Localization of transforming growth factor beta in association with neuromuscular junctions in adult human muscle

Transforming growth factors-beta 1, 2, and 3 are known for their regulatory function in embryogenesis, fibrogenesis, and tissue repair of different ce ll types. A trophic function of TGF-beta subclasses for motoneurons has bee n shown in vitro. TGF-beta 1 is a potent survival factor for cultured embry onic rat motoneurons. In addition, TGF-beta 1 stimulates proliferation of r at Schwann cells. Recently, TGF-beta 2 has been reported to be associated w ith the subsynaptic nuclei of mature rat neuromuscular junctions. In this s tudy, we investigated the expression of TGF-beta 1, 2, and 3 at neuromuscul ar junctions in skeletal muscle of II adults without neuromuscular disease. On muscle biopsies, neuromuscular junctions were depicted by acetylcholine esterase reaction and acetylcholine receptor antibodies. TGF-beta 1, 2, an d 3 were stained immunohistochemically with monoclonal antibodies. Some mus cle fibers showed low levels of inhomogeneous immunoreactivity for both TGF -beta I and TGF-beta 3. Intense immunoreactivity of TGF-beta 1 and 3 was sh own at the postsynaptic area of neuromuscular junctions. TGF-beta 2 was exp ressed in the same subcellular distribution, but less strongly. In conclusi on, the colocalization of TGF-beta with neuromuscular junctions may suggest a significant function in neuromuscular communication.