DLL1/NOTCH1 signaling pathway maintain angiogenesis in meniscus development and degeneration.

OBJECTIVES: The decline in vascular capacity within the meniscus is a well-documented phenomenon during both development and degeneration. Maintaining vascular integrity has been proposed as a potential therapeutic strategy for osteoarthritis. Therefore, our study aims to investigate the characteristics of endothelial cells and blood vessels in embryonic and degenerated meniscus tissues. METHODS: Human embryonic and mature menisci were used for histological analyses. Single-cell RNA sequencing was used to identify cell clusters and their significant genes in embryo meniscus to uncover characteristic of endothelial cells. Computer analysis and various staining techniques were used to characterize vessels in development and osteoarthritis meniscus. RESULTS: Vessels structure first observed in E12w and increasing in E14w. Vessels were veins majorly and arteries growth in E35w. Endothelial cells located not only perivascular but also in the surface of meniscus. The expression of DLL1 was observed to be significantly altered in endothelial cells within the vascular network that failed to form. Meniscus tissues affected by osteoarthritis, characterized by diminished vascular capacity, displayed reduced levels of DLL1 expression. Experiment in vitro confirmed DLL1/NOTCH1 be vital to angiogenesis. CONCLUSION: Lack of DLL1/NOTCH1 signaling pathway was mechanism of vascular declination in development and degenerated meniscus.

Meniscal fibrocartilage regeneration inspired by meniscal maturational and regenerative process.

Meniscus is a complex and crucial fibrocartilaginous tissue within the knee joint. Meniscal regeneration remains to be a scientific and translational challenge. We clarified that mesenchymal stem cells (MSCs) participated in meniscal maturation and regeneration using MSC-tracing transgenic mice model. Here, inspired by meniscal natural maturational and regenerative process, we developed an effective and translational strategy to facilitate meniscal regeneration by three-dimensionally printing biomimetic meniscal scaffold combining autologous synovium transplant, which contained abundant intrinsic MSCs. We verified that this facilitated anisotropic meniscus-like tissue regeneration and protected cartilage from degeneration in large animal model. Mechanistically, the biomechanics and matrix stiffness up-regulated Piezo1 expression, facilitating concerted activation of calcineurin and NFATc1, further activated YAP-pSmad2/3-SOX9 axis, and consequently facilitated fibrochondrogenesis of MSCs during meniscal regeneration. In addition, Piezo1 induced by biomechanics and matrix stiffness up-regulated collagen cross-link enzyme expression, which catalyzed collagen cross-link and thereby enhanced mechanical properties of regenerated tissue.

Tricomposite gelatin-carboxymethylcellulose-alginate bioink for direct and indirect 3D printing of human knee meniscal scaffold.

The development of technologies that could ease the production of customizable patient-specific tissue engineering constructs having required biomechanical properties and restoring function in damaged tissue is the need of the hour. In this study, we report the optimization of composite, bioactive and biocompatible tripolymeric hydrogel bioink, suitable for both direct and indirect printing of customizable scaffolds for cartilage tissue engineering applications. A customized hierarchical meniscal scaffold was designed using solid works software and developed using a negative mould made of polylactic acid (PLA) filament and by a direct 3D printing process. A composite tripolymeric bioink made of gelatin, carboxymethyl cellulose (CMC) and alginate was optimized and characterized for its printability, structural, bio-mechanical and bio-functional properties. The optimized composite hydrogel bioink was extruded into the negative mould with and without live cells, cross-linked and the replica of meniscus structure was retrieved aseptically. The cellular proliferation, apatite formation, and extracellular matrix secretion from negative printed meniscal scaffold were determined using MTT, live/dead and collagen estimation assays. A significant increase in collagen secretion, cellular proliferation and changes in biomechanical properties was observed in the 3D scaffolds with MG63-osteosarcoma cells indicating its suitability for cartilage tissue engineering.

Proteomic Analysis of the Meniscus Cartilage in Osteoarthritis.

The distribution of differential extracellular matrix (ECM) in the lateral and medial menisci can contribute to knee instability, and changes in the meniscus tissue can lead to joint disease. Thus, deep proteomic identification of the lateral and medial meniscus cartilage is expected to provide important information for treatment and diagnosis of various knee joint diseases. We investigated the proteomic profiles of 12 lateral/medial meniscus pairs obtained from excess tissue of osteoarthritis patients who underwent knee arthroscopy surgery using mass spectrometry-based techniques and measured 75 ECM protein levels in the lesions using a multiple reaction monitoring (MRM) assay we developed. A total of 906 meniscus proteins with a 1% false discovery rate (FDR) was identified through a tandem mass tag (TMT) analysis showing that the lateral and medial menisci had similar protein expression profiles. A total of 131 ECM-related proteins was included in meniscus tissues such as collagen, fibronectin, and laminin. Our data showed that 14 ECM protein levels were differentially expressed in lateral and medial lesions (p < 0.05). We present the proteomic characterization of meniscal tissue with mass spectrometry-based comparative proteomic analysis and developed an MRM-based assay of ECM proteins correlated with tissue regeneration. The mass spectrometry dataset has been deposited to the MassIVE repository with the dataset identifier MSV000087753.

Anti-Inflammatory Effects of Conditioned Medium of Periodontal Ligament-Derived Stem Cells on Chondrocytes, Synoviocytes, and Meniscus Cells.

Osteoarthritis (OA) is the most common type of arthritis, afflicting millions of people in the world. Elevation of inflammatory mediators and enzymatic matrix destruction is often associated with OA. Therefore, the objective of this study was to investigate the effects of conditioned medium from periodontal ligament-derived stem cells (PDLSCs) on inflammatory and catabolic gene expressions of chondrocytes, synoviocytes, and meniscus cells under in vitro inflammatory condition. Stem cells were isolated from human periodontal ligaments. Conditioned medium was collected and concentrated 20 × . Chondrocytes, synoviocytes, and meniscus cells were isolated from pig knees and divided into four experimental groups: serum-free media, serum-free media+interleukin-1ß (IL-1ß) (10 ng/mL), conditioned media (CM), and CM+IL-1ß. Protein content and extracellular vesicle (EV) miRNAs of CM were analyzed by liquid chromatography-tandem mass spectrometry and RNA sequencing, respectively. It was found that the IL-1ß treatment upregulated the expression of IL-1ß, tumor necrosis factor-α (TNF-α), MMP-13, and ADAMTS-4 genes in the three cell types, whereas PDLSC-conditioned medium prevented the upregulation of gene expression by IL-1ß in all three cell types. This study also found that there was consistency in anti-inflammatory effects of PDLSC CM across donors and cell subcultures, while PDLSCs released several anti-inflammatory factors and EV miRNAs at high levels. OA has been suggested as an inflammatory disease in which all intrasynovial tissues are involved. PDLSC-conditioned medium is a cocktail of trophic factors and EV miRNAs that could mediate different inflammatory processes in various tissues in the joint. Introducing PDLSC-conditioned medium to osteoarthritic joints could be a potential treatment to prevent OA progression by inhibiting inflammation.

Gene expression profiling of primary fibrochondrocyte cultures in traumatic and degenerative meniscus lesions.

PURPOSE: This study aimed to investigate how fibroblastic and chondrocytic properties of human meniscal fibrochondrocytes are affected in culture conditions according to the type of meniscal pathology and localization, and to provide basic information for tissue-engineering studies. METHODS: Primary fibrochondrocyte cultures were prepared from meniscus samples of patients who had either traumatic tear or degeneration due to osteoarthritis. Cultures were compared in terms of mRNA expression levels of COL1A1, COL2A1, COMP1, HIF1A, HIF2A, and SOX9 and secreted total collagen and sulfated sGAG levels according to the type of meniscal pathology, anatomical localization, and the number of subcultures. RESULTS: mRNA expression levels of COL1A1, COMP1, HIF1A, HIF2A, and SOX9 were found to be increased in subsequent subcultures in all specimens. COL1A1 mRNA expression levels of both lateral and medial menisci of patients with traumatic tear were significantly higher than in patients with degenerative pathology, indicating a more fibroblastic character. P1 subculture of lateral and P3 or further subculture of medial meniscus showed more fibroblastic characteristics in patients with degenerative pathology. Furthermore, in patients with degenerative pathology, the subcultures of the lateral meniscus (especially on the inner part) presented more chondrocytic characteristics than did those of medial meniscus. CONCLUSIONS: The mRNA expression levels of the cultures showed significant differences according to the anatomical localization and pathology of the meniscus, indicating distinct chondrocytic and fibroblastic features. This fundamental knowledge would help researchers to choose more efficient cell sources for cell-seeding of a meniscus scaffold, and to generate a construct resembling the original meniscus tissue.

Role of the Hypoxia-Inducible Factor Pathway in Normal and Osteoarthritic Meniscus and in Mice after Destabilization of the Medial Meniscus.

OBJECTIVE: Meniscus injury and the hypoxia-inducible factor (HIF) pathway are independently linked to osteoarthritis pathogenesis, but the role of the meniscus HIF pathway remains unclear. We sought to identify and evaluate HIF pathway response in normal and osteoarthritic meniscus and to examine the effects of Epas1 (HIF-2α) insufficiency in mice on early osteoarthritis development. METHODS: Normal and osteoarthritic human meniscus specimens were obtained and used for immunohistochemical evaluation and cell culture studies for the HIF pathway. Meniscus cells were treated with pro-inflammatory stimuli, including interleukins (IL)-1ß, IL-6, transforming growth factor (TGF)-α, and fibronectin fragments (FnF). Target genes were also evaluated with HIF-1α and HIF-2α (Epas1) overexpression and knockdown. Wild-type (n = 36) and Epas1+/- (n = 30) heterozygous mice underwent destabilization of the medial meniscus (DMM) surgery and were evaluated at 2 and 4 weeks postoperatively for osteoarthritis development using histology. RESULTS: HIF-1α and HIF-2α immunostaining and gene expression did not differ between normal and osteoarthritic meniscus. While pro-inflammatory stimulation significantly increased both catabolic and anabolic gene expression in the meniscus, HIF-1α and Epas1 expression levels were not significantly altered. Epas1 overexpression significantly increased Col2a1 expression. Both wild-type and Epas1+/- mice developed osteoarthritis following DMM surgery. There were no significant differences between genotypes at either time point. CONCLUSION: The HIF pathway is likely not responsible for osteoarthritic changes in the human meniscus. Additionally, Epas1 insufficiency does not protect against osteoarthritis development in the mouse at early time points after DMM surgery. The HIF pathway may be more important for protection against catabolic stress.

An animal model study on the gene expression profile of meniscal degeneration.

Meniscal degeneration is a very common condition in elderly individuals, but the underlying mechanisms of its occurrence are not completely clear. This study examines the molecular mechanisms of meniscal degeneration. The anterior cruciate ligament (ACL) and lateral collateral ligament (LCL) of the right rear limbs of seven Wuzhishan mini-pigs were resected (meniscal degeneration group), and the left rear legs were sham-operated (control group). After 6 months, samples were taken for gene chip analysis, including differentially expressed gene (DEG) analysis, gene ontology (GO) analysis, clustering analysis, and pathway analysis. The selected 12 DEGs were validated by real time reverse transcription-polymerase chain reaction (RT-PCR). The two groups showed specific and highly clustered DEGs. A total of 893 DEGs were found, in which 537 are upregulated, and 356 are downregulated. The GO analysis showed that the significantly affected biological processes include nitric oxide metabolic process, male sex differentiation, and mesenchymal morphogenesis, the significantly affected cellular components include the endoplasmic reticulum membrane, and the significantly affected molecular functions include transition metal ion binding and iron ion binding. The pathway analysis showed that the significantly affected pathways include type II diabetes mellitus, inflammatory mediator regulation of TRP channels, and AMPK signaling pathway. The results of RT-PCR indicate that the microarray data accurately reflects the gene expression patterns. These findings indicate that several molecular mechanisms are involved in the development of meniscal degeneration, thus improving our understanding of meniscal degeneration and provide molecular therapeutic targets in the future.

The underlying mechanism of partial anterior cruciate ligament injuries to the meniscus degeneration of knee joint in rabbit models.

BACKGROUND: The diagnosis, treatment, and efficacy evaluation of anterior cruciate ligament (ACL) partial rupture remains controversial. This research aims to investigate the underlying mechanism of partial ACL injuries to the meniscus degeneration in the rabbit knee. METHODS: Sixty New Zealand white rabbits were randomly divided into three groups including an experimental group, a sham group (n = 6), and a blank control group (n = 6). The experimental group is composed of an anteromedial bundle (AMB) rupture group (n = 24) and a posterolateral bundle (PLB) rupture group (n = 24). Rabbits in the experimental group were subjected to right hind limbs knee surgery to induce ACL part injury under the arthroscopy. Finally, eight rabbits including 6 in the model group and 2 in the control group were sampled randomly on the 2nd, 4th, and 8th weeks respectively. We observed the typical form of the meniscus through HE staining. Expressions of inflammatory factors including interleukin-1ß (IL-1ß) and IL-17 in the knee joint fluid were determined by means of an ELISA. Analysis of the mRNA expressions of matrix metalloproteinases-13(MMP-13) was performed to evaluate the inflammatory mediators in the pathogenesis of the meniscus. RESULTS: HE staining results showed that the surface was rough and the tissues were loose displaying collagen fibers of varying thickness. Both IL-1ß and IL-17 in the synovial fluid and the positive rate of MMP-13 in addition to MMP-13 mRNA showed a demonstrable increase treads from the 2nd to the 8th week. The significant difference was found (P < 0.05) compared to the control group. CONCLUSION: We conclude that the elevated levels of IL-1ß and IL-17, along with increased MMP13 expression, resulted in meniscus degradation in the rabbit knee joint model with partial ACL injury.

Meniscal tissue engineering via 3D printed PLA monolith with carbohydrate based self-healing interpenetrating network hydrogel.

Failure of bioengineered meniscus implant after transplantation is a major concern owing to mechanical failure, lack of chondrogenic capability and patient specific design. In this article, we have, for the first time, fabricated a 3D printed scaffold with carbohydrate based self-healing interpenetrating network (IPN) hydrogels-based monolith construct for load bearing meniscus tissue. 3D printed PLA scaffold was surface functionalized and embedded with self-healing IPN hydrogel for interfacial bonding further characterized by micro CT. Using collagen (C), alginate (A) and oxidized alginate (ADA), we developed self-healing IPN hydrogels with dual crosslinking (Ca2+ based ionic crosslinking and Schiff base (A-A, A-ADA)) capability and studied their physicochemical properties. Further, we studied human stem cells behaviour and chondrogenic differentiation potential within these IPN hydrogels. In-vivo heterotopic implantation confirmed biocompatibility of the monolith showing the feasibility of using carbohydrate based IPN hydrogel embedded in 3D printed scaffold for meniscal tissue development.

Morphological changes in synovial mesenchymal stem cells during their adhesion to the meniscus.

Synovial mesenchymal stem cells (MSCs) are an attractive cell source for transplantation because of their high chondrogenic potential, especially in areas like the meniscus of the knee. A synovial MSC suspension placed onto the meniscus for 10 min promoted healing of repaired meniscal tears that generally do not heal. Here, we quantified the proportion of human synovial MSCs that adhered to a porcine abraded meniscus, clarified their morphological changes, and revealed the mechanism by which the synovial MSCs adhered to the meniscus. The numbers of adhering cells at immediately after 10, 60 min and 6, 24 h after suspension placement were calculated. The meniscus surface was examined by scanning electron microscopy, and 50 cells were randomly selected at each time period, classified, and quantified for each of the six donors. Approximately 28% of the synovial MSCs immediately adhered to the meniscus after placement and the proportion of adhered cells increased further with time. All cells maintained a round shape for 60 min, and then transformed to a mixture of round and semi-flattened cells. By 24 h, flattened cells covered the meniscus. Microspikes were observed in 36% of the floating synovial MSCs and in 76% of the cells on the meniscus shortly after placement on the meniscus, then the proportion of cells with pseudopodia increased. The bleb-dominant cell proportion significantly decreased, and the smooth-dominant cell proportion increased within 60 min. Microspikes or the bodies of synovial MSCs were trapped by meniscal fibers immediately after placement. The proportion of adhered cells increased with time, and the cell morphology changed dynamically for 24 h as the synovial MSCs adhered to the meniscus. The MSCs in the round morphological state had a heterogeneous morphology. The microspikes, and the subsequent development of pseudopodia, may play an important role in adhesion onto the meniscus.

Biomechanically, structurally and functionally meticulously tailored polycaprolactone/silk fibroin scaffold for meniscus regeneration.

Meniscus deficiency, the most common and refractory disease in human knee joints, often progresses to osteoarthritis (OA) due to abnormal biomechanical distribution and articular cartilage abrasion. However, due to its anisotropic spatial architecture, complex biomechanical microenvironment, and limited vascularity, meniscus repair remains a challenge for clinicians and researchers worldwide. In this study, we developed a 3D printing-based biomimetic and composite tissue-engineered meniscus scaffold consisting of polycaprolactone (PCL)/silk fibroin (SF) with extraordinary biomechanical properties and biocompatibility. We hypothesized that the meticulously tailored composite scaffold could enhance meniscus regeneration and cartilage protection. Methods: The physical property of the scaffold was characterized by scanning electron microscopy (SEM) observation, degradation test, frictional force of interface assessment, biomechanical testing, and fourier transform infrared (FTIR) spectroscopy analysis. To verify the biocompatibility of the scaffold, the viability, morphology, proliferation, differentiation, and extracellular matrix (ECM) production of synovium-derived mesenchymal stem cell (SMSC) on the scaffolds were assessed by LIVE/DEAD staining, alamarBlue assay, ELISA analysis, and qRT-PCR. The recruitment ability of SMSC was tested by dual labeling with CD29 and CD90 by confocal microscope at 1 week after implantation. The functionalized hybrid scaffold was then implanted into the meniscus defects on rabbit knee joint for meniscus regeneration, comparing with the Blank group (no scaffold) and PS group. The regenerated meniscus tissue was evaluated by histological and immunohistochemistry staining, and biomechanical test. Macroscopic and histological scoring was performed to assess the outcome of meniscus regeneration and cartilage protection in vivo. Results: The combination of SF and PCL could greatly balance the biomechanical properties and degradation rate to match the native meniscus. SF sponge, characterized by fine elasticity and low interfacial shear force, enhanced energy absorption capacity of the meniscus and improved chondroprotection. The SMSC-specific affinity peptide (LTHPRWP; L7) was conjugated to the scaffold to further increase the recruitment and retention of endogenous SMSCs. This meticulously tailored scaffold displayed superior biomechanics, structure, and function, creating a favorable microenvironment for SMSC proliferation, differentiation, and extracellular matrix (ECM) production. After 24 weeks of implantation, the histological assessment, biochemical contents, and biomechanical properties demonstrated that the polycaprolactone/silk fibroin-L7 (PS-L7) group was close to the native meniscus group, showing significantly better cartilage protection than the PS group. Conclusion: This tissue engineering scaffold could greatly strengthen meniscus regeneration and chondroprotection. Compared with traditional cell-based therapies, the meniscus tissue engineering approach with advantages of one-step operation and reduced cost has a promising potential for future clinical and translational studies.

Entrapped in cage (EiC) scaffolds of 3D-printed polycaprolactone and porous silk fibroin for meniscus tissue engineering.

The meniscus has critical functions in the knee joint kinematics and homeostasis. Injuries of the meniscus are frequent, and the lack of a functional meniscus between the femur and tibial plateau can cause articular cartilage degeneration leading to osteoarthritis development and progression. Regeneration of meniscus tissue has outstanding challenges to be addressed. In the current study, novel Entrapped in cage (EiC) scaffolds of 3D-printed polycaprolactone (PCL) and porous silk fibroin were proposed for meniscus tissue engineering. As confirmed by micro-structural analysis the entrapment of silk fibroin was successful, and all scaffolds had excellent interconnectivity (≥99%). The EiC scaffolds had more favorable micro-structure compared with the PCL cage scaffolds by improving the pore size while keeping the interconnectivity almost the same. When compared with the PCL cage, the entrapment of porous silk fibroin into the PCL cage decreased the high compressive modulus in a favorable matter in the wet state thanks to the silk fibroin's high swelling properties. The in vitro studies with human stem cells or meniscocytes seeded constructs, demonstrated that the EiC scaffolds had superior cell adhesion, metabolic activity, and proliferation compared to the PCL cage scaffolds. Upon subcutaneous implantation of scaffolds in nude mice, all groups were free of adverse incidents, and mildly invaded by inflammatory cells with neovascularization, while the EiC scaffolds showed better tissue infiltration. The results of this work indicated that the EiC scaffolds of PCL and silk fibroin are favorable for meniscus tissue engineering, and the findings are encouraging for further studies using a larger animal model.

FOXO1 and FOXO3 transcription factors have unique functions in meniscus development and homeostasis during aging and osteoarthritis.

The objective of this study was to examine FoxO expression and FoxO function in meniscus. In menisci from human knee joints with osteoarthritis (OA), FoxO1 and 3 expression were significantly reduced compared with normal menisci from young and old normal donors. The expression of FoxO1 and 3 was also significantly reduced in mouse menisci during aging and OA induced by surgical meniscus destabilization or mechanical overuse. Deletion of FoxO1 and combined FoxO1, 3, and 4 deletions induced abnormal postnatal meniscus development in mice and these mutant mice spontaneously displayed meniscus pathology at 6 mo. Mice with Col2Cre-mediated deletion of FoxO3 or FoxO4 had normal meniscus development but had more severe aging-related damage. In mature AcanCreERT2 mice, the deletion of FoxO1, 3, and 4 aggravated meniscus lesions in all experimental OA models. FoxO deletion suppressed autophagy and antioxidant defense genes and altered several meniscus-specific genes. Expression of these genes was modulated by adenoviral FoxO1 in cultured human meniscus cells. These results suggest that FoxO1 plays a key role in meniscus development and maturation, and both FoxO1 and 3 support homeostasis and protect against meniscus damage in response to mechanical overuse and during aging and OA.

Meniscus regeneration combining meniscus and mesenchymal stromal cells in a degradable meniscus implant: an in vitro study.

Meniscus regeneration is an unmet clinical need as damage to the meniscus is common and causes early osteoarthritis. The aim of the present study was to investigate the feasibility of a one-stage cell-based treatment for meniscus regeneration by augmenting a resorbable collagen-based implant with a combination of recycled meniscus cells and mesenchymal stromal cells (MSCs). Cell communication and fate of the different cell types over time in co-culture were evaluated by connexin 43 staining for gap junctions and polymerase chain reaction (PCR) to discriminate between meniscus cells and MSCs, based on a Y-chromosome gene. To define optimal ratios, human meniscus cells and bone-marrow-derived MSCs were cultured in different ratios in cell pellets and type I collagen hydrogels. In addition, cells were seeded on the implant in fibrin glue by static seeding or injection. Cellular communication by gap junctions was shown in co-culture and a decrease in the amount of MSCs over time was demonstrated by PCR. 20 : 80 and 10 : 90 ratios showed significantly highest glycosaminoglycan and collagen content in collagen hydrogels. The same statistical trend was found in pellet cultures. Significantly more cells were present in the injected implant and cell distribution was more homogenous as compared to the statically seeded implant. The study demonstrated the feasibility of a new one-stage cell-based procedure for meniscus regeneration, using 20 % meniscus cells and 80 % MSCs seeded statically on the implant. In addition, the stimulatory effect of MSCs towards meniscus cells was demonstrated by communication through gap junctions.

Meniscus-Derived Matrix Scaffolds Promote the Integrative Repair of Meniscal Defects.

Meniscal tears have a poor healing capacity, and damage to the meniscus is associated with significant pain, disability, and progressive degenerative changes in the knee joint that lead to osteoarthritis. Therefore, strategies to promote meniscus repair and improve meniscus function are needed. The objective of this study was to generate porcine meniscus-derived matrix (MDM) scaffolds and test their effectiveness in promoting meniscus repair via migration of endogenous meniscus cells from the surrounding meniscus or exogenously seeded human bone marrow-derived mesenchymal stem cells (MSCs). Both endogenous meniscal cells and MSCs infiltrated the MDM scaffolds. In the absence of exogenous cells, the 8% MDM scaffolds promoted the integrative repair of an in vitro meniscal defect. Dehydrothermal crosslinking and concentration of the MDM influenced the biochemical content and shear strength of repair, demonstrating that the MDM can be tailored to promote tissue repair. These findings indicate that native meniscus cells can enhance meniscus healing if a scaffold is provided that promotes cellular infiltration and tissue growth. The high affinity of cells for the MDM and the ability to remodel the scaffold reveals the potential of MDM to integrate with native meniscal tissue to promote long-term repair without necessarily requiring exogenous cells.

Dual-energy computed tomography in calcium pyrophosphate deposition: initial clinical experience.

OBJECTIVE: To determine the dual-energy computed tomography (DECT) attenuation properties of meniscal calcifications in calcium pyrophosphate deposition (CPPD) in vivo, and assess whether DECT was able to discriminate meniscal CPP deposits from calcium hydroxyapatite (HA) in subchondral and trabecular bone. METHOD: Patients with clinical suspicion of crystal-related arthropathy (gout and/or CPPD) and knee DECT scans were retrospectively assigned to CPPD (n = 19) or control (n = 21) groups depending on the presence/absence of chondrocalcinosis on DECT. Two observers drew standardized regions of interest (ROI) in meniscal calcifications, non-calcified menisci, as well as subchondral and trabecular bone. Five DECT parameters were obtained: CT numbers (HU) at 80 and 140 kV, dual-energy index (DEI), electron density (ρe), and effective atomic number (Zeff). The four different knee structures were compared within/between patients and controls using linear mixed models, adjusting for confounders. RESULTS: Meniscal calcifications (n = 89) in CPPD patients had mean ± SD CT numbers at 80 and 140 kV of 257 ± 64 and 201 ± 48 HU, respectively; with a DEI of 0.023 ± 0.007, and ρe and Zeff of 140 ± 35 and 8.8 ± 0.3, respectively. Meniscal CPP deposits were readily distinguished from calcium HA in subchondral and trabecular bone (p ≤ 0.001), except at 80 kV separately (p = 0.74). Zeff and ρe both significantly differed between CPP deposits and calcium HA in subchondral and trabecular bone (p < 0.0001). CONCLUSION: This proof-of-concept study shows that DECT has the potential to discriminate meniscal CPP deposits from calcium HA in subchondral and trabecular bone in vivo, paving the way for the non-invasive biochemical signature assessment of intra- and juxta-articular calcium crystal deposits.

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.

The Meniscus Tear: A Review of Stem Cell Therapies.

Meniscal injuries have posed a challenging problem for many years, especially considering that historically the meniscus was considered to be a structure with no important role in the knee joint. This led to earlier treatments aiming at the removal of the entire structure in a procedure known as a meniscectomy. However, with the current understanding of the function and roles of the meniscus, meniscectomy has been identified to accelerate joint degradation significantly and is no longer a preferred treatment option in meniscal tears. Current therapies are now focused to regenerate, repair, or replace the injured meniscus to restore its native function. Repairs have improved in technique and materials over time, with various implant devices being utilized and developed. More recently, strategies have applied stem cells, tissue engineering, and their combination to potentiate healing to achieve superior quality repair tissue and retard the joint degeneration associated with an injured or inadequately functioning meniscus. Accordingly, the purpose of this current review is to summarize the current available pre-clinical and clinical literature using stem cells and tissue engineering for meniscal repair and regeneration.

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.