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MEFISTO - Meniscal functionalised scaffold to prevent knee Osteoarthritis onset after meniscectomy

Periodic Reporting for period 2 - MEFISTO (MEFISTO - Meniscal functionalised scaffold to prevent knee Osteoarthritis onset after meniscectomy)

Reporting period: 2020-12-01 to 2022-05-31

Meniscal injuries are one of the most common orthopaedic disorders with increasing incidence due to active live styles across all age groups. The preferred approach to treat the injured meniscus has been the removal of damaged tissue (meniscectomy), a practice that has expanded with the advent of arthroscopy.
The meniscus-deficient knee has been associated with poor clinical outcomes due to impaired load-bearing and deterioration of articular cartilage, which with time progresses to osteoarthritis (OA) Whilst understanding of meniscal function and management of meniscal injuries has evolved and the consequences of meniscus loss are known, meniscectomy remains a common treatment as it is simple and fast, and not all meniscal tears are repairable. Thus, an increased incidence of post-meniscectomy OA is expected in Europe in the coming years. Management of younger and active patients with meniscus loss is particularly challenging. They often suffer from disability and need early knee replacement that will place huge costs and burdens on health systems. Although meniscal repair and replacement has advanced tremendously, options are still limited. Meniscal allograft implantation for total meniscus loss is complicated by limited availability and local regulatory restrictions. For partial meniscus loss an acellular synthetic scaffold is available, but indications are limited and long-term results controversial. Tissue engineering approaches are not yet available for clinical use. Thus, currently available treatment options for meniscectomy patients are limited.
MEFISTO’s objective is to develop innovative approaches using bioactive functionalised materials for meniscus tissue replacement as a strategy to prevent the onset of a post-meniscectomy OA epidemic. Our three-pronged approach is to develop two novel treatment solutions for meniscus loss, to provide a predictive treatment algorithm based on morphologic profiling of meniscectomized patients, and to analyse the socio-economic environment. The treatment solutions follow two different strategies: one is a bioactive, degradable scaffold for the regeneration of the native meniscus for younger patients with early degeneration and the other is a bioactive, non-degradable meniscal implant, designed as a drug delivery system to modulate the inflammatory environment for patients with advanced knee OA.
Work along different tasks has been performed for the MEFISTO project.
For the morphological profiling of meniscectomized patients clinical and imaging (MRI) data have been collected for 120 asymptomatic (low-risk) and 120 symptomatic (high-risk) post-meniscectomy patients and 22 healthy knee controls. MRI scans were manually segmented and a catalogue with 240 accurate post-meniscectomy 3D knee models was built. To speed up the process, automated segmentation of MRIs by neural networks was applied but has not yet resulted in a general segmentation algorithm. Statistical shape analysis of the 3D knee models was performed and strategies to identify automated classifiers for high- versus low-risk knees with good prediction have been investigated. Input geometry, loading and boundary conditions have been defined for the FE model to investigate the shape-contact force relation within the knee.
For the bioactive degradable scaffold, a collagen bio-ink material was selected for 3D printing. A cost-effective 3D printing method was developed, and a human size collagen meniscus implant based on medial meniscus MRI data could be printed. Printability of the collagen scaffold was further optimized to obtain good porosity and a dual-zone meniscus structure. The 3D printed dual-zone meniscus was reinforced to allow suturing. Our specialists in peptide technology and for drug-loaded micro/nanoparticles developed methods for the functionalization of the collagen bio-ink, to achieve modulation of angiogenesis and stem cell response. Novel dendrimer/peptide complexes, as well as micro/nanoparticles loaded with active factors were manufactured and were successfully incorporated into collagen scaffolds, in a zonally dependent manner to mimic the anisotropic structure of human meniscus. Samples of the functionalized human size medial meniscus were printed and are available for handling tests.
The non-biodegradable meniscal implant with drug delivery capabilities is developed from a biocompatible medical grade polymer (PCU). Two 3D printing manufacturing paths were investigated: direct implant printing using PCU powder by SLS and printing of metal tooling for patient specific implants by injection molding. Implants were manufactured with both methods and mechanically tested with good results. This method of 3D printed metal tooling for injection molding of implants was selected to produce the implants needed for the sheep study. For functionalization of the non-degradable implant, the implant surface was coated with polymeric layers that release anti-inflammatory drugs with defined release kinetics. Plasma treatment of the implant surface improved adhesion of the polymer/drug coating on the surface and enabled coated samples to withstand mechanical testing. A method to functionalize PCU implants with anti-inflammatory peptide complexes was also developed.
Our experts in pre-clinical evaluation have established in-vitro immunotoxicology, biocompatibility and efficacy models for testing of printed scaffolds with and without functionalization. Initial testing of functionalized non-biodegradable constructs, free drugs and dendrimers was done. For the in-vivo animal testing, two submissions to local ethics committees were completed. For the sheep study, the study protocol was finalized.
Dissemination of the project is ongoing through the MEFISTO website, social media channels, and presentations at orthopaedic conferences. An educational documentary on meniscus, its anatomy, injuries, and current treatment options has been produced and was presented at international congresses.
The technological innovation lies in the development of novel bioactive implants that interact with the surrounding articular tissues in a pre-determined fashion for different degrees of joint degeneration.
Currently, there are no reliable predictive factors for OA progression in a post meniscectomy knee. Most meniscus patients present severe symptoms to the surgeon, too late for reconstructive procedures which puts their knee at risk of requiring joint replacement. Thus, early identification and treatment of high-risk patients pre-disposed to knee OA after meniscectomy is vital. The impact of MEFISTO is expected to be significant, as there are many patients who have had and still undergo meniscectomy. The solutions developed in MEFISTO aim at preventing patients from receiving early joint replacement after meniscus loss. This will reduce costs and morbidity associated with early OA and decrease the social burden on health systems. A socio-economic analysis for the cost-effectiveness of meniscal substitutes in Europe and an impact assessment of the benefits of MEFISTO for healthcare is done. The methods for the health-economic model and relevant input parameters were defined and first data was collected to assess the MEFISTO impact and key performance indicators were defined through interactions with health care professionals and patient associations.
The MEFISTO concept