KLD-12

3D hydrogel synthetic scaffold culture embeds cells, spheroids, organoids, or tissue fragments inside a hydrated crosslinked polymer network so that cells receive matrix and cell-cell cues in three dimensions rather than from a flat plastic surface. A literature-supported model protocol is PEG-4MAL hydrogel culture, in which four-arm maleimide-terminated PEG is functionalized with cysteine-containing adhesive peptides such as RGD and crosslinked with protease-degradable peptides such as GPQ-W; this creates a defined, modular scaffold that supports human organoid generation and culture. The readouts are scaffold-supported growth, morphology, lumen formation, budding, viability, proliferation, lineage-marker expression, and matrix-dependent expansion or differentiation; reported assays include transmitted-light imaging, immunofluorescence, in situ hybridization, qRT-PCR, and rheological characterization.

MSC chondrogenic differentiation is commonly induced by culturing bone marrow-derived mesenchymal stromal/stem cells as high-density three-dimensional pellets or micromass aggregates in defined chondrogenic medium containing TGF-β family stimulation; the readout is formation of cartilage-like extracellular matrix, especially sulfated proteoglycans, aggrecan, and type II collagen. The assay detects chondrogenesis by pellet enlargement, metachromatic or Alcian blue/Safranin O staining of proteoglycan-rich matrix, immunodetection of type II collagen and aggrecan, and gene-expression changes in cartilage matrix markers; hypertrophic or fibrocartilaginous drift can be assessed by collagen X and collagen I readouts when included.