Functional tissue engineering in articular cartilage repair: is there a role for electromagnetic biophysical stimulation?

Hyaline cartilage lesions represent an important global health problem. Several approaches have been developed in the last decades to resolve this disability cause, including tissue engineering, but to date, there is not a definitive procedure that is able to promote a repair tissue with the same mechanical and functional characteristics of native cartilage, and to obtain its integration in the subchondral bone. The need of resolutive technologies to obtain a "more effective" tissue substitutes has led Butler to propose the "Functional Tissue Engineering" (FTE) paradigm, whose principles are outlined in a so-called FTE road map. It consists of a two-phase strategy: in vitro tissue engineering and clinically surgery evaluation. The first phase, based on construct development, should take into account not only the chondrocyte biology, as their sensitivity to biochemical and physical stimuli, the risk of dedifferentiation in culture, and the ability to produce extracellular matrix, but also the features of suitable scaffolds. The in vivo phase analyzes the inflammatory microenvironment where the construct will be placed, because the cytokines released by synoviocytes and chondrocytes could affect the construct integrity, and, in particular, cause matrix degradation. The use of pulsed electromagnetic fields (PEMFs) represents an innovative therapeutic approach, because it is demonstrated that this physical stimulus increases the anabolic activity of chondrocytes and cartilage explants with consequent increase of matrix synthesis, but, at the same time, PEMFs limit the catabolic effects of inflammatory cytokines, reducing the construct degradation inside the surgical microenvironment. PEMFs mediate an up-regulation of A2A adenosine receptors and a potentiation of their anti-inflammatory effects.