Allelic Depletion of grem1 Attenuates Diabetic Kidney Disease

Abstract

OBJECTIVEGremlin (grem1) is an antagonist of the bone morphogenetic protein family that plays a key role in limb bud development and kidney formation. There is a growing appreciation that altered grem1 expression may regulate the homeostatic constraints on damage responses in diseases such as diabetic nephropathy.RESEARCH DESIGN AND METHODSHere we explored whether knockout mice heterozygous for grem1 gene deletion (grem1+/−) exhibit protection from the progression of diabetic kidney disease in a streptozotocin-induced model of type 1 diabetes.RESULTSA marked elevation in grem1 expression was detected in the kidneys and particularly in kidney tubules of diabetic wild-type mice compared with those of littermate controls. In contrast, diabetic grem1+/− mice displayed a significant attenuation in grem1 expression at 6 months of diabetes compared with that in age- and sex-matched wild-type controls. Whereas the onset and induction of diabetes were similar between grem1+/− and wild-type mice, several indicators of diabetes-associated kidney damage such as increased glomerular basement membrane thickening and microalbuminuria were attenuated in grem1+/− mice compared with those in wild-type controls. Markers of renal damage such as fibronectin and connective tissue growth factor were elevated in diabetic wild-type but not in grem1+/− kidneys. Levels of pSmad1/5/8 decreased in wild-type but not in grem1+/− diabetic kidneys, suggesting that bone morphogenetic protein signaling may be maintained in the absence of grem1.CONCLUSIONSThese data identify grem1 as a potential modifier of renal injury in the context of diabetic kidney disease.

Deletion of Gremlin1 increases cell proliferation and migration responses in mouse embryonic fibroblasts

“…Grem1−/− embryos were readily isolated from grem1+/− crosses, although at lower than expected Mendelian frequencies (data not shown). These fibroblasts provided a robust model in which to test proliferative responses in the total absence of Grem1, as opposed to previous experiments examining cells with reduced Grem1 expression [20,22]. We have previously shown that Grem1 expression is detected in MEFs isolated from E13.5 embryos [22].…”

“…1. Generation of mouse embryo fibroblasts (MEFs).MEFs were generated from E13.5 embryos of grem1+/− crosses and genomic DNA isolated as described in [22]. A. PCR reactions to detect the wild-type grem1 allele or recombinant LacZ allele were performed to identify wild-type, grem1+/− or grem1−/− cells.…”

“…RNA was isolated using Trizol® (Invitrogen) and reverse transcription reactions were carried out as described [22]. Real-time quantitative PCR was carried out on an ABI Prism 7700 sequence detection system (Applied Biosystems) using the TaqMan Universal PCR Master Mix, VIC-labelled 18s rRNA as an endogenous control and FAM labelled TaqMan probe sets provided by Applied Biosystems (Id1: Mm00775963_g1; PAI-1: Mm00435860_m1).…”

“…The trypsinised embryo was added to the plate, mixed and incubated at 37°C in a humidified chamber of 95% air and 5% CO 2 for 24 h. Major debris was removed, cells were trypsinised and passaged as normal. Genotyping was carried out as previously described [22].…”

Gremlin1 and chronic pancreatitis: a new clinical target and biomarker?

“…Increased Gremlin1 expression has been identified in fibrosis associated with kidney, lung, heart and liver disease [10,11]. Targeting Gremlin1 by gene deletion or shRNA knockdown reduced the severity of kidney disease in mouse models of diabetic nephropathy (DN) [12,13]. A genetic variant of Gremlin1 is associated with increased risk of diabetic nephropathy [14].…”