The morphological and biochemical response of avian embryonic sympathoadrenal cells to nerve growth factor is developmentally regulated

Abstract

Cellular differentiation is a stepwise process where environmental factors are essential key components to direct cells to their final phenotype. The sympathoadrenal (SA) system is one of the principal models used to study the role of environmental factors in the development of the peripheral nervous system. Two major cell types originate from the SA progenitor: the principal neurons of the sympathetic ganglia and the chromaffin cells of the adrenal medulla. These cells are directed to their final phenotype by a series of environmental factors, of which nerve growth factor (NGF) and glucocorticoids, are the best studied. Previously, we have shown that 11-day embryonic chick sympathetic cell cultures increased their neuropeptide Y (NPY) protein and mRNA levels in the presence of NGF. In contrast, NGF had no such effect in chromaffin cell cultures from the same developmental stage. These results were unexpected since both cells types respond morphologically to NGF. To determine if these cells can gain or lose their capacity to respond to NGF, morphological and biochemical studies were done at earlier stages using immunocytochemical, radioimmunoassay and polymerase chain reaction (PCR) techniques. Interestingly we found that in E-7 chromaffin cells there is a biochemical and morphological response to NGF, while E-7 sympathetic cells lack this response. Our observations show a developmental point of regulation of morphological and biochemical properties by NGF and reveal an age dependent capacity of SA cells to acquire or lose competence to an environmental factor.