We used the technique of in situ hybridization to determine if cells expressing PDGF B-chain
mRNA can be detected in a model of mesangial proliferative
nephritis in the rat induced with antibody directed against the
Thy 1 antigen present on the mesangial cell membrane. The method involved hybridization with a
digoxigenin-labeled
cRNA probe for the murine PDGF B-chain followed by detection with an anti-
digoxigenin-
alkaline phosphatase conjugate and subsequent colorimetric reaction. In normal rats (N = 4), the majority of glomeruli (74%) were negative for PDGF B-chain
mRNA, whereas 65% of glomeruli from rats with mesangial proliferative
nephritis (N = 4) had segmental or diffuse staining for PDGF B-chain
mRNA in a mesangial pattern. The difference, as measured using a semiquantitative scale, was significant (mean scores 0.4 +/- 0.2 vs. 1.9 +/- 0.2; scale 0 to 3+; P less than 0.001). The increase in PDGF B-chain
mRNA positive cells localized to areas of hypercellularity and was associated with a significant increase in cells positive for PDGF B-chain by immunostaining with a specific
monoclonal antibody (0.8 +/- 0.1 vs. 1.7 +/- 0.4, scale 0 to 3+, normal vs. diseased rats, P less than 0.005).
Complement depletion, which prevents the mesangial cell proliferation, also prevented the increase in cells expressing PDGF B-chain
mRNA and
protein. Thus, this method of in situ hybridization can successfully detect cells expressing PDGF
mRNA in active
glomerulonephritis, and may be useful for detecting cells expressing genes for other
growth factors and
cytokines in both human and experimental models of glomerular injury.