Enhanced proliferation, apoptosis, and matrix accumulation by mesangial cells derived from HIV-1 transgenic mice

Background: Mice, transgenic for HIV-1 genes, have been demonstrated to develop renal lesions mimicking HIV-associated nephropathy. Focal glomerulosclerosis (FGS) has been reported to be the predominant glomerular lesion in these animals. In the other models of FGS, the accumulation of mesangial matrix and mesangial cell proliferation have been shown to be the preceding abnormalities. We evaluated the proliferation, apoptosis, and matrix accumulation by mesangial cells derived from mice transgenic for HIV-1 genes as well as from nontransgenic mice. Methods: Mesangial cells were cultured from mice transgenic for HIV-1 genes (HTrMC) and nontransgenic mice (NTrMC) of the same age and sex. The growth rate of HTrMC and NTrMC was determined under identical conditions. Morphologic evaluation of apoptosis was performed by staining cells with Hoechst (H)-33342 and propidium iodide. Accumulation of mesangial cell collagen type IV, laminin, and fibronectin was measured by the dot blot assay. Total RNA was extracted from HTrMC and NTrMC and Northern blots were generated. These blots were probed with specific probes for TGF-beta, proteoglycan (P16), and GAPDH. Results: Mesangial cells (HTrMC) derived from transgenic mice had greater (P < 0.004) proliferation when compared to mesangial cells (NTrMCs) from nontransgenic mice (HTrMCs, 4.2 +/- 0.3 vs NTrMCs, 3.0 +/- 0.2 x 10(4) cells/well). HTrMCs also showed enhanced (P < 0.0001) apoptosis compared to NTrMCs (HTrMCs, 13.2 +/- 1.5% vs NTrMCs, 3.1 +/- 0.5% apoptotic cells/field). HTrMCs accumulated an increased (P < 0.02) amount of collagen type IV (HTrMCs, 5659.7 +/- 472.8 vs NTrMCs, 3882.2 +/- 339.7 ng/well); whereas NTrMCs accumulated a greater amount of laminin when compared to HTrMCs (HTrMCs, 12.8 vs NTrMCs, 29.6 +/- 2.9 ng/well). HTrMCs also showed an enhanced mRNA expression of TGF-beta and an attenuated expression of proteoglycan(P16). Conclusions: These results suggest that mesangial cells derived from mice transgenic for HIV-1 genes have enhanced proliferation and collagen accumulation. The enhanced expression of TGF-beta may have contributed to enhanced HTrMC proliferation and the accumulation of collagen. The present study provides the basis for a hypothesis that mesangial cells may be contributing to the development of focal glomerulosclerosis in mice transgenic for HIV-1 genes.