Differential Zonal Expression and Adrenocorticotropin Regulation of Secreted Protein Acidic and Rich in Cysteine (SPARC), a Matricellular Protein, in the Midgestation Human Fetal Adrenal Gland: Implications for Adrenal Development

Context: Matricellular proteins are a group of secreted, multifunctional extracellular matrix glycoproteins that includes thrombospondins (TSPs), tenascin-C, and secreted protein acidic and rich in cysteine (SPARC). They may be implicated in the dynamic developmental processes of the human fetal adrenal (HFA) in which the outer, definitive zone (DZ) cells are postulated to proliferate, migrate centripetally, differentiate, and populate the inner, steroidogenic fetal zone (FZ). Objective: The objective of the study was to identify a matricellular molecule that likely plays a major role in HFA development. Design: Studies involved RNA, cryosections, and cell cultures from 14- to 23-wk HFAs and human adult adrenal RNA. Main Outcome Measures: Measures included transcripts encoding matricellular proteins, using real-time quantitative RT-PCR; SPARC localization by immunostaining; and ACTH regulation of SPARC expression and secretion by quantitative RT-PCR and Western blot. Results: SPARC HFA mRNA was 100-, 700-...