Meniscus reconstruction: today's achievements and premises for the future

No Differences in 2-Year Reoperation Rates for Meniscus Allograft Transplant With Concomitant Cartilage Restoration or Osteotomy: A National Database Study

PURPOSE

To investigate reoperation rates after meniscus allograft transplant (MAT), comparing rates with and without concomitant articular cartilage and osteotomy procedures using a national insurance claims database.

METHODS

We performed a retrospective cohort study of patients who underwent MAT from 2010 to 2021 with a minimum 2-year follow-up using the PearlDiver database. Using Current Procedural Terminology and International Classification of Diseases codes, we identified patients who underwent concomitant procedures including chondroplasty or microfracture, cartilage restoration defined as osteochondral graft or autologous chondrocyte implantation (ACI), or osteotomy. Univariate logistic regressions identified risk factors for reoperation. Reoperations were classified as knee arthroplasty, interventional procedures, or diagnostic or debridement procedures.

RESULTS

The study included 750 patients with an average age of 29.6 years (interquartile range: 21.0-36.8) and average follow-up time was 5.41 years (SD: 2.51). Ninety-day, 2-year, and all-time reoperation rates were 1.33%, 14.4%, and 27.6%, respectively. MAT with cartilage restoration was associated with increased reoperation rate at 90 days (odds ratio: 4.88; 95% confidence interval: 1.38-19.27; P = .015); however, there was no significant difference in reoperation rates at 2 years or to the end of follow-up. ACI had increased reoperation rates at 90 days (odds ratio: 6.95; 95% confidence interval: 1.45-25.96; P = .006), with no difference in reoperation rates 2 years postoperatively or to the end of follow-up. Osteochondral autograft and allograft were not associated with increased reoperation rates.

CONCLUSIONS

In our cohort, 14.4% of patients had a reoperation within 2 years of MAT. Nearly 1 in 4 patients undergoing MAT had concomitant cartilage restoration, showing that it is commonly performed on patients with articular cartilage damage. Concomitant osteochondral autograft, osteochondral allograft, chondroplasty, microfracture, and osteotomy were not associated with any significant difference in reoperation rates. ACI was associated with increased reoperation rates at 90 days, but not later.

LEVEL OF EVIDENCE

Level IV, retrospective cohort study.

Repairing Avascular Meniscal Lesions by Recruiting Endogenous Targeted Cells Through Bispecific Synovial-Meniscal Aptamers

BACKGROUND

Tissue engineering is a promising treatment option for meniscal lesions in the avascular area, but a favorable cell source and its utilization in tissue-engineered menisci remain uncertain. Therefore, a more controllable and convenient method for cell recruitment is required.

HYPOTHESIS

Circular bispecific synovial-meniscal (S-M) aptamers with a gelatin methacryloyl (GelMA) hydrogel can recruit endogenous synovial and meniscal cells to the site of the defect, thereby promoting in situ meniscal regeneration and chondroprotection.

STUDY DESIGN

Controlled laboratory study.

METHODS

Synovial and meniscal aptamers were filtered through systematic evolution of ligands by exponential enrichment (SELEX) and cross-linked to synthesize the S-M aptamer. A GelMA-aptamer system was constructed. An in vitro analysis of the bi-recruitment of synovial and meniscal cells was performed, and the migration and proliferation of the GelMA-aptamer hydrogel were also tested. For the in vivo assay, rabbits (n = 90) with meniscal defects in the avascular zone were divided into 3 groups: repair with the GelMA-aptamer hydrogel (GelMA-aptamer group), repair with the GelMA hydrogel (GelMA group), and no repair (blank group). Regeneration of the repaired meniscus and degeneration of the cartilage were assessed by gross and histological evaluations at 4, 8, and 12 weeks postoperatively. The mechanical properties of repaired menisci were also evaluated.

RESULTS

In vitro synovial and meniscal cells were recruited simultaneously by the S-M aptamer with high affiliation and specificity. The GelMA-aptamer hydrogel promoted the migration of targeted cells. Compared with the other groups, the GelMA-aptamer group showed enhanced fibrocartilaginous regeneration, lower cartilage degeneration, and better mechanical strength at 12 weeks after meniscal repair.

CONCLUSION/CLINICAL RELEVANCE

Bispecific S-M aptamers could be used for avascular meniscal repair by recruiting endogenous synovial and meniscal cells and promoting fibrocartilaginous regeneration.

Use of contralateral lateral meniscus for medial meniscal allograft transplantation: a cadaveric study

PURPOSE

Meniscal allografts are a preferred alternative to menisectomy in cases of irrepairable meniscal tears in young patients. Biological meniscal allograft transplantation requires a cadaveric donor, limiting its availability for transplantation. We are exploring the possibility of using contralateral lateral meniscus for medial meniscal allograft transplantation, as it can be easily procured from proximal tibial cuts from total knee replacement.

METHODS

Ten paired knees from five formalin-fixed Indian male cadavers were dissected. Outer and inner circumferences of the medial and meniscus, area of the articular surface of the medial tibial plateau covered by the native medial meniscus and transplanted lateral meniscus were noted. Measurements were taken using software ImageJ (National Institute of Health). The mean of the recordings from two independent observers was taken as the final value. Inter-observer and intra-observer reliability were also calculated.

RESULTS

The mean inner circumference of the medial meniscus was significantly larger than the lateral meniscus (p < 0.0001). However, outer circumferences were not significantly different from each other (p = 0.1). Area of the tibial plateau covered by the native medial meniscus was smaller than the area covered by the transplanted lateral meniscus, though the difference was not statistically significant. Inter-observer reliability and intra-observer reliability were good (ICC 0.904 and 0.927, respectively).

CONCLUSION

Based on measurements of the outer circumference of medial and lateral menisci, lateral meniscal allograft can be matched for transplantation on the contralateral medial side from the donor with same dimensions of the tibial plateau. Further clinical studies are necessary to prove the clinical significance of this cadaveric study.

LEVEL OF EVIDENCE

Diagnostic study.

Meniscus repair: up-to-date advances in stem cell-based therapy

The meniscus is a semilunar fibrocartilage between the tibia and femur that is essential for the structural and functional integrity of the keen joint. In addition to pain and knee joint dysfunction, meniscus injuries can also lead to degenerative changes of the knee joint such as osteoarthritis, which further affect patient productivity and quality of life. However, with intrinsic avascular property, the tearing meniscus tends to be nonunion and the augmentation of post-injury meniscus repair has long time been a challenge. Stem cell-based therapy with potent regenerative properties has recently attracted much attention in repairing meniscus injuries, among which mesenchymal stem cells were most explored for their easy availability, trilineage differentiation potential, and immunomodulatory properties. Here, we summarize the advances and achievements in stem cell-based therapy for meniscus repair in the last 5 years. We also highlight the obstacles before their successful clinical translation and propose some perspectives for stem cell-based therapy in meniscus repair.

Bone Marrow Aspirate Concentrate for the Treatment of Avascular Meniscus Tears in a One-Step Procedure-Evaluation of an In Vivo Model

Avascular meniscus tears show poor intrinsic regenerative potential. Thus, lesions within this area predispose the patient to developing knee osteoarthritis. Current research focuses on regenerative approaches using growth factors or mesenchymal stem cells (MSCs) to enhance healing capacity within the avascular meniscus zone. The use of MSCs especially as progenitor cells and a source of growth factors has shown promising results. However, present studies use bone-marrow-derived BMSCs in a two-step procedure, which is limiting the transfer in clinical praxis. So, the aim of this study was to evaluate a one-step procedure using bone marrow aspirate concentrate (BMAC), containing BMSCs, for inducing the regeneration of avascular meniscus lesions. Longitudinal meniscus tears of 4 mm in size of the lateral New Zealand White rabbit meniscus were treated with clotted autologous PRP (platelet-rich plasma) or BMAC and a meniscus suture or a meniscus suture alone. Menisci were harvested at 6 and 12 weeks after initial surgery. Macroscopical and histological evaluation was performed according to an established Meniscus Scoring System. BMAC significantly enhanced regeneration of the meniscus lesions in a time-dependent manner and in comparison to the PRP and control groups, where no healing could be observed. Treatment of avascular meniscus lesions with BMAC and meniscus suturing seems to be a promising approach to promote meniscus regeneration in the avascular zone using a one-step procedure.

Materials and structures used in meniscus repair and regeneration: a review

Meniscus is a vital functional unit in knee joint. It acts as a lubricating structure, a nutrient transporting structure, as well as shock absorber during jumping, twisting and running and offers stability within the knee joint. It helps in load distribution, in bearing the tensile hoop stresses and balancing by providing a cushion effect between hard surfaces of two bones. Meniscus may be injured in sports, dancing, accident or any over stressed condition. Any meniscal lesion can lead to a gradual development of osteoarthritis or erosion of bone contact surface due to disturbed load and contact stress distribution caused by injury/pain. Once injured, the possibilities of self-repair are rare in avascular region of meniscus, due to lack of blood supply in avascular region. Meniscus has vascular and avascular regions in structure. Majority of the meniscus parts turn avascular with increase in age.

Purpose of this review is to highlight advances in meniscus repair with special focus on tissue engineering using textile/fiber based scaffolds, as well as the recent technical advances in scaffolds for meniscus recon- struction/ regeneration treatment.

Combined autologous chondrocyte implantation and meniscus reconstruction for large chondral defect in the lateral compartment due to discoid lateral meniscus tear: A case report

Discoid lateral meniscus tear leads to large chondral defect in the lateral compartment of the knee joint. There are few effective treatments for large chondral defect in both the tibial and femoral sides with severe degenerative lateral meniscus. We have developed a combined autologous chondrocyte implantation and meniscus reconstruction technique using hamstring tendon. This technique allows biological reconstruction and avoids knee arthroplasty.

•

Discoid lateral meniscus tear leads to large chondral defect.

•

A combination of autologous chondrocyte implantation and meniscus reconstruction technique using hamstring tendon is introduced.

•

This novel method allows biological reconstruction.

Tissue Engineering of Large Full-Size Meniscus Defects by a Polyurethane Scaffold: Accelerated Regeneration by Mesenchymal Stromal Cells

The endogenous healing potential of avascular meniscal lesions is poor. Up to now, partial meniscectomy is still the treatment of choice for meniscal lesions within the avascular area. However, the large loss of meniscus substance predisposes the knee for osteoarthritic changes. Tissue engineering techniques for the replacement of such lesions could be a promising alternative treatment option. Thus, a polyurethane scaffold, which is already in clinical use, loaded with mesenchymal stromal cells, was analyzed for the repair of critical meniscus defects in the avascular zone. Large, approximately 7 mm broad meniscus lesions affecting both the avascular and vascular area of the lateral rabbit meniscus were treated with polyurethane scaffolds either loaded or unloaded with mesenchymal stromal cells. Menisci were harvested at 6 and 12 weeks after initial surgery. Both cell-free and cell-loaded approaches led to well-integrated and stable meniscus-like repair tissue. However, an accelerated healing was achieved by the application of mesenchymal stromal cells. Dense vascularization was detected throughout the repair tissue of both treatment groups. Overall, the polyurethane scaffold seems to promote the vessel ingrowth. The application of mesenchymal stromal cells has the potential to speed up the healing process.

Meniscal repair and regeneration: Current strategies and future perspectives

The management of meniscal injuries remains difficult and challenging. Although several clinical options exist for the treatment of such injuries, complete regeneration of the damaged meniscus has proved difficult due to the limited healing capacity of the tissue. With the advancements in tissue engineering and cell-based technologies, new therapeutic options for patients with currently incurable meniscal lesions now potentially exist. This review will discuss basic anatomy, current repair techniques and treatment options for loss of meniscal integrity. Specifically, we focus on the possibility and feasibility of the latest tissue engineering approaches, including 3D printing technologies. Therefore, this discussion will facilitate a better understanding of the latest trends in meniscal repair and regeneration, and contribute to the future application of such clinical therapies for patients with meniscal injuries.

Effect of serum and platelet-rich plasma on human early or advanced degenerative meniscus cells

PURPOSE

The purpose of this in vitro study was to evaluate the migratory, proliferating, and extracellular matrix (ECM) forming effect of human serum (HS) and platelet-rich plasma (PRP) on meniscus cells derived from human knees with early or advanced degenerative changes.

MATERIALS AND METHODS

Medial menisci from knees with early degenerative changes (n = 5; mean Kellgren score of 1) undergoing arthroscopic meniscal surgery and advanced degenerative changes (n = 5; mean Kellgren score of 4) undergoing total knee replacement were collected. Cell migration and proliferation upon stimulation with HS and PRP were assessed by migration and proliferation assays. Induction of meniscal ECM was evaluated histologically by hematoxylin and eosin, collagen type I, and alcian blue staining and by gene expression analysis of meniscus-related genes in pellets that have been stimulated with 10% HS or 5% PRP.

RESULTS

Meniscal cells from knees with early and advanced degenerative changes were significantly attracted by 2.5%-30% PRP or 10% HS. Cell proliferation was significantly increased upon stimulation with 10% HS or 5% PRP. Both cell groups showed the formation of a well-structured, meniscus-like ECM after stimulation with 10% HS, whereas stimulation with 5% PRP led to inhomogeneous, more fibrous ECM. Stimulation with 10% HS showed a significant induction of aggrecan and COMP, while 5% PRP showed no inducing effect.

CONCLUSIONS

Only stimulation with HS showed the formation of meniscal ECM as well as cell proliferating and migratory effects on meniscal cells derived from knees with early or advanced degenerative changes. Thus, we suggest that the selected stimulating factor itself and not the status of the knee may primarily affect repair processes. HS may have a potential to augment in meniscal repair procedures.

Characteristics of meniscus progenitor cells migrated from injured meniscus

Serious meniscus injuries seldom heal and increase the risk for knee osteoarthritis; thus, there is a need to develop new reparative therapies. In that regard, stimulating tissue regeneration by autologous stem/progenitor cells has emerged as a promising new strategy. We showed previously that migratory chondrogenic progenitor cells (CPCs) were recruited to injured cartilage, where they showed a capability in situ tissue repair. Here, we tested the hypothesis that the meniscus contains a similar population of regenerative cells. Explant studies revealed that migrating cells were mainly confined to the red zone in normal menisci: However, these cells were capable of repopulating defects made in the white zone. In vivo, migrating cell numbers increased dramatically in damaged meniscus. Relative to non-migrating meniscus cells, migrating cells were more clonogenic, overexpressed progenitor cell markers, and included a larger side population. Gene expression profiling showed that the migrating population was more similar to CPCs than other meniscus cells. Finally, migrating cells equaled CPCs in chondrogenic potential, indicating a capacity for repair of the cartilaginous white zone of the meniscus. These findings demonstrate that, much as in articular cartilage, injuries to the meniscus mobilize an intrinsic progenitor cell population with strong reparative potential. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1966-1972, 2017.

Relevance of meniscal cell regional phenotype to tissue engineering

PURPOSE

Meniscus contains heterogeneous populations of cells that have not been fully characterized. Cell phenotype is often lost during culture; however, culture expansion is typically required for tissue engineering. We examined and compared cell-surface molecule expression levels on human meniscus cells from the vascular and avascular regions and articular chondrocytes while documenting changes during culture-induced dedifferentiation.

MATERIALS AND METHODS

Expressions of 16 different surface molecules were examined by flow cytometry after monolayer culture for 24 h, 1 week, and 2 weeks. Menisci were also immunostained to document the spatial distributions of selected surface molecules.

RESULTS

Meniscus cells and chondrocytes exhibited several similarities in surface molecule profiles with dynamic changes during culture. A greater percentage of meniscal cells were positive for CD14, CD26, CD49c, and CD49f compared to articular chondrocytes. Initially, more meniscal cells from the vascular region were positive for CD90 compared to cells from the avascular region or chondrocytes. Cells from the vascular region also expressed higher levels of CD166 and CD271 compared to cells from the avascular region. CD90, CD166, and CD271-positive cells were predominately perivascular in location. However, CD166-positive cells were also located in the superficial layer and in the adjacent synovial and adipose tissue.

CONCLUSIONS

These surface marker profiles provide a target phenotype for differentiation of progenitors in tissue engineering. The spatial location of progenitor cells in meniscus is consistent with higher regenerative capacity of the vascular region, while the surface progenitor subpopulations have potential to be utilized in tears created in the avascular region.

Isolation, Characterization, and Multipotent Differentiation of Mesenchymal Stem Cells Derived from Meniscal Debris

This study aimed to culture and characterize mesenchymal stem cells derived from meniscal debris. Cells in meniscal debris from patients with meniscal injury were isolated by enzymatic digestion, cultured in vitro to the third passage, and analyzed by light microscopy to observe morphology and growth. Third-passage cultures were also analyzed for immunophenotype and ability to differentiate into osteogenic, adipogenic, and chondrogenic lineages. After 4-5 days in culture, cells showed a long fusiform shape and adhered to the plastic walls. After 10-12 days, cell clusters and colonies were observed. Third-passage cells showed uniform morphology and good proliferation. They expressed CD44, CD90, and CD105 but were negative for CD34 and CD45. Cultures induced to differentiate via osteogenesis became positive for Alizarin Red staining as well as alkaline phosphatase activity. Cultures induced to undergo adipogenesis were positive for Oil Red O staining. Cultures induced to undergo chondrogenesis were positive for staining with Toluidine Blue, Alcian Blue, and type II collagen immunohistochemistry, indicating cartilage-specific matrix. These results indicate that the cells we cultured from meniscal debris are mesenchymal stem cells capable of differentiating along three lineages. These stem cells may be valuable source for meniscal regeneration.

Effect of Human Serum and 2 Different Types of Platelet Concentrates on Human Meniscus Cell Migration, Proliferation, and Matrix Formation

PURPOSE

To evaluate the effect of 10% human serum (HS), 5% platelet-rich plasma (PRP), and 5% autologous conditioned plasma (ACP) on migration, proliferation, and extracellular matrix (ECM) synthesis of human meniscus cells.

METHODS

Cell migration and proliferation on stimulation with HS, PRP, and ACP were assessed by chemotaxis assays and measurement of genomic DNA content. Meniscus cells were cultivated in pellets stimulated with 10% HS, 5% PRP, or 5% ACP. Meniscal ECM formation was evaluated by histochemical staining of collagen type I, type II, and proteoglycans and by analysis of fibrochondrocyte marker gene expression.

RESULTS

Human meniscus cells were significantly attracted by all 3 blood-derived products (10% HS and 5% ACP: P = .0001, 5% PRP: P = .0002). Cell proliferation at day 9 was significantly increased on stimulation with 10% HS (P = .0001) and 5% PRP (P = .0002) compared with 5% ACP and controls. Meniscus cell pellet cultures showed the formation of a well-structured meniscal ECM with deposition of collagen type I, type II, and proteoglycans on stimulation with 10% HS, whereas 5% PRP or 5% ACP resulted in the formation of an inhomogeneous and more fibrous ECM. Stimulation with 10% HS and 5% ACP showed a significant induction of fibrochondrocyte marker genes such as aggrecan (HS: P = .0002, ACP: P = .0147), cartilage oligomeric matrix protein (HS: P = .0002, ACP: P = .0005), and biglycan (HS: P = .0002, ACP: P = .0003), whereas PRP showed no inducing effect.

CONCLUSIONS

Among all tested blood-derived products, only stimulation with HS showed the formation of a meniscal ECM as well as positive cell proliferating and migrating effects in vitro. Regarding a potential biological repair of nonvascular meniscus lesions, our results may point toward the use of HS as a beneficial augment in regenerative meniscus repair approaches.

CLINICAL RELEVANCE

Our findings may suggest that HS might be a beneficial augment for meniscus repair.

Cell-Based Strategies for Meniscus Tissue Engineering

Meniscus injuries remain a significant challenge due to the poor healing potential of the inner avascular zone. Following a series of studies and clinical trials, tissue engineering is considered a promising prospect for meniscus repair and regeneration. As one of the key factors in tissue engineering, cells are believed to be highly beneficial in generating bionic meniscus structures to replace injured ones in patients. Therefore, cell-based strategies for meniscus tissue engineering play a fundamental role in meniscal regeneration. According to current studies, the main cell-based strategies for meniscus tissue engineering are single cell type strategies; cell coculture strategies also were applied to meniscus tissue engineering. Likewise, on the one side, the zonal recapitulation strategies based on mimicking meniscal differing cells and internal architectures have received wide attentions. On the other side, cell self-assembling strategies without any scaffolds may be a better way to build a bionic meniscus. In this review, we primarily discuss cell seeds for meniscus tissue engineering and their application strategies. We also discuss recent advances and achievements in meniscus repair experiments that further improve our understanding of meniscus tissue engineering.

In Vitro Testing of Scaffolds for Mesenchymal Stem Cell-Based Meniscus Tissue Engineering-Introducing a New Biocompatibility Scoring System

A combination of mesenchymal stem cells (MSCs) and scaffolds seems to be a promising approach for meniscus repair. To facilitate the search for an appropriate scaffold material a reliable and objective in vitro testing system is essential. This paper introduces a new scoring for this purpose and analyzes a hyaluronic acid (HA) gelatin composite scaffold and a polyurethane scaffold in combination with MSCs for tissue engineering of meniscus. The pore quality and interconnectivity of pores of a HA gelatin composite scaffold and a polyurethane scaffold were analyzed by surface photography and Berliner-Blau-BSA-solution vacuum filling. Further the two scaffold materials were vacuum-filled with human MSCs and analyzed by histology and immunohistochemistry after 21 days in chondrogenic media to determine cell distribution and cell survival as well as proteoglycan production, collagen type I and II content. The polyurethane scaffold showed better results than the hyaluronic acid gelatin composite scaffold, with signs of central necrosis in the HA gelatin composite scaffolds. The polyurethane scaffold showed good porosity, excellent pore interconnectivity, good cell distribution and cell survival, as well as an extensive content of proteoglycans and collagen type II. The polyurethane scaffold seems to be a promising biomaterial for a mesenchymal stem cell-based tissue engineering approach for meniscal repair. The new score could be applied as a new standard for in vitro scaffold testing.

Meniscus repair using mesenchymal stem cells - a comprehensive review

The menisci are a pair of semilunar fibrocartilage structures that play an essential role in maintaining normal knee function. Injury to the menisci can disrupt joint stability and lead to debilitating results. Because natural meniscal healing is limited, an efficient method of repair is necessary. Tissue engineering (TE) combines the principles of life sciences and engineering to restore the unique architecture of the native meniscus. Mesenchymal stem cells (MSCs) have been investigated for their therapeutic potential both in vitro and in vivo. This comprehensive review examines the English literature identified through a database search using Medline, Embase, Engineering Village, and SPORTDiscus. The search results were classified based on MSC type, animal model, and method of MSC delivery/culture. A variety of MSC types, including bone marrow-derived, synovium-derived, adipose-derived, and meniscus-derived MSCs, has been examined. Research results were categorized into and discussed by the different animal models used; namely murine, leporine, porcine, caprine, bovine, ovine, canine, equine, and human models of meniscus defect/repair. Within each animal model, studies were categorized further according to MSC delivery/culture techniques. These techniques included direct application, fibrin glue/gel/clot, intra-articular injection, scaffold, tissue-engineered construct, meniscus tissue, pellets/aggregates, and hydrogel. The purpose of this review is to inform the reader about the current state and advances in meniscus TE using MSCs. Future directions of MSC-based meniscus TE are also suggested to help guide prospective research.

Meniscus tissue engineering using a novel combination of electrospun scaffolds and human meniscus cells embedded within an extracellular matrix hydrogel

Meniscus injury and degeneration have been linked to the development of secondary osteoarthritis (OA). Therapies that successfully repair or replace the meniscus are, therefore, likely to prevent or delay OA progression. We investigated the novel approach of building layers of aligned polylactic acid (PLA) electrospun (ES) scaffolds with human meniscus cells embedded in extracellular matrix (ECM) hydrogel to lead to formation of neotissues that resemble meniscus-like tissue. PLA ES scaffolds with randomly oriented or aligned fibers were seeded with human meniscus cells derived from vascular or avascular regions. Cell viability, cell morphology, and gene expression profiles were monitored via confocal microscopy, scanning electron microscopy (SEM), and real-time polymerase chain reaction (PCR), respectively. Seeded scaffolds were used to produce multilayered constructs and were examined via histology and immunohistochemistry. Morphology and mechanical properties of PLA scaffolds (with and without cells) were influenced by fiber direction of the scaffolds. Both PLA scaffolds supported meniscus tissue formation with increased COL1A1, SOX9, and COMP, yet no difference in gene expression was found between random and aligned PLA scaffolds. Overall, ES materials, which possess mechanical strength of meniscus and can support neotissue formation, show potential for use in cell-based meniscus regeneration strategies.

A new method for meniscus repair using type I collagen scaffold and infrapatellar fat pad

AIM

The aim of this study was to investigate a new method for meniscal repair by combinative transplantation with type I collagen scaffold and infrapatellar fat pad.

METHODS

Two-mm cylindrical defects at the anterior part of bilateral medial menisci were prepared in nine Japanese white rabbits. The 18 knees were equally divided into three groups: I, no treatment; II, collagen scaffold transplantation; and III, collagen scaffold and infrapatellar fat pad transplantation. Another three rabbits (six knees) underwent sham surgery and served as controls. Rabbits were sacrificed at eight weeks after transplantation. Surface area of the medial meniscus was evaluated using macrophotographs. Ishida score for meniscal regeneration was used for assessment. To evaluate the composition of regenerated tissue, immunohistochemistry was analyzed with anti-type I and anti-type II collagen antibodies, and anti-Ki67 antibody. To investigate the effects of collagen scaffold on human meniscus, cells were isolated from human meniscus and infrapatellar fat pad, and cultured with collagen scaffold for three weeks. After that, gene expression was evaluated by using quantitative real-time polymerase chain reaction.

RESULTS

In group I, the meniscus shrank anterior to posterior, and the surface area was significantly less than that of normal meniscus. However, the surface area was maintained in group III. Ishida score and Ki67-positive cell ratio in group III were significantly higher than that in any other group, and staining with type I and type II collagen was similar to that of the control. Expression of matrix metalloproteinase was significantly lower in cocultures of collagen scaffold, meniscus cell, and infrapatellar fat pad cell than in monocultured meniscus cell, and expression of interleukin-1β was not increased.

CONCLUSION

This new method for meniscal repair by combinative transplantation with type I collagen scaffold and infrapatellar fat pad showed meniscal regeneration and potential for suppressing inflammation.

Why menisci show higher healing rate when repaired during ACL reconstruction? Growth factors release can be the explanation

PURPOSE

Healing rate of meniscus repair is higher when the suture is associated with anterior cruciate ligament reconstruction. A possible explanation can be a different pattern of release of growth factors between anterior cruciate ligament reconstruction and isolated meniscus surgery. Hypothesis of this study is that the concentrations of bFGF, TGF-β and platelet-derived growth factor (PDGF) in joint fluid, immediately after single-bundle anterior cruciate ligament reconstruction and arthroscopic partial meniscectomy, can be different.

METHODS

Twenty consecutive patients underwent partial medial meniscectomy and twenty consecutive patients underwent single-bundle anterior cruciate ligament reconstruction with hamstring grafts were enrolled in the study. Thirty minutes after the end of the surgical procedure, a sample of joint fluid, as well of venous blood, was collected from all the patients. Concentrations of growth factors were determined by enzyme-linked immunosorbent assay.

RESULTS

The peripheral blood concentration of TGF-β, bFGF and PDGF was comparable between partial meniscectomy and anterior cruciate ligament reconstruction groups. No differences between the two surgical techniques were also found in term of TGF-β and bFGF joint fluid concentration, whereas joint PDGF concentration of anterior cruciate ligament reconstruction patients was significantly higher than the one found in partial meniscectomy patients.

CONCLUSIONS

A significant growth factors release was detected in the knee joint during arthroscopic surgery. PDGF concentration was significantly higher in anterior cruciate ligament reconstructed knee than in the meniscectomy group. PDGF can play an important role enhancing the healing response of meniscus suture and can be one of the biological reasons of the higher meniscal healing rate in anterior cruciate ligament reconstructed knee.

Enhanced depth-independent chondrocyte proliferation and phenotype maintenance in an ultrasound bioreactor and an assessment of ultrasound dampening in the scaffold

Chondrocyte-seeded scaffolds were cultured in an ultrasound (US)-assisted bioreactor, which supplied the cells with acoustic energy around resonance frequencies (~5.0 MHz). Polyurethane-polycarbonate (BM), chitosan (CS) and chitosan-n-butanol (CSB) based scaffolds with varying porosities were chosen and the following US regimen was employed: 15 kPa and 60 kPa, 5 min per application and 6 applications per day for 21 days. Non-stimulated scaffolds served as control. For BM scaffolds, US stimulation significantly impacted cell proliferation and depth-independent cell population density compared to controls. The highest COL2A1/COL1A1 ratios and ACAN mRNA were noted on US-treated BM scaffolds compared to controls. A similar trend was noted on US-treated cell-seeded CS and CSB scaffolds, though COL2A1/COL1A1 ratios were significantly lower compared to BM scaffolds. Expression of Sox-9 was also elevated under US and paralleled the COL2A1/COL1A1 ratio. As an original contribution, a simplified mathematical model based on Biot theory was developed to understand the propagation of the incident US wave through the scaffolds and the model analysis was connected to cellular responses. Scaffold architecture influenced the distribution of US field, with the US field being the least attenuated in BM scaffolds, thus coupling more mechanical energy into cells, and leading to increased cellular activity.

Updates in biological therapies for knee injuries: menisci

The preservation of meniscal tissue is paramount for long-term joint function, especially in younger patients who are athletically active. Many studies have reported encouraging results following the repair of meniscus tears, including both simple longitudinal tears located in the periphery and complex multiplanar tears that extend into the central third avascular region. However, most types of meniscal lesions are managed with a partial meniscectomy. Options to restore the meniscus range from an allograft transplantation to the use of synthetic and biological technologies. Recent studies have demonstrated good long-term outcomes with meniscal allograft transplantation, although the indications and techniques continue to evolve, and the long-term chondroprotective potential of this approach has yet to be determined. Several synthetic implants, most of which are approved in the European market, have shown some promise for replacing part of or the entire meniscus, including collagen meniscal implants, hydrogels, and polymer scaffolds. Currently, there is no ideal implant generated by means of tissue engineering. However, meniscus tissue engineering is a fast developing field that promises to develop an implant that mimics the histologic and biomechanical properties of a native meniscus.