Formation of cartilage repair tissue in articular cartilage defects pretreated with microfracture and covered with cell‐free polymer‐based implants

Abstract

The aim of our study was to evaluate the mid-term outcome of a cell-free polymer-based cartilage repair approach in a sheep cartilage defect model in comparison to microfracture treatment. Cell-free, freeze-dried implants (chondrotissue 1 ) made of a poly-glycolic acid (PGA) scaffold and hyaluronan were immersed in autologous serum and used for covering microfractured full-thickness articular cartilage defects of the sheep (n ¼ 4). Defects treated with microfracture only served as controls (n ¼ 4). Six months after implantation, cartilage implants and controls were analyzed by immunohistochemical staining of type II collagen, histological staining of proteoglycans, and histological scoring. Histological analysis showed the formation of a cartilaginous repair tissue rich in proteoglycans. Histological scoring documented significant improvement of repair tissue formation when the defects were covered with the cell-free implant, compared to controls treated with microfracture. Immunohistochemistry showed that the cell-free implant induced cartilaginous repair tissue and type II collagen. Controls treated with microfracture showed marginal formation of a mixed-type repair tissue consisting of cartilaginous tissue and fibro-cartilage. Covering of microfractured defects with the cell-free polymer-based cartilage implant is suggested to be a promising treatment option for cartilage defects and improves the regeneration of articular cartilage. ß

A Cell-free Scaffold-based Cartilage Repair Provides Improved Function Hyaline-like Repair at One year

“…Previous scaffold application with a PRP gel showed better histologic total scores than for the microfracture-only group [19] and resulted in proteoglycan-enriched and type II collagen-positive repair tissue [4]. Our histologic findings at the 9-month followup are in line with those of previous studies [4,7,8] showing the formation of hyaline-like cartilage repair tissue with type II collagen.…”

“…In a previous study reporting 67 patients with 2 years followup comparing ACI with microfracture, none of the 55 of 67 patients with predominantly hyaline-like cartilage repair tissue had later failure [15]. Preclinical studies, covering microfractured ovine cartilage defects with a PGA-hyaluronan scaffold immersed with autologous serum, showed hyaline-like repair tissue formation in contrast to inferior fibrocartilage formation in a noncovered microfracture control group [7,8]. Clinical case report studies suggest the use of this technique for cartilage repair resulted in defect filling, formation of hyaline-like cartilage, and improvement in patients 0 pain and knee function at the 1-and 2-year followups [22,38].…”

“…Polymers like PGA-hyaluronan for in vivo cartilage tissue repair reportedly gave rise to hyaline cartilage in animal studies [7,8] and in clinical applications [22,38]. PRP has been used in trauma and orthopaedic surgery [1,27,30] because it is an autologous source of various growth factors [21].…”

Human platelet‐rich plasma stimulates migration and chondrogenic differentiation of human subchondral progenitor cells

“…PRP stimulated cartilage repair after microfracture in the ovine model, even more effectively when it was used as a gel. 38 The chondrotissue matrix of a resorbable polyglycolic acid-hyaluronan scaffold immersed with autologous serum improved the quality of microfracture-induced cartilage repair in ovine joint defects 4 and has been shown to be clinically effective at 1-and 2-year follow-up. 5,6 The injection of PRP in knees with chronic degenerative symptoms revealed a beneficial effect on pain reduction and improvement in knee function in younger patients at 1-year followup.…”

“…Six months after implantation, histological staining showed the formation of cartilaginous repair tissue that was superior to the repair tissue formed after microfracture alone. 3,4 Recently, in first clinical cases, microfractured cartilage defects of the knee were covered with the cell-free PGA-hyaluronan implant. One-to 2-year follow-up showed good to excellent defect filling and the formation of hyaline-like cartilage repair tissue.…”