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Osteostatin-coated porous titanium can improve early bone regeneration of cortical bone defects in rats.

Tissue engineering. Part A (2015-01-30)
Johan van der Stok, Daniel Lozano, Yoke Chin Chai, Saber Amin Yavari, Angela P Bastidas Coral, Jan A N Verhaar, Enrique Gómez-Barrena, Jan Schrooten, Holger Jahr, Amir A Zadpoor, Pedro Esbrit, Harrie Weinans
ABSTRACT

A promising bone graft substitute is porous titanium. Porous titanium, produced by selective laser melting (SLM), can be made as a completely open porous and load-bearing scaffold that facilitates bone regeneration through osteoconduction. In this study, the bone regenerative capacity of porous titanium is improved with a coating of osteostatin, an osteoinductive peptide that consists of the 107-111 domain of the parathyroid hormone (PTH)-related protein (PTHrP), and the effects of this osteostatin coating on bone regeneration were evaluated in vitro and in vivo. SLM-produced porous titanium received an alkali-acid-heat treatment and was coated with osteostatin through soaking in a 100 nM solution for 24 h or left uncoated. Osteostatin-coated scaffolds contained ∼0.1 μg peptide/g titanium, and in vitro 81% was released within 24 h. Human periosteum-derived osteoprogenitor cells cultured on osteostatin-coated scaffolds did not induce significant changes in osteogenic (alkaline phosphatase [ALP], collagen type 1 [Col1], osteocalcin [OCN], runt-related transcription factor 2 [Runx2]), or angiogenic (vascular endothelial growth factor [VEGF]) gene expression; however, it resulted in an upregulation of osteoprotegerin (OPG) gene expression after 24 h and a lower receptor activator of nuclear factor kappa-B ligand (RankL):OPG mRNA ratio. In vivo, osteostatin-coated, porous titanium implants increased bone regeneration in critical-sized cortical bone defects (p=0.005). Bone regeneration proceeded until 12 weeks, and femurs grafted with osteostatin-coated implants and uncoated implants recovered, respectively, 66% and 53% of the original femur torque strength (97±31 and 77±53 N·mm, not significant). In conclusion, the osteostatin coating improved bone regeneration of porous titanium. This effect was initiated after a short burst release and might be related to the observed in vitro upregulation of OPG gene expression by osteostatin in osteoprogenitor cells. Long-term beneficial effects of osteostatin-coated, porous titanium implants on bone regeneration or mechanical strength were not established here and may require optimization of the pace and dose of osteostatin release.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Calcein-AM, BioReagent, suitable for fluorescence, ≥95.0% (HPLC)
Sigma-Aldrich
Calcein AM solution, 4 mM in DMSO, ≥90% (HPLC), solution
Sigma-Aldrich
Diethyl azodicarboxylate solution, 40 wt. % in toluene
Sigma-Aldrich
Calcein-AM, Small Package (20 X 50 μg ), ≥95.0% (HPLC)
Sigma-Aldrich
Ethidium homodimer, suitable for fluorescence, ~90% (HPCE)