Abstract 1514: CC Chemokine Receptor-1 (CCR-1) Recruits Host-Derived Intimal Smooth Muscle-like Cell in Graft Arterial Disease
Graft arterial disease (GAD) limits long-term solid organ allograft survival. GAD lesions contain smooth muscle-like cells (SMLC), leukocytes, and extracellular matrix. The majority of intimal SMLC derive from host precursor cells, but the mechanisms of their recruitment and proliferation remain unknown. Recent studies have demonstrated the presence of certain chemokines in allografts during the development of GAD lesions. This study tested the hypothesis that specific chemokines could recruit SMLC in GAD.
Method and Results: Primary cultures of intimal SMLC were prepared from murine aortic allografts; after 8–12-weeks, murine aortic allografts no longer contain donor medial SMC, enabling selective SMLC isolation. We compared primary cultures of intimal SMLC from murine aortic allografts with primary medial smooth muscle cell (SMC) cultured from native aortas. RNase Protection assay showed that SMLC only expressed CCR-1 mRNA, but no detectable mRNA expression of CCR-1 as well as other chemokine receptors (e.g., CCR-2 through -5, and CXCR-2, -3, and -4) by medial SMC. Binding assay and immunohistochemistry demonstrated functional CCR-1 on SMLC. CCR-1 ligands, C10 and RANTES induced concentration-dependent proliferation of the SMLC, but not medial SMC. C10 and RANTES also induced migration of the SMLC; C10 (371 ± 76 μm/day, n=3, p <0.005), or RANTES (543 ± 38 μm/day, n=3, p < 0.0001) vs. control (29 ± 15 μm/day, n=3). RANTES induced phosphorylation of c-jun N-terminal kinase (JNK) in SMLC and the selective JNK inhibitor (SP600125) abrogated RANTES-induced SMLC proliferation. Finally, aortic allografts in CCR1- deficient hosts showed significantly reduced GAD compared to allografts in wild-type recipients. Allografts in CCR1-deficient hosts show significantly reduced GAD lesion intimal areas (1.42 ± 3.23 x 104 μm2, n=9, p<0.001) compared to allografts in WT recipients (2.28 ± 1.60 x 105 μm2, n=12).
Conclusion: Blockade of CCR-1 signaling attenuates GAD in murine aortic transplantation. Allograft intimal SMLC, but not native medial SMC, express functional CCR-1 that contributes to GAD by regulating their recruitment and proliferation. These studies suggest a novel and important therapeutic strategy for preventing allograft arteriopathy.