Clinical Replacement Strategies for Meniscus Tissue Deficiency

Meniscal Allograft versus Synthetic Graft in Treatment Outcomes of Meniscus Repair: A Mini-review and Meta-analysis

Meniscal injuries are highly correlated with osteoarthritis (OA) onset and progression. Although meniscal allograft transplantation (MAT) is a therapeutic option to restore meniscal anatomy, a shortage of donor material and the donor-derived infectious risk may be concerns in clinics. This review summarizes the literature reporting meniscus repair status in preclinical models and clinical practice using allografts or synthetic grafts. The advantages and limitations of biodegradable polymer-based meniscal scaffolds, applied in preclinical studies, are discussed. Then, the long-term treatment outcomes of patients with allografts or commercial synthetic scaffolds are compared. A total of 47 studies are included in our network meta-analysis. Compared with the meniscal allografts, the commercial synthetic products significantly improved clinical treatment outcomes in terms of the Knee Injury and Osteoarthritis Outcome Score (KOOS), Visual Analog Scale (VAS) scores, and Lysholm scores. In addition, development strategies for the next generation of novel synthetic scaffolds are proposed through optimization of structural design and fabrication, and selection of cell sources, external stimuli, and active ingredients. This review may inspire researchers and surgeons to design and fabricate clinic-orientated grafts with improved treatment outcomes.

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 minimum 2 year follow-up using the PearlDiver database. Using Current Procedural Terminology (CPT) and International Classification of Diseases (ICD) 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

750 patients were included 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). 90-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 (OR: 4.88; 95% CI: 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 (OR: 6.95; 95% CI: 1.45-25.96; p=.006), with no difference in reoperation rates 2 years post-operatively or to the end of follow-up. Osteochondral autograft and allograft were not associated with increased reoperation rates.

CONCLUSION

14.4% of patients in our cohort had a reoperation within 2 years of MAT. Nearly one in four 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.

Current advances in engineering meniscal tissues: insights into 3D printing, injectable hydrogels and physical stimulation based strategies

The knee meniscus is the cushioning fibro-cartilage tissue present in between the femoral condyles and tibial plateau of the knee joint. It is largely avascular in nature and suffers from a wide range of tears and injuries caused by accidents, trauma, active lifestyle of the populace and old age of individuals. Healing of the meniscus is especially difficult due to its avascularity and hence requires invasive arthroscopic approaches such as surgical resection, suturing or implantation. Though various tissue engineering approaches are proposed for the treatment of meniscus tears, three-dimensional (3D) printing/bioprinting, injectable hydrogels and physical stimulation involving modalities are gaining forefront in the past decade. A plethora of new printing approaches such as direct light photopolymerization and volumetric printing, injectable biomaterials loaded with growth factors and physical stimulation such as low-intensity ultrasound approaches are being added to the treatment portfolio along with the contemporary tear mitigation measures. This review discusses on the necessary design considerations, approaches for 3D modeling and design practices for meniscal tear treatments within the scope of tissue engineering and regeneration. Also, the suitable materials, cell sources, growth factors, fixation and lubrication strategies, mechanical stimulation approaches, 3D printing strategies and injectable hydrogels for meniscal tear management have been elaborated. We have also summarized potential technologies and the potential framework that could be the herald of the future of meniscus tissue engineering and repair approaches.

Development of a highly concentrated collagen ink for the creation of a 3D printed meniscus

The most prevalent extracellular matrix (ECM) protein in the meniscus is collagen, which controls cell activity and aids in preserving the biological and structural integrity of the ECM. To create stable and high-precision 3D printed collagen scaffolds, ink formulations must possess good printability and cytocompatibility. This study aims to overlap the limitation in the 3D printing of pure collagen, and to develop a highly concentrated collagen ink for meniscus fabrication. The extrusion test revealed that 12.5 % collagen ink had the best combination of high collagen concentration and printability. The ink was specifically designed to have load-bearing capacity upon printing and characterized with respect to rheological and extrusion properties. Following printing of structures with different infill, a series of post-processing steps, including salt stabilization, pH shifting, washing, freeze-drying, crosslinking and sterilization were performed, and optimised to maintain the stability of the engineered construct. Mechanical testing highlighted a storage modulus of 70 kPa for the lower porous structure while swelling properties showed swelling ratio between 9 and 11 after 15 min of soaking. Moreover, human avascular and vascular meniscus cells cultured on the scaffolds deposited a meniscus-like matrix containing collagen I, II and glycosaminoglycans after 28 days of culture. Finally, as proof-of-concept, human size 3D printed meniscus scaffold were created.

Short-term transplantation effect of a tissue-engineered meniscus constructed using drilled allogeneic acellular meniscus and BMSCs

During the construction of tissue-engineered meniscus, the low porosity of extracellular matrix restricts the flow of nutrient solution and the migration and proliferation of cells, thus affecting the tissue remodeling after transplantation. In this study, the canine allogeneic meniscus was drilled first and then decellularized. The drilled tissue-engineered menisci (Drilled Allogeneic Acellular Meniscus + Bone Marrow Mesenchymal Stem Cells, BMSCs) were transplanted into the knee joints of model dogs. On the basis of ensuring the mechanical properties, the number of the porosity and the cells implanted in allogeneic acellular meniscus was significantly increased. The expression levels of glycosaminoglycans and type II collagen in the drilled tissue-engineered meniscus were also improved. It was determined that the animals in the experimental group recovered well-compared with those in the control group. The graft surface was covered with new cartilage, the retraction degree was small, and the tissue remodeling was good. The surface wear of the femoral condyle and tibial plateau cartilage was light. The results of this study showed that increasing the porosity of allogeneic meniscus by drilling could not only maintain the mechanical properties of the meniscus and increase the number of implanted cells but also promote cell proliferation and differentiation. After transplantation, the drilled tissue-engineered meniscus provided a good remodeling effect in vivo and played a positive role in repairing meniscal injury, protecting articular cartilage and restoring knee joint function.

Selective Extracellular Matrix Guided Mesenchymal Stem Cell Self-Aggregate Engineering for Replication of Meniscal Zonal Tissue Gradient in a Porcine Meniscectomy Model

Degenerative meniscus tears (DMTs) are prevalent findings in osteoarthritic knees, yet current treatment is mostly limited to arthroscopic partial meniscectomy rather than regeneration, which further exacerbates arthritic changes. Translational research regarding meniscus regeneration is hindered by the complex, composite nature of the meniscus which exhibit a gradient from inner cartilage-like tissue to outer fibrous tissue, as well as engineering hurdles often requiring growth factors and cross-linking agents. Here, a meniscus zonal tissue gradient is proposed using zone-specific decellularized meniscus extracellular matrix (DMECM) and autologous synovial mesenchymal stem cells (SMSC) via self-aggregation without the use of growth factors or cross-linking agents. Combination with zone-specific DMECM during self-aggregation of MSCs forms zone-specific meniscus tissue that reflects the respective DMECM harvest site. The implantation of these constructs leads to the regeneration of meniscus tissue resembling the native meniscus, demonstrating inner cartilaginous and outer fibrous characteristics as well as recovery of native meniscal microarchitecture in a porcine partial meniscectomy model at 6 months. In all, the findings offer a potential regenerative therapy for DMTs that may improve current partial meniscectomy-based patient care.