Morphological characterization of Neuromuscular Junctions in mice model of Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is the most common disease involving motor neurons. The molecular mechanisms underlying the defects of neuromuscular junctions (NMJ) observed in ALS are not known but these defects suggest an altered plasticity of the junction itself. It has been demonstrated that motor units with different physiological and morphogenetic properties (slow, fast-fatigue resistant, fast-fatiguable; Fasyn Desyn) are differently susceptible to ALS-induced damages and denervation. We have analysed the NMJs of soleus, a DeSyn muscle with a predominance of Slow motor units, and we did not observe any morphological alteration neither at an early stage of disease (14 weeks) or at the end stage (20 weeks), percentage of innervation of NMJs, which is an index of muscular functionality is preserved as well as in control littermates animals. We also analysed diaphragm, a DeSyn muscle with a mixed composition of motor units (slow, fast-fatigue resistant, fast-fatiguable); diaphragm is more sensitive to the alterations due to the disease; in fact we observed a reduction in percentage of innervation of NMJs of diaphragms of SOD1G93A mice compared to WT littermates. These data are collected both at the clinical onset of pathology (P80-P90) and at the end stage (20 weeks) when the reduction of the percentage of innervation is more important. In the second part of our work we studied the effectiveness of a pharmacologic treatment with Nandrolone. Data collected from this study show that Nandrolone seems to act as well at the presynaptic level (innervation of NMJ is preserved), and at postsynaptic elements (it restores the size of myofibers). We are collecting data about mitochondrial and synaptic vesicles pool in presynaptic elements of treated and untreated mice. Preliminary data about Nandrolone treatment seems to indicate that Nandrolone, in our samples, induces a reduction of mitochondrial size ands seems to preserve their integrity of mitochondria in fact we did not observe any alteration of morphology of these organelles; we are also evaluating size, number and distributions of synaptic vesicles. In this way we think to obtain a better understanding and a more complete overview about Nandrolone action in our experimental model of ALS mice