Tyrosine hydroxylase, chromogranin A, and steroidogenic acute regulator as markers for successful separation of human adrenal medulla.

ABSTRACT

Progress in high throughput "-omic" techniques now allows the simultaneous measurement of expression levels of thousands of genes and promises the improved understanding of the molecular biology of diseases such as cancer. Detection of the dysfunction of molecular pathways in diseases requires healthy control tissue. This is difficult to obtain from pheochromocytomas (PHEOs), rare chromaffin tumors derived from adrenal medulla. The two options for obtaining adrenal tissue are (1) whole organ removal post-mortem or during radical nephrectomy; (2) removal during PHEO surgery. Access to high quality normal adrenal tissue is limited. Removal of whole adrenals during nephrectomy is rare, because of improved surgical techniques. For adrenals removed post-mortem, the lag time to proper organ perfusion causes uncontrolled tissue degradation. Adjacent normal adrenal tissue can almost never be obtained from resected PHEOs, because they often replace the entire medulla or are well-encapsulated. If a margin of normal adrenal is attached to a resected PHEO, it seldom contains any medulla. The clean separation of medulla and cortex is further complicated, because their border is convoluted, and because adult adrenal consists of approximately 90% cortex. Thus, the quality of separation has to be evaluated with specific medullary and cortical markers. We describe the successful dissection of highly pure, medullary tissue from adrenals snap-frozen upon resection during radical nephrectomy or after brain death. Separation quality has been verified by quantitative reverse transcription with polymerase chain reaction for the medullary enzymes, tyrosine hydroxylase, and chromogranin A, and for the cortical enzyme, steroidogenic acute regulator.