Purpose

1) to report the clinical and radiographic outcomes of meniscus repair procedures in patients age 60 or older and compare them to matched patients who were treated with meniscectomy, and 2) to identify procedural failures.

Methods and Materials

The study cohort included patients over 60 years of age who underwent meniscus repair at a single medical institution (Mayo Clinic, Rochester, MN, USA). Medical records were reviewed to obtain demographic information, clinical history, physical exam findings, imaging details, and treatment details. The study cohort were matched by age (within 5 years), sex, BMI (within 5 years), and tear location (medial or lateral) with a comparative cohort. All patients were interviewed and completed a questionnaire comprising of IKDC (International Knee Documentation Committee Subjective Knee Form), KOOS and the Lysholm Knee Scoring Scale.

Results

81 patients (52 F: 29 M; 81 total knees) over the age of 60 with meniscus tears were included with a mean follow-up duration of 42.2 (±23.6) months. Mean age was 64.5 ( 4.4) years. Most knees had a tear of the medial meniscus (72.8%), while the lateral meniscus was torn in 27.2% of cases. In the majority of tears involved the meniscus root (56.8%), followed by the posterior horn (34.6%), and the mid-body (8.6%). At follow-up, the IKDC Subjective Knee Form Score was 78.9 ± 13.4 in the repair group and 56.0 (±15.4) in the meniscectomy group, the KOOS Knee Injury and Osteoarthritis Outcome Score 86.6 (±11.9) and 61.7 (±16.2) and the Lysholm Score 88.3 (±13.3) and 68.7 (±15.2) respectively. All scores were significantly superior in the repair group compared to the meniscectomy group (P < .001).

Conclusion

Meniscus repair provides superior clinical results at mean follow up of 42.2 months compared to partial meniscectomy. Meniscus repair should be considered when indicated even in patients at or over the age of 60.

Purpose

This research longitudinally tests the clinical trial hypothesis that investigational subjects realize superior improvements in knee-related pain, function, and quality of life, to control subjects, through 3 years of follow-up.

Methods and Materials

242 subjects (176 investigational, 66 control) treated in 2 prospective, concurrent clinical trials in the U.S., and pooled for analysis. Subjects had persistent knee pain and one or more previous partial meniscectomies at least 6 months before trial entry. Patient-reported knee pain, function, and quality of life were assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS). Treatment cessation was defined as any investigational subject discontinuing the per-protocol treatment by permanent prosthesis removal, or control subjects undergoing any surgical procedure on the index knee. The investigational and control cohorts analyzed were compared at each time point using a two tailed t-test.

Results

The magnitude of improvement from baseline to 3 years was statistically superior in the investigational cohort, compared to the control cohort for all 6 KOOS subscales (Figure 1). Improvement in KOOS Overall and KOOS Pain for the investigational and control cohorts at 3 years were 26.4 vs 10.4 points, and 26.9 vs 15.4 points, respectively. Controls experienced a 35% decline in KOOS Overall improvement between the 2-year and 3-year timepoint (15.9 declined to 10.4). Treatment cessation through 3 years was 31% higher in the control cohort than the investigational cohort (19.6% vs.15.0%).

Conclusion

Results demonstrate statistically and clinically significant superiority for relief of knee pain and improvement in function compared to non-surgical care alone. Between 2 and 3 years, NUsurface KOOS scores remained stable, while Controls regressed. The magnitude of change from baseline to 3 years remained superior for the investigational cohort, even when accounting for subjects undergoing device exchange or repositioning.

Purpose

Meniscal tissue loss has been hypothesized as a risk factor in cartilage healing following regenerative procedures. The objective of this study was to investigate the effect of the meniscus’s condition on the clinical outcome of an aragonite-based scaffold implantation in knee joint surface lesions.

Methods and Materials

Subjects were enrolled into a large multicenter RCT. They were randomized to receive either an aragonite-based scaffold (Agili-C™, CartiHeal Ltd., Israel) (n=167) or arthroscopic debridement/microfractures (control group, n=84). The two treatment groups were further stratified based on the condition of the meniscus, differentiating between subjects who had previous partial meniscectomy, those who underwent concomitant partial meniscectomy during the study treatment, and those who presented an intact meniscus. The magnitude of change in the KOOS score was evaluated at 6, 12, 18 and 24 months to assess whether previous meniscectomy or concurrent meniscectomy correlated with clinical outcome. Furthermore, results were compared between the scaffold and the control group.

Results

In the scaffold group, 94 subjects had an intact meniscus, 23 had previous partial meniscectomy, and 47 required concomitant meniscectomy during study treatment. No significant difference was noted between the 3 sub-groups regarding KOOS score change from baseline to 24 months: previous meniscectomy patients showed an increase of 39.5 points, concomitant meniscectomy 42.9 points, and intact meniscus 43.2 points (p=n.s.). A significant improvement in the scaffold group (all 3 subgroups) was found compared to the control group, where previous meniscectomy patients (n=18) increased 15.3 points, concomitant meniscectomy (n=18) 29.3 points, and intact meniscus (n=44) 30.9 points (p<0.0001), with a larger treatment effect observed in subjects with previous meniscectomy, mostly due to the lower degree of improvement in the control group.

Conclusion

The aragonite-based scaffold provided a comparable clinical performance, not dependent on the meniscus’s condition (previous, concurrent or no meniscectomy), with significantly better outcomes than control group.

Purpose

Meniscal allograft transplantation (MAT) represents established surgical procedures with proven outcomes. Yet, storage as frozen specimens and limited cellular repopulation may impair graft viability and performance, and lead to the most common complications of shrinkage and graft tear. We hypothesize that a cell-based injection therapy combining human mesenchymal stromal cells (MSCs) and meniscus cells (MC) may enhance meniscus allograft cell repopulation, viability and healing after implantation.

Methods and Materials

Both MSCs and MCs were obtained from single donors, during a liposuction procedure and total knee arthroplasty respectively, based on IRB approved protocols. For all experiments, passage 4 MCs and MSCs were suspended with lactated ringers containing cell ratios 100% MSC, 80:20% MSC:MC or 100% MCs. MSCs membranes were labelled with PKH26 Red Fluorescent Cell Linker (Sigma-Aldrich) to investigate cell ratio and migration over time. All allografts, acquired through JRF Ortho®, were manually injected with 50ml solution, containing 0,7*10E6 cells of one of the cell ratios, each accompanied by a mock injected control sample. Injected allografts and medium were collected on multiple timepoints for histological and biochemical analysis. For each experiment, a minimum of n=3 was used per experimental group. Data are presented as a mean-standard deviation and statistical analysis was performed by multiple unpaired t tests.

Results

All groups show living cells (live/dead stain) on day 28 using confocal microscopy with a general repopulation of the graft, especially for grafts treated with cell ratios 80:20% (MSC:MC) and 100% (MC) (Fig.1 and 2). Positive immunofluorescence stain for connexin-43 was achieved for all cell ratios, indicating cell-cell communication through gap junctions. DsDNA analysis revealed a significant difference in DNA content between treated groups and controls.

Conclusion

Biological enhancement of meniscus allograft transplantation through early repopulation of the allograft is feasible with a cell-based injection therapy with monocultures of native MCs or cocultures of MSCs and meniscus cells.

Purpose

Within biofabrication, the recreation of spatially distributed vasculature is paramount, as vascular capillary ingrowth into avascular tissues can lead to tissue matrix alterations, and subsequent pathology. Multi-material 3D bioprinting is a potentially tool to recreate complex anisotropic tissue features, although to date, building complex constructs with stable vascularized and non-vascularized regions remains a challenge.

Methods and Materials

We developed a pro- and anti-angiogenic bioink by the supplementation of type I collagen (col-1) microfibers (MFs), and decellularized cartilage-derived (CdECM) MFs respectively, to an endothelial cell (EC)-laden fibrin-based bioink. By extrusion-based bioprinting, the bioinks were deposited into an anatomical meniscus shaped construct with a biomimetic outer vascularized zone containing ECs and mesenchymal stromal cells (MSCs), and an inner fibrocartilagenous zone with meniscus progenitor cells (MPCs), cultured for 14 days. To co-facilitate both microvessel formation and MPC-derived matrix formation, we tested different compositions of chondrogenic and endothelial cell culture medium formulations.

Results

The supplementation of CdECM MFs to the EC-laden fibrin-based bioinks lead to a reduction of the total microvessel length of 29%, as compared to supplementation of pro-angiogenic col-1 MFs (Figure 1). After 3D bioprinting of the zonal meniscus construct, the vascular network was confined in the outer zone (Figure 2). The co-culture of ECs and MPCs was succesful by switching from endothelial cell culture medium (EGM-2) to 10 or 25% v/v chondrogenic differentiation medium in EGM-2 medium at day 7, resulting in both EC-derived vascular networks and MPC type I collagen deposition.

Figure 1

Figure 2

Conclusion

Here, we present two bioinks that facilitate and inhibit vascular formation, by supplementation of col-1 or CdECM MFs, which were bioprinted in a biomimetic meniscus construct. This provides new strategies for grafts development of partially avascular tissues, and applications including in vitro models of vascular-to-avascular tissue interfaces, cancer progression, and for testing anti-angiogenic therapies.

Purpose

Meniscus replacement using acellular scaffolds (CMI) and allografts (meniscus allograft transplantation) are established treatment options when meniscus repair is unfeasible. Outcomes show satisfying mid-to long-term pain relief while 70% of grafts show size reduction suggesting vitality issues such as incomplete integration in the host. Analysis of in vivo biopsies show evidence of cellular repopulation while it remains controversial to what extent. Further research is needed to elucidate meniscus repopulation and remodeling to enhance meniscus tissue regeneration. We investigated in-vitro scaffold repopulation and neo-tissue formation using a novel human tissue model. This “donut and hole” model allows for the analysis of specific repopulation features such as cell types and cell migration direction.

Methods and Materials

Human meniscus tissue from patients undergoing total knee arthroplasty, allografts (JRF Ortho®) and CMI (Stryker), were obtained, cut using an 8- and 4-mm circular biopsy punch and reconstructed according to Fig.1. Tissue constructs were cultured up to 40 days in DMEM and analyzed using LIVE/DEAD assay (ThermoFisher) and histology (SafraninO and H&E).

Results

At day 0 and 7, the presence of living cells was limited to the living meniscus samples. On day 14, living cells appear at the interface of the acellular allograft. On later timepoints, cells repopulate the surface of the allograft tissue, this was not observed for the CMI. On day 40, cells derived from the living meniscus tissue repopulated the superficial layers of the allografts while deep tissue repopulation was absent (Fig.1). Remarkably, tissue construct 1A showed earlier and more extensive repopulation in comparison with construct 1B while it is generally accepted that cells involved in meniscus graft repopulation originate from the adjacent synovium (Fig.2)(Arnocszky 1992).

Conclusion

Initial results show cellular ingrowth and time dependent repopulation of the frozen allograft which suggests this in-vitro model will allow us to investigate cellular repopulation and remodeling of acellular scaffolds and allografts.

Purpose

Learning to understand meniscus tissue has gained increasing attention. Cell to cell communication and metabolism modulation are essential components. We hypothesize that meniscus cells have a similar pericellular matrix as articular cartilage chondrons. The aim of this study was to investigate optimal isolation protocols, and identify the entity and composition of a meniscon. Furthermore, we want to explore the therapeutic potential of meniscons in meniscus tissue engineering and repair, similar to the use of chondrons for articular cartilage repair.

Methods and Materials

Cartilaginous tissue was obtained from patients undergoing total knee arthroplasty based on IRB-approved protocols. Finely minced meniscus and articular cartilage tissue were digested using two different protocols: 1. 0,3% (w/v) dispase(Gibco), 0,2% (w/v) collagenase-II in DMEM supplemented with 1% P/S (5-hours), 2. Rapid digestion using Liberase-MNP (45-minutes). Isolated meniscons and chondrons were mounted using cytocentrifugation and stained with Picrosirius Red and immunostained for type VI-collagen. TEM was performed to analyze cell morphology. To investigate zonal differences in meniscus, meniscons from inner and outer regions were isolated and compared for morphology and cell/meniscon ratios. Meniscons and meniscus cells were cultured up to 14 days in fibrin glue and analyzed using biochemical assays.

Results

Meniscons and chondrons were successfully isolated using both protocols and stained positive for Picrosirius Red and type VI-collagen (Fig.1). For both chondron and meniscon, TEM shows the cell nucleus and membrane surrounded by the pericellular matrix (Fig.2). A significant higher ratio of meniscon/cell was observed for meniscons isolated from the inner meniscus vs the outer meniscus.

Conclusion

Similarly to chondrons, meniscons can be isolated from meniscus tissue using rapid digestion methods that yield meniscus cells plus their pericellular matrix. Chondrons have been used to improve repair of cartilage injuries. Similarly, meniscons could potentially be used in combination with current therapies, or by themselves, to enhance the repair of meniscus injuries.