INTRODUCTION. Articular cartilage has excellent biomechanical properties, but due its avascular nature and the low proliferation capacity of mature chondrocytes, the regeneration process usually produces fibrocartilage scars, with worse biomechanical properties. For this reason, articular cartilage traumatic injuries and degenerative pathology are frequent causes of pain and disability.
Currently, tissue engineering techniques are expanding for the treatment of these injuries, through the design of scaffolds that support the chondrocytes while ensuring enough resistance to allow the limb to bear weight but not isolating them, since tensions are important signals for differentiation and formation of hyaline extracellular matrix.
Our objective was to design and synthetize a three-dimensional scaffold in the form of microspheres and implant it in a porcine animal model to evaluate the quality of the newly formed tissue.
METHODOLOGY. We used microspheres synthetized from two different biomaterials: polylactic acid (PLA) and platelet-rich plasma (PRP), since this type of scaffold showed good results in a rabbit model. To keep the microsphere scaffold in place, we also used a 100 µm PLA membrane.
Surgical interventions were performed in a porcine experimentation model, creating a full-thickness chondral lesion, 6 mm in diameter, in the weight-bearing part of the medial condyles (n = 24 knees). Three different treatment groups were formed: (a) control group without microspheres, covered with PLA membrane, (b) control group with a Novocart (Braun®), an approved treatment for cartilage lesions in humans, and (c) experimental group with PRP and PLA microspheres, covered with PLA membrane. In addition, microfractures were performed on the subchondral bone in all groups, before assigning them to a treatment group.
Ten months after surgery, the femurs were obtained and processed with the histological technique. Haematoxylin-eosin staining was used, and the histological analysis was performed with the ICRS II scale, which was modified by adding three items: microsphere presence, membrane presence and inflammation around the area of the remaining biomaterial.
RESULTS. In most ICRS II scale items, the experimental group with microspheres and the Novocart control group had similar results, with a tendency to have better results than the control group without microspheres. We found no traces of biomaterial in any sample of the microspheres group, while they were found in 2 of the 8 Novocart samples. The global result of the ICRS II scale had a similar trend in the experimental and Novocart groups. There were no inflammatory areas around biomaterials used.
CONCLUSION. The overall ICRS II score appears to be similar when comparing the PRP and PLA microsphere scaffolds group with the Novocart group, an already approved treatment for articular cartilage injuries. No microspheres were found in any sample after 10 months, which could show that they are reabsorbed at an adequate rate to add support for chondrocyte migration without leaving debris in the newly formed articular cartilage.