Effects of recombinant human bone morphogenic protein-2 and human bone marrow-derived stromal cells on in vivo bone regeneration of chitosan-poly(ethylene oxide) hydrogel.

In vivo bone regeneration of chitosan-poly(ethylene oxide) (PEO) hydrogel in rat carlvarial defects was evaluated by using both human bone marrow-derived stromal cells (hMSCs) and recombinant human bone marrow protein-2 (rhBMP-2) for 4 and 8 weeks. In situ chitosan-PEO hydrogel was fabricated by mixing the precursor solutions of both chitosan-acrylate and PEO-thiol. Fabrication of the injectable hydrogels was modulated from within a minute to hours by controlling the temperature and pHs of the precursor solution. Gel swellings were dependent on the conditions of pHs and temperatures of the precursor solutions, showing higher gel swelling in basic water than in either acidic or neutral water. The compression strengths and in vitro degradation of hydrogels were also evaluated by controlling the concentrations of both precursor solutions and lysozyme, respectively, by referencing to the morphology of the control hydrogel with no enzyme added. Hydrogels showed sustained release of rhodamine-B over time. After implantation of the injectable hydrogels in rat calvarial defects for 4 and 8 weeks, in vivo bone regenerations were compared with by evaluating the degrees of new bone formations with Soft X-ray, microcomputed tomography, and histological stainings of hematoxylin and eosine Y and Masson's trichrome. Degrees of in vivo bone regeneration were controlled by encapsulating in advance either hMSCs, rhBMP-2, or both in the precursor solutions of the hydrogel. The defect implanted with hydrogel only showed higher amount of bone tissue regeneration than that of the control defect site. The defect sites with hydrogel containing both hMSCs and rhBMP-2 demonstrated highest amount of bone tissue regeneration among the samples.