Therapeutic Potential of Traditional Chinese Medicine in Peripheral Nerve Regeneration

傳統中藥於外周神經系統再生的治療潛力

Student thesis: Doctoral Thesis

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Award date24 Nov 2017

Abstract

Functional outcomes following peripheral nerve injury are limited largely due to extremely slow intrinsic axonal growth capacities (1mm/day) of injured neurons. Tremendous developments in surgical nerve repair strategies, especially in proximal lesions still report suboptimal recovery without altering regenerative capacity of axotomized neurons. No drug is currently available for treating peripheral nerve trauma patients. To this grim situation, we attempted to augment regenerative capacities of neurons as a therapeutic approach by exploring regenerative potential of traditional Chinese medicine (TCM). Medicinal mushroom Antrodia cinnamomoea (Niu-Chang-Chih in Chinese) and Naringin (You-Pi-Gan in Chinese) from TCM fulfilled our notion through modulation of axonal growth rates of injured primary dorsal root ganglia (DRG) neurons in vitro, ex vivo an in vivo.

TCM (A. cinnamomea extract M8 and Naringin) treated adult male mice demonstrated significant improvements in restoration of sciatic nerve crush injury induced lost functions. We assessed functional recovery and axonal regeneration by multiple approaches such as, a battery of behavioral tests, electromyographic assessment, immunohistochemistry of regenerating nerve and extent of synapse formation with target muscle.

Moreover, one of the significant findings of current study is the identification of antrodin B, an active ingredient from A. cinnamomea singularly responsible for robust axonal growth. However, in vivo effects of antrodin B are limited on peripheral nerve regeneration when administered orally. We developed biodegradable nanoparticle based drug delivery system for sustained antrodin B in vivo availability. Targeted delivery of antordin B loaded poly (lactic-co-glycolic acid) nanoparticles turbocharged axotomized neurons with substantial restoration of sensory and motor functions.

Next, the underlying determinants of TCM induced accelerated neurite outgrowth from adult DRG cultured neurons were identified by expression analysis using RNA microarray approach coupled with bioinformatics analysis. Comparative analysis of microarray data from two TCM, namely antrodin B and naringin revealed shared differentially expressed genes in both TCM treated neurons with large number of olfactory receptors differentially expressed in both TCM datasets. Subsequently microarray derived differentially expressed genes were validated using reverse transcription quantitative polymerase chain reaction. We performed loss of function assay for candidate genes through small interfering RNA (siRNA) to investigate their potential role in neuro-regeneration. Plasmalemma vesicle associated protein (Plvap) knockdown induced robust neurite outgrowth from cultured DRG neurons, suggesting it as a potential determinant of axonal regeneration. Thus, expression data from TCM treated neurons provide opportunities for the investigation of novel genes / pathways in mediating peripheral nerve regeneration.

Beside TCM therapeutic potential investigations, in current study we identified antrodin B mediates axonal growth through modulation of mitochondria dynamics including size and transportation in regenerating axons. Enhancing mitochondria fusion in cultured DRG neurons resulted in augmented neurite outgrowth and significantly larger mitochondria were observed in distal axonal segments. Cultured neurons with mitochondria fusion modulations demonstrated higher axonal transport of mitochondria. It suggested possible involvement of mitochondria fusion in mediating axonal regeneration.

Thus, several of our findings suggest that TCM accelerate axonal growth leading to successful functional recovery in mouse model of peripheral nerve injury and may result in huge clinical benefits and antrodin B would be most likely to be of value in this notion.

    Research areas

  • Traditional Chinese Medicine, Peripheral nerve regeneration, Functional recovery, Antrodia cinnamomoea, Antrodin B, Naringin, Mitochondria fusion, Axonal regeneration