[Preparation and property of recombinant human bone morphogenetic protein-2 loaded hydrogel nanospheres and their biological effects on the proliferation and differentiation of bone mesenchymal stem cells].

Purpose: To prepare and study the recombinant human bone morphogenetic protein-2 loaded dextran-based hydrogel nanospheres (rhBMP(2)-dex-NPs) sustained release system, and to evaluate its biological effects on cultured rabbit bone mesenchymal stem cells(BMSCs).

Methods: The rhBMP(2)-dex-NPs were prepared by improved emulsion polymerization method. Their morphology, size and size distribution, encapsulated ratio and stability were assessed by routine procedure. Dynamic dialysis method was used to determine the release characteristics of rhBMP(2)-dex-NPs in vitro. Cell culture technique and MTT colorimetric assay were used to evaluate the proliferation and differentiation of the BMSCs, ALP kit was used to evaluate the ALP activity of the BMSCs so as to show the differentiation of the cells by adding the rhBMP(2)-dex-NPs to the DMEM culture medium (B group) or rhBMP2 only (A group). Adding dex-NPs without rhBMP2 (C group) and adding nothing (D group) were taken as the controls. The results were analyzed by statistical analysis software (SPSS10.0).

Results: The shape of rhBMP(2)-dex-NPs was spherical, with a size distribution of 20 nm. The encapsulated ratio was 83% and rhBMP(2)-dex-NPs could be kept more than 6 months under 4 degrees C without decomposition , destruction or deposition. The release profile in vitro was in accordance with two phases kinetics law, and more than 80% of the encapsulated rhBMP(2) can be released during 12 days. Statistical analysis showed that rhBMP(2)-dex-NPs had biological activity, and could enhance both proliferation and differentiation of rabbit BMSCs significantly, the effect of the rhBMP(2)-dex-NPs was significantly higher than that of rhBMP(2) (P<0.01). During the first 3 days, the proliferation and differentiation of BMSCs between group A and B had no significance (P>0.05), but much faster than group C and D. After 5 to 7 days, rhBMP(2)-dex-NPs could enhance BMSCs proliferation and differentiation continually, but rhBMP2 had no enhancement any more. 7 days later, the difference between group A and B become much more significant (P<0.001).

Conclusions: The rhBMP(2)-dex-NPs can release rhBMP2 more than 12 days and have long-drawn biological effects. To encapsulate rhBMP2 into dextran-based hydrogel nanospheres may be an effective way of growth factor controlled release in tissue engineering.