- SPARC is expressed by mesangial cells in experimental mesangial proliferative nephritis and inhibits platelet-derived-growth-factor-medicated mesangial cell proliferation in vitro. Pichler, R.H., Bassuk, J.A., Hugo, C., Reed, M.J., Eng, E., Gordon, K.L., Pippin, J., Alpers, C.E., Couser, W.G., Sage, E.H., Johnson, R.J. Am. J. Pathol. (1996)