Inflammation, oxidation and venous neointimal hyperplasia precede vascular injury from AVF creation in CKD patients

Abstract

Purpose: Intimal hyperplasia (IH), a well-recognized cause of dialysis vascular access failure, is generally believed to be an acquired pathologic lesion. Recent data suggests that IH is present prior to AVF creation. We sought to determine whether pre-existing inflammation and oxidation co-exist with IH prior to their incorporation into an AVF conduit, as their presence may predispose the AVF to further IH following AVF creation.

Methods: At the time of first AV access surgery, vein segments were collected from ten Stage 4 and 5 CKD patients undergoing AVF creation 6-12 months prior to anticipated dialysis initiation. Morphometry and immunohistochemistry was performed to detect inflammatory markers IL-6, TGF-ß1, and TNFa, and markers of DNA oxidative damage (8-Hydroxy-2'-deoxyguanosine [HNE]) and lipid peroxidation (4-Hydroxy-2-Nonenal [8OHdG]).

Results: The degree of IH severity was variable. IL-6, TGF-ß1, and TNFa co-localized with a-smooth muscle actin prominently within the venous intima and media. Although more diffuse, HNE and 8OHdG were intensely expressed in parallel with the inflammatory markers. In spite of these findings, however, neither extant IH nor the intensity of inflammatory or oxidative markers were associated with primary or secondary AVF failure at 12 month follow-up.

Conclusions: Not only does venous IH pre-exist, but inflammation and oxidation markers are present within veins used for the AVF conduit prior to its creation in CKD patients as early as one year before dialysis is commenced. Nevertheless, short and long-term AVF outcomes were not associated with the inflammatory or oxidative burden, suggesting the complexity of AVF dysfunction in humans with CKD.

Fig. 1

Marked intimal hyperplasia (indicated by double arrows, H and E staining) and severe luminal stenosis in the basilic vein of a pre-dialysis Stage 4 CKD (GFR=20 mL/min) patient prior to AVF creation.

Fig. 2

Representative photomicrographs of inflammatory biomarker immunoreactivity in vein segment of CKD patient obtained at the time of AVF creation. (A) a-smooth muscle actin (B) TNF-a (C) TGF-b and (D) IL-6. Note that neointima and media show abundant staining (dark brown) of a-SMA, reflecting VSMC’s and that a similar pattern of staining is present for inflammatory markers.

Fig. 3

Local lipid peroxidation (HNE) and DNA oxidation (8-OHdG) are present in vein of CKD patient prior to vascular injury. (A, C). Colon control tissue with no evidence of HNE or 8-OHdG. (B) Localization of HNE (brown) in venous tissue. Note pattern of increased neointimal and media staining, with staining of the adventitia and neovasculature (magnification, x20). (D) Expression of 8-OHdG in neointima and media, with somewhat more diffuse pattern of staining.

Fig. 4

Inflammatory and oxidative mediators (relative expression/μm2) within veins of CKD patients (n=10) at the time of AVF creation. Note the lack of difference in mediator expression in veins used for AVF which remained patent or failed during a 12 month follow-up period.