Transforming growth factor-beta signaling via ALK1 and ALK5 regulates distinct functional pathways in vein graft intimal hyperplasia

Bradshaw, A.; Low, E.; Schwartze, J. T.; Kurkiewicz, A.; Pek, M.; Kelly, D.; Shaw, A.; Thorikay, M.; McClure, J.; McBride, M.; Arias-Rivas, S.; Francis, S. E.; Morrell, N.; Delles, C.; Herzyk, P.; Havenga, M. J.; Nicklin, S. A.; ten Dijke, P.; Baker, A. H.

doi:10.1101/860320

bioRxiv · 10.1101/860320

Transforming growth factor-beta signaling via ALK1 and ALK5 regulates distinct functional pathways in vein graft intimal hyperplasia

Bradshaw, A.·Low, E.·Schwartze, J. T.·Kurkiewicz, A.·Pek, M.·Kelly, D.·Shaw, A.·Thorikay, M.·McClure, J.·McBride, M.·Arias-Rivas, S.·Francis, S. E.·Morrell, N.·Delles, C.·Herzyk, P.·Havenga, M. J.·Nicklin, S. A.·ten Dijke, P.·Baker, A. H.

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Abstract

RationaleTransforming growth factor-beta (TGF{beta}) is tightly regulated at multiple levels, with regulation at the receptor level now recognized as a key determinant of the cellular response to this pleiotropic cytokine. TGF{beta} promotes saphenous vein graft neointima formation after coronary artery bypass graft (CABG) surgery, inducing smooth muscle cell (SMC) hyperplasia and fibrosis by signaling via activin receptor-like kinase 5(ALK5). However, the role of the alternate TGF{beta} receptor ALK1 remains completely unknown. ObjectiveTo define the receptor pathways activated by TGF{beta} in SMCs and their mechanistic importance during CABG neointima formation. Methods and resultsRadioligand co-IP assays revealed direct interactions between TGF{beta}, ALK5 and ALK1 in primary saphenous vein graft SMC (HSVSMC) from patients undergoing CABG. Knockdown and pharmacological inhibition of ALK5 or ALK1 in HSVSMC significantly attenuated TGF{beta}-induced phosphorylation of receptor-regulated (R)-Smads 2/3 and 1/5, respectively. Microarray profiling followed by qRT-PCR validation showed that TGF{beta} induced distinct transcriptional networks downstream of ALK5 or ALK1, associated with HSVSMC contractility and migration, respectively and confirmed using migration assays as well as qRT-PCR and western blot assays of contractile SMC markers. scRNAseq analysis of TGF{beta}-treated HSVSMC identified distinct subgroups of cells showing ALK5 or ALK1 transcriptional responses, while RNA velocity analyses indicated divergence in differentiation towards ALK5 or ALK1-dominant lineages. ALK1, ALK5 and their downstream effectors pSmad1/5 and pSmad2/3 were localized to SMA+ neointimal SMCs in remodelled mouse vein grafts. Pharmacological inhibition or genetic ablation of Smad1/5 substantially reducing neointima formation following acute vascular injury. Notably, expression and activation of ALK1, ALK5 and their respective downstream R-Smads was already evident in hyperplastic saphenous veins prior to grafting. ConclusionsWhilst canonical TGF{beta} signaling via ALK5 promotes a contractile HSVSMC phenotype, transactivation of ALK1 by TGF{beta} induces neointima formation by driving cell migration. Restoring the balance between ALK1 and ALK5 in HSVSMC may represent a novel therapeutic strategy for vein graft failure.

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Bradshaw, A., Low, E., Schwartze, J. T., Kurkiewicz, A., Pek, M., Kelly, D., Shaw, A., Thorikay, M., McClure, J., McBride, M., Arias-Rivas, S., Francis, S. E., Morrell, N., Delles, C., Herzyk, P., Havenga, M. J., Nicklin, S. A., ten Dijke, P., Baker, A. H.. 2019-11-29. Transforming growth factor-beta signaling via ALK1 and ALK5 regulates distinct functional pathways in vein graft intimal hyperplasia. https://doi.org/10.1101/860320

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