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The secreted glycoprotein sclerostin has recently emerged as a key negative regulator of Wnt signaling in bone and has stimulated considerable interest as a potential target for therapeutics designed to treat conditions associated with low bone mass, such as osteoporosis. We have determined the structure of sclerostin, which resulted in the identification of a previously unknown binding site for heparin, suggestive of a functional role in localizing sclerostin to the surface of target cells. We have also mapped the interaction site for an antibody that blocks the inhibition of Wnt signaling by sclerostin. This shows minimal overlap with the heparin binding site and highlights a key role for this region of sclerostin in protein interactions associated with the inhibition of Wnt signaling. The conserved N-and C-terminal arms of sclerostin were found to be unstructured, highly flexible, and unaffected by heparin binding, which suggests a role in stabilizing interactions with target proteins.

Wnt-modulator in surface ectoderm (WISE) is a secreted modulator of Wnt signaling expressed in the adult kidney. Activation of Wnt signaling has been observed in renal transplants developing interstitial fibrosis and tubular atrophy; however, whether WISE contributes to chronic changes is not well understood. Here, we found moderate to high expression of WISE mRNA in a rat model of renal transplantation and in kidneys from normal rats. Treatment with a neutralizing antibody against WISE improved proteinuria and graft function, which correlated with higher levels of b-catenin protein in kidney allografts. In addition, treatment with the anti-WISE antibody reduced infiltration of CD68 + macrophages and CD8 + T cells, attenuated glomerular and interstitial injury, and decreased biomarkers of renal injury. This treatment reduced expression of genes involved in immune responses and in fibrogenic pathways. In summary, WISE contributes to renal dysfunction by promoting tubular atrophy and interstitial fibrosis.

We have conducted three studies to examine the role of TNFalpha in islet destruction in female nonobese diabetic mouse (NOD) mice, a model of human autoimmune diabetes, using polyethylene glycolated (PEGylated) soluble TNF receptor type I (PEG sTNF-RI) as TNFalpha antagonist. PEG sTNF-RI (3 mg/kg, sc) was given every other day to NOD mice from age wk 8 for 12 wk (study 1), from age wk 12 for 8 wk (study 2), or from age wk 8 for 3 wk, with cyclophosphamide (6 mg/mouse) injected at wk 9 to accelerate the onset of diabetes (study 3). Diabetic incidence was reduced (control vs. PEG sTNF-RI) from 68.7% (11 of 16) to 18.3% (3 of 16) in study 1, from 84.6% (11 of 13) to 28.5% (4 of 14) in study 2, and from 66.6% (8 of 12) to 23.1% (3 of 13) in study 3, respectively. The incidence of insulitis was also reduced from 91.6% (11 of 12) to 12.5% (2 of 16) in study 1 and from 100% (7 of 7) to 16.6% (2 of 12) in study 2 by PEG sTNF-RI. PEG sTNF-RI also largely preserved islet insulin content, reduced mRNA of inducible nitric oxide synthase and IL-6 in pancreases, and lowered plasma corticosterone, glycerol, and free fatty acid levels. These results confirm a pathogenic role of TNFalpha in mediating insulitis in NOD mice and suggest the prophylactic and therapeutic potential of PEG sTNF-RI for human autoimmune diabetes.

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