Innervation of the endomyocardium in the first period after heart transplantation.

Serial endomyocardial biopsies from 5 patients during the first 3 months after heart transplantation were studied by immunohistochemistry for the neural markers neurofilament 200 kD, neuron-specific protein 9.5 (PGP9.5), S100 (Schwann cell marker), and tyrosine hydroxylase (TH). In normal endomyocardium, nerves immunoreactive for neurofilament 200 kD and PGP9.5 occurred in the interstitium around blood vessels, in close contact with myocyte fibrils. Immunoreactive fibers identified for S100 and TH were also present. In biopsies taken after transplantation, the basic nerve structure in neurofilament labeling was intact. There was a disappearance of immunolabeling for PGP9.5, S100, and TH during the first month after transplantation. Immunoreactivity reappeared during the second month, at first in the interstitium around blood vessels. This was observed for PGP9.5 and TH between 4 and 6 weeks after transplantation, and for S100 (in two of five patients) starting after 6 weeks. There was no apparent relation between reappearance and occurrence of rejection.