Real-time optical manipulation of cardiac conduction in intact hearts.

KEY POINTS: Although optogenetics has clearly demonstrated the feasibility of cardiac manipulation, current optical stimulation strategies lack the capability to react acutely to ongoing cardiac wave dynamics. Here, we developed an all-optical platform to monitor and control electrical activity in real-time. The methodology was applied to restore normal electrical activity after atrioventricular block and to manipulate the intraventricular propagation of the electrical wavefront. The closed-loop approach was also applied to simulate a re-entrant circuit across the ventricle. The development of this innovative optical methodology provides the first proof-of-concept that a real-time all-optical stimulation can control cardiac rhythm in normal and abnormal conditions. ABSTRACT: Optogenetics has provided new insights in cardiovascular research, leading to new methods for cardiac pacing, resynchronization therapy and cardioversion. Although these interventions have clearly demonstrated the feasibility of cardiac manipulation, current optical stimulation strategies do not take into account cardiac wave dynamics in real time. Here, we developed an all-optical platform complemented by integrated, newly developed software to monitor and control electrical activity in intact mouse hearts. The system combined a wide-field mesoscope with a digital projector for optogenetic activation. Cardiac functionality could be manipulated either in free-run mode with submillisecond temporal resolution or in a closed-loop fashion: a tailored hardware and software platform allowed real-time intervention capable of reacting within 2 ms. The methodology was applied to restore normal electrical activity after atrioventricular block, by triggering the ventricle in response to optically mapped atrial activity with appropriate timing. Real-time intraventricular manipulation of the propagating electrical wavefront was also demonstrated, opening the prospect for real-time resynchronization therapy and cardiac defibrillation. Furthermore, the closed-loop approach was applied to simulate a re-entrant circuit across the ventricle demonstrating the capability of our system to manipulate heart conduction with high versatility even in arrhythmogenic conditions. The development of this innovative optical methodology provides the first proof-of-concept that a real-time optically based stimulation can control cardiac rhythm in normal and abnormal conditions, promising a new approach for the investigation of the (patho)physiology of the heart.

Effects of ultrasound and selenium on human neurons in vitro.

As the effects of ultrasound on human brain functions might bear therapeutic potential, in this study, we examined the effects of diagnostic, i.e. non-thermal, ultrasound, on morphology, networking, and metabolic activity of SH- SY5Y human neurons in culture, as well as on the expression of GAP-43, Hsp90 and VEGF proteins, with and without selenium in the culture medium. The rationale for studying selenium lays in the observation that selenium improves functional neurologic outcome in traumatic brain injury and, therefore, analysis of the interactions between ultrasound and selenium may be of clinical interest. In the presence of selenium, ultrasound increased the overall number and length of elongations arising from the neuron bodies, thus reflecting an increase in the complexity of neuronal networks and circuits. The expression of GAP-43, Hsp90 and VEGF and metabolic activity of SH-SY5Y neurons, studied as markers of cell damage, were not affected by ultrasound or selenium. This study suggests that ultrasound may modulate neuronal networking in vitro without inducing cellular or molecular damage and highlights the potential role of selenium in the ultrasound-elicited cellular responses.

Recovery of 0.1Hz microvascular skin blood flow in dysautonomic diabetic (type 2) neuropathy by using Frequency Rhythmic Electrical Modulation System (FREMS).

Synchronized oscillation of smooth muscle cells tension in arterioles is the main control system of microvascular skin blood flow. An important autogenic vasomotion activity is recognized in 0.1Hz oscillations through power spectrum analysis of laser Doppler flowmetry. Severe dysautonomia in diabetic neuropathy is correlated with loss of 0.1Hz vasomotor activity, hence with impaired blood microcirculation. FREMS is a novel transcutaneous electrotherapy characterized by sequences of electrical stimuli of high voltage and low pulse duration which vary both in frequency and duration. We have evaluated the changes in laser Doppler flow in the volar part of the forearm before, during and after FREMS. Normal controls (n=10, 6 females, age range 21-39 years) demonstrated significant 0.1Hz vasomotion power spectra at baseline conditions associated with large oscillations of adrenergic cutaneous sweat activity sampled from the hand; people with diabetes type 2 and severe dysautonomia (n=10, 5 females, age range 63-75 years) displayed a significant decrease of 0.1Hz vasomotion power spectra. During FREMS application we observed an increase (p<0.05) of 0.1Hz vasomotion power spectra only in the diabetic group, despite persistence of adrenergic cutaneous sweat activity suppression in this group. However, after the application of the stimuli, the relative energy values around the 0.1Hz peak remained significantly higher than preapplication values in the diabetic group (p<0.05). From these findings, we suggest that FREMS is able to synchronize smooth cell activity, inducing and increasing 0.1Hz vasomotion, independently from the autonomic nervous system.