Freeze-Dried Chitosan-PRP Injectable Surgical Implants for Meniscus Repair: Pilot Feasibility Studies in Ovine Models

Clinical management of meniscus tears often involves partial meniscectomy, which can lead to Osteoarthritis (OA). Meniscus repair augmentation strategies are being developed to compensate for the tissue’s limited healing response. The purpose of the study was to assess the feasibility of using implants composed of freeze-dried Chitosan (CS) solubilized in Platelet-Rich Plasma (PRP) to improve meniscus repair in ovine models. Lyophilized formulations containing 1% (w/v) chitosan (degree of deacetylation 82% and number average molar mass 38 kDa), 1% (w/v) trehalose and 42.2 mM calcium chloride were solubilized in autologous PRP and applied to surgically induced meniscus lacerations. In the first study, bilateral tears in 7 ewes were treated by suturing, trephination and injecting either CS-PRP (10 knees) or PRP (4 knees) into the tears. In the second study, unilateral tears in 6 ewes were treated by suturing, trephination and injecting CS-PRP in the tears (2 knees), wrapping the meniscus with a collagen membrane and injecting CS-PRP in the tears and under the wrap (2 knees) or wrapping only (2 knees). CS-PRP implants were partly resident in the tears and trephination channels at 1 day, where they induced cell recruitment from the vascularized periphery of the menisci. Complete repair and seamless repair tissue integration were observed in 1 out of 4 CS-PRP treated defects in the first study after 3 months and in 1 out of 2 CS-PRP treated defects in the second study after 6 weeks, while there was no healing with PRP or wrapping alone. These pilot feasibility studies demonstrated that CS-PRP injectable implants display some potential to improve meniscus repair outcomes in pre-clinical models and could overcome some of the current limitations of meniscus repair by assisting in restoring meniscus structure and function.