Decellularized extracellular matrix (ECM) has recently gained a lot of interest as an instructive biomaterial for regenerative medicine applications. In this study, the ability of adult human mesenchymal stem cell (hMSC)-derived ECM to rescue the phenotype of osteoarthritic (OA) chondrocytes and to further stimulate the differentiation of healthy (HL) chondrocytes was evaluated. ECMs were prepared by decellularizing hMSCs cultured in basic medium (BM) and chondrogenic medium (CM). The obtained ECM was then combined with a polymeric solution of Poly (ε-caprolactone) (PCL) dissolved in 1, 1, 1, 3, 3, 3-hexafluoro-2-propanol (HFIP) and electrospun meshes were fabricated. Electrospun ECM scaffolds were characterized using scanning electron microscopy (SEM) and picrosirius red staining was used to confirm the presence of collagen. OA and HL chondrocytes were cultured on scaffolds containing hMSC ECM in BM or CM and compared to PCL electrospun scaffolds without ECM. Metabolic activity and chondrogenic gene expression were assessed by Alamar blue assay and quantitative PCR (qPCR) analysis, respectively. The ECM presence resulted in a significant difference in chondrocyte metabolic activity compared to PCL scaffolds alone. HL chondrocytes cultured for 21 days in chondrogenic medium on electrospun scaffolds containing hMSC ECM from BM showed a significant increase in collagen II and aggrecan expression compared to hMSC ECM from CM and PCL scaffolds without ECM incorporation. No significant influence of hMSC ECM presence on the chondrogenic signature of OA chondrocytes was found. The influence of decellularized hMSC ECM on HL chondrocytes suggests that hMSC-derived ECM scaffolds are promising candidates for cartilage tissue engineering applications.

Spatiotemporal control over engineered tissues is highly desirable for various biomedical applications as it emulates the dynamic behavior of natural tissues. Current spatiotemporal biomaterial functionalization approaches are based on cytotoxic, technically challenging, or non-scalable chemistries, which has hampered their widespread usage. Here we report a strategy to spatiotemporally functionalize (bio)materials based on competitive supramolecular complexation of avidin and biotin analogs. Specifically, an injectable hydrogel is orthogonally post-functionalized with desthiobiotinylated moieties using multivalent neutravidin. In situ exchange of desthiobiotin by biotin enables spatiotemporal material functionalization as demonstrated by the formation of long-range, conformal, and contra-directional biochemical gradients within complex-shaped 3D hydrogels. Temporal control over engineered tissue biochemistry is further demonstrated by timed presentation and sequestration of growth factors using desthiobiotinylated antibodies. The method’s universality is confirmed by modifying hydrogels with biotinylated fluorophores, peptides, nanoparticles, enzymes, and antibodies. Overall, this work provides a facile, cytocompatible, and universal strategy to spatiotemporally functionalize materials.

Osteoblasts derived from mouse skulls have increased osteoclastogenic potential compared to long bone osteoblasts when stimulated with 1,25(OH)2 vitamin D3 (vitD3). This indicates that bone cells from specific sites can react differently to biochemical signals, e.g., during inflammation or as emitted by bioactive bone tissue-engineering constructs. Given the high turn-over of alveolar bone, we hypothesized that human alveolar bone-derived osteoblasts have an increased osteogenic and osteoclastogenic potential compared to the osteoblasts derived from long bone. The osteogenic and osteoclastogenic capacity of alveolar bone cells and long bone cells were assessed in the presence and absence of osteotropic agent vitD3. Both cell types were studied in osteogenesis experiments, using an osteogenic medium, and in osteoclastogenesis experiments by co-culturing osteoblasts with peripheral blood mononuclear cells (PBMCs). Both osteogenic and osteoclastic markers were measured. At day 0, long bones seem to have a more late-osteoblastic/preosteocyte-like phenotype compared to the alveolar bone cells as shown by slower proliferation, the higher expression of the matrix molecule Osteopontin (OPN) and the osteocyte-enriched cytoskeletal component Actin alpha 1 (ACTA1). This phenotype was maintained during the osteogenesis assays, where long bone-derived cells still expressed more OPN and ACTA1. Under co-culture conditions with PBMCs, long bone cells also had a higher Tumor necrose factor-alfa (TNF-α) expression and induced the formation of osteoclasts more than alveolar bone cells. Correspondingly, the expression of osteoclast genes dendritic cell specific transmembrane protein (DC-STAMP) and Receptor activator of nuclear factor kappa-Β ligand (RankL) was higher in long bone co-cultures. Together, our results indicate that long bone-derived osteoblasts are more active in bone-remodeling processes, especially in osteoclastogenesis, than alveolar bone-derived cells. This indicates that tissue-engineering solutions need to be specifically designed for the site of application, such as defects in long bones vs. the regeneration of alveolar bone after severe periodontitis.