Biological Treatment in Cartilage Injuries

Abstract

In occidental societies, a great number of people practice sport regularly at all ages. In this context, cartilage injury incidences have become higher and higher. They are frequently diagnosed during knee arthroscopy even in asymptomatic patients. However, patients commonly present with pain, recurrent effusion, and loss of function. Concomitantly with the increasing incidence, the expectations of patients about function restore have risen as well. Since articular cartilage is characterized by a poor intrinsic regenerative capacity, treatment of these lesions is particularly challenging. Orthopedic surgeons should face this pathology not only because it is symptomatic but also for the risk of more extensive joint damage and further degeneration of the whole articular compartment. Several therapeutic strategies have been developed, both conservative and surgical. In this chapter we will focus on infiltrative therapies, such as platelet-rich plasma (PRP), mesenchymal stem cells (MSCs), and bioengineered osteochondral scaffolds. Platelet-rich plasma (PRP) is a concentrate obtained from autologous blood containing high concentrations of human platelets and platelet-derived growth factors. They are capable of modulating the early healing response and influencing inflammation, angiogenesis, and cell migration. PRP is a safe procedure, and clinical outcome is encouraging, even if it is difficult to establish PRP efficacy because authors have used different PRP formulations, with a large inter-product variability. Another powerful tool for cartilage repair emerging in recent years is mesenchymal stem cells (MSC). Their regenerative effects are due to their immunomodulatory and anti-inflammatory action but above all to their structural contribution to tissue repair. They have a capacity for self-renewal, stemness maintenance, and the marked ability to differentiate into a variety of connective tissues. MSCs can be isolated from human sources other than the bone marrow, such as adipose tissue. Studies available suggest a potential for these cell-based treatments to be developed and to represent a promising new approach with preliminary interesting findings. Nevertheless, many aspects remain to be clarified and optimized. The awareness of the involvement of the subchondral bone in many of these lesions resulted in the need to develop cell-free treatment strategies focused on the entire osteochondral unit. Therefore, surgical techniques move on from autologous chondrocyte implantation (ACI) and autograft or allograft osteochondral implantation to new bioengineered scaffolds. Ideally, a scaffold should have the following characteristics: Three-dimensional and highly porous with an interconnected pore network for cell growth and flow transport of nutrients and metabolic waste. Biocompatible and bioresorbable with a controllable degradation and resorption rate to match cell/tissue growth in vitro and/or in vivo. Suitable surface chemistry for cell attachment, proliferation, and differentiation and mechanical properties to match those of the tissues at the site of implantation. Among them MaioRegen® and, more recently, Agili-C® have shown some of the most promising results.