Hypothesis: VSMC metabolic reprogramming via HIF-1α–PDK1 axis suppresses tropoelastin transcription and promotes osteogenic trans‑differentiation, driving arterial stiffness and calcification

Hypothesis

VSMC metabolic reprogramming driven by HIF‑1α–PDK1 signaling suppresses tropoelastin (ELN) transcription and pushes cells toward an osteogenic phenotype, thereby linking arterial stiffness to active calcification.

Mechanistic Rationale

Recent work shows that VSMC phenotypic switching and inflammation are central to stiffness [1][2]. Yet the drop in tropoelastin synthesis remains poorly linked to these cellular states [3]. We propose that sustained HIF‑1α activation—common in atherosclerotic plaques under oscillatory shear and hypoxia—up‑regulates pyruvate dehydrogenase kinase 1 (PDK1). PDK1 phosphorylates and inhibits pyruvate dehydrogenase, shunting pyruvate away from mitochondria and toward lactate production. This metabolic shift lowers acetyl‑CoA availability for histone acetylation at the ELN promoter, reducing tropoelastin transcription. Simultaneously, HIF‑1α directly binds osteogenic promoters such as RUNX2, favoring a calcifying VSMC state. The combined effect yields stiff, calcified arteries without requiring elastin fragmentation as a primary cause.

Testable Predictions

1. In human carotid plaques, high HIF‑1α and PDK1 expression will correlate with low ELN mRNA and high RUNX2 levels at the single‑cell level.
2. Pharmacologic inhibition of PDK1 (e.g., with dichloroacetate) in ex‑vivo plaque cultures will increase ELN transcription and decrease alkaline phosphatase activity, a marker of osteogenic VSMCs.
3. Genetic knockdown of HIF‑1α in VSMCs of atherosclerotic mice will preserve elastin content and reduce calcification despite unchanged lipid load.

Experimental Approach

• Obtain fresh human carotid endarterectomy specimens (BiKE) and perform spatial transcriptomics coupled with immunofluorescence for HIF‑1α, PDK1, ELN, and RUNX2 [4][5].
• Quantify co‑localization using image‑analysis pipelines; calculate correlation coefficients across plaque regions.
• Culture VSMCs isolated from plaques under hypoxic, oscillatory‑flow conditions; treat with dichloroacetate or siRNA against PDK1/HIF‑1α.
• Measure ELN expression by qPCR, acetyl‑CoA levels by LC‑MS, and osteogenic differentiation via Alizarin Red staining and RUNX2 western blot.
• Validate findings in ApoE‑/‑ mice fed Western diet, with VSMC‑specific Hif1a knockout; assess arterial stiffness by pulse‑wave velocity and calcification by von Kossa staining.

If PDK1 inhibition restores tropoelastin and blocks osteogenic shift, the hypothesis gains support; failure to observe these changes would falsify the proposed mechanistic link between metabolic reprogramming, elastin loss, and calcification.