Enhanced regeneration of rabbit mandibular defects through a combined treatment of electrical stimulation and rhBMP-2 application

Abstract

We evaluated the new bone regeneration of a rabbit mandibular defect using hBMSCs under electrical stimulation combined with rhBMP-2 in this study. An inner scaffold prepared by setting a collagen sponge with hBMSCs and hydrogel was placed into a polycaprolactone (PCL) outer box, and an electrical stimulation device was installed between the inner scaffold and the outer box. There were three experimental groups depending on electrical stimulation and application of rhBMP-2. The experimental group was divided into the following three groups. Group 1, in which rhBMP-2 (5 μg/defect) was added to hydrogel and electrical stimulation was not applied; Group 2, in which rhBMP-2 (5 μg/defect) was added as in Group 1 and electrical stimulation was applied; and Group 3, in which electrical stimulation was applied and rhBMP-2 (5 μg/defect) was injected directly into defect site. The delivered electrical stimulation was charge-balanced bi-phasic electric current pulses, and electrical stimulation was conducted for 7 days. The stimulation parameters of the bi-phasic electrical current set at an amplitude of 20 μA, a duration of 100 μs and a frequency of 100 Hz. Four weeks after surgery, new bone formation in each group was evaluated using radiography, histology, and micro-computed tomography (μCT). Groups 2 and 3 exhibited a significant increase in new bone formation compared to Group 1, while Group 3 showed the highest level of new bone regeneration. In a comparison between two groups, Group 2 showed a higher bone volume (BV) by 260 % (p < 0.01) compared with Group 1, and Group 3 showed a higher BV by 442 % (p < 0.01) compared with Group 1. The trend of the bone surface density (ratio of new bone to the real defect volume, BS/TV), trabecular number, and connectivity was identical to that of the BV. The total bone mineral density (BMD) of Groups 2 and 3 showed values higher by the ratios of 103 % (p < 0.01) and 107.5 % (p < 0.01) compared with Group 1, respectively. Part BMD for Groups 2 and 3 showed higher values by the ratios of 104.9 % (p < 0.01) and 122.4 % (p < 0.01) compared with Group 1, respectively. These results suggest that the combined treatment of electrical stimulation, hBMSCs, a collagen sponge, hydrogel, and rhBMP-2 was effective for bone regeneration of large-size mandibular defects. The application of rhBMP-2 with an injection following electrical stimulation demonstrated better efficiency as regards bone regeneration.

Synthesis of and in vitro and in vivo evaluation of a novel TGF-β1-SF-CS three-dimensional scaffold for bone tissue engineering

“…To evaluate the mechanical recovery of bone grafts in rabbit models of segmental radius defects, bending test configurations have been reported ( 53 – 55 ). Our studies have shown that both three-point bending resulted in similar outcomes when testing the mechanical integrity of rabbit mandible ( 53 ). In agreement with this study, the primary failure mode for bending was a short oblique fracture.…”

Implantable electrical stimulation bioreactor with liquid crystal polymer based electrodes for enhanced bone regeneration at mandibular large defects in rabbit

“…Defect area to be resected (rectangular shape; 15 mm long, 7 mm high from the mandibular inferior border) was marked on the mandibular bone under the tooth and osteotomized by rotary drilling machine, where alveolar bone with teeth was preserved with continuity with the residual mandibular bone. Because mandibular stabilization with mini-9 plates after the resection of mandibular body including the alveolar bone with teeth was unstable [33], postoperative dislocation of anterior segment with loosening of mini-plates and screws occurred in our previous experiments due to the strong jaw movement. The bioreactors were positioned into the defect side, stabilized with screws on the neighboring mandibular bone (Fig 4), and the electric stimulator with battery coin were implanted at the submandibular area and then the incision sites were sutured layer by layer.…”

“…Increased calcium level might lead to an increased nitric oxide levels, which acts in a physiological context through increased synthesis of cyclic guanosine monophosphate (cGMP) and subsequent activation of protein kinase G, which was associated with cell division and nucleic acid synthesis [48]. ES also made the cellular environment more suitable for osteogenesis [33]. The effect of ES included increased gene expression of type I collagen and prostaglandin [30], growth factors (BMP-2, IGF-1, VEGF), and chemokines with receptors [34].…”

“…Electric stimulator was designed using a custom designed chip (CMOS 0.18 µm foundry, Samsung electronics, Suwon, Korea) previously fabricated [34]. The circuit configuration of the stimulation chip was described in the previous study [33,34]. The integrated chip was wire bonded on the printed circuit board with additional components soldered [33].…”

“…The circuit configuration of the stimulation chip was described in the previous study [33,34]. The integrated chip was wire bonded on the printed circuit board with additional components soldered [33]. The biphasic electric current pulses were generated by the electric stimulator, where the parameters of the pulses were set as amplitude of 20 μA, duration of 100 μs, and frequency of 100 Hz.…”