Unsuspected Plasticity of Single Neurons after Connection of the Corticospinal Tract with Peripheral Nerves in Spinal Cord Lesions

OBJECTIVE: To report an unsuspected adaptive plasticity of single upper motor neurons and of primary motor cortex found after microsurgical connection of the spinal cord with peripheral nerve via grafts in paraplegics and focussed discussion of the reviewed literature. METHODS: The research aimed at making paraplegics walk again, after 20 years of experimental surgery in animals. Amongst other things, animal experiments demonstrated the alteration of the motor endplates receptors from cholinergic to glutamatergic induced by connection with upper motor neurons. The same paradigm was successfully performed in paraplegic humans. The nerve grafts were put into the ventral-lateral spinal tract randomly, without possibility of choosing the axons coming from different areas of the motor cortex. RESULTS: The patient became able to selectively activate the re-innervated muscles she wanted without concurrent activities of other muscles connected with the same cortical areas. CONCLUSION: Authors believe that unlike in nerve or tendon transfers, where the whole cortical area corresponding to the transfer changes its function a phenomenon that we call "brain plasticity by areas", in our paradigm due to the direct connection of upper motor neurons with different peripheral nerves and muscles via nerve grafts motor learning occurs based on adaptive neuronal plasticity so that simultaneous contractions of other muscles are prevented. We propose to call it adaptive functional "plasticity by single neurons". We speculate that this phenomenon is due to the simultaneous activation of neurons spread in different cortical areas for a given specific movement, whilst the other neurons of the same areas connected with peripheral nerves of different muscles are not activated at the same time. Why different neurons of the same area fire at different times according to different voluntary demands remains to be discovered. We are committed to solve this enigma hereafter.

Comparison between differential expressed miRNA of osteoblast-like cells cultured with P-15 vs. bio-oss

Bio-Oss is composed of anorganic bovine bone whereas P-15 is an analog of the cell binding domain of collagen. Both are widely used in several bone regeneration procedures in oral surgery. How these biomaterials act on osteoblast activity to promote bone formation is poorly understood. We attempted to get more insight using microRNA microarray techniques to investigate the translation regulation in osteoblasts exposed to P- 15 and Bio-Oss. By using miRNA microarrays containing 329 probe designed -from Human miRNA sequence, we identified in osteoblast-like cells line [MG-63] cultured with Bio-Oss[R] [Geistlich, Wolhusen, Switzerland] and P-15 [Ceramed, Lakewood, CO] several miRNA which expression is significantly modified. There were 4 up-regulated miRNA [i.e. let-7c, mir-27a, mir-125a, mir-30c] and 5 down-regulated miRNA [i.e. mir-23a, mir-320, let-7b, mir-145, mir-128a]. P-15 acts preferentially on homeobox genes whereas Bio-Oss activates preferentially extravellular matrix componets, cytokines and hormones. P-15 and Bio-Oss enhance the translation process of different BMPs: BMP1 and BMP4 the first material and BMP 3 and 11 the second one