Tricalcium phosphate

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.

Mesenchymal stromal/stem cells can be induced toward an osteoblast-like lineage in vitro by culture in osteogenic medium containing dexamethasone, ascorbic acid or ascorbate-2-phosphate, and β-glycerophosphate; the differentiation process is commonly evaluated by alkaline phosphatase activity, osteogenic marker expression, collagenous matrix formation, and calcium-rich matrix mineralization. The main readouts are alkaline phosphatase activity as an early osteogenic marker and Alizarin Red S staining as a calcium-deposit readout for mineralized extracellular matrix; Alizarin Red S can be inspected microscopically or extracted and measured colorimetrically at 405 nm.