An accumulation of IGF-I and IGF-binding proteins in human umbilical cord.

It is known that extracellular matrix components (ECM) may serve as a storage site to concentrate and stabilize growth factors in the vicinity of cells. IGF-I is expressed in most fetal tissues and it is involved in anabolic effects on protein and sulphated glycosaminoglycans biosynthesis, cell proliferation and differentiation. We demonstrated that human umbilical cord (UC) tissues contain large amounts of IGF-I and IGF-I-binding proteins (BP-3 and BP-1). Particularly Wharton's jelly appears to be an abundant reservoir of IGF-I and BPs. Relatively low amount of cells and large amounts of collagen and glycosaminoglycans in UC tissues (especially in Wharton's jelly) suggest that IGF-I may play a major role in stimulation of these cells to produce ECM components. The specific BPs in these tissues may be important modulators of IGF-I action during fetal development.