Remodeling of tissue-engineered bone structures in vivo

Implant design for bone regeneration is expected to be optimized when implant structures resemble the anatomical situation of the defect site. We tested the validity of this hypothesis by exploring the feasibil- ity of generating different in vitro engineered bone-like structures originating from porous silk fibroin scaffolds decorated with RGD sequences (SF-RGD), seeded with human mesenchymal stem cells (hMSC). Scaffolds with small (106–212 lm), medium (212–300 lm), and large pore diameter ranges (300– 425 lm) were seeded with hMSC and subsequently differentiated in vitro into bone-like tissue resem- bling initial scaffold geometries and featuring bone-like structures. Eight weeks after implantation into calvarial defects in mice, the in vitro engineered bone-like tissues had remodeled into bone featuring dif- ferent proportions of woven/lamellar bone bridging the defects. Regardless of pore diameter, all implants integrated well, vascularization was advanced, and bone marrow ingrowth had started. Ultimately, in this defect model, the geometry of the in vitro generated tissue-engineered bone structure, trabecular- or plate-like, had no significant impact on the healing of the defect, owing to an efficient remodeling of its structure after implantation.