Beyond the matrix: exploring tenascin-c (TNC) as a crucial player in diabetic cardiovascular dysfunction
Authors: Aykac I , Arnold Z , Dostal C , Szabo L , Pokreisz P , Varadi B , Agg B , Szekeres M , Nadasy G , Hallstroem S , Hamdani N , Ferdinandy P , Podesser B K , Kiss A 
Published: May 2024

Abstract

Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Burgermeister Found Wien-Project number : 21001

Introduction
Diabetic cardiomyopathy (CMP) is a complex manifestation of diabetes-linked cardiac and vascular dysfunction, but the molecular pathogenesis is still largely unknown. Notably the expression of Tenascin-C (TNC), an extracellular matrix glycoprotein, contributes to the development of cardiovascular diseases and diabetic patients have elevated serum TNC levels. However, the role and mechanism of TNC to diabetic CMP progression remains elusive.

Purpose
Here, we longitudinally evaluated functional and molecular role of TNC in CMP-induced cardiovascular dysfunction in a murine model. In addition, we used RNA sequencing with cardiac tissues from non-diabetic and diabetic wild type (wt) and TNC KO mice for further investigation.

Methods
Diabetes was induced in adult male mice, wt (AJ) and TNC-KO strains, by repeated Streptozotocin (STZ) injections (50 mg/kg). Echocardiography, myography, hemodynamics, histology, molecular and cellular analyses were performed to assess the role of TNC in diabetes-associated CV complications. Additionally, RNA-sequencing was analyzed in left ventricular (LV) tissue samples from diabetic and non-diabetic wt and TNC-KO mice providing further molecular insights.

Results
TNC KO mice showed preserved LV ejection fraction, and endothelium-dependent relaxation (p&lt;0.05 and p&lt;0.001, respectively), reduced cardiac fibrosis and distinctive coronary vessel characteristics, implying enhanced LV perfusion. In addition, the plasma levels of oxidative stress marker malondialdehyde was significantly alleviated in TNC KO diabetic mice in comparison to diabetic wt mice. Cardiomyocytes from diabetic wt mice exhibited stiffness (Fpassive and Factive), which was corrected to control level in cardiomyocytes from TNC KO diabetic hearts. Further, ex vivo isolated heart experiments demonstrated that the administration of recombinant human TNC (80 ng/ml) resulted in a significant reduction in LV hemodynamics (p&lt;0.01) and myocardial energetics (ATP levels, p&lt;0.01). Analysis of RNA sequencing data demonstrated that decreased expression of matrix remodeling genes Serpin1 and Ccn1 links to alleviation of fibrosis in TNC KO diabetic heart. Furthermore, Gene Ontology (GO) enrichment analysis shed light on mitochondrial changes in diabetic hearts. Our pathway analysis also identified that Hsp90aa1 as a crucial gene associated with preprotein import into the mitochondrial membrane, may suggest potential mitochondrial dysfunction in diabetic hearts.

Conclusion
In conclusion, lack of TNC improved long-term cardiac function in diabetes by reducing cardiac fibrosis, vascular dysfunction, oxidative stress and cardiac energetics. Thus, inhibition of TNC may prevent the diabetic heart from extensive fibrosis and energetics dysfunction that accelerates the development of HF, providing a potential targeted therapy.