A novel nonviral gene delivery tool of BMP‐2 for the reconstitution of critical‐size bone defects in rats

Abstract

The osseointegration of bone implants, implant failure, and the bridging of critical-size bone defects are frequent clinical challenges. Deficiencies in endogenous bone healing can be resolved through the local administration of suitable recombinant growth factors (GFs). In preclinical models, gene-therapy-supported bone healing has proven promising for overcoming certain limitations of GFs. We report the dose-dependent bridging of critical-size mandibular bone defects (CSDs) in a rat model using a non-viral BMP-2-encoding copolymer-protected gene vector (pBMP-2) embedded in poly(d, l-lactide) (PDLLA) coatings on titanium discs that were used to cover drill holes in the mandibles of 53 male Sprague Dawley rats. After sacrificing, the mandibles were subjected to micro-computed tomography (µCT), micro-radiography, histology, and fluorescence analyses to evaluate bone regeneration. pBMP-2 in PDLLA-coated titanium implants promoted partial bridging of bone defects within 14 days and complete defect healing within 112 days when the DNA dose per implant did not exceed 2.5 µg. No bridging was observed in untreated control CSDs. Thus, the delivery of plasmid DNA coding for BMP-2 appears to be a potent method for controlled new-bone formation with an inverse dose dependency. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2441-2455, 2016.

Comparative analysis of bone regeneration behavior using recombinant human BMP‐2 versus plasmid DNA of BMP‐2

“…To constrain excessive bone growth, we have investigated pBMP‐2 as a promising alternative and compared it with rhBMP‐2. Indeed, as has previously been shown, pBMP‐2‐shielded implant materials promote bone regeneration in a spatio‐temporally controlled manner and have exhibited promising results …”

“…Because no dose‐related differences were found in terms of the amount of NB formation, the final dose decision of 62.5 μg was set in accordance to studies by Gruber et al and Schliephake et al and in terms of the prestudy with plasmid doses of up to 100 μg pBMP‐2. In these other subgroups with pBMP‐2, doses higher than 2.5 μg have shown counterproductive effects on bone regeneration . Because dose finding studies have already been performed, the focus of this study was set on the comparative analysis of the respective osteoinductive effects of recombinant or gene therapeutic BMP‐2 application.…”

“…RhBMP‐2 and pBMP‐2 have been widely investigated in preclinical settings and proven to influence osteogenesis positively by stimulating local cell growth and differentiation, although in different ways. Basing our work on previous studies in vivo and in vitro concerning the optimization of applied doses, we have now applied rhBMP‐2 and pBMP‐2 in mandibular critical size defects (CSD) of Sprague–Dawley rats and evaluated bone regeneration after four different time points. The aim of this study has been to generate and compare two different bone‐inducing surface coatings based on BMP‐2 as an osteoinductive GF in an attempt to solve the problem as to which is better: proteins or genes.…”

Functional analysis of bioactivated and antiinfective PDLLA – coated surfaces

“…Compared with viral vectors, nonviral gene vectors are less immunogenic and are not integrated into the host's genome, so insertional mutagenesis is avoided . The results of the luciferase tests proved that the genes are expressed in a time‐limited manner, which is desirable because of the severe side effects of uncontrolled tissue proliferation during regenerative processes, such as bone healing . Therefore, this method was used in this study.…”

“…[21][22][23] The results of the luciferase tests proved that the genes are expressed in a time-limited manner, which is desirable because of the severe side effects of uncontrolled tissue proliferation during regenerative processes, such as bone healing. 24 Therefore, this method was used in this study.…”