Organoids

Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) possess the potential for chondrogenic differentiation, offering a promising alternative source for cartilage regeneration. To address the limited availability and expansion capacity of autologous chondrocytes, we investigated the effect of co-overexpression of Sox9, TGFβ1, and type II collagen (Col II) on the chondrogenic differentiation of hUC-MSCs using both 2D and 3D pellet culture systems. Following transfection, the cells exhibited a chondrocyte-like morphology and a marked downregulation of the stemness marker Stro-1. After 21 days in a 3D pellet culture system, the cells formed cartilage-like tissue characterized by the strong expression of chondrocyte-specific genes (Sox9, TGFβ1, Col II, Aggrecan) along with the significant secretion of sulfated glycosaminoglycans (sGaGs). These effects were attributed to enhanced cell–cell contact and extracellular matrix interactions promoted by the 3D environment. Our findings suggest that genetically modified hUC-MSCs cultured in a 3D pellet system represent a robust in vitro model for cartilage regeneration, with potential applications in transplantation and drug toxicity screening.

Organoids are three-dimensional multicellular structures that mimic key aspects of native tissues consisting ideal tools to study organ development and pathophysiology when incorporated in customized bioscaffolds. In vivo, the extracellular matrix (ECM) maintains tissue integrity and regulates cell adhesion, migration, differentiation, and survival through biochemical and mechanical signals. Tissue-derived decellularized extracellular matrix (dECM) can preserve organ-specific biochemical signals and cell-adhesive motifs, creating a bioactive environment that supports physiologically relevant organoid growth. 3D bioprinting technology marks a transformative phase in organoid research by enhancing the structural and functional complexity of organoid models and expanding their application in pharmacology and regenerative medicine. These systems enhance tissue modeling and drug testing while adhering to the principles of animal replacement, reduction, and refining (3Rs) in research. Remaining challenges include donor variability, limited mechanical stability, and the lack of standardized decellularization protocols that can be addressed by adopting quality and safety metrics. The combination of dECM-based biomaterials and 3D bioprinting holds great potential for the development of human-relevant, customizable, and ethically sound in vitro models for regenerative medicine and personalized therapies. In this review, we discuss the latest (2021–2025) developments in applying extracellular matrix bioprinting techniques to organoid technology, presenting examples for the most commonly referenced organoid types.

Organoids consisting of primary human cells, i.e., astrocytes, pericytes, and endothelial cells, form a functional blood–brain barrier (BBB) in vitro. The ability of FITC-dextran (70 kDa), calcium phosphate nanoparticles (100 nm), Escherichia coli bacteria (2 µm), and MS2 coliphages (27 nm, a model for viruses) to penetrate the BBB under normoxic and hypoxic conditions (2.5% oxygen) for up to 12 days was assessed by fluorescence microscopy and confocal laser scanning microscopy. All agents were fluorescently labeled to trace them inside the organoids. Under normoxia, FITC-dextran, calcium phosphate nanoparticles, E. coli bacteria and MS2 coliphages did not penetrate the BBB. However, oxygen deficiency (hypoxia) triggered the penetration of the BBB by FITC-dextran and E. coli cells. This was underscored by a strong hypoxic center inside the organoids that developed in the presence of E. coli bacteria.