Increased extracellular matrix synthesis and mRNA in mesangial cells grown in high-glucose medium

Abstract

Nodular expansion of glomerular mesangium with increased amounts of extracellular matrix (ECM) material is pathognomic of diabetic nephropathy. The precise mechanisms involved in this accumulation are unknown. Recently, we reported using a solid-phase enzyme-linked immunosorbent assay (ELISA) technique that glomerular mesangial cells, the principal cell type residing in glomerular mesangium, accumulate 50-60% more fibronectin (FN), laminin (LM), and type IV collagen (T-IV) when cultured in medium containing high glucose (30 mM) (S. H. Ayo, R. A. Rodnik, J. Garoni, W. F. Glass II, and J. I. Kreiberg. Am. J. Pathol. 136: 1339-1348, 1990). ECM assembly is controlled by its rate of synthesis and degradation, as well as its binding and rate of incorporation into the ECM. To elucidate the mechanisms involved, pulse-chase experiments were designed to estimate ECM protein synthesis from the incorporation of Trans-35S [( 35S]methionine, [35S]cysteine) into immunoprecipitated FN, LM, and T-IV. mRNA levels were examined, and degradation rates were estimated from the disappearance of radioactivity from matrix proteins in mesangial cells previously incubated with Trans-35S. One week of growth in 30 mM glucose resulted in approximately 40-50% increase in the synthesis of all three matrix proteins compared with 10 mM glucose-grown cells. This was accompanied by a significant increase in the transcripts for all three matrix proteins (approximately twofold). The specific activity of the radiolabel in trichloroacetic acid-precipitable cell protein showed no difference between cells grown in 10 or 30 mM glucose, indicating that total protein synthesis was unchanged. After 1 wk, the rate of FN, LM, and T-IV collagen degradation was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural changes in renal arterioles in Type I diabetic patients

“…It seems reasonable to assume that the underlying mechanism for all of these changes is a metabolically determined increase in matrix production. This is strongly supported by in vitro studies showing increased production by cultured mesangial cells if grown in high glucose [18]. Similarly, myomedial cells isolated from larger arteries (aorta) increase matrix production when cultured in serum from diabetic patients [19].…”

Hyperglycemia‐induced TGFβ and fibronectin expression in embryonic mouse heart

“…Cultured rodent or human endothelial cells exposed to hyperglycemia (360 -540 mg/dl glucose) demonstrate increased ECM (collagen and FN) protein or mRNA expression (Cagliero et al, 1988;Spiro et al, 1995;Mueller et al, 1997). Cultured renal mesangial cells exposed to hyperglycemia demonstrate increased expression of ECM components, including FN, collagen, laminin, and others (Ayo et al, 1991;Nahman et al, 1992;Wahab et al, 1996). Diabetic mice have increased TGF␤1 mRNA and ECM deposition in renal glomeruli and myocardium (Yang et al, 1995;Chen et al, 2001), and ECM proteins accumulate in the kidney, skin, heart, and blood vessels of human diabetic patients (Mauer et al, 1981;Osterby, 1983).…”

High glucose level inhibits capacitative Ca 2 + influx in cultured rat mesangial cells by a protein kinase C-dependent mechanism

“…This concept has been developed in different cell systems derived fom target organs for the complications of diabetes [26,27]. Extensive evidence has been provided that mesangial cells of the kidney glomerulus grown in high glucose media express a secretory phenotype, with increased matrix production and a decreased proliferative rate [28][29][30][31]. In addition, the cells appear less sensitive to the vasomotor action of peptides and autacoids that activated phospholipase C-coupled receptors [8,10].…”