Tenascin-C expression in renal biopsies from patients with tubulointerstitial nephritis and its relation to disease activity and prognosis

Tenascin-C (TNC) is an extracellular matrix protein that is transiently expressed in close association with tissue remodeling in various organs. Expression of TNC in patients with tubulointerstitial nephritis (TIN) is not well-characterized. Using renal biopsy specimens from 25 patients with TIN and 8 patients with thin basement membrane disease (controls), we assessed immunohistochemical staining for TNC and investigated its relation with clinicopathologic data. TNC was undetectable in the controls, but TNC was observed in the interstitium of specimens from all patients with TIN, and strong TNC staining was detected within active tubulitis lesions. TNC was not principally expressed in glomeruli, and it was also absent from scar tissue. Comparison with Sirius red staining revealed that TNC was present where collagen fibers had not yet formed. The percent area of TNC within the interstitium (% TNC-positive area) showed a significant negative correlation with illness duration and significant positive correlations with the serum CRP level and eGFR aggravation, both of which reflect disease activity. On the other hand, no correlation was found between % TNC-positive area and eGFR recovery during 2 years of follow up. Examination of renal biopsy specimens from TIN patients revealed that TNC appears during the active stage of inflammation and then disappears with healing. This suggests that TNC expression reflects TIN disease activity, but not prognosis.