Aim: 

The extra-adrenal Zuckerkandl's paraganglion (ZP) is used as a source of chromaffin cells for transplantation in parkinsonian animals. Aging or corticoids can affect its viability, and this tissue needs further characterisation. The objectives were: i) to compare the main morpho-functional characteristics of prepubertal and old ZPs, ii) to discern phenotypic changes after sub-chronic dexamethasone, and iii) to study the presence of stem cells in extradrenal tissue.

Methods: 

For these purposes, immunostaining methods, stereology, voltammetry, cell culture, western blotting, and ELISA were employed.

Results: 

The findings revealed that paraganglia were composed of mesenchymal tissue and chromaffin cells. In prepubertal rats, chromaffin cells are arranged as "cell nests" or small cell clusters. In old paraganglia, cells form clusters or are dispersed throughout the mesenchyma. Chromaffin cells possess a rounded morphology (diameter, 12 to 15 mm), with intracytoplasmic granules containing catecholamines. Prepubertal and old ZP chromaffin cells are mostly noradrenergics, and a few of them are dopaminergics. Aging reduces the amount of chromaffin tissue (28% in prepubertal rats vs. 11% in old animals), and induces the presence of adrenergic cells. Both prepubertal and old cells express the neurotrophic factors GDNF and TGF-b₁, aging leading to reduced levels of both growth factors. Dexamethasone (50mg/Kg daily, 5 days) leads to the expression of phenylethanolamine-N-methyl-transferase (PNMT) in prepubertal paraganglia, and to a higher content and release of adrenaline. Finally, prepubertal ZPs possess stem cells located inside the cell nests. There are fusiform-like EGFR+/GFAP+ cells, and rounded SOX2+ cells that seem to be the immediate precursors of chromaffin cells because progressively express TH and/or DBH.

Conclusion: 

Extra-adrenal paraganglia contain chromaffin cells arranged as cell nests, the chromaffin tissue and catecholamine/trophic content is reduced with aging, dexamethasone induces PNMT expression, and extra-adrenal tissue contains stem cells.

Supported by grants to EFE from Junta de Andalucia (BIO127, and Proyectos de Excelencia, EXC/2006/CVI127-1716), and Red de Terapia Celular (Instituto Carlos III, RD06).