Metformin pretreatment suppresses alterations to the articular cartilage ultrastructure and knee joint tissue damage secondary to type 2 diabetes mellitus in rats.

Osteoarthritis (OA) secondary to diabetes affects millions of people worldwide and can lead to disability. The protective effect of metformin pretreatment against alterations to the articular cartilage ultrastructure induced by type 2 diabetes mellitus (T2DM) associated with the inhibition of oxidative stress and inflammation has not been investigated before. Therefore, we induced T2DM in rats (the model group) using high carbohydrate and fat diet and a single injection of streptozotocin (50 mg/kg body weight). The protective group of rats started metformin (200 mg/kg body weight) treatment 14 days before diabetic induction and continued on metformin until the end of the experiment at week 12. Harvested tissues obtained from knee joints were prepared for staining with hematoxylin and eosin (H&E), safranin o staining, and electron microscopy. Histology images showed that OA was developed in the T2DM rats as demonstrated by a substantial damage to the articular cartilage and profound chondrocyte and territorial matrix ultrastructural alterations, which were partially protected by metformin. In addition, metformin significantly (p < .05) reduced hyperglycemia, glycated hemoglobin (HbA1 c), malondialdehyde (MDA), high sensitivity C-reactive protein (hs-CRP), and interleukin-6 blood levels induced by diabetes. Furthermore, a significant (p ≤ 0.015) correlation between either OA cartilage grade score or the thickness of the articular cartilage and the blood levels of HbA1 c, hs-CRP, MDA, superoxide dismutase (SOD) were observed. These findings demonstrate effective protection of the articular cartilage by metformin against damage induced secondary to T2DM in rats, possibly due to the inhibition of hyperglycemia and biomarkers of oxidative stress and inflammation.

Ultrastructure and three-dimensional architecture of the anterior cruciate ligament in the knee joints of young and old monkeys.

We examined the ultrastructure of the anterior cruciate ligament and assessed age-related changes by comparing the ligaments of young and old monkeys. Ultrathin sections of the anterior cruciate ligament were observed by transmission electron microscopy. The three-dimensional architecture of collagen fibers in the ligament was examined by scanning electron microscopy after tissue specimens were treated with 2 N NaOH to digest the extracellular matrix. At the surface layer of the cruciate ligament in young monkeys, fusiform-shaped fibroblasts actively produced collagen fibrils. The ligament consisted of parallel bundles of dense collagen fibrils of approximately 200 nm in diameter. Collagen fibrils appeared to run linearly. Ligament fibrocytes in the deep layer had a stellate form. Ligament fibrocytes decreased in number and showed marked atrophy in old age. Collagen fibrils had a looser configuration in older monkeys. Despite atrophy of fibroblasts in the deep layer of the anterior cruciate ligament, the area with atrophic fibroblasts in the ligament expands with age, which can likely cause deterioration of and a reduction in collagen fibers. This information can be applied in studies on the cause of the low repair ability of and aging-related changes in the anterior cruciate ligament in humans.

Construction and biocompatibility of a thin type I/II collagen composite scaffold.

Articular cartilage injury is a common type of damage observed in clinical practice. A matrix-induced autologous chondrocyte implant was developed to repair articular cartilage as an advancement on the autologous chondrocyte implant procedure. Here, we establish a thin double layer of collagen as a novel and effective bioscaffold for the regeneration of cartilaginous lesions. We created a collagen membrane with double layers using a cover slip, a cover slip, and the collagen was then freeze-dried under vacuum. Carbodiimide as a crosslinking agent was used to obtain a relatively stable collagen construction. The thickness of the knee joint cartilage from grown rabbits was measured from a frozen section. Both type I and type II collagens were characterized using Sodium dodecylsulfate/polyacrylamide gel electrophoresis (SDS-PAGE) and ultraviolet absorption peaks. The aperture size of the scaffold was observed using a scanning electron microscope (SEM). The degradation of the scaffolds in vitro was tested through digestion using collagenase solution. The mechanical capacity of the scaffolds was assessed under dynamic compression. The influence of the scaffold on chondrocyte proliferation was assessed using the methyl thiazolyl tetrazolium (MTT) colourimetric assay and scanning electron microscopy. The frozen sections of the rabbit femoral condyle showed that the thickness of the weight-bearing area of the articular cartilage was less than 1 mm. The results of the SDS-PAGE and ultraviolet absorption peaks of the collagens were in agreement with the standard photographs in the references. SEM showed that the aperture size of the cross-linked scaffold was 82.14 ± 15.70 µm. The in vitro degradation studies indicated that Carbodiimide cross-linking can effectively enhance the biostability of the scaffolds. The Carbodiimide cross-linking protocol resulted in a mean value for the samples that ranged from 8.72 to 15.95 MPa for the compressive strength. The results of the MTT demonstrated that the scaffold had promoted chondrocyte proliferation and SEM observations showed that the scaffold was a good adhesive and growth material for chondrocytes. Thin type I/II collagen composite scaffold can meet the demands of cartilage tissue engineering and have good biocompatibility.

PLGA-Based Nanoparticles: a Safe and Suitable Delivery Platform for Osteoarticular Pathologies.

PURPOSE: Despite the promising applications of PLGA based particles, studies examining the fate and consequences of these particles after intra-articular administration in the joint are scanty. This study was carried out to evaluate the neutrality of the unloaded delivery system on different articular cell types. To facilitate tracking, we have thus developed a fluorescent core of particles, combined to a hyaluronate shell for cell recognition. METHODS: Fluorescence pictures were taken at time intervals to assess the internalization and the corresponding inflammatory response was monitored by RT-qPCR and biochemical measurements. After NPs pre-treatment, mesenchymal stem cells (MSCs) were cultured into chondrogenic, adipogenic or osteogenic differentiation media, to investigate if NPs exposure interferes with differentiation ability. Finally, intra-articular injections were performed in healthy rat knees and joint's structure analysed by histological studies. RESULTS: Particles were detected in cytoplasm 8 h after exposure. Internalization led to a slight and reversible increase of inflammatory markers, but lower than in inflammatory conditions. We have confirmed particles exposure minimal neutrality on MSCs pluripotency. Histological exams of joint after intra-articular injections do not demonstrate any side effects of NPs. CONCLUSIONS: Our findings suggest that such a delivery platform is well tolerated locally and could be used to deliver active molecules to the joint.

Collagen fibre and fibril ultrastructural arrangement of the superficial medial collateral ligament in the human knee.

PURPOSE: The aim of the study was to investigate the collagen fibre ultrastructural arrangement and collagen fibril diameters in the superficial medial collateral ligament (sMCL) in the human knee. Considering sMCL's distinctive functions at different angles of knee flexion, it was hypothesized a significant difference between the collagen fibril diameters of each portion of the sMCL. METHODS: Fourteen sMCL from seven fresh males (by chance because of the availability) cadavers (median age 40 years, range 34-59 years) were harvested within 12 h of death. sMCLs were separated into two orders of regions for analysis. The first order (divisions) was anterior, central and posterior. Thereafter, each division was split into three regions (femoral, intermediate and tibial), generating nine portions. One sMCL from each cadaver was used for transmission electron microscopy (TEM) and morphometric analyses, whereas the contralateral sMCL was processed for light microscopy (LM) or scanning electron microscopy (SEM). RESULTS: LM and SEM analyses showed a complex tridimensional architecture, with the presence of wavy collagen fibres or crimps. TEM analysis showed significant differences in median collagen fibril diameter among portions inside the anterior, central and posterior division of the sMCL (p < 0.0001 within each division). Significant differences were also present among the median [interquartile range] collagen fibril diameters of anterior (39.4 [47.8-32.9]), central (38.5 [44.4-34.0]) and posterior (41.7 [52.2-35.4]) division (p = 0.0001); femoral (38.2 [45.0-32.7]), intermediate (40.3 [47.3-36.1]) and tibial (40.7 [55.0-32.2]) region (p = 0.0001). CONCLUSIONS: Human sMCL showed a complex architecture that allows restraining different knee motions at different angles of knee flexion. The posterior division of sMCL accounted for the largest median collagen fibril diameter. The femoral region of sMCL accounted for the smallest median collagen fibril diameter. The presence of crimps in the medial collateral ligament, previously identified in the rat, was confirmed in humans (taking into consideration differences between these two species).

A multi-scale structural study of the porcine anterior cruciate ligament tibial enthesis.

Like the human anterior cruciate ligament (ACL), the porcine ACL also has a double bundle structure and several biomechanical studies using this model have been carried out to show the differential effect of these two bundles on macro-level knee joint function. It is hypothesised that if the different bundles of the porcine ACL are mechanically distinct in function, then a multi-scale anatomical characterisation of their individual enthesis will also reveal significant differences in structure between the bundles. Twenty-two porcine knee joints were cleared of their musculature to expose the intact ACL following which ligament-bone samples were obtained. The samples were fixed in formalin followed by decalcification with formic acid. Thin sections containing the ligament insertion into the tibia were then obtained by cryosectioning and analysed using differential interference contrast (DIC) optical microscopy and scanning electron microscopy (SEM). At the micro-level, the anteromedial (AM) bundle insertion at the tibia displayed a significant deep-rooted interdigitation into bone, while for the posterolateral (PL) bundle the fibre insertions were less distributed and more focal. Three sub-types of enthesis were identified in the ACL and related to (i) bundle type, (ii) positional aspect within the insertion, and (iii) specific bundle function. At the nano-level the fibrils of the AM bundle were significantly larger than those in the PL bundle. The modes by which the AM and PL fibrils merged with the bone matrix fibrils were significantly different. A biomechanical interpretation of the data suggests that the porcine ACL enthesis is a specialized, functionally graded structural continuum, adapted at the micro-to-nano scales to serve joint function at the macro level.

Light and electron microscopic detection of inflammation-targeting liposomes encapsulating high-density colloidal gold in arthritic mice.

OBJECTIVE: We have previously demonstrated the efficient and time-dependent transvascular localization of Sialyl Lewis X (SLX)-liposomes to inflammatory sites, but the final target of the SLX-liposomes remained uncertain. The aim of this study was to identify the target cells of the liposomes within the inflamed joints of collagen antibody-induced arthritis (CAIA) model mice. METHODS: SLX-liposomes and unlabeled liposomes encapsulating high-density colloidal gold were administered intravenously into the caudal vein of CAIA mice on day 5 after induction of arthritis when the inflammatory score was maximal (n = 6 per group). Six hours or 24 h after liposome administration, animals were euthanized and hind limbs and ankles were excised without perfusion. After fixation, synovial tissues were examined by light microscopy after silver enhancement of colloidal gold or by transmission electron microscopy. RESULTS: Silver-enhanced signals were detected within the cells around E-selectin-positive blood vessels in the synovium of the SLX-liposome group. These cells were positive for the macrophage/monocyte marker F4/80 or neutrophil marker Ly-6G. Transmission electron microscopy detected the colloidal gold signals together with liposome-like structures within the phagosomes of synovial macrophages. Transmission electron microscopy and energy dispersive X-ray spectrometry could determine gold elements in the lysosomes of synovial macrophages. CONCLUSIONS: The results of the current study demonstrate that SLX-liposomes primarily targeting E-selectin in activated endothelial cells could potentially deliver their contents into inflammatory cells around synovial blood vessels in arthritic joints.

The medial synovial fold of the posterior cruciate ligament: cadaveric investigation together with magnetic resonance imaging and histology.

OBJECTIVE: The purposes of our study were to analyze magnetic resonance imaging (MRI) and cadaveric findings concerning the medial synovial fold of the posterior cruciate ligament (PCL) and to classify the types of fold according to anatomic location. METHODS: Two musculoskeletal radiologists reviewed MR images of 17 cadaveric knees to classify the types of medial fold of the PCL by consensus. The MRI types were divided into 3 groups. In type A, there was no definitive medial fold; and in type B, inferior-short type, there was a small protrusion of the medial border. Type C, inferior-long type, had a long enough fold to exceed the imaginary line, which is connecting between the medial tibial condyle and posterolateral aspect of the medial femoral condyle. Correlations were sought between the findings derived from the MRI studies and cadaveric dissections. Histologic analyses of the medial fold were also performed. RESULTS: On MRI, the most common type of medial fold was type B (76.4%), followed by type C (11.8%) and type A (11.8%). In the cadaveric investigation, the medial folds of both types B and C were found to project into the medial femorotibial joint. Moreover, there was also a protruding medial fold at the superior aspect of the PCL in the A. Histologic examination of the medial folds revealed collagenous tissue surrounded by synovial cells. CONCLUSIONS: Medial folds of the PCL are normal synovial structures that can be seen by MRI and in cadaveric studies in a large proportion of the population.

Cell and matrix morphology in articular cartilage from adult human knee and ankle joints suggests depth-associated adaptations to biomechanical and anatomical roles.

OBJECTIVE: Marked differences exist between human knee and ankle joints regarding risks and progression of osteoarthritis (OA). Pathomechanisms of degenerative joint disease may therefore differ in these joints, due to differences in tissue structure and function. Focusing on structural issues, which are design goals for tissue engineering, we compared cell and matrix morphologies in different anatomical sites of adult human knee and ankle joints. METHODS: Osteochondral explants were acquired from knee and ankle joints of deceased persons aged 20-40 years and analyzed for cell, matrix and tissue morphology using confocal and electron microscopy (EM) and unbiased stereological methods. Morphological variations disclosing an association between joint type (knee vs ankle) and biomechanical role (convex vs concave articular surfaces) were identified by a 2-way analysis of variance (ANOVA) and a post-hoc analysis. RESULTS: Knee cartilage exhibited higher cell densities in the superficial zone than ankle cartilage. In the transitional zone, higher cell densities were observed in association with convex vs concave articular surfaces, without significant differences between knee and ankle cartilage. Highly uniform cell and matrix morphologies were evident throughout the radial zone in the knee and ankle, regardless of tissue biomechanical role. Throughout the knee and ankle cartilage sampled, chondron density was remarkably constant at approximately 4.2 × 10(6) chondrons/cm(3). CONCLUSION: Variation in cartilage cell and matrix morphologies with changing joint and biomechanical environments suggests that tissue structural adaptations are performed primarily by the superficial and transitional zones. Data may aid the development of site-specific cartilage tissue engineering, and help to identify conditions where OA is likely to occur.

Immunolocalization of water channel aquaporins in human knee articular cartilage with intact and early degenerative regions.

Aquaporins (AQPs), a family of water channel proteins expressed in various cells and tissues, serve as physiological pathways of water and small solute transport. Articular cartilage is avascular tissue with unique biomechanical structure, a major component of which is "water". Our objective is to investigate the immunolocalization and expression pattern changes of AQPs in articular cartilage with normal and early degenerative regions in the human knee joint, which is the joint most commonly involved in osteoarthritis (OA). Two isoforms (AQPs 1 and 3) of AQPs were examined by immunohistochemical analyses using isoform-specific antibodies with cartilage samples from OA patients undergoing total knee arthroplasty. AQP 1 and AQP 3 were expressed in human knee articular cartilage and were localized in chondrocytes, both in the intact and early degenerative cartilage regions. Compared to the intact cartilage, both AQP 1 and AQP 3 immunopositive cells were observed at the damaged surface area in the degenerative region. These findings suggest that these AQPs play roles in metabolic water regulation in articular cartilage of load bearing joints and that they are responsible for OA onset.

[Morphological peculiarities of the synovial membrane of human knee joint in mature age].

The structural and functional reorganization of the synovial membrane of the knee joint capsule was studied in 22 individuals of mature age (30-65 years) of both genders with the use of light and electron microscopy, histochemistry, immunohistochemistry and morphometry. The morpho-functional peculiarities of the synovial membrane remodeling in the II period of mature age included: increase the in the synovial intima thickness; significant accumulation of type IV collagen at the border of synovial intima with the subintimal fibrovascular layer of synovial membrane; activation of matrix metalloproteinases MMP-2 and MMP-9; increased cell proapoptotic activity in synovial intima. Collectively, these changes may initiate the disturbances in fluid production and the development of the degenerative-dystrophic processes in the articular cartilage at this stage of ontogenesis.

Quantitative analysis of collagen network structure and fibril dimensions in cartilage repair with autologous chondrocyte transplantation.

OBJECTIVE: The aim of this study was to undertake a stereological analysis to quantify the dimensions of the collagen network in the repair tissue of porcine joints after they had been subjected to autologous chondrocyte transplantation (ACT). METHOD: ACT was used to repair cartilage lesions in knee joints of pigs. Electron-microscopic stereology, immunostaining for type II collagen, and quantitative polarized-light microscopy were utilized to study the collagen fibrils in the repair tissue 3 and 12 months after the operation. RESULTS: The collagen volume density (V(V)) was lower in the repair tissue than in normal cartilage at 3 months (20.4 vs. 23.7%) after the operation. The collagen surface density (S(V), 1.5·10(-2) vs. 3.1·10(-2) nm(2)/nm(3)) and V(V) increased with time in the repair tissue (20.4 vs. 44.7%). Quantitative polarized-light microscopy detected a higher degree of collagen parallelism in the repair tissue at 3 months after the operation (55.7 vs. 49.7%). In contrast, 1 year after the operation, fibril parallelism was lower in the repair tissue than in the control cartilage (47.5 vs. 69.8%). CONCLUSION: Following ACT, V(V) and S(V) increased in the repair tissue with time, reflecting maturation of the tissue. One year after the operation, there was a lower level of fibril organization in the repair tissue than in the control cartilage. Thus, the newly synthesized collagen fibrils in the repair tissue appeared to form a denser network than in the control cartilage, but the fibrils remained more randomly oriented.

Collagen morphology in human meniscal attachments: a SEM study.

Qualitative analysis of meniscal attachments from five human knees was completed using scanning electron microscopy (SEM). In addition, quantitative analysis to determine the collagen crimping angle and length in each attachment was done. Morphological differences were revealed between the distinct zones of the attachments from the meniscus transition to the bony insertion. Collagen fibers near to the meniscus appeared inhomogeneous in a radial cross-section view. The sheath surrounding the fibers seemed loose compared with the membrane wrapping around the fibers in the menisci. The midsubstance of human meniscal attachments was composed of collagen fibers running parallel to the longitudinal axis, with a few fibers running obliquely, and others transversely. The bony insertion showed that the crimping pattern vanishes as the collagen fibers approach the fibrocartilagenous enthesis. There were no differences between attachments for crimping angle or length. Collagen crimping angles for all attachments were similar with values of approximately 22°. Crimp length values tended to be smaller for the medial attachments (MA: 4.76 ± 1.95 µm; MP: 3.72 ± 2.31 µm) and higher for the lateral (LA: 6.49 ± 2.34 µm, LP: 6.91 ± 2.29 µm). SEM was demonstrated to be an effective method for revealing the morphology of fibrous connective tissue. The data of collagen fiber length and angle found in this study will allow for better development of microstructural models of meniscal attachments. This study will help to better understand the relation between the morphology and the architecture of collagen and the mechanical behavior of meniscal attachments.

Investigation of calcium crystals in OA knees.

For studies on matrix mineralization in osteoarthritis (OA), a clear analytical approach is necessary to identify and to quantify mineralization in the articular cartilage. The aim of this study is to develop an effective algorithm to quantify and to identify cartilage mineralization in the experimental setting. Four patients with OA of the knee undergoing total knee replacement and four control patients were included. Cartilage calcification was studied by digital contact radiography (DCR), field emission scanning electron microscopy (FE-SEM) X-ray element analysis and Raman spectroscopy (RS). DCR revealed mineralization in all OA cartilage specimens. No mineralization was observed in the control cartilage. Patient I showed rhomboid shaped crystals with a mean Ca:P molar ratio of 1.04 indicated the presence of calcium pyrophosphate dihydrate (CPPD) crystals, while Patients II, III and IV presented carbonate-substituted hydroxyapatite (HA). RS also showed the presence of CPPD crystals in Patient I while Patients II, III and IV revealed spectra confirming the presence of HA crystals. In the corresponding chondrocyte cell culture analyzed with SEM, the presence of CPPD crystals in the culture of Patient I and HA crystals in the culture of Patient II, III and IV was confirmed. No mineralization was found in the cell culture of the controls. The differentiation between BCP and CPPD crystals plays an important role, and the techniques presented here provide an accurate differentiation of these two types of crystals. For quantification of articular cartilage mineralization, DCR is a simple and accurate method.

Histological and ultrastructural evaluation of the early healing of the lateral collateral ligament epiligament tissue in a rat knee model.

BACKGROUND: In this study, we evaluated the changes which occurred in the epiligament, an enveloping tissue of the ligament, during the ligament healing. We assessed the association of epiligament elements that could be involved in ligament healing. METHODS: Thirty-two 8-month old male Wistar rats were used in this study. In twenty-four of them the lateral collateral ligament of the knee joint was surgically transected and was allowed to heal spontaneously. The evaluation of the epiligament healing included light microscopy and transmission electron microscopy. RESULTS: At the eight, sixteenth and thirtieth day after injury, the animals were sacrificed and the ligaments were examined. Our results revealed that on the eight and sixteenth day post-injury the epiligament tissue is not completely regenerated. Till the thirtieth day after injury the epiligament is similar to normal, but not fully restored. CONCLUSION: Our study offered a more complete description of the epiligament healing process and defined its important role in ligament healing. Thus, we provided a base for new strategies in ligament treatment.

Etoricoxib decreases subchondral bone mass and attenuates biomechanical properties at the early stage of osteoarthritis in a mouse model.

Etoricoxib, a selective Cyclooxygenase-2 (COX-2) inhibitor, is commonly used in osteoarthritis (OA) for pain relief, however, little is known about the effects on subchondral bone. In the current study, OA was induced via destabilization of the medial meniscus (DMM) in C57BL/6 mice. Two days after surgery, mice were treated with different concentrations of Etoricoxib. Four weeks after treatment, micro computed tomography (Micro-CT) analysis, histological analysis, atomic force microscopy (AFM) analysis, and scanning electron microscopy (SEM) were performed to evaluate OA progression. We demonstrated that Etoricoxib inhibited osteophyte formation in the subchondral bone. However, it also reduced the bone volume fraction (BV/TV), lowered trabecular thickness (Tb.Th), and more microfractures and pores were observed in the subchondral bone. Moreover, Etoricoxib reduced the elastic modulus of subchondral bone. Exposure to Etoricoxib further increased the empty/total osteocyte ratio of the subchondral bone. Etoricoxib did not show significant improvement in articular cartilage destruction and synovial inflammation in early OA. Together, our observations suggested that although Etoricoxib can relieve OA-induced pain and inhibit osteophyte formation in the subchondral bone, it can also change the microstructures and biomechanical properties of subchondral bone, promote subchondral bone loss, and reduce subchondral bone quality in early OA mice.

Autologous chondrocyte implantation to repair knee cartilage injury: ultrastructural evaluation at 2 years and long-term follow-up including muscle strength measurements.

Autologous chondrocyte implantation (ACI) usually results in improvement in clinical scores. However, long-term isokinetic muscle strength measurements have not been reported. Biopsies from the repair tissue have shown variable proportions of hyaline-like cartilage. In this study, 21 consecutive patients were treated with autologous cartilage implantations in the knee. Mean size of the lesions was 5.5 cm(2). Follow-up arthroscopy with biopsy was performed at 2 years in 19 patients. The biopsies were examined with both light microscopy and transmission electron microscopy (TEM) techniques including immunogold analysis of collagen type 1. Patient function was evaluated with modified 10-point scales of the Cincinnati knee rating system obtained preoperatively and at 1 and 8.1 years. Isokinetic quadriceps and hamstrings muscle strength testing was performed at 1, 2 and 7.4 years. Light microscopy and TEM both showed predominately fibrous cartilage. The immunogold analysis showed a high percentage of collagen type I. At 7.4 years, the total work deficits when compared with the contra-lateral leg for isokinetic extension were 19.1 and 11.4%, and for isokinetic flexion 11.8 and 8.5% for 60 and 240 masculine/s, respectively. Mean pain score improved from 4.3 preoperatively to 6.3 at 1 year (p = 0.031) and 6.6 at 8.1 years (p = 0.013). Overall health condition score improved from 4.1 preoperatively to 6.1 at 1 year (p = 0.004) and 6.5 at 8.1 years (p = 0.008). Three patients later went through revision surgery with other resurfacing techniques and are considered failures. In summary, the formation of fibrous cartilage following ACI was confirmed by TEM with immunogold histochemistry. Although the functional scores were generally good, strength measurements demonstrated that the surgically treated leg remained significantly weaker.

Articular cartilage in the knee joint of the African elephant, Loxodonta africana, Blumenbach 1797.

Knee joints of one adult and three juvenile African elephants were dissected. The specific features of the articular cartilage with particular reference to matrix components were studied by light and electron microscopy and immunohistochemistry. The elephant knee joint cartilage contains an unusually low concentration of proteoglycans resulting in rather eosinophilic staining properties of the matrix. The very thick collagen fibers of the cartilage possibly represent collagen I. Except for the different thickness of cartilage at the weight-bearing surfaces of femur (approximately 6.7 mm) and tibia (approximately 11.2 mm) in juvenile elephants, light and electron microscopy did not reveal distinct topographical differences in cartilage structure, perhaps because of the high congruency of the articulating surfaces and resulting uniform load distribution in the knee. The number of cell profiles per section area of both femoral (approximately 950 cell profiles/mm(2)) and tibial cartilage (approximately 898 cell profiles/mm(2)) was low, indicating excessive matrix production by the chondrocytes during cartilage development. These unique properties could be a result of the enormous compressive load resting on the elephant knee. Maintenance of the equilibrium between biological function and resistance to compression seems to be crucial in the elephant knee joint cartilage. Any disturbance that interferes with this equilibrium appears to lead to arthrotic alterations, as particularly seen in captive elephants.

[Morphological criteria of the state of the microcirculation and the lymphatic drainage in the synovial membrane of the knee joint under normal and pathological conditions].

Using transmission electron microscopy, the ultrastructural organization of the endothelium of blood and lymphatic capillaries and the structures of the interstitium of synovial membrane were studied in the patients with osteoarthrosis of a knee joint of I-II and II-III stages. Material, obtained from the patients with traumatic lesions of the knee joint components, was used as a control. The structural signs indicative of the microcirculation and lymphatic drainage disturbances were detected in the synovial membrane and were most expressed in II-III stages of osteoarthrosis. These included: the decrease of the volumetric density of all the types of micropinocytotic vesicles and the cisterns of rough endoplasmic reticulum, the decrease of the numerical density of attached and free polysomal ribosomes, the accumulation of erythrocytes and thrombocytes in the lumen of blood capillaries, the increase of the number of open-type interendotheliocyte contacts in the lymph capillaries, the increase of the size and the decrease of the electron density of the pericapillary and the interstitial spaces.

Ultrastructural change of the subchondral bone increases the severity of cartilage damage in osteoporotic osteoarthritis of the knee in rabbits.

Osteoporotic osteoarthritis is a phenotype of osteoarthritis (OA) manifested as fragile and osteoporotic subchondral bone. However, the ultrastructural features of subchondral bone in osteoporosis OA have not been determined. The study was aimed to investigate the ultrastructural dynamic changes of subchondral bone in osteoporotic OA model and how the ultrastructural damage in the subchondral bone caused by osteoporosis deteriorated the cartilage damage in OA. Eighteen rabbits were equally randomized to three groups, including the control, the OA and the osteoporotic OA groups. The structural changes of cartilage were evaluated by HE and safranin-O fast green staining, the Mankin's grading system was used to assess the stage of OA progression. And microstructural or ultrastructural changes in subchondral bone were assessed by micro-computed tomography or by scanning electron microscopy. According to the changes of cartilage histopathology, the OA group was in the early pathological stage of OA while the osteoporotic OA group was in the middle stage of OA based on Mankin's grading system. In addition, the damage of cartilage surface, reduction in the number of chondrocytes and the matrix staining were more increased in the osteoporotic OA group compared to the OA group. Compared to the OA group, the subchondral bone in the microstructure and ultrastructure in the osteoporotic OA group showed more microfracture changes in trabecular bone with more destructions of the tree-like mesh. Moreover, the collagen fibers were random rough with a fewer amount of bone lacunae in subchondral cortical plate in the osteoporotic OA group compared to the OA group. These findings indicated that the subchondral bone ultrastructure in the osteoporotic OA model was characterized by the destruction of the network structure and collagen fibers. The subchondral bone ultrastructural damage caused by osteoporosis may change mechanical properties of the upper cartilage and aggravate OA cartilage. Therefore, early diagnosis and treatment of osteoporosis is of great significance to prevent early OA from further developing osteoporotic OA.