Self-assembling peptide nanofibers coupled with neuropeptide substance P for bone tissue engineering.

The number of patients requiring flat bone transplantation continues to increase worldwide. Cell transplantation has been successfully applied clinically; however, it causes another defect site and the time requirements to harvest cells and expand them are considerable. In this study, KLD12/KLD12-SP (KLD12+KLD12-substance P [SP]) was designed to mimic endogenous tissue-healing processes. The structures of KLD12, KLD12-SP, and KLD12/KLD12-SP were observed by transmission electron microscopy and circular dichroism spectra. KLD12/KLD12-SP nanofibers (5-10 nm) were created under physiological conditions by formation of a β-sheet structure. The ability of mesenchymal stem cells (MSCs) to recruit KLD12/KLD12-SP was observed by using an in vivo fluorescence imaging system. Labeled human bone marrow stromal cells supplied via an intravenous injection were recruited to the scaffold containing KLD12/KLD12-SP. Polylactic acid/beta-tricalcium phosphate (PLA/β-TCP) scaffolds filled with KLD12/KLD12-SP were applied to repair calvarial defects. The composite constructs (groups: defect, PLA/β-TCP, PLA/β-TCP/KLD12, and PLA/β-TCP/KLD12/KLD12-SP) were implanted into rat defect sites. Bone tissue regeneration was evaluated by observing gross morphology by hematoxylin and eosin and Masson's trichrome staining at 12 and 24 weeks after surgery. Gross morphology showed that the defect site was filled with new tissue that was integrated with host tissue in the KLD12/KLD12-SP group. In addition, from the staining data, cells were recruited to the defect site and lacunae structures formed in the KLD12/KLD12-SP group. From these results, the PLA/β-TCP+KLD12/KLD12-SP composite construct was considered for enhancement of bone tissue regeneration without cell transplantation.