Noninvasive sub-organ ultrasound stimulation for targeted neuromodulation
Victoria Cotero, Ying Fan, Tea Tsaava, Adam M. Kressel, Ileana Hancu, Paul Fitzgerald, Kirk Wallace, Sireesha Kaanumalle, John Graf, Wayne Rigby, Tzu-Jen Kao, Jeanette Roberts, Chitresh Bhushan, Suresh Joel, Thomas R. Coleman, Stavros Zanos, Kevin J. Tracey, Jeffrey Ashe, Sangeeta S. Chavan, Christopher Puleo
Nature Communications 2019, 10 · 10.1038/s41467-019-08750-9
Abstract
Tools for noninvasively modulating neural signaling in peripheral organs will advance the study of nerves and their effect on homeostasis and disease. Herein, we demonstrate a noninvasive method to modulate specific signaling pathways within organs using ultrasound (U/S). U/S is first applied to spleen to modulate the cholinergic anti-inflammatory pathway (CAP), and US stimulation is shown to reduce cytokine response to endotoxin to the same levels as implant-based vagus nerve stimulation (VNS). Next, hepatic U/S stimulation is shown to modulate pathways that regulate blood glucose and is as effective as VNS in suppressing the hyperglycemic effect of endotoxin exposure. This response to hepatic U/S is only found when targeting specific sub-organ locations known to contain glucose sensory neurons, and both molecular (i.e. neurotransmitter concentration and cFOS expression) and neuroimaging results indicate US induced signaling to metabolism-related hypothalamic sub-nuclei. These data demonstrate that U/S stimulation within organs provides a new method for site-selective neuromodulation to regulate specific physiological functions.
Abstract via europepmc.
Exposures
Exposure 1: Splenic ultrasound stimulation (cholinergic anti-inflammatory pathway), pressure sweep
Target: splanchnic nerve — “spleen (nerve terminals/innervation points of the splenic ganglia, cholinergic anti-inflammatory pathway)”
Device: Sonic Concepts · Sonic Concepts · H106 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 1,100 | ✓✓✓ |
| Pulse duration (ms) | 0.136 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 2,000 | ✓✓✓ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 27.272% | |
| Sonication duration (s) | 60 | ✓✓✓ |
| Free-field pressure (kPa) | 30, 1,720swept | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
Pulse center frequency 1.1 MHz, pulse repetition period 0.5 ms (2000 Hz PRF), 136.36 microsecond pulse length; pulse amplitude/pressure varied across experiments from 0.03-1.72 MPa (most main-text figures used 0.83 MPa, within the most effective range of 0.25-0.83 MPa). A single ultrasound stimulus did not surpass 1 min; a second 1-min stimulus could be applied. Voltage-to-pressure calibration was performed in degassed water with a needle hydrophone.
Exposure 2: Hepatic (porta hepatis) ultrasound stimulation, main experiments (0.83 MPa)
Target: vagus nerve — “porta hepatis (liver; hepatic vagal sensory afferents/glucose-sensitive neurons)”
Device: Sonic Concepts · Sonic Concepts · H106 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 1,100 | ✓✓✓ |
| Pulse duration (ms) | 0.136 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 2,000 | ✓✓✓ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 27.272% | |
| Sonication duration (s) | 60 | ✓✓✓ |
| Free-field pressure (kPa) | 830 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
Same HIFU system and pulse parameters as the splenic experiments (1.1 MHz, 2000 Hz PRF, 136.36 microsecond pulse length), fixed at 0.83 MPa; U/S was image-guided to the porta hepatis region of the liver, a single stimulus not surpassing 1 min.
Exposure 3: Hepatic (porta hepatis) ultrasound stimulation during diffusion-weighted fMRI (MR-compatible transducer)
Target: vagus nerve — “porta hepatis (liver; hepatic vagal sensory afferents/glucose-sensitive neurons)”
Device: not reported
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 1,470 | ✓✓✓ |
| Pulse duration (ms) | 0.15 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 2,000 | ✓?⚑ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 30% | ⚑ |
| Sonication duration (s) | 60 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported | |
| Pressure, domain unspecified (kPa) | 3,200 | ✓✓✓ |
An MR-compatible ultrasound probe (1.47 MHz) coupled to the abdomen via a gel/water-filled cone focused on the porta hepatis. Each ultrasound treatment lasted 60 s, with square-wave pulses applied at 150/350 microsecond on/off periods; sound pressure at the focal point was approximately 3.2 MPa. Applied to 6 of 10 rats undergoing DfMRI; the other 4 rats received LPS with no US treatment.
Flags from extraction
exposures[0].target— No target ID in the taxonomy corresponds to 'spleen'; splanchnic_nerve (viscera-innervating sympathetic nerve) was used as the closest match to the splenic nerve terminals actually targeted.exposures[1].target— No target ID corresponds to 'liver' or its hepatic vagal branch specifically; vagus_nerve was used as the closest match since the porta hepatis target contains hepatic vagal sensory afferents.exposures[2].timing.pulse_repetition_frequency_hz— Not stated directly as a frequency; derived from the stated 150/350 microsecond on/off periods (period = 500 microseconds -> 2000 Hz), matching the PRF used in the other exposures.exposures[2].timing.duty_cycle_pct— Computed directly from the stated 150 microsecond on-time over the 500 microsecond total on/off period (30%); not stated as a duty cycle by the paper.n_subjects— This paper reports dozens of partially overlapping rat and mouse cohorts (typically n=3-12) across many figures/sub-experiments (spleen dose-response, kinetics, duration-of-effect, knockout/denervation mechanism studies, liver studies, DfMRI) without a single overall total; recorded are the largest distinct group sizes explicitly stated for ultrasound-stimulated animals in the primary spleen, liver, and DfMRI experiments. Mouse knockout/denervation cohort sizes (Figs. 4-5) are not included as they were not clearly stated as a single n in the extracted text.sham_type— Sham/control animals received LPS without ultrasound ('LPS, -U/S'), but the paper does not state whether the ultrasound transducer/probe was still positioned (inactive) or omitted entirely during sham sessions.exposures[0].free_field— Pressure values are drawn from a voltage-to-pressure calibration performed in degassed water (free field) with a needle hydrophone; the paper does not discuss derating for the actual tissue path to the spleen/liver.