In collaboration with Drs. AF MIranda from Columbia University, New York, and MP King from Thomas Jefferson University, Philadelphia, we developed muscle culture laboratory at the Institute of Pathophysiology of the Ljubljana Medical School and introduced an experimental model of the in vitro innervated human muscle. In this model muscle cells grow from the satellite cells isolated from the pieces of the human muscle routinely discarded at the orthopaedic operations. Myotubes are then innervated by the motoneuron extending from the embryonic rat spinal cord. This experimental model permits manipulation and observation of the synaptogenesis of the neuromuscular junction (NMJ) at all stages which is practically impossible under in vivo conditions. This is also the only model that allows investigation of the NMJ formation on the human muscle. In the continuation of our work we studied the development and differentiation of the cellular components which constitute this experimental system and found that differentiation of neuronal and glial components practically follows the schedule described under in vivo conditions (published in: Mars et al., J Comp Neur, 2001; 438: 239-251). Our experimental model was also used in the investigation of the effects of agrin on the development of the functional NMJ on the human muscle. By blocking agrin with the specific anti-agrin monoclonal antibodies we demonstrated that agrin is dispensable during the initial stages of the NMJ formation but is essential for the formation of full number of functional NMJs in our system (published in: Mars et al., Neuroscience, 2003, 118 (1): 87-97). We also demonstrated that one part of AChE in the developing NMJ is derived by motor nerve (Jevsek et al., submitted) and that this enzyme as well as the related butyrylcholinesterase are both synthesized exclusively in the motor neurons in the ventral horns of the spinal cord. (published in: Mis et al., J Histochem and Cytochem, 2003, 51(12): 1633-1644). Our studies have elucidated the molecular mechanisms underlying the formation of the mammalian NMJ. In some respects they are the only investigations carried out on human muscle. The results were published in the international, peer-reviewed journals, and presented at the international conferences.