The Occurrence of Senescence in the Arteriovenous Fistula in the Rat.

Background: Maturational failure of dialysis arteriovenous fistulas (AVFs) not uncommonly occurs and is of considerable and timely importance. Our prior studies demonstrate that senescence, a phenotypic process that promotes vascular and other diseases, occurs in the murine AVF. In the present study, we examined whether senescence also occurs in the rat AVF model and the effect of compounds that inhibit or accelerate senescence.

Methods: The rat AVF was created in the femoral vessels by an end vein-side artery anastomosis. We assessed in the AVF the expression of critical drivers of senescence, specifically, the cell cycle inhibitors p16Ink4a and p21Cip1, and such indices of a senescence phenotype as senescence-associated β-galactosidase (SA-β-gal) activity, SA-β-gal staining, and a senescence-associated secretory phenotype (SASP). We examined the effects of compounds that retard or accelerate senescence on AVF blood flow.

Results: The AVF evinced upregulation of p16Ink4a and p21Cip1 when assessed 3 days after AVF creation. The AVF also demonstrated increased SA-β-gal activity in the artery and vein; staining for SA-β-gal in the AVF artery, anastomosis, and vein; and a prominent SASP. Fisetin, an established senolytic that is protective in other models of vascular injury, when administered for 3 weeks, increased AVF blood flow and outward remodeling. Hemin, when administered for 3 weeks, decreased AVF blood flow. We demonstrate that hemin is a novel inducer of a senescence phenotype in endothelial cells, as reflected by several senescence indices. However, when administered relatively acutely (for 5 days) hemin increased AVF blood flow via HO-dependent mechanisms, as the latter was entirely prevented by a competitive inhibitor of HO activity.

Conclusions: The rat AVF exhibits senescence within 3 days of its creation. Chronic administration of a senolytic compound (fisetin) increases AVF blood flow, whereas chronic administration of a pro-senescence compound (hemin) decreases AVF blood flow.