Intrinsic nanomechanical changes in live diabetic cardiomyocytes

Abstract

Patients with diabetes develop a cardiomyopathy that is independent of both coronary artery disease and hypertension and contributes to mortality and morbidity caused by diabetes. The mechanisms underlying the development of diabetic cardiomyopathy are poorly understood. Several reports showed that an early manifestation of diabetic myocardial dysfunction is an increased diastolic left ventricular (LV) stiffness. This increase is usually attributed to myocardial fibrosis or to myocardial deposition of advanced glycation end products. Alteration of the stiffness (resting tension) of the diabetic cardiomyocyte was also proposed to be an important factor contributing to increased LV stiffness. Some of these data were obtained from isolated cardiomyocytes from human frozen biopsy samples that had been thawed, mechanically disrupted, and incubated with Triton X-100, disrupting sarcolemmal and sarcoplasmic membranes. We therefore determined the stiffness of live isolated cardiomyocytes from control and streptozotocin-treated mice using atomic force microscopy (AFM) nanoindentation. We show that 3 months of type 1 diabetes provoked fragmentation and disorder of myocardial fibers, interstitial collagen deposition, reduction in SERCA2a calcium pump expression and changes in F-actin organization. Moreover, we show that live isolated diabetic cardiomyocytes are stiffer than control cardiomyocytes when tested in Tyrode buffer with different ionic compositions. Hence, it is very likely that intrinsic mechanical changes of cardiomyocytes are an important factor in increasing myocardial stiffness in vivo.

Characterization of adhesion properties of the cardiomyocyte integrins and extracellular matrix proteins using atomic force microscopy

“…These results may be helpful for studying cardiac disease with accumulation of ECM, such as diabetes, by studying particular interactions between ECM proteins and their integrins on CMs. 49,50 It has been reported that the conformation or function of integrins may be influenced by cations (such as Ca 2+ or Mg 2+ ). 23 Recent study showed that the increment in concentration of extracellular magnesium (from 0 to 5 mM) would enhance the integrins binding ability in human thyroid follicular carcinoma cell line, characterized by AFM and traditional bulk technique.…”