Glomerular matrix: synthesis, turnover and role in mesangial expansion.

The extracellular matrix has an integral role in development, homeostasis and pathology of the glomerulus. Three spatially distinct matrices are present in the glomerulus: the mesangium, and basement membranes of the capillary loops and Bowman's capsule. Each is dominated by basement membrane components, but is distinct in organization and composition. Many matrix components influence cell behavior directly, through specific interactions with receptors, or indirectly through growth factor sequestration. Growth factors may be of great importance in development and disease progression in the glomerulus, and may be central to mesangial expansion. In addition, changes in matrix composition accompany and contribute to the pathological condition, such as the accumulation of matrix in diabetes mellitus.