# Regeneration of Articular Cartilage Using Membranes of Polyester Scaffolds in a Rabbit Model
###### Abstract  
One promising method for cartilage regeneration involves combining known methods, such as the microfracture technique with biomaterials, e.g., scaffolds (membranes). The most important feature of such implants is their appropriate rate of biodegradation, without the production of toxic metabolites. This study presents work on two different membranes made of polyester (L-lactide-co-\(\epsilon\)-caprolactone-PLCA) named \"PVP and \"Z\". The difference between them was the use of different pore precursors--polyvinylpyrrolidone in the \"PVP\" scaffold and gelatin in the \"Z\" scaffold. These were implemented in the articular cartilage defects of rabbit knee joints (defects were created for the purpose of the study). After 8, 16, and 24 weeks of observation, and the subsequent termination of the animals, histopathology and gel permeation chromatography (GPC) examinations were performed. Statistical analysis proved that the membranes support the regeneration process. GPC testing proved that the biodegradation process is progressing exponentially, causing the membranes to degrade at the appropriate time. The surgical technique we used meets all the requirements without causing the membrane to migrate after implantation. The \"PVP\" membrane is better due to the fact that after 24 weeks of observation there was a statistical trend for higher histological ratings. It is also better because it is easier to implant due to its lower fragility then membrane \"Z\". We conclude that the selected membranes seem to support the regeneration of articular cartilage in the rabbit model. s 202  
They can damage the cartilage, causing pain, stiffness, movement limitations, and even disability. This can be direct trauma to the cartilage--most often a sharp strike to a bone or repeated microtrauma, the overload causing gradual damage. Repeated damage leads to the formation of defects on the surface. AC lacks blood supply and the neural system, so it has limited regenerative capacity. Moreover, the regenerate process becomes less effective as the human body ages. Leaving defects untreated leads to the development of a degenerative disease [1; 2; 3; 4; 5; 6; 7; 8; 9]. Treatment techniques currently used include microfractures (MF), mosaicplasty, osteochondral allograft transplantation, and autologous chondrocyte implantation. Microfractures are now the gold standard of treatment. This technique consists in making the defect within the cartilage damage deep enough to cause the outflow of mesenchymal stem cells (MSC) from the bone marrow. However, due to the specific structure of cartilage (lack of blood vessels, layered structure), none of the abovementioned techniques achieves satisfactory results. The resulting regenerated tissue is often of poor quality: is fibrous-like cartilage, or does not have an appropriate layered structure; therefore, it has reduced mechanical resistance. Some techniques are complex and time-consuming, making them unavailable for many patients. Another problem is the size of the defect. The larger the defect, the more difficult it is to repair with known techniques. Currently, research is focused on combining the microfracture technique with the simultaneous use of scaffolds (3D membranes) to improve the regenerative capacity of cartilage [10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. A scaffold is a spatial structure that takes the form of membranes, hydrogels, or nonwovens. Such an implant can be colonized by autologous chondrocytes or mesenchymal stem cells (MSCs). It serves as a temporary matrix that provides a suitable environment for cells that guarantee success in the cartilage regeneration process [16; 26; 27; 28; 29]. Such scaffolds have already been successfully applied in patients [10; 26]. The ideal biomaterial should enable the transport of nutrients to chondrocytes and allow the elimination of metabolites; it should also be completely biodegradable and biocompatible.