Macroscopic and histopathologic analysis of human knee menisci in aging and osteoarthritis

Core-Shell Nanofibrous Scaffolds for Repair of Meniscus Tears

Electrospinning is an attractive method of fabricating nanofibers that replicate the ultrastructure of the human meniscus. However, it is challenging to approximate the mechanical properties of meniscal tissue while maintaining the biocompatibility of collagen fibers. Our objective was to determine if functionalizing polylactic acid (PLA) nanofibers with collagen would enhance their biocompatibility. We therefore used coaxial electrospinning to generate core-shell nanofibers with a core of PLA for mechanical strength and a shell of collagen to enhance cell attachment and matrix synthesis. We characterized the nanostructure of the engineered scaffolds and measured the hydrophilic and mechanical properties. We assessed the performance of human meniscal cells seeded on coaxial electrospun scaffolds to produce meniscal tissue by gene expression and histology. Finally, we investigated whether these cell-seeded scaffolds could repair surgical tears created ex vivo in avascular meniscal explants. Histology, immunohistochemistry, and mechanical testing of ex vivo repair provided evidence of neotissue that was significantly better integrated with the native tissue than with the acellular coaxial electrospun scaffolds. Human meniscal cell-seeded coaxial electrospun scaffolds may have potential in enhancing repair of avascular meniscus tears. Impact Statement The success of any tissue-engineered meniscus graft relies on its ability to mimic native three-dimensional microstructure, support cell growth, produce tissue-specific matrix, and enhance graft integration into the repair site. Polylactic acid scaffolds possess the desired mechanical properties, whereas collagen scaffolds induce better cell attachment and enhanced tissue regeneration. We therefore fabricated nanofibrous scaffolds that combined the properties of two biomaterials. These novel coaxial scaffolds more closely emulated the structure, mechanical properties, and biochemical composition of native meniscal tissue. Our findings of meniscogenic tissue generation and integration in meniscus defects have the potential to be translated to clinical use.

Surface analysis of sheep menisci after meniscectomy via infrared attenuated total reflection spectroscopy

Menisci are very important fibrocartilaginous tissue, which maintain biomechanical functions and physiological stabilization of knee joint. Meniscectomy is known as a surgery to recover partial functions from acute meniscus tears. However, the late consequences of total or partial meniscectomy include signs of osteoarthritis and even ligament instability. Infrared attenuated total reflection (IR-ATR) spectroscopy is a very useful technique, which can reveal molecular characteristics via the analysis of vibrational bands. The present study has employed IR-ATR spectroscopy to investigate sheep menisci samples after meniscectomy in a label-free fashion. Several differences of peak absorbance change and peak shift were observed between the native healthy samples and the meniscectomy samples in distinct IR wavenumber regions, such as amide I band, amide II band, C-H bending band as well as the sugar band region. Combining the results from the collagen protein IR spectra, it can be speculated that six months after meniscectomy collagen fibrils on the incision lose its ordered arrangement and a decrease in the triple helical structure of collagen fibril is observed. In addition, the collagen fibrils and proteoglycan content might also be slight varied after meniscectomy.

Evaluation of Meniscal Regeneration in a Mini Pig Model Treated With a Novel Polyglycolic Acid Meniscal Scaffold

BACKGROUND

Meniscal injury is a severe impediment to movement and results in accelerated deterioration of the knee joint.

PURPOSE

To evaluate the effect of a novel meniscal scaffold prepared from polyglycolic acid coated with polylactic acid/caprolactone on the treatment of meniscal injury in a mini pig model.

STUDY DESIGN

Controlled laboratory study.

METHODS

The model was established with a 10-mm resection at the anterior medial meniscus on both knee joints. A scaffold was implanted in the right knee joint. The meniscal scaffold was inserted and sutured next to the native meniscus. The histological analysis was performed to determine meniscal regeneration with safranin O staining, cell proliferation with PCNA, inflammation with TNF, and collagen structure and production with picrosirius red and immunofluorescence. Cartilage degeneration was evaluated with Safranin O. Meniscal regeneration and joint fluid were evaluated with magnetic resonance imaging.

RESULTS

Although compressive stress and elastic modulus were significantly lower in the scaffold than in the native porcine menisci, ultimate tensile stress was similar. Implanted scaffolds were covered with tissue beginning at 4 weeks, with increased migration of proliferating cells to the implant area at 4 and 8 weeks. Scaffolds were absorbed with freshly produced collagen at 24 weeks. Cartilage degeneration was significantly lower in the meniscus-implanted group than in the meniscectomy group. Magnetic resonance imaging results did not show severe accumulation of joint fluids, suggesting negligible inflammation. Density of the implanted menisci was comparable with that of the native menisci.

CONCLUSION

Meniscal scaffold prepared from polyglycolic acid has therapeutic potential for meniscal regeneration.

CLINICAL RELEVANCE

This meniscal scaffold can improve biological knee reconstruction and prevent the increase of total knee arthroplasty.

The Meniscus in Normal and Osteoarthritic Tissues: Facing the Structure Property Challenges and Current Treatment Trends

The treatment of meniscus injuries has recently been facing a paradigm shift toward the field of tissue engineering, with the aim of regenerating damaged and diseased menisci as opposed to current treatment techniques. This review focuses on the structure and mechanics associated with the meniscus. The meniscus is defined in terms of its biological structure and composition. Biomechanics of the meniscus are discussed in detail, as an understanding of the mechanics is fundamental for the development of new meniscal treatment strategies. Key meniscal characteristics such as biological function, damage (tears), and disease are critically analyzed. The latest technologies behind meniscal repair and regeneration are assessed.

Regenerative Features of Adipose Tissue for Osteoarthritis Treatment in a Rabbit Model: Enzymatic Digestion Versus Mechanical Disruption

Evaluating cell migration after cell-based treatment is important for several disorders, including osteoarthritis (OA), as it might influence the clinical outcome. This research explores migrating expanded-adipose stromal cells (ASCs) and adipose niches after enzymatic and mechanical processes. Bilateral anterior cruciate ligament transection induced a mild grade of OA at eight weeks in adult male New Zealand rabbits. ASCs, enzymatic stromal vascular fraction (SVF), and micro fragmented adipose tissue (MFAT) were intra-articularly injected in the knee joint. Assessments of cell viability and expression of specific markers, including CD-163 wound-healing macrophages, were done. Cell migration was explored through labelling with PKH26 dye at 7 and 30 days alongside co-localization analyses for CD-146. All cells showed good viability and high percentages of CD-90 and CD-146. CD-163 was significantly higher in MFAT compared to SVF. Distinct migratory potential and time-dependent effects were observed among cell-based treatments. At day 7, both ASCs and SVF migrated towards synovium, whereas for MFAT versus cartilage, a different migration pattern was noticed at day 30. The long-term distinct cell migration of ASCs, SVF, and MFAT open interesting clinical insights on their potential use for OA treatment. Moreover, the highest expression of CD-163 in MFAT, rather than SVF, might have an important role in directly mediating cartilage tissue repair responses.

Epigenetic Mechanisms Underlying the Aging of Articular Cartilage and Osteoarthritis

Aging is a progressive and complicated bioprocess with overall decline in physiological function. Osteoarthritis (OA) is the most common joint disease in middle-aged and older populations. Since the prevalence of OA increases with age and breakdown of articular cartilage is its major hallmark, OA has long been thought of as "wear and tear" of joint cartilage. Nevertheless, recent studies have revealed that changes in the chondrocyte function and matrix components may reduce the material properties of articular cartilage and predispose the joint to OA. The aberrant gene expression in aging articular cartilage that is regulated by various epigenetic mechanisms plays an important role in age-related OA pathogenesis. This review begins with an introduction to the current understanding of epigenetic mechanisms, followed by mechanistic studies on the aging of joint tissues, epigenetic regulation of age-dependent gene expression in articular cartilage, and the significance of epigenetic mechanisms in OA pathogenesis. Our recent findings on age-dependent expression of 2 transcription factors, nuclear factor of activated T cell 1 (NFAT1) and SOX9, and their roles in the formation and aging of articular cartilage are summarized in the review. Chondrocyte dysfunction in aged mice, which is mediated by epigenetically regulated spontaneous reduction of NFAT1 expression in articular cartilage, is highlighted as an important advance in epigenetics and cartilage aging. Potential therapeutic strategies for age-related cartilage degeneration and OA using epigenetic molecular tools are discussed at the end.

T2 mapping of the meniscus is a biomarker for early osteoarthritis

Purpose

To evaluate in vivo T₂ mapping as quantitative, imaging-based biomarker for meniscal degeneration in humans, by studying the correlation between T₂ relaxation time and degree of histological degeneration as reference standard.

Methods

In this prospective validation study, 13 menisci from seven patients with radiographic knee osteoarthritis (median age 67 years, three males) were included. Menisci were obtained during total knee replacement surgery. All patients underwent pre-operative magnetic resonance imaging using a 3-T MR scanner which included a T₂ mapping pulse sequence with multiple echoes. Histological analysis of the collected menisci was performed using the Pauli score, involving surface integrity, cellularity, matrix organization, and staining intensity. Mean T₂ relaxation times were calculated in meniscal regions of interest corresponding with the areas scored histologically, using a multi-slice multi-echo postprocessing algorithm. Correlation between T₂ mapping and histology was assessed using a generalized least squares model fit by maximum likelihood.

Results

The mean T₂ relaxation time was 22.4 ± 2.7 ms (range 18.5–27). The median histological score was 10, IQR 7–11 (range 4–13). A strong correlation between T₂ relaxation time and histological score was found (r_s = 0.84, CI 95% 0.64–0.93).

Conclusion

In vivo T₂ mapping of the human meniscus correlates strongly with histological degeneration, suggesting that T₂ mapping enables the detection and quantification of early compositional changes of the meniscus in knee OA.

Key Points

• Prospective histology-based study showed that in vivo T₂mapping of the human meniscus correlates strongly with histological degeneration.

• Meniscal T₂mapping allows detection and quantifying of compositional changes, without need for contrast or special MRI hardware.

• Meniscal T₂mapping provides a biomarker for early OA, potentially allowing early treatment strategies and prevention of OA progression.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06091-1) contains supplementary material, which is available to authorized users.

Rigid-body modeling of knee cartilage and meniscus using experimental pressure-strain curves

Rigid-body knee models have gained popularity thanks to computational speed and ease of setup compared to finite element models-showing exciting potential for clinical patient-specific models in the future. However, Rigid-body studies in general have encountered difficulty in modeling cartilage and especially meniscus material properties, often relying on computationally costly optimization techniques. This paper presents two new methods to alleviate the difficulty-one to define model contact pressure and one to define meniscus internal forces-and is the first to our knowledge to use experimental pressure-strain curves from the literature to simulate cartilage and meniscus behavior in a rigid body model. This paper describes the methodology to derive the proof of concept model and preliminary results from a gait simulation based on ISO 14243-1.

Morphological and ultrastructural analysis of normal, injured and osteoarthritic human knee menisci

The human meniscus plays a crucial role for transmission and distribution of load across the knee, as well as shock absorption, joint stability, lubrication, and congruity. The aim of this study was to compare the complex geometry, and unique ultrastructure and tissue composition of the meniscus in healthy (control) and pathological conditions to provide understanding of structural changes that could be helpful in the future design of targetted therapies and improvement of treatment indications. We analyzed meniscus samples collected from 3 healthy multi-organ donors (median age, 66 years), 5 patients with traumatic meniscal tear (median age, 41 years) and 3 patients undergoing total knee replacement (TKR) for end-stage osteoarthritis (OA) (median age, 72 years). We evaluated the extracellular matrix (ECM) organization, the appearance and distribution of areas of calcification, and modifications of cellular organization and structure by electron microscopy and histology. The ECM structure was similar in specimens from traumatic meniscus tears compared to those from patients with late-stage OA, showing disorganization of collagen fibers and increased proteoglycan content. Cells of healthy menisci showed mainly diffuse chromatin and well preserved organelles. Both in traumatic and in OA menisci, we observed increased chromatin condensation, organelle degeneration, and cytoplasmic vacuolization, a portion of which contained markers of autophagic vacuoles. Areas of calcification were also observed in both traumatic and OA menisci, as well as apoptotic- like features that were particularly prominent in traumatic meniscal tear samples. We conclude that meniscal tissue from patients with traumatic meniscal injury demonstrate pathological alterations characteristic of tissue from older patients undergoing TKR, suggesting that they have high susceptibility to develop OA.

The Fate of the Contralateral Knee in Patients With a Lateral Discoid Meniscus

PURPOSE

To analyze the survivorship of the lateral meniscus (LM) in the contralateral knee after surgery for symptomatic torn discoid lateral meniscus (DLM) and to determine its associated factors.

METHODS

Two hundred ninety-six patients who underwent arthroscopic meniscectomy for torn symptomatic DLM were reviewed retrospectively. Patients were classified into subgroups based on demographic, clinical, and radiologic variables. The survivorship analysis of the LM on the contralateral knee was calculated using the Kaplan-Meier method, and comparison among the subgroups was conducted using the log-rank test. The predicted prognostic factors associated with survivorship were determined using Cox proportional hazard regression analysis.

RESULTS

Of the 296 patients, 51 (17%) had arthroscopic surgery in the contralateral knee during the study period. The group ≥40 years old had significantly worse survival than the group <40 (log-rank test, P < .001). In terms of radiologic variables, the group with Kellgren-Lawrence grade 3 or 4 had significantly poorer survivorship than that with grade 1 or 2 (log-rank test, P = .045). Age ≥40 years was associated with poorer survivorship (hazard ratio, 3.235; 95% confidence interval, 1.782-5.875; P < .001). Kellgren-Lawrence grades 3 and 4 in the contralateral knee were associated with poorer survival (hazard ratio, 2.071; 95% confidence interval, 1.061-4.043; P = .033). The cumulative survival rate at 10 years of the LM in the contralateral knee after surgery for symptomatic torn DLM was 81%.

CONCLUSIONS

Patients with a lateral discoid meniscus have a risk of a similar condition in the contralateral knee. Increased risks of symptomatology are associated with age and degenerative changes.

LEVEL OF EVIDENCE

Level IV, retrospective uncontrolled case series.

Introduction of an MR-based semi-quantitative score for assessing partial meniscectomy and relation to knee joint degenerative disease: data from the Osteoarthritis Initiative

OBJECTIVES

To develop an MR-based semi-quantitative meniscus scoring technique for postoperative assessment of the degree of meniscal resection, to test its reproducibility, and to study the relationship between the amount of resection and degenerative disease burden.

METHODS

We studied the right knee of 135 participants from the Osteoarthritis Initiative that underwent meniscal surgery an average of 14 years previously. The amount of meniscal resection was assessed on baseline 3.0-T MRIs and calculated as meniscus resection score (MenRS) with a range of 0 to 18. Knee abnormalities at baseline and 48 months were graded using a modified Whole-Organ Magnetic Resonance Imaging Score (WORMS). Subjects were also stratified according to meniscal resection performed after injury versus without preceding injury. Statistical analysis included intra-class correlation coefficient (ICC) to determine reproducibility as well as regression models and partial correlations to correlate MenRS with WORMS outcomes.

RESULTS

ICC values for intra- and inter-observer reproducibility of MenRS were 0.980 and 0.977, respectively. Overall, the amount of meniscal resection showed a significant correlation with baseline WORMS grades: higher MenRS was associated with higher total WORMS grades (p = 0.004) and cartilage (p = 0.004) and ligament (p < 0.001) subscores. However, no significant association between MenRS and change in WORMS grades over 48 months was found. The relationship between MenRS and baseline WORMS grades did not change after adjusting for a reported history of knee injury.

CONCLUSIONS

Postoperative assessment of the knee following partial meniscectomy using the newly developed MenRS showed excellent reproducibility and significant cross-sectional correlation with WORMS gradings.

KEY POINTS

• The newly developed semi-quantitative MR-based meniscal resection score demonstrated excellent reproducibility. • A significant correlation between the amount of meniscal resection measured using the newly developed score and the degree of overall knee joint degenerative disease and cartilage defects was found.

Connective Tissue and Age-Related Diseases

We begin this chapter by describing normal characteristics of several pertinent connective tissue components, and some of the basic changes they undergo with ageing. These alterations are not necessarily tied to any specific disease or disorders, but rather an essential part of the normal ageing process. The general features of age-induced changes, such as skin wrinkles, in selected organs with high content of connective or soft tissues are discussed in the next part of the chapter. This is followed by a section dealing with age-related changes in specific diseases that fall into at least two categories. The first category encompasses common diseases with high prevalence among mostly ageing populations where both genetic and environmental factors play roles. They include but may not be limited to atherosclerosis and coronary heart disease, type II diabetes, osteopenia and osteoporosis, osteoarthritis, tendon dysfunction and injury, age-related disorders of spine and joints. Disorders where genetics plays the primary role in pathogenesis and progression include certain types of progeria, such as Werner syndrome and Hutchinson-Gilford progeria belong to the second category discussed in this chapter. These disorders are characterized by accelerated signs and symptoms of ageing. Other hereditary diseases or syndromes that arise from mutations of genes encoding for components of connective tissue and are less common than diseases included in the first group will be discussed briefly as well, though they may not be directly associated with ageing, but their connective tissue undergoes some changes compatible with ageing. Marfan and Ehlers-Danlos syndromes are primary examples of such disorders. We will probe the role of specific components of connective tissue and extracellular matrix if not in each of the diseases, then at least in the main representatives of these disorders.

Considerations for translation of tissue engineered fibrocartilage from bench to bedside

Fibrocartilage is found in the knee meniscus, the temporomandibular joint (TMJ) disc, the pubic symphysis, the annulus fibrosus of intervertebral disc, tendons, and ligaments. These tissues are notoriously difficult to repair due to their avascularity, and limited clinical repair and replacement options exist. Tissue engineering has been proposed as a route to repair and replace fibrocartilages. Using the knee meniscus and TMJ disc as examples, this review describes how fibrocartilages can be engineered toward translation to clinical use. Presented are fibrocartilage anatomy, function, epidemiology, pathology, and current clinical treatments because they inform design criteria for tissue engineered fibrocartilages. Methods for how native tissues are characterized histomorphologically, biochemically, and mechanically to set gold standards are described. Then, provided is a review of fibrocartilage-specific tissue engineering strategies, including the selection of cell sources, scaffold or scaffold-free methods, and biochemical and mechanical stimuli. In closing, the Food and Drug Administration paradigm is discussed to inform researchers of both the guidance that exists and the questions that remain to be answered with regard to bringing a tissue engineered fibrocartilage product to the clinic.

Inflammatory molecules produced by meniscus and synovium in early and end-stage osteoarthritis: a coculture study

The aim of this study was to identify the molecules and pathways involved in the cross-talk between meniscus and synovium that may play a critical role in osteoarthritis (OA) pathophysiology. Samples of synovium and meniscus were collected from patients with early and end-stage OA and cultured alone or cocultured. Cytokines, chemokines, metalloproteases, and their inhibitors were evaluated at the gene and protein levels. The extracellular matrix (ECM) changes were also investigated. In early OA cultures, higher levels of interleukin-6 (IL-6) and IL-8 messenger RNA were expressed by synovium and meniscus in coculture compared with meniscus cultured alone. RANTES release was significantly increased when the two tissues were cocultured compared with meniscus cultured alone. Increased levels of matrix metalloproteinase-3 (MMP-3) and MMP-10 proteins, as well as increased release of glycosaminoglycans and aggrecan CS846 epitope, were observed when synovium was cocultured with meniscus. In end-stage OA cultures, increased levels of IL-8 and monocyte chemoattractant protein-1 (MCP-1) proteins were released in cocultures compared with cultures of meniscus alone. Chemokine (C-C motif) ligand 21 (CCL21) protein release was higher in meniscus cultured alone and in coculture compared with synovium cultured alone. Increased levels of MMP-3 and 10 proteins were observed when tissues were cocultured compared with meniscus cultured alone. Aggrecan CS846 epitope release was increased in cocultures compared with cultures of either tissue cultured alone. Our study showed the production of inflammatory molecules by synovium and meniscus which could trigger inflammatory signals in early OA patients, and induce ECM loss in the progressive and final stages of OA pathology.

Orientation dependence and decay characteristics of T2 * relaxation in the human meniscus studied with 7 Tesla MR microscopy and compared to histology

Purpose

To evaluate: (1) the feasibility of MR microscopy T₂* mapping by performing a zonal analysis of spatially matched T₂* maps and histological images using microscopic in‐plane pixel resolution; (2) the orientational dependence of T₂* relaxation of the meniscus; and (3) the T₂* decay characteristics of the meniscus by statistically evaluating the quality of mono‐ and biexponential model.

Methods

Ultrahigh resolution T₂* mapping was performed with ultrashort echo time using a 7 Tesla MR microscopy system. Measurement of one meniscus was performed at three orientations to the main magnetic field (0, 55, and 90°). Histological assessment was performed with picrosirius red staining and polarized light microscopy. Quality of mono‐ and biexponential model fitting was tested using Akaike Information Criteria and F‐test.

Results

(1) The outer laminar layer, connective tissue fibers from the joint capsule, and the highly organized tendon‐like structures were identified using ultra‐highly resolved MRI. (2) Highly organized structures of the meniscus showed considerable changes in T₂* values with orientation. (3) No significant biexponential decay was found on a voxel‐by‐voxel–based evaluation. On a region‐of‐interest–averaged basis, significant biexponential decay was found for the tendon‐like region in a fiber‐to‐field angle of 0°.

Conclusion

The MR microscopy approach used in this study allows the identification of meniscus substructures and to quantify T₂* with a voxel resolution approximately 100 times higher than previously reported. T₂* decay showed a strong fiber‐to‐field angle dependence reflecting the anisotropic properties of the meniscal collagen fibers. No clear biexponential decay behavior was found for the meniscus substructures.

Application of adult mesenchymal stem cells in bone and vascular tissue engineering

Tissue engineering is a very promising field of regenerative medicine. Life expectancy has been increasing, and tissue replacement is increasingly needed in patients suffering from various degenerative disorders of the organs. The use of adult mesenchymal stem cells (e.g. from adipose tissue or from bone marrow) in tissue engineering seems to be a promising approach for tissue replacements. Clinical applications can make direct use of the large secretome of these cells, which can have a positive influence on other cells around. Another advantage of adult mesenchymal stem cells is the possibility to differentiate them into various mature cells via appropriate culture conditions (i.e. medium composition, biomaterial properties, and dynamic conditions). This review is focused on current and future ways to carry out tissue replacement of damaged bones and blood vessels, especially with the use of suitable adult mesenchymal stem cells as a potential source of differentiated mature cells that can later be used for tissue replacement. The advantages and disadvantages of different stem cell sources are discussed, with a main focus on adipose-derived stem cells. Patient factors that can influence later clinical applications are taken into account.

Movement and joints: effects of overuse on anuran knee tissues

Movement plays a main role in the correct development of joint tissues. In tetrapods, changes in normal movements produce alterations of such tissues during the ontogeny and in adult stages. The knee-joint is ideal for observing the influence of movement disorders, due to biomechanical properties of its components, which are involved in load transmission. We analyze the reaction of knee tissues under extreme exercise in juveniles and adults of five species of anurans with different locomotor modes. We use anurans as the case study because they undergo great mechanical stress during locomotion. We predicted that (a) knee tissues subjected to overuse will suffer a structural disorganization process; (b) adults will experience deeper morphological changes than juveniles; and (c) morphological changes will be higher in jumpers compared to walkers. To address these questions, we stimulated specimens on a treadmill belt during 2 months. We performed histological analyses of the knee of both treated and control specimens. As we expected, overuse caused structural changes in knee tissues. These alterations were gradual and higher in adults, and similar between jumpers and walkers species. This study represents a first approach to the understanding of the dynamics of anuran knee tissues during the ontogeny, and in relation to locomotion. Interestingly, the alterations found were similar to those observed in anurans subjected to reduced mobility and also to those described in joint diseases (i.e., osteoarthritis and tendinosis) in mammals, suggesting that among tetrapods, changes in movement generate similar responses in the tissues involved.

Three-dimensional mapping of the joint space for the diagnosis of knee osteoarthritis based on high resolution computed tomography: Comparison with radiographic, outerbridge, and meniscal classifications

One of the most important characteristic of knee osteoarthritis (OA) is the joint space (JS) width narrowing. Measurements are usually performed on two dimensional (2D) X-rays. We propose and validate a new method to assess the 3D joint space at the medial knee compartment using high resolution peripheral computed tomography images. A semi-automated method was developed to obtain a distance 3D map between femur an tibia with the following parameters: volume, minimum, maximum, mean, standard deviation, median, asymmetry, and entropy. We analyzed 71 knee specimens (mean age: 85 years), radiographs were performed for the Kellgren Lawrence (KL) score grading. In a subgroup of 41 specimens, the histopathological Outerbridge and meniscal classifications were performed and then cores were harvested from the tibial plateau in three different positions (posterior, central, and peripheral) and imaged at 10 µm of resolution to measure the cartilage thickness. Minimum, maximum, mean, and median were statistically lower and entropy higher between knee specimens classified as KL = 0 and KL = 3-4. Gr1 and 2 were statistically different from Gr3-4 for minimum, asymmetry, entropy using the Outerbridge classification and Gr1 was statistically different from Gr3-4 using the meniscal classification. Asymmetry, minimum, mean, median and entropy were significantly correlated with cartilage thickness. Parameters extracted from a 3D map of the medial joint space indicate local variations of JS and are related to local measurements of tibial cartilage thickness, and could be consequently useful to identify early OA. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:2380-2391, 2018.

Meniscal extrusion and degeneration during the course of osteoarthritis in the Murine collagenase-induced osteoarthritis model

Meniscal damage is, despite its major role in knee osteoarthritis (OA), often neglected in OA animal models. We evaluated structural meniscal degeneration during the course of OA in the murine collagenase-induced OA (CIOA) model. To investigate this, OA was induced in the knee joints of 33 male C57BL/6 mice by an intra-articular injection of 10U collagenase. The mice were sacrificed after 1, 3, 7, 14, 28, and 56 days, and the knees were harvested and processed for histological analysis. As control, six knees were obtained from 16-week-old mice in which no OA was induced. Meniscal damage, meniscal extrusion, and articular cartilage damage were evaluated on thionin-stained sections. Associations between parameters of interest were evaluated with Spearman rho correlation tests. When compared to non-OA knees, meniscal extrusion was visible from day 1 onwards and meniscal degeneration had a tendency to increase over time. The meniscus damage appeared around the same time as articular cartilage damage (day 14-28) and was statistically significantly more pronounced anterior than posterior, and no differences were seen between medial and lateral menisci. Meniscus and articular cartilage damage were moderately associated in the CIOA knees (ρ = 0.57; 95%CI [0.23-0.78]). Our findings suggest that the CIOA model is a valuable model to study the role of meniscal damage during OA progression and can support the development of future preventative treatment strategies. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res 36:2416-2420, 2018.

An electrospun fiber reinforced scaffold promotes total meniscus regeneration in rabbit meniscectomy model

Low vascularization in meniscus limits its regeneration ability after injury, and tissue engineering is the most promising method to achieve meniscus regeneration. In this study, we fabricated a kind of composite scaffold by decellularized meniscus extracellular matrix/polycaprolactone (DMECM/PCL) electrospinning fibers and porous DMECM, in which DMECM/PCL fibers were used as reinforcing component. The tensile modulus of the composite scaffold in longitudinal and crosswise directions were 8.5 ± 1.9 and 2.3 ± 0.3 MPa, respectively. Besides that, the DMECM/PCL electrospinning fibers enhanced suture resistance of the composite scaffold more than 5 times than DMECM scaffold effectively. In vitro cytocompatibility showed that the porous structure provided by DMECM component facilitated meniscus cells' proliferation. DMECM was also the main component to regulate cell behaviors, which promoted meniscus cells expressing extracellular matrix related genes such as COL I, COL II, SOX9 and AGG. Rabbits with total meniscectomy were used as animal model to evaluated the composited scaffolds performance in vivo at 3 and 6 months. Results showed that rabbits with scaffold implanting could regenerate neo-menisci in both time points. The neo-menisci had similar histology structure and biochemical content with native menisci. Although neo-menisci had inferior tensile modulus than native ones, its modulus was improved with implanting time prolonging. MRI imaging showed the signal of neo-meniscus in the body is clear, and X-ray imaging of knee joints demonstrated the implantation of scaffolds could relief joint space narrowing. Moreover, rabbits with neo-menisci had better cartilage condition in femoral condyle and tibial plateau compared than meniscectomy group.

STATEMENT OF SIGNIFICANCE

We fabricated the meniscus scaffold by combining porous decellularized meniscus extracellular matrix (DMECM) and DMECM/PCL electrospinning fibers together, which used the porous structure of DMECM, and the good tensile property of electrospinning fibers. We believe single material cannot satisfy increasing needs of scaffold. Therefore, we combined not only materials but also fabrication methods together to develop scaffold to make good use of each part. DMECM in electrospinning fibers also made these two components possible to be integrated through crosslinking. Compared to existing meniscus scaffold, the composite scaffold had (1) soft structure and extrusion would not happen after implantation, (2) ability to be trimmed to suitable shape during surgery, and (3) good resistance to suture.

Calcification of the acetabular labrum of the hip: prevalence in the general population and relation to hip articular cartilage and fibrocartilage degeneration

Background

Meniscal calcification is considered to play a relevant role in the pathogenesis of osteoarthritis of the knee. Little is known about the biology of acetabular labral disease and its importance in hip pathology. Here, we analyze for the first time the calcification of the acetabular labrum of the hip (ALH) and its relation to hip cartilage degeneration.

Methods

In this cross-sectional post-mortem study of an unselected sample of the general population, 170 ALH specimens and 170 femoral heads from 85 donors (38 female, 47 male; mean age 62.1 years) were analyzed by high-resolution digital contact radiography (DCR) and histological degeneration grade. The medial menisci (MM) from the same 85 donors served as an intra-individual reference for cartilage calcification (CC). Scanning electron microscopy (SEM), energy dispersive analysis (ED) and Raman spectroscopy were performed for characterization of ALH CC.

Results

The prevalence of CC in the ALH was 100% and that in the articular cartilage of the hip (ACH) was 96.5%. Quantitative analysis revealed that the amount of ALH CC was higher than that in the ACH (factor 3.0, p < 0.001) and in the MM (factor 1.3, p < 0.001). There was significant correlation between the amount of CC in the fibrocartilage of the left and right ALH (r = 0.70, p < 0.001). Independent of age, the amount of ALH CC correlated with histological degeneration of the ALH (Krenn score) (r = 0.55; p < 0.001) and the ACH (Osteoarthritis Research Society International (OARSI), r = 0.69; p < 0.001). Calcification of the ALH was characterized as calcium pyrophosphate dihydrate deposition.

Conclusion

The finding that ALH fibrocartilage is a strongly calcifying tissue is unexpected and novel. The fact that ALH calcification correlates with cartilage degeneration independent of age is suggestive of an important role of ALH calcification in osteoarthritis of the hip and renders it a potential target for the prevention and treatment of hip joint degeneration.

Engineered Healing of Avascular Meniscus Tears by Stem Cell Recruitment

Meniscus injuries are extremely common with approximately one million patients undergoing surgical treatment annually in the U.S. alone. Upon injury, the outer zone of the meniscus can be repaired and expected to functionally heal but tears in the inner avascular region are unlikely to heal. To date, no regenerative therapy has been proven successful for consistently promoting healing in inner-zone meniscus tears. Here, we show that controlled applications of connective tissue growth factor (CTGF) and transforming growth factor beta 3 (TGFβ3) can induce seamless healing of avascular meniscus tears by inducing recruitment and step-wise differentiation of synovial mesenchymal stem/progenitor cells (syMSCs). A short-term release of CTGF, a selected chemotactic and profibrogenic cue, successfully recruited syMSCs into the incision site and formed an integrated fibrous matrix. Sustain-released TGFβ3 then led to a remodeling of the intermediate fibrous matrix into fibrocartilaginous matrix, fully integrating incised meniscal tissues with improved functional properties. Our data may represent a novel clinically relevant strategy to improve healing of avascular meniscus tears by recruiting endogenous stem/progenitor cells.

Cellular and molecular meniscal changes in the degenerative knee: a review

Background

The important role of knee menisci to maintain adequate knee function is frequently impaired since early stages of knee joint degeneration. A better understanding of meniscal impairment may help the orthopaedic surgeon to orient the treatment of the degenerative knee. This review focuses on changes in meniscal cells and matrix when degeneration is in progress.

Main body

Differences in the meniscal structure and metabolism have been investigated in the degenerative knee, both in experimental animal models and in surgical specimens. Cell population reduction, extracellular matrix disorganization, disturbances in collagen and non-collagen protein synthesis and/or expression have been found in menisci along with knee degeneration. These changes are considered disease-specific, different from those due to aging.

Conclusion

Significant cellular and matrix differences are found in menisci during knee degeneration. These investigations may help to further progress in the understanding of knee degeneration and in the search of more biological treatments.

The Pathobiology of the Meniscus: A Comparison Between the Human and Dog

Serious knee pain and related disability have an annual prevalence of approximately 25% on those over the age of 55 years. As curative treatments for the common knee problems are not available to date, knee pathologies typically progress and often lead to osteoarthritis (OA). While the roles that the meniscus plays in knee biomechanics are well characterized, biological mechanisms underlying meniscus pathophysiology and roles in knee pain and OA progression are not fully clear. Experimental treatments for knee disorders that are successful in animal models often produce unsatisfactory results in humans due to species differences or the inability to fully replicate disease progression in experimental animals. The use of animals with spontaneous knee pathologies, such as dogs, can significantly help addressing this issue. As microscopic and macroscopic anatomy of the canine and human menisci are similar, spontaneous meniscal pathologies in canine patients are thought to be highly relevant for translational medicine. However, it is not clear whether the biomolecular mechanisms of pain, degradation of extracellular matrix, and inflammatory responses are species dependent. The aims of this review are (1) to provide an overview of the anatomy, physiology, and pathology of the human and canine meniscus, (2) to compare the known signaling pathways involved in spontaneous meniscus pathology between both species, and (3) to assess the relevance of dogs with spontaneous meniscal pathology as a translational model. Understanding these mechanisms in human and canine meniscus can help to advance diagnostic and therapeutic strategies for painful knee disorders and improve clinical decision making.

Labral calcification in end-stage osteoarthritis of the hip correlates with pain and clinical function

The acetabular labrum of the hip (ALH) is recognized as a clinically important structure, but knowledge about the pathophysiology of this fibrocartilage is scarce. In this prospective study we determined the prevalence of ALH calcification in patients with end-stage osteoarthritis (OA) and analyzed the relationship of cartilage calcification (CC) with hip pain and clinical function. Cohort of 80 patients (70.2 ± 7.6years) with primary OA scheduled for total hip replacement. Harris Hip Score (HHS) was recorded preoperatively. Total ALH and femoral head (FH) were sampled intraoperatively. CC of the ALH and FH was analyzed by high-resolution digital contact radiography. Histological degeneration of the ALH (Krenn-Score) and FH (OARSI-Score) was determined. Multivariate linear regression model and partial correlation analyses were performed. The prevalence of cartilage calcification both in the ALH and FH was 100%, while the amount of CC in the ALH was 1.55 times higher than in the FH (p < 0.001). There was a significant inverse regression between the amount of calcification of both the ALH and the FH and preoperative HHS (β_ALH  = -2.1, p = 0.04), (β_FH  = -2.9, p = 0.005), but pain was influenced only by ALH calcification (β_ALH  = -2.7, p = 0.008). Age-adjusted, there was a significant correlation between cartilage calcification and histological degeneration (ALH:r_s  = 0.53, p < 0.001/FH: r_s  = 0.30, p = 0.007). Fibrocartilage and articular cartilage calcification are inseparable pathological findings in end-stage osteoarthritis of the hip. Fibrocartilage calcification is associated with poor and painful hip function.

CLINICAL SIGNIFICANCE

ALH fibrocartilage appears to be particularly prone to calcification, which may explain higher pain levels in individuals with a high degree of ALH calcification independent of age and histological degeneration. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1248-1255, 2018.

Gene-expression changes in knee-joint tissues with aging and menopause: implications for the joint as an organ

Background

When considering the “joint as an organ”, the tissues in a joint act as complementary components of an organ, and the “set point” is the cellular activity for homeostasis of the joint tissues. Even in the absence of injury, joint tissues have adaptive responses to processes, like aging and menopause, which result in changes to the set point.

Purpose

The purpose of this study in a preclinical model was to investigate age-related and menopause-related changes in knee-joint tissues with the hypothesis that tissues will change in unique ways that reflect their differing contributions to maintaining joint function (as measured by joint laxity) and the differing processes of aging and menopause.

Methods

Rabbit knee-joint tissues from three groups were evaluated: young adult (gene expression, n=8; joint laxity, n=7; water content, n=8), aging adult (gene expression, n=6; joint laxity, n=7; water content, n=5), and menopausal adult (gene expression, n=8; joint laxity, n=7; water content, n=8). Surgical menopause was induced with ovariohysterectomy surgery and gene expression was assessed using reverse-transcription quantitative polymerase chain reaction.

Results

Aging resulted in changes to 37 of the 150 gene–tissue combinations evaluated, and menopause resulted in changes to 39 of the 150. Despite the similar number of changes, only eleven changes were the same in both aging and menopause. No differences in joint laxity were detected comparing young adult rabbits with aging adult rabbits or with menopausal adult rabbits.

Conclusion

Aging and menopause affected the gene-expression patterns of the tissues of the knee joint differently, suggesting unique changes to the set point of the knee. Interestingly, aging and menopause did not affect knee-joint laxity, suggesting that joint function was maintained, despite changes in gene expression. Taken together, these findings support the theory of the joint as an organ where the tissues of the joint adapt to maintain joint function.

Cartilage regeneration and ageing: Targeting cellular plasticity in osteoarthritis

Ageing processes play a major contributing role for the development of Osteoarthritis (OA). This prototypic degenerative condition of ageing is the most common form of arthritis and is accompanied by a general decline, chronic pain and mobility deficits. The disease is primarily characterized by articular cartilage degradation, followed by subchondral bone thickening, osteophyte formation, synovial inflammation and joint degeneration. In the early stages, osteoarthritic chondrocytes undergo phenotypic changes that increase cell proliferation and cluster formation and enhance the production of matrix-remodelling enzymes. In fact, chondrocytes exhibit differentiation plasticity and undergo phenotypic changes during the healing process. Current studies are focusing on unravelling whether OA is a consequence of an abnormal wound healing response. Recent investigations suggest that alterations in different proteins, such as TGF-ß/BMPs, NF-Kß, Wnt, and Cx43, or SASP factors involved in signalling pathways in wound healing response, could be directly implicated in the initiation of OA. Several findings suggest that osteoarthritic chondrocytes remain in an immature state expressing stemness-associated cell surface markers. In fact, the efficacy of new disease-modifying OA drugs that promote chondrogenic differentiation in animal models indicates that this may be a drug-sensible state. In this review, we highlight the current knowledge regarding cellular plasticity in chondrocytes and OA. A better comprehension of the mechanisms involved in these processes may enable us to understand the molecular pathways that promote abnormal repair and cartilage degradation in OA. This understanding would be advantageous in identifying novel targets and designing therapies to promote effective cartilage repair and successful joint ageing by preventing functional limitations and disability.

Osteoarthritis and the Complement Cascade

Accumulating evidence demonstrates that complement activation is involved in the pathogenesis of osteoarthritis (OA). However, the intimate complement regulation and cross talk with other signaling pathways in joint-associated tissues remain incompletely understood. Recent insights are summarized and discussed here, to put together a more comprehensive picture of complement involvement in OA pathogenesis. Complement is regulated by several catabolic and inflammatory mediators playing a key role in OA. It seems to be involved in many processes observed during OA development and progression, such as extracellular cartilage matrix (ECM) degradation, chondrocyte and synoviocyte inflammatory responses, cell lysis, synovitis, disbalanced bone remodeling, osteophyte formation, and stem cell recruitment, as well as cartilage angiogenesis. In reverse, complement can be activated by various ECM components and their cleavage products, which are released during OA-associated cartilage degradation. There are, however, some other cartilage ECM components that can inhibit complement, underlining the diverse effects of ECM on the complement activation. It is hypothesized that complement might also be directly activated by mechanical stress, thereby contributing to OA. The question arises whether keeping the complement activation in balance could represent a future therapeutic strategy in OA treatment and in the prevention of its progression.

Analysis of human menisci degeneration via infrared attenuated total reflection spectroscopy

Degeneration of human meniscal tissue induces impairment of normal knee functions, and is a highly relevant etiology of knee joint tears and osteoarthritis.

Short-Term Homing of Hyaluronan-Primed Cells: Therapeutic Implications for Osteoarthritis Treatment

The evaluation of key factors modulating cell homing following injection can provide new insights in the comprehension of unsolved biological questions about the use of cell therapies for osteoarthritis (OA). The main purpose of this in vivo study was to investigate the biodistribution of an intra-articular injection of mesenchymal stromal cells (MSCs) and bone marrow concentrate (BMC) in a rabbit OA model and whether the additional use of sodium hyaluronate (HA) could modulate their migration and delay joint degeneration. OA was surgically induced in adult male New Zealand rabbits. A group of animals was used to test the biodistribution of labeled cells alone or with HA at 7 and 14 days to investigate cell migration. The efficacy of treatments was evaluated in other experimental groups at 2 months. Histology and immunohistochemistry for markers identifying anabolic and catabolic processes in the cartilage and meniscus, or macrophage subset population in the synovial membrane, were performed. Kruskal-Wallis test, followed by post hoc Dunn's test, and Spearman's rank-order correlation method were used. MSCs and BMC preferentially migrate toward tissue areas showing OA features in the meniscus and cartilage and in detail near inflammatory zones in the synovial membrane. The combination with HA contributed to boost cell migration toward articular cartilage. In general, both labeled cells combined with HA were found near cell cluster and fissures in the cartilage and meniscus, respectively, and close to areas of synovial membrane showing mainly anti-inflammatory macrophages. A promotion of joint repair was observed at different levels for all treatments, although BMC-HA treatment resulted as the best strategy to support joint repair. This last, displayed a good protein expression of type II collagen in the cartilage, as well as the presence of anti-inflammatory macrophages in the synovial membrane at 2 months from the treatment. Studies tracking cell biodistribution indicate that priming progenitor cells with HA modulated cell homing favoring not only attachment but also their integration within articular cartilage.

Sustained intra-cartilage delivery of low dose dexamethasone using a cationic carrier for treatment of post traumatic osteoarthritis

Disease-modifying osteoarthritis drugs (DMOADs) should reach their intra-tissue target sites at optimal doses for clinical efficacy. The dense, negatively charged matrix of cartilage poses a major hindrance to the transport of potential therapeutics. In this work, electrostatic interactions were utilised to overcome this challenge and enable higher uptake, full-thickness penetration and enhanced retention of dexamethasone (Dex) inside rabbit cartilage. This was accomplished by using the positively charged glycoprotein avidin as nanocarrier, conjugated to Dex by releasable linkers. Therapeutic effects of a single intra-articular injection of low dose avidin-Dex (0.5 mg Dex) were evaluated in rabbits 3 weeks after anterior cruciate ligament transection (ACLT). Immunostaining confirmed that avidin penetrated the full cartilage thickness and was retained for at least 3 weeks. Avidin-Dex suppressed injury-induced joint swelling and catabolic gene expression to a greater extent than free Dex. It also significantly improved the histological score of cell infiltration and morphogenesis within the periarticular synovium. Micro-computed tomography confirmed the reduced incidence and volume of osteophytes following avidin-Dex treatment. However, neither treatment restored the loss of cartilage stiffness following ACLT, suggesting the need for a combinational therapy with a pro-anabolic factor for enhancing matrix biosynthesis. The avidin dose used caused significant glycosaminoglycan (GAG) loss, suggesting the use of higher Dex : avidin ratios in future formulations, such that the delivered avidin dose could be much less than that shown to affect GAGs. This charge-based delivery system converted cartilage into a drug depot that could also be employed for delivery to nearby synovium, menisci and ligaments, enabling clinical translation of a variety of DMOADs.

The interrelation of osteoarthritis and diabetes mellitus: considering the potential role of interleukin-10 and in vitro models for further analysis

INTRODUCTION

Today, not only the existence of an interrelation between obesity/adipositas and osteoarthritis (OA) but also the association of OA and diabetes mellitus (DM) are widely recognized. Nevertheless, shared influence factors facilitating OA development in DM patients still remain speculative up until now. To supplement the analysis of clinical data, appropriate in vitro models could help to identify shared pathogenetic pathways. Informative in vitro studies could later be complemented by in vivo data obtained from suitable animal models.

MATERIALS AND METHODS

Therefore, this detailed review of available literature was undertaken to discuss and compare the results of currently published in vitro studies focusing on the interrelation between OA, the metabolic syndrome and DM and to propose models to further study the molecular pathways.

RESULTS

The survey of literature presented here supports the hypothesis that the pathogenesis of OA in DM is based on imbalanced molecular pathways with a putative crucial role of antiinflammatory cytokines such as IL-10.

CONCLUSION

Future development of versatile micro-scaled in vitro models such as combining DM and OA on chip could allow the identification of common pathogenetic pathways and might help to develop novel therapeutic strategies.

Age-related changes in the knee meniscus

BACKGROUND

Aging is the most prominent risk factor for the development of osteoarthritis (OA), which affects knees and causes major health burdens. Meniscal dysfunction mostly based on degeneration contributes to the development and progression of knee OA. Meniscal degeneration is caused by various extrinsic factors, such as repetitive trauma or leg malalignment, while meniscal aging is considered as internal changes, such as molecular or cellular changes. Little is known about age-related changes in the meniscus. Therefore, this review aimed to summarize and clarify the understanding of the aged meniscus.

METHODS

There are few articles about natural aging in the meniscus, because most reports only demonstrate the effects of OA on the meniscus. We searched PubMed (1948 to November 2016) to identify and summarize all English-language articles evaluating natural aging in the meniscus.

RESULTS

There is evidence of compositional change in the meniscus with aging, involving cells, collagens, and proteoglycans. In addition, as recent reports on the natural aging of cartilage have indicated, senescence of the meniscal cells may also lead to disruption of meniscal cells and tissue homeostasis. Due to the low turnover rate of collagen, accumulation of advanced glycation end-products largely contributes to tissue stiffness and vulnerability, and finally results in degenerative changes or tears. Furthermore, environmental factors such as joint fluid secreted by inflamed synovium could also contribute to meniscal tissue deterioration.

CONCLUSIONS

Age-related changes induce meniscal tissue vulnerability and finally lead to meniscal dysfunction.

Autologous Bone Marrow Concentrate in a Sheep Model of Osteoarthritis: New Perspectives for Cartilage and Meniscus Repair

INTRODUCTION

Cell-based therapies are becoming a valuable tool to treat osteoarthritis (OA). This study investigated and compared the regenerative potential of bone marrow concentrate (BMC) and mesenchymal stem cells (MSC), both engineered with Hyaff(®)-11 (HA) for OA treatment in a sheep model.

METHODS

OA was induced via unilateral medial meniscectomy. Bone marrow was aspirated from the iliac crest, followed by concentration processes or cell isolation and expansion to obtain BMC and MSC, respectively. Treatments consisted of autologous BMC and MSC seeded onto HA. The regenerative potential of bone, cartilage, menisci, and synovia was monitored using macroscopy, histology, immunohistochemistry, and micro-computed tomography at 12 weeks post-op. Data were analyzed using the general linear model with adjusted Sidak's multiple comparison and Spearman's tests.

RESULTS

BMC-HA treatment showed a greater repair ability in inhibiting OA progression compared to MSC-HA, leading to a reduction of inflammation in cartilage, meniscus, and synovium. Indeed, the decrease of inflammation positively contributed to counteract the progression of fibrotic and hypertrophic processes, known to be involved in tissue failure. Moreover, the treatment with BMC-HA showed the best results in allowing meniscus regeneration. Minor healing effects were noticed at bone level for both cell strategies; however, a downregulation of subchondral bone thickness (Cs.Th) was found in both cell treatments compared to the OA group in the femur.

CONCLUSION

The transplantation of BMC-HA provided the best effects in supporting regenerative processes in cartilage, meniscus, and synovium and at less extent in bone. On the whole, both MSC and BMC combined with HA reduced inflammation and contributed to switch off fibrotic and hypertrophic processes. The observed regenerative potential by BMC-HA on meniscus could open new perspectives, suggesting its use not only for OA care but also for the treatment of meniscal lesions, even if further analyses are necessary to confirm its healing potential at long-term follow-up.

Delivery of epidermal growth factor receptor inhibitor via a customized collagen scaffold promotes meniscal defect regeneration in a rabbit model

Meniscal injury is one of the most common knee joint injuries, which remains an intractable challenge in clinical practice to date. Aberrant epidermal growth factor receptor (EGFR) activation levels in both human and mice menisci following injury, prompted us to investigate the functional role of EGFR by utilizing an inducible cartilage-specific EGFR-deficient mouse model. We demonstrated that conditional EGFR deletion in mice resulted in increased partial meniscectomy-induced ECM production within the meniscus, which is comparable to utilization of the small molecule EGFR inhibitor, gefitinib, to block EGFR activity. Here, we combined intra-articular delivery of gefitinib with an implanted customized collagen scaffold to substitute for lost meniscal tissue, as well as to promote meniscal regeneration and prevent osteoarthritis (OA) progression in a rabbit meniscectomy model.

STATEMENT OF SIGNIFICANCE

The main novelty of this study is the finding of a new application for small molecule EGFR inhibitor in meniscal injury therapy. This study also highlights the importance of using a customized collagen scaffold to provide robust mechanical strength and effectively promote meniscus regeneration. In summary, our study finds that intra-articular delivery of gefitinib together with implantation of a customized, multi-layer collagen scaffold not only enhanced meniscal regeneration, but also protected articular cartilage from degeneration in rabbit model. These results provide valuable insight for meniscal tissue engineering studies and clinical practice.

* The Ovine Model for Meniscus Tissue Engineering: Considerations of Anatomy, Function, Implantation, and Evaluation

Meniscus injuries represent one of the most-common intra-articular knee injuries. The current treatment options include meniscectomy and allograft transplantation, both with poor long-term outcomes. Therefore, there is a need for regenerative techniques to restore meniscal function. To preclinically test scaffolds for meniscus replacement, large animal models need to be established and standardized. This review establishes the anatomical and compositional similarities between human and sheep menisci and provides guidance for implantation and evaluation of such devices. The ovine meniscus represents a scaled-down version of the human meniscus, with only slight structural differences that can be addressed during device fabrication. Implantation protocols in sheep remain a challenge, as the meniscus cannot be visualized with the arthroscopic-assisted procedures commonly performed in human patients. Thus, we recommend the appropriate implantation protocols for meniscus visualization, ligamentous restoration, and surgical fixation of both total and partial meniscus replacement devices. Last, due to the lack of standardization in evaluation techniques, we recommend a comprehensive battery of tests to evaluate the efficacy of meniscus replacement implants. We recommend other investigators utilize these surgical and testing techniques to establish the ovine model as the gold standard for preclinical evaluation of meniscus replacement devices.

[Incidence of knee injuries : Numbers for outpatient and inpatient care in Germany]

BACKGROUND

Musculoskeletal illnesses and injuries are among the most common ailments in the Federal Republic of Germany. In 2008 they generated costs of nearly 29 billion euros. Figures about their incidence and prevalence are necessary for a demand-oriented planning of future patient-centred care.

METHOD

Pseudonymised data of 3.8 million people insured by AOK Baden-Württemberg between 2008 and 2013 were evaluated. The diagnoses were assigned to nine injury groups. For outpatient care confirmed diagnoses were considered, and for inpatient care both primary and secondary diagnoses were considered. For all patients with structural knee injuries, it was evaluated whether they made use of one of five eligible treatment paradigms either in the quarter in which they were injured or in the following quarter.

RESULTS

418,257 patients were treated in 2013 for at least one new-onset injury (10.9 % of all insurees); 86,783 insurees (2.3 % of all insurees) had a newly occurring knee injury. The vast majority of the patients were treated by specialist doctors. While magnetic resonance imaging clearly increased during the observation period, the incidence of surgical therapy did not change. Striking are the different age distributions regarding the types of injuries, with a high injury incidence amongst young men and a significant increase in injuries between 2008 and 2013, especially amongst women.

CONCLUSION

For the first time, the data quantify the knee injury incidences of a large cohort in Germany. They show which inpatient and outpatient health care services have been claimed and that an age- and gender-adapted prevention and an increased awareness are needed.

Meniscal Preservation is Important for the Knee Joint

Native joint preservation has gained importance in recent years. This is mostly to find solutions for limitations of arthroplasty. In the knee joint, the menisci perform critical functions, adding stability during range of motion and efficiently transferring load across the tibiofemoral articulation while protecting the cartilage. The menisci are the most common injury seen by orthopedicians, especially in the younger active patients. Advances in technology and our knowledge on functioning of the knee joint have made meniscus repair an important mode of treatment. This review summarizes the various techniques of meniscus tear repair and also describes biological enhancements of healing.

Meniscal regeneration after resection of the anterior half of the medial meniscus in mice

Various animal studies have indicated that reduced meniscal function significantly exacerbates articular-cartilage degeneration. Despite the importance of meniscal function for joint homeostasis and prevention of osteoarthritis, the healing process after meniscal injury and the regenerative process after meniscus removal have not been studied in detail. In this study, we examined the process of meniscal regeneration and cartilage degeneration after meniscectomy in mice. The left anterior halves of the medial menisci in male C57Bl/6J mice were resected, and histological assessment of the process of meniscal regeneration was conducted on day 3 and 2, 4, and 6 weeks after the surgical procedure. Extensive macrophagic infiltration into the synovial membrane around the meniscectomized area was observed on day 3. Synovial hyperplasia was detected 2 weeks after the operation. At this stage, synovial tissue was filled with many fibroblastic cells, which underwent chondrocytic differentiation and produced cartilage matrices by 4 weeks after the operation. At 6 weeks, regenerated tissues resembled those of an intact meniscus. The articular cartilage at the interface of the resected meniscus significantly degenerated between 2 and 4 weeks after the surgical procedure, but subtle progression in cartilage degeneration was observed between 4 and 6 weeks. This finding is suggestive of a balance between meniscal regeneration and cartilage homeostasis. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1958-1965, 2017.

Equine meniscal degeneration is associated with medial femorotibial osteoarthritis

BACKGROUND

There is limited information available concerning normal equine meniscal morphology, its degeneration and role in osteoarthritis (OA).

OBJECTIVES

To characterise normal equine meniscal morphology and lesions and to explore the relationship between equine meniscal degeneration and femorotibial OA.

STUDY DESIGN

Ex vivo cadaveric study.

METHODS

Menisci were harvested from 7 normal joints (n = 14 menisci) and 15 joints with OA (n = 30 menisci). A macroscopic femorotibial OA score (cartilage degeneration and osteophytosis) was employed to measure disease severity in each compartment. The femoral and tibial meniscal surfaces were scored for macroscopic fibrillation and tears (1-4). Histological sections (regions: cranial and caudal horn; body) were also scored for microscopic fibrillation and tears (0-3) and inner border degeneration (0-3).

RESULTS

Partial meniscal tears were present on both femoral and tibial surfaces in all 3 regions and most frequently identified on the femoral surface of the cranial horn of the medial meniscus and body of the lateral meniscus. There was a significantly positive correlation between the global medial meniscal macroscopic scores and osteophyte (r = 0.7, P = 0.002) or cartilage degeneration (r = 0.5, P = 0.03) scores within the medial femorotibial joint. The global medial meniscal macroscopic score was greater (P = 0.004) in the advanced OA joints compared with control joints.

MAIN LIMITATIONS

The menisci were principally from abattoir specimens without a known clinical history because of the challenge in obtaining a large number of specimens with a clinical diagnosis of femorotibial OA.

CONCLUSIONS

This study is the first to describe normal equine meniscal morphology and lesions. Meniscal lesions were identified in all segments and on both articular surfaces. Meniscal degeneration significantly correlated with OA severity in the equine medial femorotibial joint. The relationship between OA and meniscal pathology remains to be elucidated.

Influence of meniscus on cartilage and subchondral bone features of knees from older individuals: A cadaver study

Objective

Cartilage and subchondral bone form a functional unit. Here, we aimed to examine the effect of meniscus coverage on the characteristics of this unit in knees of older individuals.

Methods

We assessed the hyaline cartilage, subchondral cortical plate (SCP), and subchondral trabecular bone in areas covered or uncovered by the meniscus from normal cadaver knees (without degeneration). Bone cores harvested from the medial tibial plateau at locations uncovered (central), partially covered (posterior), and completely covered (peripheral) by the meniscus were imaged by micro-CT. The following were measured on images: cartilage volume (Cart.Vol, mm³) and thickness (Cart.Th, mm); SCP thickness (SCP.Th, μm) and porosity (SCP.Por, %); bone volume to total volume fraction (BV/TV, %); trabecular thickness (Tb.Th, μm), spacing (Tb.Sp, μm), and number (Tb.N, 1/mm); structure model index (SMI); trabecular pattern factor (Tb.Pf); and degree of anisotropy (DA).

Results

Among the 28 specimens studied (18 females) from individuals with mean age 82.8±10.2 years, cartilage and SCP were thicker at the central site uncovered by the meniscus than the posterior and peripheral sites, and Cart.Vol was greater. SCP.Por was highest in posterior samples. In the upper 1–5 mm of subchondral bone, central samples were characterized by higher values for BV/TV, Tb.N, Tb.Th, and connectivity (Tb.Pf), a more plate-like trabecular structure and lower anisotropy than with other samples. Deeper down, at 6–10 mm, the differences were slightly higher for Tb.Th centrally, DA peripherally and SMI posteriorly.

Conclusions

The coverage or not by meniscus in the knee of older individuals is significantly associated with Cart.Th, SCP.Th, SCP.Por and trabecular microarchitectural parameters in the most superficial 5 mm and to a lesser extent the deepest area of subchondral trabecular bone. These results suggest an effect of differences in local loading conditions. In subchondral bone uncovered by the meniscus, the trabecular architecture resembles that of highly loaded areas.

Meniscal Tissue Engineering Using Aligned Collagen Fibrous Scaffolds: Comparison of Different Human Cell Sources

Hydrogel and electrospun scaffold materials support cell attachment and neotissue development and can be tuned to structurally and mechanically resemble native extracellular matrix by altering either electrospun fiber or hydrogel properties. In this study, we examined meniscus tissue generation from different human cell sources including meniscus cells derived from vascular and avascular regions, human bone marrow-derived mesenchymal stem cells, synovial cells, and cells from the infrapatellar fat pad (IPFP). All cells were seeded onto aligned electrospun collagen type I scaffolds and were optionally encapsulated in a tricomponent hydrogel. Single or multilayered constructs were generated and cultivated in defined medium with selected growth factors for 2 weeks. Cell viability, cell morphology, and gene-expression profiles were monitored using confocal microscopy, scanning electron microscopy, and quantitative polymerase chain reaction (qPCR), respectively. Multilayered constructs were examined with histology, immunohistochemistry, qPCR, and for tensile mechanical properties. For all cell types, TGFβ1 and TGFβ3 treatment increased COL1A1, COMP, Tenascin C (TNC), and Scleraxis (SCX) gene expression and deposition of collagen type I protein. IPFP cells generated meniscus-like tissues with higher meniscogenic gene expression, mechanical properties, and better cell distribution compared to other cell types studied. We show proof of concept that electrospun collagen scaffolds support neotissue formation and IPFP cells have potential for use in cell-based meniscus regeneration strategies.

The frequency of cartilage lesions in non-injured knees with symptomatic meniscus tears: results from an arthroscopic and NIR- (near-infrared) spectroscopic investigation

INTRODUCTION

Are symptomatic tear injuries to the menisci of the knee frequently or always associated with cartilage damage to the corresponding articular surfaces and other joint surfaces, respectively?

METHODS

A total of 137 patients (medial n = 127; lateral n = 10) underwent a meniscus resection. These patients showed no signs of a clear radiographic arthrosis and no MRI-detectable cartilage lesions > grade II. Traumatic injury was ruled out with a thorough medical history. The indication for operation was made exclusively on the basis of distinct, clinically apparent meniscus signs. In addition to the ICRS classification, all articular surfaces were examined spectroscopically (NIRS, near-infrared spectroscopy).

RESULTS

In 76.6% (n = 105) of all knees examined, clear cartilage damage (ICRS-grade III/IV) was found. For 43.8%, these were in the area of the patella, while for 34.3% they were in the area of the medial femur, and for 17.5%, in the area of the medial tibial plateau. More rarely, this damage was localized to the area of the trochlea (8.8%) or the lateral joint compartment (femoral 2.2%, tibial 15.3%). There were no significant differences between patients with medial or lateral meniscus lesions with respect to the distribution pattern of the joint injuries. During spectroscopic examination, pathological values were demonstrated (objective evidence of cartilage degeneration) in at least one of the examined articular surfaces (media n = 6, range 1-6).

CONCLUSION

Through our investigations, a high, if not complete, concomitance of degenerative cartilage lesions and degenerative meniscus damage was demonstrated. From this it can be concluded that the entity of "isolated degenerative meniscus damage" clearly does not exist in practice. It is therefore highly probable that degenerative meniscus lesions, as a part of general joint degeneration, are to be interpreted in the context of the development of arthrosis. The practical consequences still are unclear. Patients after partial meniscectomy need a longer follow-up to detect potential cartilage lesions as well as an OA progression.

Transplantation of autologous synovial mesenchymal stem cells promotes meniscus regeneration in aged primates

Transplantation of aggregates of synovial mesenchymal stem cells (MSCs) enhanced meniscus regeneration in rats. Anatomy and biological properties of the meniscus depend on animal species. To apply this technique clinically, it is valuable to investigate the use of animals genetically close to humans. We investigated whether transplantation of aggregates of autologous synovial MSCs promoted meniscal regeneration in aged primates. Chynomolgus primates between 12 and 13 years old were used. After the anterior halves of the medial menisci in both knees were removed, an average of 14 aggregates consisting of 250,000 synovial MSCs were transplanted onto the meniscus defect. No aggregates were transplanted to the opposite knee for the control. Meniscus and articular cartilage were analyzed macroscopically, histologically, and by MRI T1rho mapping at 8 (n = 3) and 16 weeks (n = 4). The medial meniscus was larger and the modified Pauli's histological score for the regenerated meniscus was better in the MSC group than in the control group in each primate at 8 and 16 weeks. Mankin's score for the medial femoral condyle cartilage was better in the MSC group than in the control group in all primates at 16 weeks. T1rho value for both the regenerated meniscus and adjacent articular cartilage in the MSC group was closer to the normal meniscus than in the control group in all primates at 16 weeks. Transplantation of aggregates of autologous synovial MSCs promoted meniscus regeneration and delayed progression of degeneration of articular cartilage in aged primates. This is the first report dealing with meniscus regeneration in primates. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1274-1282, 2017.