The regenerative effect of different growth factors and platelet lysate on meniscus cells and mesenchymal stromal cells and proof of concept with a functionalized meniscus implant.

Meniscus regeneration could be enhanced by targeting meniscus cells and mesenchymal stromal cells (MSCs) with the right growth factors. Combining these growth factors with the Collagen Meniscus Implant (CMI®) could accelerate cell ingrowth and tissue formation in the implant and thereby improve clinical outcomes. Using a transwell migration assay and a micro-wound assay, the effect of insulin-like growth factor-1, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), transforming growth factor beta 1 (TGF-ß1), fibroblast growth factor, and platelet lysate (PL) on migration and proliferation of meniscus cells and MSCs was assessed. The formation of extracellular matrix under influence of the above-mentioned growth factors was assessed after 28 days of culture of both MSCs and meniscus cells. As a proof of concept, the CMI® was functionalized with a VEGF binding peptide and coated with platelet-rich plasma (PRP) for clinical application. Our results demonstrate that PDGF, TGF-ß1, and PL stimulate migration, proliferation, and/or extracellular matrix production of meniscus cells and MSCs. Additionally, the CMI® was successfully functionalized with a VEGF binding peptide and PRP which increased migration of meniscus cell and MSC into the implant. This study demonstrates proof of concept of functionalizing the CMI® with growth factor binding peptides. A CMI® functionalized with the right growth factors holds great potential for meniscus replacement after partial meniscectomy.

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.

Anterior and Rotational Knee Laxity Does Not Affect Patient-Reported Knee Function 2 Years After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: While a primary goal of anterior cruciate ligament (ACL) reconstruction is to reduce pathologically increased anterior and rotational knee laxity, the relationship between knee laxity after ACL reconstruction and patient-reported knee function remains unclear. HYPOTHESIS: There would be no significant correlation between the degree of residual anterior and rotational knee laxity and patient-reported outcomes (PROs) 2 years after primary ACL reconstruction. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: From a prospective multicenter nested cohort of patients, 433 patients younger than 36 years of age injured in sports with no history of concomitant ligament surgery, revision ACL surgery, or surgery of the contralateral knee were identified and evaluated at a minimum 2 years after primary ACL reconstruction. Each patient underwent Lachman and pivot-shift evaluation as well as a KT-1000 arthrometer assessment along with Knee injury and Osteoarthritis Outcome Score and subjective International Knee Documentation Committee (IKDC) scores. A proportional odds logistic regression model was used to predict each 2-year PRO score, controlling for preoperative score, age, sex, body mass index, smoking, Marx activity score, education, subsequent surgery, meniscal and cartilage status, graft type, and range of motion asymmetry. Measures of knee laxity were independently added to each model to determine correlation with PROs. RESULTS: Side-to-side manual Lachman differences were IKDC A in 246 (57%) patients, IKDC B in 183 (42%) patients, and IKDC C in 4 (<1%) patients. Pivot-shift was classified as IKDC A in 209 (48%) patients, IKDC B in 183 (42%) patients, and IKDC C in 11 (2.5%) patients. The mean side-to-side KT-1000 difference was 2.0 ± 2.6 mm. No significant correlations were noted between pivot-shift or anterior tibial translation as assessed by Lachman or KT-1000 and any PRO. All predicted differences in PROs based on IKDC A versus B pivot-shift and anterior tibial translation were less than 4 points. CONCLUSION: Neither the presence of IKDC A versus B pivot-shift nor increased anterior tibial translation of up to 6 mm is associated with clinically relevant decreases in PROs 2 years after ACL reconstruction.

The Importance of the Knee Joint Meniscal Fibrocartilages as Stabilizing Weight Bearing Structures Providing Global Protection to Human Knee-Joint Tissues.

The aim of this study was to review aspects of the pathobiology of the meniscus in health and disease and show how degeneration of the meniscus can contribute to deleterious changes in other knee joint components. The menisci, distinctive semilunar weight bearing fibrocartilages, provide knee joint stability, co-ordinating functional contributions from articular cartilage, ligaments/tendons, synovium, subchondral bone and infra-patellar fat pad during knee joint articulation. The meniscus contains metabolically active cell populations responsive to growth factors, chemokines and inflammatory cytokines such as interleukin-1 and tumour necrosis factor-alpha, resulting in the synthesis of matrix metalloproteases and A Disintegrin and Metalloprotease with ThromboSpondin type 1 repeats (ADAMTS)-4 and 5 which can degrade structural glycoproteins and proteoglycans leading to function-limiting changes in meniscal and other knee joint tissues. Such degradative changes are hall-marks of osteoarthritis (OA). No drugs are currently approved that change the natural course of OA and translate to long-term, clinically relevant benefits. For any pharmaceutical therapeutic intervention in OA to be effective, disease modifying drugs will have to be developed which actively modulate the many different cell types present in the knee to provide a global therapeutic. Many individual and combinatorial approaches are being developed to treat or replace degenerate menisci using 3D printing, bioscaffolds and hydrogel delivery systems for therapeutic drugs, growth factors and replacement progenitor cell populations recognising the central role the menisci play in knee joint health.

Cellular and Chemical Gradients to Engineer the Meniscus-to-Bone Insertion.

Tissue-engineered menisci hold promise as an alternative to allograft procedures but require a means of robust fixation to the native bone. The insertion of the meniscus into bone is critical for meniscal function and inclusion of a soft tissue-to-bone interface in a tissue engineered implant can aid in the fixation process. The native insertion is characterized by gradients in composition, tissue architecture, and cellular phenotype, which are all difficult to replicate. In this study, a soft tissue-to-bone interface is tissue engineered with a cellular gradient of fibrochondrocytes and mesenchymal stem cells and subjected to a biochemical gradient through a custom media diffusion bioreactor. These constructs, consisting of interpenetrating collagen and boney regions, display improved mechanical performance and collagen organization compared to controls without a cellular or chemical gradient. Media gradient exposure produces morphological features in the constructs that appear similar to the native tissue. Collectively, these data show that cellular and biochemical gradients improve integration between collagen and bone in a tissue engineered soft tissue-to-bone construct.

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.

Surgical Feasibility of a One-Stage Cell-Based Arthroscopic Procedure for Meniscus Regeneration: A Cadaveric Study.

IMPACT STATEMENT: Meniscus injury remains the most common indication for orthopedic surgery, but loss of functioning meniscus tissue is strongly correlated with development of early osteoarthritis. However, current clinical options for tissue engineering of the meniscus are limited. This study demonstrates the feasibility of combining human meniscus cells with mesenchymal stromal cells to enhance a meniscus scaffold for meniscus regeneration in a one-stage solution for partial meniscal deficiency.

Early intervention of swimming exercises attenuate articular cartilage destruction in a rat model of anterior cruciate ligament and meniscus knee injuries.

AIM: The anterior cruciate ligament (ACL) and meniscus injuries often cause post-traumatic knee osteoarthritis (PTOA), which can place great limitations on patients. But to date there is no effective therapy to delay the progression of cartilage destruction in PTOA. This study aimed to compare the effects of early versus delayed swimming exercise on the chondroprotective effects in a rat PTOA model with ACL and meniscus injuries. MAIN METHODS: Thirty-two adult male Sprague-Dawley rats received unilateral ACL transection and medial meniscectomy (ACLMT). These were randomly allocated to four groups: early swimming (eSW), delayed swimming (dSW), sham-operated early swimming (sham-eSW) and sham-operated delayed swimming (sham-dSW). Swimming (30 min per session) continuing for 28 days was started three days and three months after ACLMT surgery as a protocol for eSW and dSW intervention. Cartilage quality was assessed by Mankin HHGS examination (H&E, Safranin-O stain) and collagen type II (CoII) and matrix metalloproteases-13 (MMP13) immunohistochemistry. KEY FINDINGS: ACLMT induced the PTOA histopathological changes, inhibited CoII and enhanced MMP13 expressions in cartilage for both sham-eSW and sham-dSW groups. eSW intervention significantly enhanced CoII expression and suppressed MMP13 overexpression in superficial and transitional zones of cartilage, as well as better Mankin scores, corresponding to sham-swimming controls (P < 0.05). dSW intervention provided less enhancement of CoII expression and improvement of histopathological scoring, but significantly reduced MMP13 overexpression compared to animals in eSW (P < 0.05). SIGNIFICANCE: Early intervention by swimming at very early stages of cartilage damage provides greater benefits than delayed intervention when PTOA has already developed.

Biomechanics of Knee Joints after Anterior Cruciate Ligament Reconstruction.

This study aimed to investigate the biomechanical properties of anterior cruciate ligament (ACL); tibial, femoral articular cartilage; and meniscus in knee joints receiving computer-aided or conventional ACL reconstruction. Three-dimensional (3D) knee joint finite element models were established for healthy volunteers (normal group) and patients receiving computer-aided surgery (CAS) or conventional (traditional surgery [TS]) ACL reconstruction. The stress and stress distribution on the ACL, tibial, femoral articular cartilage, and meniscus were examined after force was applied on the 3D knee joint finite element models. No significant differences were observed in the stress on ACL among normal group, CAS group, and TS group when a femoral backward force was loaded. However, when a vertical force of 350 N was loaded on the knee joints, TS group had significant higher stress on the articular cartilage and meniscus than the other two groups at any flexion angle of 0, 30, 60, and 90 degrees. However, no significant differences were observed between CAS group and normal group. In conclusion, computer-aided ACL reconstruction has advantages over conventional surgery approach in restoring the biomechanical properties of knee joints, thus reducing the risk of damage to the knee joint cartilage and meniscus after ACL reconstruction.

Fiber development and matrix production in tissue-engineered menisci using bovine mesenchymal stem cells and fibrochondrocytes.

Mesenchymal stem cells (MSCs) have been investigated with promising results for meniscus healing and tissue engineering. While MSCs are known to contribute to extracellular matrix (ECM) production, less is known about how MSCs produce and align large organized fibers for application to tissue engineering the meniscus. The goal of this study was to investigate the capability of MSCs to produce and organize ECM molecules compared to meniscal fibrochondrocytes (FCCs). Bovine FCCs and MSCs were encapsulated in an anatomically accurate collagen meniscus using monoculture and co-culture of each cell type. Each meniscus was mechanically anchored at the horns to mimic the physiological fixation by the meniscal entheses. Mechanical fixation generates a static mechanical boundary condition previously shown to induce formation of oriented fiber by FCCs. Samples were cultured for 4 weeks and then evaluated for biochemical composition and fiber development. MSCs increased the glycosaminoglycan (GAG) and collagen production in both co-culture and monoculture groups compared to FCC monoculture. Collagen organization was greatest in the FCC monoculture group. While MSCs had increased matrix production, they lacked the fiber organization capabilities of FCCs. This study suggests that GAG production and fiber formation are linked. Co-culture can be used as a means of balancing the synthetic properties of MSCs and the matrix remodeling capabilities of FCCs for tissue engineering applications.

Enhanced cellular infiltration of human adipose-derived stem cells in allograft menisci using a needle-punch method.

BACKGROUND: The meniscus plays a crucial role in knee joint stability, load transmission, and stress distribution. Meniscal tears are the most common reported knee injuries, and the current standard treatment for meniscal deficiency is meniscal allograft transplantation. A major limitation of this approach is that meniscal allografts do not have the capacity to remodel and maintain tissue homeostasis due to a lack of cellular infiltration. The purpose of this study was to provide a new method for enhanced cellular infiltration in meniscal allografts. METHODS: Twenty medial menisci were collected from cadaveric human sources and split into five experimental groups: (1) control native menisci, (2) decellularized menisci, (3) decellularized menisci seeded with human adipose-derived stem cells (hASC), (4) decellularized needle-punched menisci, and (5) decellularized needle-punched menisci seeded with hASC. All experimental allografts were decellularized using a combined method with trypsin EDTA and peracetic acid. Needle punching (1-mm spacing, 28 G microneedle) was utilized to improve porosity of the allograft. Samples were recellularized with hASC at a density of 250 k/g of tissue. After 28 days of in vitro culture, menisci were analyzed for mechanical, biochemical, and histological characteristics. RESULTS: Menisci maintained structural integrity and material properties (compressive equilibrium and dynamic moduli) throughout preparations. Increased DNA content was observed in the needle-punched menisci but not in the samples without needle punching. Histology confirmed these results, showing enhanced cellular infiltration in needle-punched samples. CONCLUSIONS: The enhanced infiltration achieved in this study could help meniscal allografts better remodel post-surgery. The integration of autologous adipose-derived stem cells could improve long-term efficacy of meniscal transplantation procedures by helping to maintain the meniscus in vivo.

Role of scaffold mean pore size in meniscus regeneration.

UNLABELLED: Recently, meniscus tissue engineering offers a promising management for meniscus regeneration. Although rarely reported, the microarchitectures of scaffolds can deeply influence the behaviors of endogenous or exogenous stem/progenitor cells and subsequent tissue formation in meniscus tissue engineering. Herein, a series of three-dimensional (3D) poly(ε-caprolactone) (PCL) scaffolds with three distinct mean pore sizes (i.e., 215, 320, and 515µm) were fabricated via fused deposition modeling. The scaffold with the mean pore size of 215µm significantly improved both the proliferation and extracellular matrix (ECM) production/deposition of mesenchymal stem cells compared to all other groups in vitro. Moreover, scaffolds with mean pore size of 215µm exhibited the greatest tensile and compressive moduli in all the acellular and cellular studies. In addition, the relatively better results of fibrocartilaginous tissue formation and chondroprotection were observed in the 215µm scaffold group after substituting the rabbit medial meniscectomy for 12weeks. Overall, the mean pore size of 3D-printed PCL scaffold could affect cell behavior, ECM production, biomechanics, and repair effect significantly. The PCL scaffold with mean pore size of 215µm presented superior results both in vitro and in vivo, which could be an alternative for meniscus tissue engineering. STATEMENT OF SIGNIFICANCE: Meniscus tissue engineering provides a promising strategy for meniscus regeneration. In this regard, the microarchitectures (e.g., mean pore size) of scaffolds remarkably impact the behaviors of cells and subsequent tissue formation, which has been rarely reported. Herein, three three-dimensional poly(ε-caprolactone) scaffolds with different mean pore sizes (i.e., 215, 320, and 515µm) were fabricated via fused deposition modeling. The results suggested that the mean pore size significantly affected the behaviors of endogenous or exogenous stem/progenitor cells and subsequent tissue formation. This study furthers our understanding of the cell-scaffold interaction in meniscus tissue engineering, which provides unique insight into the design of meniscus scaffolds for future clinical application.