Premature senescence of skin fibroblasts from insulin-dependent diabetic patients with kidney disease

Abstract

Diabetic glomerulopathy develops in a subset only of patients with insulin-dependent diabetes (IDDM) and early, in its course, is characterized by cell hypertrophy and by excessive extracellular matrix production. These observations suggest that an alteration in the control of cell growth processes may contribute to its pathogenesis and be related to the susceptibility to kidney disease. We therefore investigated whether the development of diabetic nephropathy is associated with abnormalities of cell growth and morphology. Cultured skin fibroblasts from 14 IDDM patients with nephropathy (DN) were compared with those of 10 IDDM patients without nephropathy (D) and of 14 control non-diabetic subjects (C). Cell volume (in arbitrary units) and total protein content (μg/10,000 cells) were increased in serially passage skin fibroblasts of IDDM patients with nephropathy (DN = 809.5 ± 33.1 and 1.93 ± 0.38 vs. D = 764.4 ± 31.5 and 1.5 ± 0.37, P = 0.0006 and P = 0.03, respectively). These hypertrophic cells had a tendency to a slower duplication rate and excited a dissociation of the DNA and cytoplasmic cell-cycles, resulting in a higher proportion of tetraploid cells (DN = 25 ± 15% vs. D = 6 ± 4%, P = 0.005; and vs. C = 10 ± 8%, P = 0.04). The frequency of terminally differentiated post-mitotic fibrocytes, cells specialized for extracellular matrix production, was higher in patients with nephropathy compared to that patients without nephropathy and normal controls (DN = 34 ± 14% vs. D = 21 ± 10%, P = 0.02; and vs. C = 19 ± 12%, P = 0.008). That early differentiation was specific feature of cells derived from patients with diabetic nephropathy was confirmed by the study of cell life- span which demonstrated that these cells aged prematurely (log rank test χ2 = 10,012; P = 0.0067). We concluded that an acceleration of cell aging is a peculiar feature of diabetic kidney disease and may contribute to its pathological tissue changes.