Evaluation of a polyelectrolyte complex (PEC) composed of chitin derivatives and chitosan, which promotes the rat calvarial osteoblast differentiation

Rat osteoblasts (rOB) isolated from rat calvaria were cultured on polyelectrolyte complex (PEC) composed of phosphated and carboxymethylated chitin (PCHN and CCHN) as a polyanion, and chitosan (CS) as a polycation to evaluate the effects of these PECs on rOB differentiation. Aggregates of rOB were observed on PPEC (CS‐PCHN) after 4 days of culture, and on CPEC (CS‐CCHN) after 2 days of culture. Furthermore, rOB growth on PECs was inhibited by aggregation. In contrast, the rOB in the tissue culture dish did not produce aggregates on the same culture day as those on the PECs, and growth was not inhibited. The alkaline phosphatase activity, which is used as an initial differentiation marker for osteoblastic cells, increased after rOB aggregation was observed on PECs. Furthermore, after 5 days of culture, the positive stain area of Von Kossa was only observed in the aggregates, and osteocalcin mRNA was expressed on each of the PECs. These results suggest that the rOB differentiation was induced earlier by PECs than with other tissue culture materials. This early inducement of rOB differentiation appears to be attributable to the formation of aggregates on PECs. In other words, the inducement of aggregation by PECs plays an important role in rOB mineralization. These studies suggest that PEC has the ability to control rOB proliferation and differentiation.