Background: Peripheral artery disease (PAD) is highly prevalent in patients with diabetes (DM) and associates with a poor prognosis. Revascularization strategies failed to improve outcome, highlighting the need to develop new strategies to promote blood vessel growth. Histone modifications have emerged as key modulators of gene expression, however their role in angiogenic response in DM remains poorly understood. The present study investigates the role of chromatin remodelling in DM-related impairment of angiogenic response. Methodology: Primary human aortic endothelial cells (HAECs) were exposed to normal glucose (NG, 5 mM) or high glucose (HG, 25 mM) for 48 hours. Gene expression profiling was performed by RNA sequencing (RNA-seq). Cell migration and tube formation were employed to study angiogenic properties in HAECs. Levels of the histone methyltransferase SETD7 and its chromatin signature at histone 3 on lysine 4 (H3K4me1) were investigated by Western blot and chromatin immunoprecipitation (ChIP). Pharmacological blockade of SETD7 was achieved by using the selective inhibitor (R)-PFI-2 while the inactive enantiomer (S)-PFI-2 was used as a control. Mice with streptozotocin-induced DM were orally treated with (R)-PFI-2 or vehicle and underwent hindlimb ischemia by femoral artery ligation. Our experimental findings were translated in endothelial cells and gastrocnemius muscle samples obtained from DM patients with PAD. Results: RNA-seq in HG-treated HAECs unveiled the histone methyltransferase SETD7 as the top-ranking transcript. SETD7 upregulation was associated with increased H3K4me1 levels as well as with impaired HAECs migration and tube formation. Both SETD7 silencing and inhibition by (R)PFI-2 rescued hyperglycemia-induced impairment of HAECs migration and tube formation, while SETD7 overexpression blunted the angiogenic response. RNA-seq and ChIP assays showed that SETD7-induced H3K4me1 enables the transcription of the angiogenesis inhibitor semaphorin-3G (SEMA-3G) by increasing chromatin accessibility to PPAR?. Moreover, SEMA-3G overexpression mimicked the impairment of angiogenic response observed during hyperglycemia. In DM mice with hindlimb ischemia, (R)-PFI-2 improved limb perfusion by suppressing SEMA-3G. Finally, RNAseq in vascular specimens from DM patients with PAD confirmed the upregulation of SETD7/SEMA3G signalling, whereas SETD inhibition restored angiogenic properties in ECs from DM patients. Conclusion: SETD7 is a novel epigenetic target to boost neovascularization in DM patients with PAD.

The authors have declared no competing interest.

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This work was supported by the Swiss National Science Foundation (n. 310030_197557), the Swiss Heart Foundation (n. FF19045), the Olga Mayenfisch Foundation, the Swiss Life Foundation, the Kurt und Senta-Hermann Stiftung, the EMDO Stiftung, the Schweizerische Diabetes-Stiftung, the Novo Nordisk Foundation and the Novartis Foundation for Biomedical Research (to F.P.); the Holcim Foundation and the Swiss Heart Foundation (to SC); the Italian Ministry of Health (Ricerca Corrente to the IRCCS MultiMedica).

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The local ethics committee (Cantonal Ethics Committee Zurich, Switzerland; BASEC-Nr. 2020-00378) approved the tissue sample collection and processing for molecular analyses. The collection of human samples was approved by the MultiMedica Research Ethics Committee and was conducted according to the principles outlined in the Declaration of Helsinki.

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