OBJECTIVETo determine whether increased expressions of gelatinases occur with aging in vivo in kidney tissue of autoimmune MRL/lpr mice by in situ zymography.

METHODSMRL/lpr mice at the age of 8 weeks, 16 weeks and 24 weeks were investigated. Kidney protein extracts were compared for activities of MMP-2/9 by gelatin zymography. Immunohistochemistry and SDS-PAGE gelatin zymography were used to determine the expressions and activities of gelatinase A (MMP-2) and gelatinase B (MMP-9). To determine the net gelatinase activities in murine lupus kidney, in situ zymography was used with autoradiographic emulsion as substrate.

RESULTSBoth gelatinase A and B were seldom detected in the kidney tissue in 8 week old mice, Increased expressions of both latent and activated form enzymes of MMP-2/9 were identified in kidney extraction by SDS-PAGE gelatin zymography and immunohistochemical staining showed both MMP-2 and MMP-9 were obviously up-regulated within glomerulus as well as tubular-interstitium in mice at the age of 16 and 24 weeks. In situ zymography showed markedly increased gelatinase activities in kidney tissue consistent with the results of immunohistochemical staining, it is mainly derived from MMPs and inhibited by EDTA but not by PMSF or aprotinin.

CONCLUSIONSThese in vivo results suggested that MMP-2/-9 expressions were significantly up-regulated with aging in murine lupus nephritis, which may play an important role in promoting the remodeling formation of ECM and thus contribute to the progression of renal damage in this model.