Sains Malaysiana 45(11)(2016): 1641–1647

 

Histological Analysis of Motoneuron Survival and Microglia Inhibition after Nerve Root Avulsion Treated with Nerve Graft Implantation and Minocycline: An Experimental Study

(Analisis Histologi Kemandirian Motoneuron dan Perencatan Mikroglia selepas Avulsi Akar Saraf Dirawat dengan Penempelan Tisu Cantuman dan Minosiklin: Suatu Kajian Eksperimen)

 

FAIZUL H. GHAZALI¹*, WUTIAN WU⁴ & JAFRI M. ABDULLAH^1,2,3

 

¹Center for Neuroscience Service and Research, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian 2, 16150 Kelantan Darul Naim, Malaysia

 

²Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia

Kubang Kerian 2, 16150 Kelantan Darul Naim, Malaysia

 

³School of Medical Sciences, Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan Darul Naim, Malaysia

 

⁴Department of Anatomy, Faculty of Medicine, University of Hong Kong, China

 

Received: 8 September 2014/Accepted: 24 March 2016

ABSTRACT

Motor vehicle accidents are the most common cause of injuries involving avulsion of the brachial plexus in humans, resulting in debilitating motor dysfunction. Lack of an established animal model to test drug treatments hinders the introduction of new pharmacological agents. Avulsion injury of cervical ventral roots can be replicated in rats, resulting in a progressive loss of the motoneurons and increase in neurotoxic expression of microglia. This is a report on the effect of prompt nerve implantation and minocycline treatment on the suppression of microglia activation and survival of motoneurons. 20 adult female Sprague-Dawley rats were used for this study, which was approved by the Animal Ethical Committee, USM (approval number /2011/(73)(346)). The animals underwent surgical avulsion of the C6 nerve root, followed by reimplantation with peripheral nerve graft and treatment with intraperitoneal minocycline. At 6 weeks postoperatively, immunohistochemistry using primary antibody Iba1 (microglia) and nicotinamide adenine dinucleotide phosphate diaphorase (NADPh) with neutral-red staining (motoneuron) under flourescence microscopy was performed at the C6 spinal cord segment and then quantified. This study showed significant reduction of microglia expression in the study group; mean ranks of control and study group were 15.2 and 11.6, respectively; U=9.5, Z=3.02, p<0.05. However, this did not translate into a significant increase of motoneuron survival in the combined group; the mean ranks of control and study group were 40.6 and 41.6, respectively; U=44.5, Z=-.0378, p>0.05. This may be due to the effect of the surgery; the surgery has the potential to cause additional trauma to the cord parenchyma, leading to further motoneuron loss and an increase in scarring around the avulsed region, thus impeding regeneration of the motoneuron.

 

Keywords: Avulsion; microglia; minocycline; motoneuron; peripheral nerve implantation

 

ABSTRAK

Kemalangan kenderaan bermotor adalah punca paling biasa kecederaan yang melibatkan avulsi pleksus brakium pada manusia yang mengakibatkan kelemahan fungsi motor. Kekurangan model haiwan yang mantap untuk menguji rawatan ubat menghalang pengenalan agen baru farmakologi. Kecederaan avulsi pangkal rahim ventral akar boleh direplikasi pada tikus yang mengakibatkan kehilangan motoneuron secara progresif dan peningkatan dalam pengekspresan neurotoksik mikroglia. Kertas ini membincangkan tentang kesan implantasi saraf pantas dan rawatan minosiklin ke atas penidasan pengaktifan mikroglia dan kemandirian motoneuron. 20 tikus dewasa betina Sprague-Dawley digunakan untuk kajian ini dan telah diluluskan oleh Jawatan Kuasa Etika Haiwan, USM (nombor kelulusan/2011/(73)(346)). Tikus tersebut telah menjalani pembedahan avulsi pada akar saraf C6, diikuti implantasi semula dengan cantuman saraf periferi dan rawatan dengan minosiklin intraperitoneum. Selepas 6 minggu pascabedah, imunohistokimia menggunakan antibodi Iba1 utama (mikroglia) dan nikotinamida adenina dinukleotida fosfat diaforase (NADPh) dengan pewarnaan merah neutral (motoneuron) di bawah mikroskop berpendarflour telah dijalankan pada segmen saraf tunjang C6 dan kemudian dikuantitikan. Kajian ini menunjukkan penurunan pengekspresan mikroglia yang ketara dalam kumpulan kajian; pangkat min kumpulan kawalan dan kajian masing-masing adalah 15.2 dan 11.6; U=9.5, Z=3.02,p<0.05. Walau bagaimanapun, ini tidak pula diterjemahkan kepada pertambahan ketara kemandirian motoneuron dalam kumpulan gabungan; pangkat min kumpulan kawalan dan kajian masing-masing adalah sebanyak 40.6 dan 41.6; U=44.5, Z=-.0378,p>0.05. Ini mungkin disebabkan oleh kesan pembedahan; pembedahan tersebut berpotensi untuk menyebabkan trauma tambahan kepada parenkima tunjang yang membawa kepada kehilangan motoneuron lebih banyak dan peningkatan parut di sekitar kawasan avulsi, oleh itu menghalang pertumbuhan semula motoneuron.

 

Kata kunci: Avulsi; mikroglia; minosiklin; motoneuron; penempelan saraf periferi

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*Corresponding author; email: dr_leyz@yahoo.com