Interstitial stroma cells are derived from the metanephric mesenchyme. The cells migrate toward the medullary zone of the kidney but do not develop into epithelial cells. During early metanephric development, fibroblast-like spindle-shaped stromal cells can be detected around the Pax2-positive cell of the cap mesenchyme and later on around nascent ureteric buds and nephrons. Stromal mesenchyme cells are characterized by expression of the transcription factor Foxd1. Foxd1-positive cell lineage derivatives differentiate to form all the cell types that comprise the mural cell layer of the kidney arteries and arterioles, including vascular smooth muscle cells, renin cells, and perivascular fibroblasts, along with mesangial cells and various cell types of the kidney interstitium, including pericytes. Later in kidney development, the stroma is divided into two distinct populations: cortical and medullary. Mature interstitial stroma cells provide structural supportive to collecting ducts, loops of Henle and vasa recta, and also produce extracellular matrix (ECM) and prostaglandins.