Published online before print August 7, 2008

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(American Journal of Pathology. 2008;173:631-642.)
© 2008 American Society for Investigative Pathology
DOI: 10.2353/ajpath.2008.080025

Tissue Transglutaminase Contributes to Interstitial Renal Fibrosis by Favoring Accumulation of Fibrillar Collagen through TGF-β Activation and Cell Infiltration

Nasim Shweke^*, Nada Boulos^*, Chantal Jouanneau^*, Sophie Vandermeersch^*, Gerry Melino, Jean-Claude Dussaule^*, Christos Chatziantoniou^*, Pierre Ronco^*¶ and Jean-Jacques Boffa^*¶

From the INSERM UMR,^* Paris, France; UPMC, Université Paris 06, Paris, France; Biochemistry Laboratory, Department of Experimental Medicine, University Tor Vergata, Rome, Italy; Department of Physiology, Assistance Publique-Hôpitaux de Paris, Hopital Saint-Antoine, Paris, France; Department of Nephrology,^¶ Assitance Publique-Hôpitaux de Paris, Hôpital Tenon, Paris, France

Renal fibrosis is defined by the exaggerated accumulation of extracellular matrix proteins. Tissue transglutaminase (TG2) modifies the stability of extracellular matrix proteins and renders the extracellular matrix resistant to degradation. In addition, TG2 also activates transforming growth factor-β (TGF-β). We investigated the involvement of TG2 in the development of renal fibrosis using mice with a knockout of the TG2 gene (KO). These mice were studied at baseline and 12 days after unilateral ureteral obstruction, which induced a significant increase in interstitial TG2 expression in wild-type mice (P < 0.001). Interstitial fibrosis was evident in both groups, but total and fibrillar collagen was considerably lower in KO mice as compared with wild-type (P < 0.001). Similarly, mRNA and protein expression of collagen I were significantly lower in KO animals (P < 0.05). A statistically significant reduction in renal inflammation and fewer myofibroblasts were observed in KO mice (P < 0.01). Free active TGF-β was decreased in KO mice (P < 0.05), although total (active + latent) TFG-β concentration did not differ between groups. These results show that mice deficient in TG2 are protected against the development of fibrotic lesions in obstructive nephropathy. This protection results from reduced macrophage and myofibroblast infiltration, as well as from a decreased rate of collagen I synthesis because of decreased TGF-β activation. Our results suggest that inhibition of TG2 may provide a new and important therapeutic target against the progression of renal fibrosis.

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