The study was aimed at the applicability of a bioink based on 4% collagen and chondrocytes for de novo cartilage formation. Extrusion-based bioprinting was used for the biofabrication. The printing parameters were tuned to obtain stable material flow. In vivo data proved the ability of the tested bioink to form a cartilage within five to six weeks after the subcutaneous scaffold implantation. Certain areas of cartilage formation were detected as early as in one week. The resulting cartilage tissue had a distinctive structure with groups of isogenic cells as well as a high content of glycosaminoglycans and type II collagen.

The aim of this study was to verify the applicability of high-concentration collagen-based bioink with MSC (ADSC) and decellularized ECM granules for the formation of cartilage tissue de novo after subcutaneous implantation of the scaffolds in rats. The printability of the bioink (4% collagen, 2.5% decellularized ECM granules, derived via 280 μm sieve) was shown. Three collagen-based compositions were studied: (1) with ECM; (2) with MSC; (3) with ECM and MSC. It has been established that decellularized ECM granules are able to stimulate chondrogenesis both in cell-free and MSC-laden scaffolds. Undesirable effects have been identified: bone formation as well as cartilage formation outside of the scaffold area. The key perspectives and limitations of ECM granules (powder) application have been discussed.

Gelatin methacryloyl (GelMA) has recently attracted increasing attention. Unlike other hydrogels, it allows for the adjustment of the mechanical properties using such factors as degree of functionalization, concentration, and photocrosslinking parameters. In this study, GelMA with a high degree of substitution (82.75 ± 7.09%) was synthesized, and its suitability for extrusion printing, cytocompatibility, and biocompatibility was studied. Satisfactory printing quality was demonstrated with the 15% concentration hydrogel. The high degree of functionalization led to a decrease in the ability of human adipose-derived stem cells (ADSCs) to adhere to the GelMA surface. During the first 3 days after sowing, proliferation was observed. Degradation in animals after subcutaneous implantation was slowed down.

3D-bioprinting is a promising technology for a tissue scaffold fabrication in the case of damaged tissue/organ replacement. Collagen is one of the most appropriate hydrogel for the purpose, due to its exceptional biocompatibility. However, the use of collagen with conventionally low concentration makes bioprinting process difficult and does not provide its high accuracy. The purpose of the study was evaluation of suitability of collagen with high concentration in case of chondrocyte-laden scaffold fabrication via 3D-bioprinting for cartilage regeneration in vitro and in vivo. The results of the study showed that inherent porosity of 4% collagen was not enough for cell survival in the case of long-term incubation in vitro. With the beginning of the scaffold incubation, cell migration to the surface and out of the scaffold was observed. The residual cells died mostly within 4 weeks. As for in vivo study, in 2 weeks after implantation of the scaffold, a weak granulomatous inflammation was observed. In 6 weeks, a connective tissue was formed in the area of implantation. In the tissue, macrophages and groups of small cells with round nuclei were found. In accordance with morphological criteria, these cells could be considered as young chondrocytes. However, its amount was not enough to initiate the formation of cartilage.