Postnatal morpho-functional development of a dog's meniscus.

This study evaluates the morpho-functional modifications that characterize meniscal development from neonatal to adult dogs. Even if menisci are recognized as essential structures for the knee joint, poor information is available about their morphogenesis, in particular in dog models. Menisci from a group of Dobermann Pinchers aged 0, 10, 30 days, and 4 years (T0, T10, T30, adult, respectively) were analyzed by SEM, histochemistry (Safranin O and Picro Sirius Red Staining analyzed under a polarized light microscope), immunofluorescences (collagen type I and II), biomechanical (compression) and biochemical analyses (glycosaminoglycans, GAGs, and DNA content). SEM analyses revealed that the T0 meniscus is a bulgy structure that during growth tends to flatten, firstly in the inner zone (T10) and then even in the outer zone (T30), until the achievement of the completely smooth adult final shape. These results were further supported by the histochemistry analyses in which the deposition of GAGs started from T30, and the presence of type I birefringent collagen fibers was observed from T0 to T30, while poorly refringent type III collagen fibers were observed in the adult dogs. Double immunofluorescence analyses also evidenced that the neonatal meniscus contains mainly type I collagen fibers, as well as the T10 meniscus, and demonstrated a more evident regionalization and crimping in the T30 and adult meniscus. Young's elastic modulus of the meniscus in T0 and T10 animals was lower than the T30 animals, and this last group was also lower than adult ones (T0-T10 vs T30 vs adult). Biochemical analysis confirmed that cellularity decreases over time from neonatal to adult (p < 0.01). The same decreasing trend was observed in GAGs deposition. These results may suggest that the postnatal development of canine meniscus may be related to the progressive functional locomotory development: after birth, the meniscus acquires its functionality over time, through movement, load, and growth itself.

Bovine Meniscus Middle Zone Tissue: Measurement of Collagen Fibril Behavior During Compression.

BACKGROUND: Type I collagen is the major component of the extracellular matrix of the knee's meniscus and plays a central role in that joint's biomechanical properties. Repair and reconstruction of tissue damage often requires a scaffold to assist the body to rebuild. The middle zone of bovine meniscus is a material that may be useful for the preparation of extracellular matrix scaffolds. METHODS: Here, synchrotron-based small-angle X-ray scattering (SAXS) patterns of bovine meniscus were collected during unconfined compression. Collagen fibril orientation, D-spacing, compression distance and force were measured. RESULTS: The collagen fibrils in middle zone meniscal fibrocartilage become more highly oriented perpendicular to the direction of compression. The D-spacing also increases, from 65.0 to 66.3 nm with compression up to 0.43 MPa, representing a 1.8% elongation of collagen fibrils perpendicular to the compression. CONCLUSION: The elasticity of the collagen fibrils under tension along their length when the meniscus is compressed, therefore, contributes to the overall elastic response of the meniscus only under loads that exceed those likely to be experienced physiologically.

No detectable remodelling in adult human menisci: an analysis based on the C14 bomb pulse.

OBJECTIVES: Bone and other human tissues remodel through life, for example, as a response to increasing load, and this prevents permanent destruction of the tissue. Non-traumatic meniscal rupture is a common musculoskeletal disease, but it is unknown if it is caused by inability of the menisci to remodel. The aim of this study was to determine whether meniscal collagen is remodelling throughout life. METHODS: The life-long turnover of the human meniscal collagens was explored by the 14C bomb pulse method. 14C levels were determined in menisci from 18 patients with osteoarthritis and 7 patients with healthy knees. RESULTS: There was a negligible turnover of the meniscal collagen in adults. This low turnover was observed in menisci from patients with knee osteoarthritis and in healthy menisci. CONCLUSION: This study provides evidence that essentially no remodelling occurs in the adult human meniscal collagen structure and explains the clinical degeneration that is often seen in menisci of middle-aged and elderly persons. It suggests that strengthening of the collagen structure of menisci, as response to physical activity, may occur during childhood, while it is not possible in the adult population.

Temporomandibular joint imaging: current clinical applications, biochemical comparison with the intervertebral disc and knee meniscus, and opportunities for advancement.

Temporomandibular disorders encompass multiple pathologies of the temporomandibular joint that manifest as middle/inner ear symptoms, headache, and/or localized TMJ symptoms. There is an important although somewhat limited role of imaging in the diagnostic evaluation of temporomandibular disorders. In this manuscript, we provide a comprehensive review of TMJ anatomy, outline potentially important features of TMJ disc ultrastructure and biochemistry in comparison with the intervertebral disc and knee meniscus, and provide imaging examples of the TMJ abnormalities currently evaluable with MRI and CT. In addition, we provide an overview of emerging and investigational TMJ imaging techniques in order to encourage further imaging research based on the biomechanical alterations of the TMJ disc.

Evaluation of culture conditions for in vitro meniscus repair model systems using bone marrow-derived mesenchymal stem cells.

Purpose: Meniscal injury and loss of meniscus tissue lead to osteoarthritis development. Therefore, novel biologic strategies are needed to enhance meniscus tissue repair. The purpose of this study was to identify a favorable culture medium for both bone marrow-derived mesenchymal stem cells (MSCs) and meniscal tissue, and to establish a novel meniscus tissue defect model that could be utilized for in vitro screening of biologics to promote meniscus repair.Materials and Methods: In parallel, we analyzed the biochemical properties of MSC - seeded meniscus-derived matrix (MDM) scaffolds and meniscus repair model explants cultured in different combinations of serum, dexamethasone (Dex), and TGF-ß. Next, we combined meniscus tissue and MSC-seeded MDM scaffolds into a novel meniscus tissue defect model to evaluate the effects of chondrogenic and meniscal media on the tissue biochemical properties and repair strength.Results: Serum-free medium containing TGF-ß and Dex was the most promising formulation for experiments with MSC-seeded scaffolds, whereas serum-containing medium was the most effective for meniscus tissue composition and integrative repair. When meniscus tissue and MSC-seeded MDM scaffolds were combined into a defect model, the chondrogenic medium (serum-free with TGF-ß and Dex) enhanced the production of proteoglycans and promoted integrative repair of meniscus tissue. As well, cross-linked scaffolds improved repair over the MDM slurry.Conclusions: The meniscal tissue defect model established in this paper can be used to perform in vitro screening to identify and optimize biological treatments to enhance meniscus tissue repair prior to conducting preclinical animal studies.

Composition of Cell Clusters in Torn Menisci and Their Extracellular Matrix Components.

Cell clusters, or groups of cells sharing a single chondron-like structure, are frequently found in degenerated areas of the osteoarthritic (OA) meniscus. However, little is known about these meniscal clusters in humans. The aim of our study was to determine the composition of the extracellular matrix deposition around cell clusters in human OA menisci. Twenty-six menisci were obtained through total knee arthroplasty from patients with OA knee joints. The specimens were subjected to safranin O staining and immunostaining for Sry-type HMG box 9 (SOX9), type II collagen, and aggrecan. Their signal density after staining was assessed using ImageJ software. Five regions of interest were analyzed within each tissue sample. The SOX9, type II collagen, and aggrecan densities were considerably higher in cluster areas than in intact superficial layers of the meniscus. In addition, a substantial difference was detected between cluster areas and degenerative areas without cell clusters. We demonstrated that cell clusters localized near fissures and clefts showed remarkable uniformity in menisci exposed to a broad range of injuries. In addition, the chondrogenic proteins SOX9, type II collagen, and aggrecan were highly expressed in these tissues.

Nociceptive and sympathetic innervations in the abaxial part of the cranial horn of the equine medial meniscus: an immunohistochemical approach.

In athletic horses, diseases leading to lameness are of great importance due to the loss of performance and the resultant economic concerns. Although stifle lesions are frequent in the hindlimb, due to the large size and complexity of the joint, and although meniscal tears have been identified as the most common soft tissue injuries in this joint, little is known about the mechanism that causes the painful sensation and thus the lameness. The aim of our study was to highlight any peripheral fibres involved in meniscal nociception in five macroscopically sound cranial horns of the equine medial meniscus, which has been one of the most common sites reported for equine meniscal injuries. Immunohistochemical stainings were performed using antibodies against Substance P in order to identify nociceptive fibres; against tyrosine hydroxylase for detecting postganglionic sympathetic fibres; and against glial fibrillary acidic proteins in order to identify Schwann cells. Our work highlights for the first time the presence of nociceptive and sympathetic fibres in equine menisci. They were found in the abaxial part of the cranial horn of the equine medial meniscus. This study suggests that when the abaxial part is injured, the meniscus itself could be the source of pain. These findings could provide a better understanding of the clinical presentation of horses with meniscal injury and contribute towards improving therapeutic strategies to alleviate pain in cases of equine meniscal injury.

Optical spectroscopic determination of human meniscus composition.

This study investigates the correlation between the composition of human meniscus and its absorption spectrum in the visible (VIS) and near infrared (NIR) spectral range. Meniscus samples (n = 24) were obtained from nonarthritic knees of human cadavers with no history of joint diseases. Specimens (n = 72) were obtained from three distinct sections of the meniscus, namely; anterior, center, posterior. Absorption spectra were acquired from each specimen in the VIS and NIR spectral range (400-1,100 nm). Following spectroscopic probing, the specimens were subjected to biochemical analyses to determine the matrix composition, that is water, hydroxyproline, and uronic acid contents. Multivariate analytical techniques, including principal component analysis (PCA) and partial least squares (PLS) regression, were then used to investigate the correlation between the matrix composition and it spectral response. Our results indicate that the optical absorption of meniscus matrix is related to its composition, and this relationship is optimal in the NIR spectral range (750-1,100 nm). High correlations (R(2) (uronic) = 86.9%, R(2) (water) = 83.8%, R(2) (hydroxyproline) = 81.7%, p < 0.0001) were obtained between the spectral predicted and measured meniscus composition, thus suggesting that spectral data in the NIR range can be utilized for estimating the matrix composition of human meniscus. In conclusion, optical spectroscopy, particularly in the NIR spectral range, is a potential method for evaluating the composition of human meniscus. This presents a promising technique for rapid and nondestructive evaluation of meniscus integrity in real-time during arthroscopic surgery.

Characterization of knee meniscal pathology: correlation of gross, histologic, biochemical, molecular, and radiographic measures of disease.

Meniscal pathology is an extremely prevalent problem, which inevitably leads to osteoarthritis and associated pain, swelling, and disability. Relatively little data are available regarding the molecular, biochemical, and histologic aspects of meniscal disease. This study characterizes meniscal pathology in the presence of symptomatic osteoarthritis and correlates clinical and basic science data in an attempt to delineate clinically relevant mechanisms of disease. Twenty-seven knees from 23 patients who underwent total knee arthroplasty comprised the affected group and 6 aged nonsymptomatic knees were used as controls. All meniscal tissues were harvested and subjectively scored for gross and histologic pathology. Biochemical analyses were performed to determine glycosaminoglycan (GAG) content, collagen (hydroxyproline) content, and water content. Real-time polymerase chain reaction analysis was conducted for genes involved in synthesis (collagens [col] 1, 2, 3, and 6), degradation (matrix metalloproteinases [MMP-1, -2, -3, -13]), and angiogenesis (vascular endothelial growth factor). Weight-bearing, anterior-posterior radiographic views were used to determine joint space measurements for lateral and medial compartments, and were subjectively scored for osteoarthritic changes. Data were compared for statistically significant differences and to determine the presence and strength of correlations among variables assessed. Affected menisci had significantly higher gross and histologic pathology scores compared with control menisci. Affected menisci had significantly higher water, proteoglycan, and collagen content compared with control menisci. Col 1, 3, and 6 gene expression levels for the affected group were significantly increased compared with controls. MMP-13 expression was significantly increased for the affected group. MMP-2 and -3 expression levels were significantly lower in the affected group compared with controls. The affected group had significantly more joint space narrowing and higher radiographic scores for medial compared with lateral compartments. Several strong and moderately strong correlations were present between variables. These data suggest that in vitro measures of meniscal pathology have potential value for understanding disease mechanisms and predicting clinical disease.

[MALDI mass spectrometry of the meniscus. Objectification of morphological findings]. / MALDI-Massenspektrometrie am Meniskus. Objektivierung morphologischer Befunde.

BACKGROUND: The classification of meniscal lesions requires correlation with clinical data. For the standardization of histopathology reports a discrimination between normal, low-grade lesions and high-grade lesions is feasible. This classification can be further specified using other methods. MATERIAL AND METHODS: Formalin-fixed, paraffin-embedded specimens of meniscal tissue from 68 patients were analyzed by matrix-assisted laser desorption ionization (MALDI) imaging. RESULTS: The classification of meniscal lesions and differentiation between low-grade and high-grade and acute versus non-acute degeneration is possible by determination of the differential expression of mass-to-charge ratios by statistical comparisons using the P-value from combined Wilcoxon and Kruskal-Wallis (PWKW) tests and a predefined average two-fold difference in intensity. CONCLUSION: The concept of a "meniscus report" is introduced for documentation of meniscus tissue specimens integrating histological, histochemical and proteomic data, thereby specifying the degree of degeneration and the assessment of acute or non-acute lesions. Mass spectrometry contributes to an objective histopathology report. An advisory opinion should always be based on close correlation of clinical and morphological evaluations.

Fibronectin splice variation in human knee cartilage, meniscus and synovial membrane: observations in osteoarthritic knee.

Fibronectin (FN) is a widely expressed molecule that can participate in development of osteoarthritis (OA) affecting cartilage, meniscus, and synovial membrane (SM). The alternatively spliced isoforms of FN in joint tissues other than cartilage have not been extensively studied previously. The present study compares FN splice variation in patients with varying degrees of osteoarthritic change. Joint tissues were collected from asymptomatic donors and patients undergoing arthroscopic procedures. Total RNA was amplified by PCR using primers flanking alternatively spliced Extra Domain A (EDA), Extra Domain B (EDB) and Variable (V) regions. EDB(+) , EDB(-) and EDA(-) and V(+) variants were present in all joint tissues, while the EDA(+) variant was rarely detected. Expression levels of EDB(+) and EDV(+) variants were similar in cartilage, synovium, and meniscal tissues. Synovial expression of V(+) FN in arthroscopy patients varied with degree of cartilage degeneration. Two V(-) isoforms, previously identified in cartilage, were also present in SM and meniscus. Fibronectin splicing in meniscus and SM bears striking resemblance to that of cartilage. Expression levels of synovial V(+) FN varied with degree of cartilage degeneration. V(+) FN should be investigated as a potential biomarker of disease stage or progression in larger populations.

Developing functional musculoskeletal tissues through hypoxia and lysyl oxidase-induced collagen cross-linking.

The inability to recapitulate native tissue biomechanics, especially tensile properties, hinders progress in regenerative medicine. To address this problem, strategies have focused on enhancing collagen production. However, manipulating collagen cross-links, ubiquitous throughout all tissues and conferring mechanical integrity, has been underinvestigated. A series of studies examined the effects of lysyl oxidase (LOX), the enzyme responsible for the formation of collagen cross-links. Hypoxia-induced endogenous LOX was applied in multiple musculoskeletal tissues (i.e., cartilage, meniscus, tendons, ligaments). Results of these studies showed that both native and engineered tissues are enhanced by invoking a mechanism of hypoxia-induced pyridinoline (PYR) cross-links via intermediaries like LOX. Hypoxia was shown to enhance PYR cross-linking 1.4- to 6.4-fold and, concomitantly, to increase the tensile properties of collagen-rich tissues 1.3- to 2.2-fold. Direct administration of exogenous LOX was applied in native cartilage and neocartilage generated using a scaffold-free, self-assembling process of primary chondrocytes. Exogenous LOX was found to enhance native tissue tensile properties 1.9-fold. LOX concentration- and time-dependent increases in PYR content (∼ 16-fold compared with controls) and tensile properties (approximately fivefold compared with controls) of neocartilage were also detected, resulting in properties on par with native tissue. Finally, in vivo subcutaneous implantation of LOX-treated neocartilage in nude mice promoted further maturation of the neotissue, enhancing tensile and PYR content approximately threefold and 14-fold, respectively, compared with in vitro controls. Collectively, these results provide the first report, to our knowledge, of endogenous (hypoxia-induced) and exogenous LOX applications for promoting collagen cross-linking and improving the tensile properties of a spectrum of native and engineered tissues both in vitro and in vivo.

Regional comparisons of porcine menisci.

The purpose of this study was to analyze histologic, biochemical, and biomechanical differences between zonal, regional, and anatomic locations of porcine menisci. We evaluated six menisci removed from pigs. Medial and lateral menisci were divided into three regions: anterior, middle, and posterior. In each portion, the central zone (CZ) and peripheral zone (PZ) were examined histologically (hematoxylin & eosin, safranin O/Fast green, and picrosiriusred staining), using scanning electron microscopy, biochemically (hydroxyproline assay for collagen content and dimethylmethylene blue assay for glycosaminoglycan [GAG] content), and biomechanically (compression testing). Collagen content in the CZ was lower than that in the PZ. GAG content in the CZ was higher than that in the PZ. GAG content in the PZ of the posterior portion was significantly higher than that in the anterior and middle portions. Compression strength in the CZ was higher than that in the PZ. The differences in cellular phenotype, vascular penetration, and ECM not only between CZ and PZ but also among the anterior, middle, and posterior portions were clarified in the immature porcine meniscus. This result helps further our understanding of the biological characteristic of the meniscus. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1602-1611, 2014.

Do not hallow until you are out of the wood! Ultrasonographic detection of CPP crystal deposits in menisci: facts and pitfalls.

PURPOSE: Ultrasonography (US) has been demonstrated to be an important tool in the diagnosis of calcium pyrophosphate (CPP) crystal deposition disease. The aim of our study was to individuate and describe possible pitfalls in US detection of such deposits in menisci. PATIENTS AND METHODS: We enrolled all patients waiting to undergo knee replacement surgery due to osteoarthritis, for one-month period. Each patient underwent US examination of the knee, focusing on the menisci. After surgery, the menisci were examined by US, macroscopically and microscopically, using the microscopic analysis as the gold standard for CPP deposition. RESULTS: 11 menisci of 6 patients have been studied. Ex vivo examination of menisci performed better in CPP identification than in vivo examination. The possible reasons of misinterpretation or misdiagnosis of the in vivo exam were identified and are extensively described in the paper. Also a new sign of CPP crystal deposits was found. CONCLUSIONS: This study permitted to highlight some difficulties in CPP crystal detection by US in menisci. Further studies are needed to define completely US CPP crystal aspect and to improve the sensibility and specificity of US in CPP deposition diagnosis.

Contrast enhanced CT attenuation correlates with the GAG content of bovine meniscus.

We determined whether contrast-enhanced computed tomography (CECT) attenuation obtained using a µCT scanner correlated with the glycosaminoglycan (GAG) content and distribution in ex vivo bovine menisci. Bovine samples were immersed in different concentrations of the contrast agents CA4+ and Ioxaglate, and the µCT images were compared to Safranin-O staining. CA4+ and Ioxaglate diffusion-in kinetics and the correlation between their CECT attenuations and GAG content were investigated. CA4+ and Ioxaglate both reached steady state in the meniscal regions within 95 h, with tau values of 20.6 ± 3.98 and 25.9 ± 3.71 h (mean ± SD), respectively. Both agents diffused preferentially through the proximal and secondarily through the distal surface. The CA4+ CECT attenuation was strongly and positively correlated with the GAG content of the meniscus regions (R(2) = 0.89, p < 0.001) at low concentrations (12 mgI/ml), while the Ioxaglate CECT attenuation was moderately and negatively correlated with the GAG content (R(2) = 0.51, p = 0.03) at 60 mgI/ml. CECT can image ex vivo menisci, and the CA4+, compared to Ioxaglate, enhanced attenuation strongly correlates with the GAG content and distribution in bovine meniscus.

Fourier transform infrared imaging and infrared fiber optic probe spectroscopy identify collagen type in connective tissues.

Hyaline cartilage and mechanically inferior fibrocartilage consisting of mixed collagen types are frequently found together in repairing articular cartilage. The present study seeks to develop methodology to identify collagen type and other tissue components using Fourier transform infrared (FTIR) spectral evaluation of matrix composition in combination with multivariate analyses. FTIR spectra of the primary molecular components of repair cartilage, types I and II collagen, and aggrecan, were used to develop multivariate spectral models for discrimination of the matrix components of the tissues of interest. Infrared imaging data were collected from bovine bone, tendon, normal cartilage, meniscus and human repair cartilage tissues, and composition predicted using partial least squares analyses. Histology and immunohistochemistry results were used as standards for validation. Infrared fiber optic probe spectral data were also obtained from meniscus (a tissue with mixed collagen types) to evaluate the potential of this method for identification of collagen type in a minimally-invasive clinical application. Concentration profiles of the tissue components obtained from multivariate analysis were in excellent agreement with histology and immunohistochemistry results. Bone and tendon showed a uniform distribution of predominantly type I collagen through the tissue. Normal cartilage showed a distribution of type II collagen and proteoglycan similar to the known composition, while in repair cartilage, the spectral distribution of both types I and II collagen were similar to that observed via immunohistochemistry. Using the probe, the outer and inner regions of the meniscus were shown to be primarily composed of type I and II collagen, respectively, in accordance with immunohistochemistry data. In summary, multivariate analysis of infrared spectra can indeed be used to differentiate collagen type I and type II, even in the presence of proteoglycan, in connective tissues, using both imaging and fiber optic methodology. This has great potential for clinical in situ applications for monitoring tissue repair.

Combining µX-ray fluorescence, µXANES and µXRD to shed light on Zn2+ cations in cartilage and meniscus calcifications.

We aimed to examine the presence of Zn, a trace element, in osteoarthritis (OA) cartilage and meniscus from patients undergoing total knee joint replacement for primary OA. We mapped Ca(2+) and Zn(2+) at the mesoscopic scale by X-ray fluorescence microanalysis (µX-ray) to determine the spatial distribution of the 2 elements in cartilage, µX-ray absorption near edge structure spectroscopy to identify the Zn species, and µX-ray diffraction to determine the chemical nature of the calcification. Fourier transform infrared spectroscopy was used to determine the chemical composition of cartilage and meniscus. Ca(2+) showed a heterogeneous spatial distribution corresponding to the calcifications within cartilage (or meniscus) or at their surface. At least 2 Zn(2+) species were present: the first may correspond to Zn embedded in protein (different Zn metalloproteins are known to prevent calcification in biological tissues), and the second may be associated with a Zn trap in or at the surface of the calcification. Calcification present in OA cartilage may significantly modify the spatial distribution of Zn; part of the Zn may be trapped in the calcification and may alter the associated biological function of Zn metalloproteins.

Regional variation in T1ρ and T2 times in osteoarthritic human menisci: correlation with mechanical properties and matrix composition.

OBJECTIVE: Changes in T1ρ and T2 magnetic resonance relaxation times have been associated with articular cartilage degeneration, but similar relationships for meniscal tissue have not been extensively investigated. This work examined relationships between T1ρ and T2 measurements and biochemical and mechanical properties across regions of degenerate human menisci. DESIGN: Average T1ρ and T2 relaxation times were determined for nine regions each of seven medial and 13 lateral menisci from 14 total knee replacement patients. Sulfated glycosaminoglycan (sGAG), collagen and water contents were measured for each region. Biomechanical measurements of equilibrium compressive, dynamic compressive and dynamic shear moduli were made for anterior, central and posterior regions. RESULTS: T1ρ and T2 times showed similar regional patterns, with longer relaxation times in the (radially) middle region compared to the inner and outer regions. Pooled over all regions, T1ρ and T2 times showed strong correlations both with one another and with water content. Correlations with biochemical content varied depending on normalization to wet or dry mass, and both imaging parameters showed stronger correlations with collagen compared to sGAG content. Mechanical properties displayed moderate inverse correlations with increasing T1ρ and T2 times and water content. CONCLUSION: Both T1ρ and T2 relaxation times correlated strongly with water content and moderately with mechanical properties in osteoarthritic menisci, but not as strongly with sGAG or collagen contents alone. While the ability of magnetic resonance imaging (MRI) to detect early osteoarthritic changes remains the subject of investigation, these results suggest that T1ρ and T2 relaxation times have limited ability to detect compositional variations in degenerate menisci.

Marrow stimulation improves meniscal healing at early endpoints in a rabbit meniscal injury model.

PURPOSE: To critically evaluate the effect of marrow stimulation (MS) on the extent of healing and the local biological environment after meniscal injury in ligamentously stable knees in a rabbit model. METHODS: A reproducible 1.5-mm cylindrical defect was created in the avascular portion of the anterior horn of the medial meniscus bilaterally in 18 New Zealand White rabbits (36 knees). In right knees (MS knees), a 2.4-mm Steinman pin was drilled into the apex of the femoral intercondylar notch and marrow contents were observed spilling into the joint. Left knees served as controls. Rabbits were killed in 3 groups (n = 6 rabbits each) at 1, 4, and 12 weeks with meniscal harvest and blinded histomorphometric and histologic evaluation using an established 3-component tissue quality score (range, 0 to 6). One-week specimens were also evaluated for the presence of proregenerative cytokines using immunohistochemistry. RESULTS: The mean proportion of the avascular zone defect bridged by reparative tissue was greater in MS knees than in controls at each endpoint (1 week, 55% v 30%, P = .02; 4 weeks, 71% v 53%, P = .047; 12 weeks, 96% v 77%, P = .16). Similarly, there was a consistent trend toward superior tissue quality scores in knees treated with MS compared with controls (1 week, 1.8 v 0.3, P = .03; 4 weeks, 4.3 v 2.8, P = .08; 12 weeks, 5.9 v 4.5, P = .21). No statistically significant differences, however, were observed at the 12-week endpoint. Increased staining for insulin-like growth factor I, transforming growth factor-ß, and platelet-derived growth factor was observed in regenerated tissue, compared with native meniscal tissue, in all specimens at 1 week. Staining density for all growth factors was similar, however, in reparative tissue of MS and control knees. CONCLUSIONS: The results of this study suggest that marrow stimulation leads to modest improvements in quality and quantity of reparative tissue bridging a meniscal defect, particularly during the early recovery period. CLINICAL RELEVANCE: Clinical evaluation of marrow stimulation techniques designed to enhance healing in isolated meniscus repair surgery may be indicated.

Using the meniscus in a capillary for small volume contact angle measurement in biochemical applications.

The contact angle is a sensitive parameter often used to define wettability. With the increasing movement toward smaller liquid volumes in many biochemical applications, a key challenge lies in how to perform measurements in the retainer holding the reagent for rapid evaluation and limited material loss. Here, we report a simple and robust method to determine the contact angle of small volumes using the microscopic imaging of a capillary meniscus that requires only the radius and meniscus height information. An error analysis of the measurement finds the method to be highly accurate. We also uncovered that illumination delivered from the liquid end of the capillary lights up the interface, thereby facilitating the measurement.