Enhanced migration of human bone marrow stromal cells in modified collagen hydrogels

Collagen I hydrogels are widely used as scaffolds for regeneration of articular cartilage defects. We hypothesised that ingrowth might be improved by removing the superficial layer of a compressed hydrogel. The control group consisted of the original unmodified product. The migration of human bone marrow stromal cells (hBMSCs) into the hydrogel was evaluated by confocal microscopy. We quantified the DNA concentration of the hydrogel for each group and time point and evaluated the chondrogenic differentiation of cells. After one week, the detectable amount of cells at the depth of 26-50 mu m was significantly higher in the modified matrix (MM) than in the non-modified matrix (NM) (p = 0.011). The maximum depth of penetration was 75 mu m (NM) and 200 mu m (MM). After three weeks, the maximum depth of penetration was 175 mu m (NM) and 200 mu m (MM). Likewise, at a depth of 0-25 mu m the amount of detectable cells was significantly higher in the MM group (p = 0.003). After 14 days, the concentration of DNA was significantly higher in the samples of the MM than in the control group (p = 0.000). Staining of histological sections and labelling with collagen II antibodies showed that a chondrogenic differentiation of cells in the scaffold can occur during in vitro cultivation. Removing the superficial layer is essential to ensuring proper ingrowth of cells within the compressed hydrogel. Compressed hydrogels contribute better to cartilage regeneration after surface modification.