Fig. 7
Cell migration to the hydrogel core from the surrounding cartilage in cartilage-hydrogel constructs. A 4 mm chondral core in osteochondral explants was excised using a biopsy punch and filled with cell-free 1% agarose hydrogel to form cartilage-hydrogel constructs and cultured in DMEM-F12 medium supplemented with 10% FBS, 1× antibiotic-antimycotic solution and 50 μg/ml L-ascorbic acid for 24 days in the presence or absence of IL-6 or TNFα. Constructs (n = 3) were exposed to cLIUS at 14 kPa (5 MHz, 2.5 Vpp), 20 min, 4 times/day (d-f). Non-cLIUS-stimulated constructs (n = 3) served as controls (a-c). Confocal micrographs demonstrate infiltrated cells from the surrounding cartilage into the hydrogel core when stained with 6 μM calceinAM (green) and 4 μM ethidium homodimer-I (red) on day 24 of culture. Live cells are represented in green and yellow arrows indicate the direction of the migration of cells from the surrounding cartilage to the hydrogel core. Yellow dotted line shows the boundary between the hydrogel core and the surrounding cartilage. Transmitted light micrographs shows the phase-contrast image of hydrogel-cartilage constructs. Scale bar represents 100 μm