Low-frequency pulsed electromagnetic field pretreated bone marrow-derived mesenchymal stem cells promote the regeneration of crush-injured rat mental nerve

Bone marrow-derived mesenchymal stem cells （BMSCs） have been shown to promote the regeneration of injured peripheral nerves. Pulsed electromagnetic field （PEMF） reportedly promotes the proliferation and neuronal differentiation of BMSCs. Low-frequency PEMF can induce the neuronal differentiation of BMSCs in the absence of nerve growth factors. This study was designed to investigate the effects of low-frequency PEMF pretreatment on the proliferation and function of BMSCs and the effects of low-frequency PEMF pre-treated BMSCs on the regeneration of injured peripheral nerve using in vitro and in vivo experiments.In in vitro experiments, quantitative DNA analysis was performed to determine the proliferation of BMSCs, and reverse transcription-polymerase chain reaction was performed to detect S100 （Schwann cell marker）, glial fibrillary acidic protein （astrocyte marker）, and brain-derived neurotrophic factor and nerve growth factor （neurotrophic factors） mRNA expression. In the in vivo experiments, rat models of crush-injured mental nerve established using clamp method were randomly injected with low-frequency PEMF pretreated BMSCs, unpretreated BMSCs or PBS at the injury site （1 × 106 cells）. DiI-labeled BMSCs injected at the injury site were counted under the fluorescence microscope to determine cell survival. One or two weeks after cell injection, functional recovery of the injured nerve was assessed using the sensory test with von Frey filaments. Two weeks after cell injection, axonal regeneration was evaluated using histomorphometric analysis and retrograde labeling of trigeminal ganglion neurons. In vitro experiment results revealed that low-frequency PEMF pretreated BMSCs proliferated faster and had greater mRNA expression of growth factors than unpretreated BMSCs. In vivo experiment results revealed that compared with injection of unpretreated BMSCs, injection of low-frequency PEMF pretreated BMSCs led to higher myelinated axon count and axon density and more DiI-labeled neurons in the trigeminal ganglia, contributing to rapider functional recovery of injured mental nerve. These findings suggest that low-frequency PEMF pretreatment is a promising approach to enhance the efficacy of cell therapy for peripheral nerve injury repair.

Recombinant human fibroblast growth factor-2 promotes nerve regeneration and functional recovery after mental nerve crush injury

Several studies have shown that fibroblast growth factor-2 （FGF2） can directly affect axon regeneration after peripheral nerve damage. In this study, we performed sensory tests and histological analyses to study the effect of recombinant human FGF-2 （rhFGF2） treatment on damaged mental nerves. The mental nerves of 6-week-old male Sprague-Dawley rats were crush-injured for 1 minute and then treated with 10 or 50 μg/mL rhFGF2 or PBS in crush injury area with a mini Osmotic pump. Sensory test using von Frey filaments at 1 week revealed the presence of sensory degeneration based on decreased gap score and increased difference score. However, at 2 weeks, the gap score and difference score were significantly rebounded in the mental nerve crush group treated with 10 μg/mL rhFGF2. Interestingly, treatment with 10 μg/mL rhFGF had a more obviously positive effect on the gap score than treatment with 50 μg/mL rhFGF2. In addition, retrograde neuronal tracing with Dil revealed a significant increase in nerve regeneration in the trigeminal ganglion at 2 and 4 weeks in the rhFGF2 groups （10 μg/mL and 50 μg/mL） than in the PBS group. The 10 μg/mL rhFGF2 group also showed an obviously robust regeneration in axon density in the mental nerve at 4 weeks. Our results demonstrate that 10 μg/mL rhFGF induces mental nerve regeneration and sensory recovery after mental nerve crush injury.

The Anatomical Research on the Mental Foramen Related to the Mental Nerve Block

Objective: The aim of this study was to observe and investigate the location of mental foramen, providing scientific and reasonable anatomic basic for clinical mental nerve block. Methods: The shape, orientations, relationship with teeth and number of accessory mental foramina in 50 (100 side) adult mental foramina were observed. The long and short diameters of the mental foramen and the distance between the mental foramen and the peripheral anatomical markers were measured by a vernier caliper, and statistical analysis of the data was performed to obtain the final results. Results: The probability of mental foramen being elliptical in shape accounted for 27%, circular for 73%;10% of the mental foramen openings are outward and 90% are outward and upward;The mental foramina were located under the first premolars in 20%, under the second premolars in 75%, and 5% situated in the bottom of the first molars. The incidence of accessory mental foramina was 1%;the long diameter of the mental foramen was (2.42 ± 0.71) mm, and the short diameter of the mental foramen was (2.15 ± 0.14) mm;the vertical distance from the mental foramen center to the alveolar crest and the lower margin of the mandible were (14.09 ± 3.23) mm and (14.56 ± 1.74) mm;the distance between the midpoints of the vertical line to the center of the mental foramen was (1.26 ± 0.97) mm;the horizontal distance from the center of the mental foramen to the anterior median line was (23.57 ± 1.82) mm. Conclusion: The point of mental nerve block was selected below and behind the second premolars, above the midline of the mandible. The distance from the anterior median line was 2.5 cm, and the mental foramen was explored forward and downward after the insertion.