs) are an attractive cell source for cartilage regeneration because of their high chondrogenic ability. In this study, we examined the synovium of patients with medial compartment knee osteoarthritis (OA) to determine the proportion of MSCs in relation to cellular compartmentalization, and to identify the culture parameters that could affect the chondrogenic potential of synovial MSCs. METHODS: Human synovium was collected from 4 different harvest sites in the knees of patients with medial compartment OA. Each synovial tissue sample was divided into 2 parts, one for histologic assessment and the other for analysis of the cell size, surface epitopes, and chondrogenic potential of colony-forming cells in vitro. RESULTS: The numbers of alpha-smooth muscle actin-positive vessels and CD31+ endothelial cells were higher in the medial outer region than in the other regions of OA synovial tissue. The numbers of these cells correlated with the number of colony-forming cells. In parallel with increasing duration of the preculture period, the size of the cells increased, while the chondrogenic potential decreased, and this was correlated with expression of CD90. CONCLUSION: Medial compartment knee OA demonstrates variability in the distribution of vessels, which results in a varying distribution of MSCs. The preculture period should be utilized to assess both the potential for expansion and the chondrogenic potential of MSCs.     

Comparison of intra-articular tenoxicam and oral tenoxicam for pain and physical functioning in osteoarthritis of the knee

This study was designed to compare efficacy of local administration of a nonsteroidal anti-inflammatory drug with systemic administration in patients with osteoarthritis (OA) of the knee. For this purpose, intra-articular tenoxicam and oral tenoxicam therapies were applied and the improvement in control of pain and physical functioning were evaluated. A total of 69 patients with OA of the knee were randomized into three groups. Patients in the first group (41 knees of 23 patients) were treated for 1–3 weeks with once weekly intra-articular injection of tenoxicam 20 mg. Patients in the second group (45 knees of 26 patients) received 20 mg/day tenoxicam orally for 3 weeks and only physical exercises were applied to the third group (32 knees of 20 patients). Physical examination of the knee joint, Western Ontario and McMaster Universities Index and the Lequesne Algofunctional Index were used as outcome measurements at baseline, and the 1st, 3rd and 6th months. More significant improvement in pain and disability parameters was observed in groups 1 and 2 than group 3 compared with baseline measures. Among the patients responses a few of the differences were statistically significant, more in favour of tenoxicam, and tenoxicam seemed to be superior to exercise alone especially at the final evaluation. There was no significant difference between the oral and intra-articular tenoxicam treatment regimens. The results of this study showed that treatment of OA of the knee with intra-articular tenoxicam is as effective as that with oral tenoxicam. It can be thought that intra-articular administration can be preferred to oral therapy due to minimal possibility of systemic side effects.     

Magnetic resonance imaging and ultrasonographic evaluation of the patients with knee osteoarthritis: a comparative study

The objectives of the present work were (1) to establish the prevalence of the abnormalities detected by magnetic resonance imaging (MRI) and ultrasonography (US); and (2) to compare these imaging techniques in detail. The study group consisted of 58 patients with symptomatic knee OA and 16 volunteer control subjects. Knee joint was evaluated for femoral condylar cartilage changes, effusion, synovial thickening and popliteal cysts using MRI and US. All knees with OA had cartilage abnormalities on US examinations and normal cartilage was detected in less than 3% of these knees by MRI. Majority of the knees with OA had effusion using US (70%) or MRI (85%). Synovial thickening observed on US (34%) and MRI (50%) were common in the knees with OA. Popliteal cysts were detected in 40% of the knees with OA using US and 35% using MRI. This study confirmed that there was a significant correlation between the MRI and US techniques for evaluating the cartilage and soft tissue changes in the patients with knee OA. There were more significant differences between the controls and the symptomatic knees which had Kellgren-Lawrence (K-L) grade 2 or more OA for the cartilage and soft tissue abnormalities on MRI and US. The prevalence of cartilage changes, effusion, synovial thickening and popliteal cyst using MRI and US were increased as the radiographic grade of OA increased. US examinations could be an alternative to initial evaluation tool to MRI in patients with knee OA.     

Intra-articular injection of high molecular weight hyaluronan after arthrocentesis as treatment for rheumatoid knees with joint effusion

OBJECTIVE: The aim of this study was to find if a complete synovial fluid aspiration before injection of intra-articular high molecular weight hyaluronan influences the treatment result for knees with rheumatoid arthritis (RA), including joint effusion and the prognostic factors related to clinical effect. METHODS: The arthritic knees including effusion were randomized to arthrocentesis or no arthrocentesis before the hyaluronan (1.9-2.5 x 10(6)) was injected into knee joints five times every week. All patients were followed up for 6 months. RESULTS: One hundred eighteen RA patients (80 knees in the arthrocentesis group, 81 knees in the no-arthrocentesis group) were included. The proportion of no relapses in the arthrocentesis group was higher than that in the no-arthrocentesis group. In the arthrocentesis group, regression analysis showed that duration of knee arthritis (<5 months), CRP (<4 mg/dl), and Larsen grade (相似文献   

Ultrasonographic findings in hemiplegic knees of stroke patients

Clinical and radiologic asymmetric arthritic differences between paralyzed and nonparalyzed limbs of stroke patients have been reported. Arthritic pathology aggravates motor dysfunction and compromises rehabilitation. Musculoskeletal ultrasonography plays an important role in showing soft tissue and the articular cartilage of the knee. Fifty-nine patients with either ischemic or hemorrhagic stroke-induced right or left hemiplegia were recruited to evaluate soft-tissue and intra-articular cartilage changes in hemiplegic knees of stroke patients using ultrasonography. An additional 15 subjects (30 knees) without knee disease or a history of knee trauma or surgery were used as controls. There were significant differences in suprapatellar effusion and patellar tendinitis between hemiplegic and nonhemiplegic knees. Suprapatellar effusion and pes anserinus tendinitis were correlated with Brunnstrom stage. The length of time since stroke onset was not significantly correlated with positive ultrasonographic findings in hemiplegic knees. In conclusion, ultrasonography is useful for detecting periarticular soft-tissue changes and intra-articular lesions in hemiplegic knees of stroke patients.     

Association between findings on delayed gadolinium-enhanced magnetic resonance imaging of cartilage and future knee osteoarthritis

OBJECTIVE: To examine the predictive value of the delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) index with regard to future radiographic osteoarthritis (OA). METHODS: In 1998, 17 knees in 11 men and 4 women with knee pain, normal results of weight-bearing radiography, and arthroscopic cartilage changes ranging from superficial fibrillation to fissuring and softening were examined using dGEMRIC. Six years later, 16 of the 17 knees were reassessed for radiographic OA changes. RESULTS: At followup, 9 of the 16 knees showed radiographic OA changes. Two of them had undergone a knee joint replacement due to OA. In the knees with radiographic OA, the dGEMRIC index at baseline was lower than that in the knees without radiographic OA (P = 0.03). CONCLUSION: The results of the present study support the dGEMRIC index as a clinically relevant measure of cartilage integrity and suggest that a low index may be predictive of the development of knee OA.     

Osteoarthritic chondrocyte–secreted morphogens induce chondrogenic differentiation of human mesenchymal stem cells

Objective

The potential of stem cells to repair compromised cartilage tissue, such as in osteoarthritis (OA), depends strongly on how transplanted cells respond to factors secreted from the residing OA chondrocytes. This study was undertaken to determine the effect of morphogenetic signals from OA chondrocytes on chondrogenic differentiation of human mesenchymal stem cells (MSCs).

Methods

The effect of OA chondrocyte–secreted morphogens on chondrogenic differentiation of human MSCs was evaluated using a coculture system involving both primary and passaged OA chondrocytes. The findings were compared against findings for human MSCs cultured in OA chondrocyte–conditioned medium. Gene expression analysis, biochemical assays, and immunofluorescence staining were used to characterize the chondrogenic differentiation of human MSCs. Mass spectrometry analysis was used to identify the soluble factors. Numerical analysis was carried out to model the concentration profile of soluble factors within the human MSC–laden hydrogels.

Results

The human MSCs cocultured with primary OA chondrocytes underwent chondrogenic differentiation even in the absence of growth factors; however, the same effect could not be mimicked using OA chondrocyte–conditioned medium or expanded cells. Additionally, the cocultured environment down‐regulated hypertrophic differentiation of human MSCs. Mass spectrometry analysis demonstrated cell–cell communication and chondrocyte phenotype–dependent effects on cell‐secreted morphogens.

Conclusion

The experimental findings, along with the results of the numerical analysis, suggest a crucial role of soluble morphogens and their local concentrations in the differentiation pattern of human MSCs in a 3‐dimensional environment. The concept of using a small number of chondrocytes to promote chondrogenic differentiation of human MSCs while preventing their hypertrophic differentiation could be of great importance in formulating effective stem cell–based cartilage repair.

     

Even low-grade synovitis significantly accelerates the clearance of protein from the canine knee: implications for measurement of synovial fluid “markers” of osteoarthritis

Objective. In recent studies, the synovial fluid concentration of molecules derived from the extracellular matrix of articular cartilage has been used to deduce the magnitude of cartilage destruction or repair in osteoarthritic (OA) joints. Because low-grade synovitis is often present in such joints, we assessed the effect of synovial inflammation on the clearance of a prototypical protein, albumin, from synovial fluid. Methods. ¹³¹-labeled albumin (RISA) was injected into 1 (control) knee of each of 14 dogs. The concentration of RISA in synovial fluid aspirated 7 hours after the injection and serial measurements of surface radioactivity were used to calculate the volume of distribution (V_d) and clearance of RISA. One week later, synovitis was induced in the contralateral knee by intraarticular injection of various quantities of calcium pyrophosphate dihydrate (CPPD) crystals, after which RISA was injected into that joint and these measurements were repeated. Results. Intraarticular injection of 500 μg of CPPD crystals produced intense synovitis, with a mean synovial fluid white blood cell (WBC) count of 43,200 cells/mm³, and values for RISA V_d and RISA clearance (36.5 ml and 33.7 μl/minute) were much higher than those for saline-injected control knees (2.7 ml and 1.5 μl/minute, respectively). Injection of 0.5 μg of CPPD also produced marked synovitis and values for V_d and RISA clearance that were 2–3-fold greater than those in the contralateral knee. The low-grade synovitis produced by only 0.05 μg of CPPD, which resulted in synovial fluid WBC counts as low as 1,000–2,000 cells/mm³, was accompanied by increases in the clearance and V_d of RISA to levels ˜40% and ˜80% higher, respectively, than those for the contralateral knee. Conclusion. Even mild synovitis, as seen in OA, may significantly increase the clearance of a protein from the joint. Synovitis is a significant variable which must be considered in studies of putative chondroprotective drugs if conclusions about the effects of drugs on cartilage metabolism are to be drawn from changes in the synovial fluid concentration of a “marker” protein.