Tissue engineering for the meniscus: a review of the literature

Regenerative Medicine for Equine Musculoskeletal Diseases

Simple Summary

Lameness due to musculoskeletal disease is the most common diagnosis in equine veterinary practice. Many of these orthopaedic disorders are chronic problems, for which no clinically satisfactory treatment exists. Thus, high hopes are pinned on regenerative medicine, which aims to replace or regenerate cells, tissues, or organs to restore or establish normal function. Some regenerative medicine therapies have already made their way into equine clinical practice mainly to treat tendon injures, tendinopathies, cartilage injuries and degenerative joint disorders with promising but diverse results. This review summarises the current knowledge of commonly used regenerative medicine treatments and critically discusses their use.

Abstract

Musculoskeletal injuries and chronic degenerative diseases commonly affect both athletic and sedentary horses and can entail the end of their athletic careers. The ensuing repair processes frequently do not yield fully functional regeneration of the injured tissues but biomechanically inferior scar or replacement tissue, causing high reinjury rates, degenerative disease progression and chronic morbidity. Regenerative medicine is an emerging, rapidly evolving branch of translational medicine that aims to replace or regenerate cells, tissues, or organs to restore or establish normal function. It includes tissue engineering but also cell-based and cell-free stimulation of endogenous self-repair mechanisms. Some regenerative medicine therapies have made their way into equine clinical practice mainly to treat tendon injures, tendinopathies, cartilage injuries and degenerative joint disorders with promising results. However, the qualitative and quantitative spatiotemporal requirements for specific bioactive factors to trigger tissue regeneration in the injury response are still unknown, and consequently, therapeutic approaches and treatment results are diverse. To exploit the full potential of this burgeoning field of medicine, further research will be required and is ongoing. This review summarises the current knowledge of commonly used regenerative medicine treatments in equine patients and critically discusses their use.

Meniscus Repair and Regeneration: A Systematic Review from a Basic and Translational Science Perspective

Meniscus injuries are among the most common athletic injuries and result in functional impairment in the knee. Repair is crucial for pain relief and prevention of degenerative joint diseases like osteoarthritis. Current treatments, however, do not produce long-term improvements. Thus, recent research has been investigating new therapeutic options for regenerating injured meniscal tissue. This review comprehensively details the current methodologies being explored in the basic sciences to stimulate better meniscus injury repair. Furthermore, it describes how these preclinical strategies may improve current paradigms of how meniscal injuries are clinically treated through a unique and alternative perspective to traditional clinical methodology.

Finite Element Modelling Simulated Meniscus Translocation and Deformation during Locomotion of the Equine Stifle

Simple Summary

Meniscal tears are one of the most common soft tissue injuries in the equine stifle joint. To date no optimal treatment strategy to heal meniscal tissue is available. Accordingly, there is a need to improve treatment for meniscal injuries and thus to identify appropriate translational animal models. A possible alternative to animal experimentation is the use of finite element modelling (FEMg). FEMg allows simulation of time dependent changes in tissues resulting from biomechanical strains. We developed a finite element model (FEM) of the equine stifle joint to identify pressure peaks and simulate translocation and deformation of the menisci at different joint angles under loading conditions. The FEM model was tested across a range of motion of approximately 30°. Pressure load was higher overall in the lateral meniscus than in the medial meniscus. Accordingly, the simulation showed higher translocation and deformation throughout the whole range of motion in the lateral compared to the medial meniscus. The results encourage further refinement of this FEM model for studying loading patterns on menisci and articular cartilages as well as the resulting mechanical stress in the subchondral bone. A functional FEM model can not only help identify segments in the femoro–tibial joint which are predisposed to injury, but also provide better understanding of the progression of certain stifle disorders, simulate treatment/surgery effects and to optimize implant/transplant properties in order to most closely resemble natural tissue.

Abstract

We developed a finite element model (FEM) of the equine stifle joint to identify pressure peaks and simulate translocation and deformation of the menisci. A series of sectional magnetic resonance images (1.5 T) of the stifle joint of a 23 year old Shetland pony gelding served as basis for image segmentation. Based on the 3D polygon models of femur, tibia, articular cartilages, menisci, collateral ligaments and the meniscotibial ligaments, an FEM model was generated. Tissue material properties were assigned based on data from human (Open knee(s) project) and bovine femoro-tibial joint available in the literature. The FEM model was tested across a range of motion of approximately 30°. Pressure load was overall higher in the lateral meniscus than in the medial. Accordingly, the simulation showed higher translocation and deformation in the lateral compared to the medial meniscus. The results encourage further refinement of this model for studying loading patterns on menisci and articular cartilages as well as the resulting mechanical stress in the subchondral bone (femur and tibia). A functional FEM model can not only help identify segments in the stifle which are predisposed to injury, but also to better understand the progression of certain stifle disorders, simulate treatment/surgery effects and to optimize implant/transplant properties.

Development of decellularized meniscus using closed sonication treatment system: potential scaffolds for orthopedics tissue engineering applications

PURPOSE

Meniscus is a fibrocartilagenous tissue that cannot effectively heal due to its complex structure and presence of avascular zone. Thus, tissue engineering and regenerative medicine offer an alternative for the regeneration of meniscus tissues using bioscaffolds as a replacement for the damaged one. The aim of this study was to prepare an ideal meniscus bioscaffold with minimal adverse effect on extracellular matrix components (ECMs) using a sonication treatment system.

METHODS

The decellularization was achieved using a developed closed sonication treatment system for 10 hrs, and continued with a washing process for 5 days. For the control, a simple immersion treatment was set as a benchmark to compare the decellularization efficiency. Histological and biochemical assays were conducted to investigate the cell removal and retention of the vital extracellular matrix. Surface ultrastructure of the prepared scaffolds was evaluated using scanning electron microscope at 5,000× magnification viewed from cross and longitudinal sections. In addition, the biomechanical properties were investigated through ball indentation testing to study the stiffness, residual forces and compression characteristics. Statistical significance between the samples was determined with p-value =0.05.

RESULTS

Histological and biochemical assays confirmed the elimination of antigenic cellular components with the retention of the vital extracellular matrix within the sonicated scaffolds. However, there was a significant removal of sulfated glycosaminoglycans. The surface histoarchitecture portrayed the preserved collagen fibril orientation and arrangement. However, there were minor disruptions on the structure, with few empty micropores formed which represented cell lacunae. The biomechanical properties of bioscaffolds showed the retention of viscoelastic behavior of the scaffolds which mimic native tissues. After immersion treatment, those scaffolds had poor results compared to the sonicated scaffolds due to the inefficiency of the treatment.

CONCLUSION

In conclusion, this study reported that the closed sonication treatment system had high capabilities to prepare ideal bioscaffolds with excellent removal of cellular components, and retained extracellular matrix and biomechanical properties.

Structure-Function relationships of equine menisci

Meniscal pathologies are among the most common injuries of the femorotibial joint in both human and equine patients. Pathological forces and ensuing injuries of the cranial horn of the equine medial meniscus are considered analogous to those observed in the human posterior medial horn. Biomechanical properties of human menisci are site- and depth- specific. However, the influence of equine meniscus topography and composition on its biomechanical properties is yet unknown. A better understanding of equine meniscus composition and biomechanics could advance not only veterinary therapies for meniscus degeneration or injuries, but also further substantiate the horse as suitable translational animal model for (human) meniscus tissue engineering. Therefore, the aim of this study was to investigate the composition and structure of the equine knee meniscus in a site- and age-specific manner and their relationship with potential site-specific biomechanical properties. The meniscus architecture was investigated histologically. Biomechanical testing included evaluation of the shore hardness (SH), stiffness and energy loss of the menisci. The SH was found to be subjected to both age and site-specific changes, with an overall higher SH of the tibial meniscus surface and increase in SH with age. Stiffness and energy loss showed neither site nor age related significant differences. The macroscopic and histologic similarities between equine and human menisci described in this study, support continued research in this field.

A Novel Approach for Meniscal Regeneration Using Kartogenin-Treated Autologous Tendon Graft

BACKGROUND

The meniscus is one of the most commonly injured parts of the body, and meniscal healing is difficult.

HYPOTHESIS

Kartogenin (KGN) induces tendon stem cells (TSCs) to differentiate into cartilage cells in vitro and form meniscus-like tissue in vivo. A damaged meniscus can be replaced with a KGN-treated autologous tendon graft.

STUDY DESIGN

Controlled laboratory study.

METHODS

In the in vitro experiments, TSCs were isolated from rabbit patellar tendons and cultured with various concentrations of KGN, from 0 to 1000 µM. The effect of KGN on the chondrogenesis of TSCs in vitro was investigated by histochemical staining and quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The in vivo experiments were carried out on 6 New Zealand White rabbits by removing a meniscus from the rabbit knee and implanting an autologous tendon graft treated with KGN or saline. The meniscus formation in vivo was examined by histological analysis and immune staining.

RESULTS

The proliferation of TSCs was promoted by KGN in a concentration-dependent manner. Both histochemical staining and qRT-PCR showed that the chondrogenic differentiation of TSCs was increased with KGN concentration. After 3 months of implantation, the tendon graft treated with KGN formed a meniscus-like tissue with a white and glistening appearance, while the saline-treated tendon graft retained tendon-like tissue and appeared yellowish and unhealthy. Histochemical staining showed that after 3 months of implantation, the KGN-treated tendon graft had a structure similar to that of normal meniscus. Many cartilage-like cells and fibrocartilage-like tissues were found in the KGN-treated tendon graft. However, no cartilage-like cells were found in the saline-treated tendon graft after 3 months of implantation. Furthermore, the KGN-treated tendon graft was positively stained by both anti-collagen type I and type II antibodies, but the saline-treated tendon graft was not stained by collagen type II.

CONCLUSION

The findings indicated that KGN can induce the differentiation of TSCs into cartilage-like cells in vitro and in vivo. The results suggest that KGN-treated tendon graft may be a good substitute for meniscal repair and regeneration.

CLINICAL RELEVANCE

This study revealed the direct effects of KGN on the chondrogenic differentiation of TSCs in vitro and in vivo. A KGN-treated autologous tendon graft induced formation of a meniscus-like tissue in vivo. This study provides a new cartilage regenerating technology for the treatment of damaged meniscus.

Osteoarthritis prevention and meniscus regeneration induced by transplantation of mesenchymal stem cell sheet in a rat meniscal defect model

Transplantation of mesenchymal stem cells (MSCs) is a potential therapy for meniscus regeneration. However, when using single cell suspension injection, there is frequently a significant loss of cells, with only a small percentage of cells remaining at the target site. This issue may be solved with the use of MSC sheets. In the present study, we investigated whether the use of MSC sheets were able to regenerate the meniscus effectively in a rat meniscectomized model. The anterior half of the medial meniscus in 10 rats was excised and an MSC sheet was transplanted in the MSC sheet treatment group, while untreated rats served as the control. After 4 and 8 weeks, the knee joints were examined by gross and histological observation. Histological observation revealed that the anterior portion of meniscus was similar to the native tissue, showing typical fibrochondrocytes surrounded by richer extracellular matrix in the MSC sheet group. In addition, predominant collagen-rich matrix bridging the interface was observed and the neo-meniscus integrated well with its host meniscus. Furthermore, degenerative changes of tibial plateau and femoral condyle occurred in the two groups. MSC sheet transplantation alleviated the degenerative changes efficiently. In conclusion, transplantation of MSC sheets may efficiently promote meniscus regeneration, as well as inhibit the progression of osteoarthritis in knee joints.

Meniscal allograft transplantation in rabbit

This study evaluated the technique for meniscal allograft transplantation using allografts preserved in glycerin 98% in rabbits. Euthanasia was performed at 70 days to compare the transplanted (TM1 to TM16) versus the contralateral meniscus (OM1 to OM16). Sixteen menisci, 8 transplanted and 8 contralateral, were submitted to gross examination, histomorphometric analysis for identification and quantification of cellular type, and for quantification and distribution of collagen fibers. A revascularization study was conducted in all of the other samples. Lengths of the OM varied from 0.9 to 1.0 cm and two TM were smaller. All TM were completely attached to the synovial membrane, except for one case that presented partial fixation. Both, TM and OM had similar amounts of chondrocytes, fibroblasts and fibrocytes, and at the horns, chondrocytes were predominant. The collagen fibers in TM were well organized throughout the body, and disorganized at the horns. These fibers in OM were organized. The amounts of collagen type I and III, and the vascularization of the perimeniscal tissue and of the edge were similar in OM and TM. These results demonstrated graft integration and thus this transplantation technique and preservation method may be recommended.

Meniscal transection rather than excision increases pain behavior and structural damage in experimental osteoarthritis in mice

OBJECTIVE

To evaluate pain behavior and structural damage in mice subjected to either meniscal transection or removal.

METHODS

Mice (10/group) were subjected to transection of the medial collateral and anterior cruciate ligaments (ACLT/MCLT) followed by either transection (meniscotomy) or removal (meniscectomy) of the medial meniscus. A control group was subjected only to transection of the ligaments. Pain was assessed using the electronic pressure-meter paw test. Cell influx, measured in joint exudates, and joint histopathology were assessed after 49 days. Four other groups subjected to meniscotomy received indomethacin, the inducible nitric oxide synthase (iNOS) inhibitor 1400W, morphine or the vehicles.

RESULTS

Both meniscotomy and meniscectomy groups displayed persistent and significant increase in pain behavior as compared to controls, being significantly more severe in the former. Cell influx was more intense in the meniscotomy as compared to the meniscectomy group. Structural damage at the tibia, but not at the femur, was also more severe in the meniscotomy group. Indomethacin and 1400W partially but significantly reduced pain whereas morphine abrogated pain behavior in meniscotomized mice.

CONCLUSION

Meniscal transection rather than resection promotes more severe pain and structural damage in mice. Administration of opioids, cyclooxygenase and nitric oxide (NO) synthase inhibitors provide analgesia in this model. Careful description of the structures damaged is crucial when reporting experimental osteoarthritis (OA).

The biomaterialist's task: scaffold biomaterials and fabrication technologies

This paper focuses on tissue engineering (TE) from the biomaterialist's point of view. With the aim of answering some simple but key questions about TE, the related literature is here reviewed. In order to obtain an engineered tissue the following steps are mandatory: (a) cell selection, (b) identification of the ideal three-dimensional scaffold for cell seeding and proliferation, (c) choice of the most suitable type of cell culture. Whereas the biotechnologist working in the TE field is responsible for optimizing the cell seeding and culture, the biomaterialist has the challenging task of optimizing the three-dimensional cell support, or scaffold. Therefore, in the present paper, scaffold properties, biomaterials and fabrication technologies are analyzed in depth and reviewed on the basis of the current literature. Finally, mention is also made of the most recently emerging and innovative technologies relating to scaffolds for TE applications.

Transplantation of aggregates of synovial mesenchymal stem cells regenerates meniscus more effectively in a rat massive meniscal defect

Transplantation of mesenchymal stem cells (MSCs) derived from synovium is a possible therapy for meniscus regeneration. We have previously reported that intraarticular injection of 5 million synovial MSCs promoted meniscal regeneration in rat meniscal defects. However, if a similar cell number per body weight were required, preparation of required human MSCs would not be practical in a clinical situation. The use of aggregates of MSCs may be one of the solutions. Here, we investigated whether the use of aggregates of synovial MSCs regenerated meniscus more effectively in a rat meniscectomized model. The total number of synovial MSCs was adjusted to 25,000 cells, and aggregates consisting of MSCs or 25,000 MSCs suspended in PBS were placed on the meniscal defects. Five million MSCs suspended in PBS were also used as another control. For the regenerated menisci, the area was larger and the histological findings were closer to that of the normal meniscus in the aggregate groups than to that in the suspension groups at 4 weeks. The effects of transplantation of aggregates were still observed at 12 weeks. Luminescence intensity remained higher at 3 weeks and thereafter in the aggregate group than in the suspension group when the same number of luciferase expressing MSCs were transplanted. We confirmed that MSCs transplanted as aggregates existed in the regenerated meniscus focally and partially. Transplantation of aggregates of synovial MSCs regenerated meniscus more effectively in a rat massive meniscal defect.

Subject-specific analysis of joint contact mechanics: application to the study of osteoarthritis and surgical planning

Advances in computational mechanics, constitutive modeling, and techniques for subject-specific modeling have opened the door to patient-specific simulation of the relationships between joint mechanics and osteoarthritis (OA), as well as patient-specific preoperative planning. This article reviews the application of computational biomechanics to the simulation of joint contact mechanics as relevant to the study of OA. This review begins with background regarding OA and the mechanical causes of OA in the context of simulations of joint mechanics. The broad range of technical considerations in creating validated subject-specific whole joint models is discussed. The types of computational models available for the study of joint mechanics are reviewed. The types of constitutive models that are available for articular cartilage are reviewed, with special attention to choosing an appropriate constitutive model for the application at hand. Issues related to model generation are discussed, including acquisition of model geometry from volumetric image data and specific considerations for acquisition of computed tomography and magnetic resonance imaging data. Approaches to model validation are reviewed. The areas of parametric analysis, factorial design, and probabilistic analysis are reviewed in the context of simulations of joint contact mechanics. Following the review of technical considerations, the article details insights that have been obtained from computational models of joint mechanics for normal joints; patient populations; the study of specific aspects of joint mechanics relevant to OA, such as congruency and instability; and preoperative planning. Finally, future directions for research and application are summarized.