Background:
Degenerative aortic valve disease (DAVD) evolves from inflammatory and fibro-calcific conditions in the aortic valve (AV). The development of DAVD is an active process with similarities to both atherosclerosis and bone formation. Furthermore, cardiovascular risk factors like type 2 diabetes mellitus (DM2) have been associated with the pathogenesis of DAVD, however, the underlying mechanism predisposing DM2 patients for DAVD have not been well investigated. We therefore performed AV tissue analysis and phenotyping of platelets and circulating inflammatory cells to identify disease-related characteristics in DAVD patients with and without DM2.

Methods:
We retrospectively analyzed 317 consecutive patients with severe symptomatic aortic stenosis (AS) with and without DM2 undergoing AV replacement. Patients were categorized by the presence of DM2 and were further stratified into slow (SP) and fast progressive (FP) AS (FPAS+DM2: n=34, FPAS-DM2: n=113, SPAS+DM2: n=43, SPAS-DM2: n=127). Cardiac workup included blood sampling for laboratory parameters, phenotyping of platelets and monocytes, and analysis of explanted valve tissue.

Results:
Immunohistochemical analysis of AVs revealed enhanced infiltration of CD3⁺ and CD68⁺ inflammatory cells in patients with DM2 (p<0.05). We found significant differences regarding valvular characteristics comparing FPAS+DM2 vs FPAS-DM2 vs SPAS+DM2 vs SPAS-DM2 (p<0.001). Interestingly, patients with DM2 also showed a systemic hyperinflammation mediated by platelets, monocytes, and platelet-leucocyte aggregates. We found a higher white blood cell and monocyte subset count and increased platelet/platelet-leucocyte aggregate activation in DM2 (p<0.05). Moreover, the three subsets of monocytes comprising classical (CD14⁺⁺CD16^-), intermediate (CD14⁺CD16⁺), and non-classical (CD14^dimCD16⁺⁺) monocytes showed different expression of established markers of adhesion, migration, and T cell activation (CD11b, CD54, CX3CR1, CD11a, CD49a, CCR2, HLA-DR) in DM2 patients (p<0.05). All three subsets of monocytes revealed a significant increase of intracellular chemokine/cytokine expression comprising macrophage migration inhibitory factor (MIF), CXCL12, and CXCL14 along with their binding receptors CXCR4/CXCR7 in DM2 (p<0.05). Platelets and platelet-leucocyte aggregates contained significant different amounts of chemokine/cytokines and increased expression of activation markers in DM2 (p<0.05). Unsupervised in-depth phenotyping identified disease-specific clusters of platelet and monocyte marker profiles in DM2, which were associated with fast progression of AS (p<0.05). Finally, principal component analysis confirmed that these cell phenotypes were strongly associated with fast progressive AS in DM2.

Conclusion:
Patients with AS and DM2 were characterized by significant alterations of local and systemic inflammation comprising platelets and monocytes, which could be linked to accelerated inflammation of AV tissue. Disease-specific cell phenotypes may help to identify DM2 patients at risk for fast progressive AS at early stages. The described inflammation-dependent mechanisms in progressive DAVD suggest that DM2 patients could be molecularly in a more unfavorable, accelerated and thereby more advanced disease stage with a higher grade of local and systemic inflammation than non-diabetic patients. Patients with DM2 might benefit from anti-inflammatory pharmacological strategies already at early stages of DAVD.