My lab has two major research focuses: 1) the use of focused ultrasound for peripheral nerve neuromodulation and 2) pediatric perioperative outcomes
1) Focused ultrasound (FUS) can modulate central and peripheral nervous system structures. Most FUS research is concentrated on its utility for transcranial modulation of neural structures and ablation of tissues. However, there is evidence that it can also alter peripheral nerve conduction, including compound action potential depression in a manner similar to local anesthetics. Yet, no work has been published assessing its effects on acute or chronic pain, nor whether it is able to differentially modulate different classes of nerve fibers. We are interested in the potential of focused ultrasound to modulate peripheral nerves and improve both acute and chronic pain. We use a rodent peripheral nerve model for our investigations.
2) Additionally, we are working with a large national healthcare dataset assessing the risk of persistent opioid use after surgery in children. We are also investigating the use of regional anesthesia, opioid use, and opioid-sparing analgesic use in pediatric patients who undergo surgery at the Lucile Packard Children’s Hospital at Stanford. Our goal is to understand how various perioperative pain management strategies affect outcomes in children who undergo surgery.
The major thrust of the research component of my academic practice is the clinically relevant study of molecular mechanisms of alcohol and anesthetic action. While an anesthesia resident at Stanford, I applied the methods of theoretical chemistry to the study of anesthetic mechanisms. This resulted in an initial abstract for a “Computers in Anesthesia” conference in 1992, which remains among the first publications describing the application of computational chemistry to the study of anesthetic mechanisms. This also opened the door for pursuing this line of research further as an ICU fellow. Since then, I have been able to set up my own hardware and software resources for our molecular modeling lab at the Palo Alto VA Hospital, and have developed a very productive collaboration with Dr. Jim Trudell, Professor of Chemistry in Anesthesia in the Stanford University Department of Anesthesia.
Dr. Trudell and I count ourselves fortunate to be among the handful of individuals in the world who are actively and successfully applying the very specialized and cutting-edge techniques of structural biology, protein bioinformatics, molecular modeling, and computational chemistry to the study of anesthetic and alcohol mechanisms. The NIH, the Department of Veterans Affairs and Stanford University have sponsored us.
Our most recent works have led to a detailed quantum mechanical description of anesthetic-protein interactions, as well as a better understanding of large-scale ion channel gating motions through the use of normal mode and molecular dynamics analyses. We now have a model of an anesthetic binding site within the gamma amino butyric acid (GABA) receptor from which we have successfully made predictions of anesthetic activity in compounds not formerly known to be anesthetics, resulting in formal patent filings. While we conducted preliminary tests in vivo, we now wish to proceed to lead compound refinement, detailed mechanistic studies of these compounds within brain slice preparation, and in vitro patch clamp ion channel testing, as well as expand animal testing into mammals. We hope to not only better define the workings of these ion channels that are linked to anesthetic states, but also to design a safer anesthetic for the most vulnerable of our patients. Ultimately, our work should lend itself to a greater understanding of human consciousness and provide an updated perspective of the human condition.
This is a picture of primate dorsal root ganglia neurons demonstrating expression of the opiate analgesic peptide leu-enkephalin after application of a recombinant herpes virus encoding the gene for human preproenkephalin to the skin.
The Clark laboratory has various projects all focused on mechanisms supporting chronic pain. The first project area involves persistent pain after injuries to the extremities, including tissue damage caused by limb fracture and surgery. Models involving laboratory animals are commonly used, although human tissue samples and translational research studies are a part of the overall program. Most of this work involves evaluating the contributions of neural activation of the innate and adaptive systems of immunity. The neurogenic underpinnings of persistent pain in the setting of limb injury, the sources and targets of inflammatory mediators, and the targets of injury-related autoimmunity are all areas of interest for the group. Ultimately, our goal is to inform the design of therapies that can be taken to early-stage clinical trials.
The second major project area involves the identification of mechanisms responsible for persistent pain after traumatic brain injury (TBI). In this context, the laboratory is interested in understanding how changes in descending systems of nociceptive modulation as well as changes in nociceptive signal transmission within the spinal cord might contribute to the very high incidence of chronic pain after even mild forms of TBI. Recent projects have focused on damage to the locus coeruleus after TBI and associated deficits in spinal noradrenergic function. Additional work involves spinal epigenetic changes leading to the enhanced expression of pain-related signaling molecules.
Over the last 5 years, the advent of high dimensional flow cytometry has revolutionized our ability to study and visualize the human immune system. Our group (a collaborative effort with Dr. Nima Aghaeepour and Dr. Martin Angst) combines high parameter mass cytometry (a.k.a Cytometry by Time of Flight Mass Spectrometry, CyTOF), with advanced bio-computational methods to study how the human immune system responds and adapts to acute physiological perturbations. The laboratory currently focuses on two clinical scenarios: surgical trauma and pregnancy.
Deep immune profiling of patients undergoing and recovering from surgery
Using high dimensional mass cytometry, we have recently shown that the signaling behavior of specific innate immune cells measured before surgery in patients’ blood was strongly associated with surgical recovery (Gaudilliere B et al. Science Translational Medicine, 2014; Fragiadakis G et al. Anesthesiology 2015). Prospective validation of reported immune correlates of surgical recovery are underway. Ongoing work in humans and animal models (in collaboration with Dr. Vivianne Tawfik and Dr. David Clark) focuses on the mechanisms by which pre-operative habilitation interventions may alter a patient’s immune state to improve recovery after surgery.
Deep Immune profiling of normal and preterm pregnancy
Our group is an integral component of a multi-disciplinary effort (led by Dr. David Stevenson, Pediatric Department) aimed at understanding the mechanisms of preterm birth, and identifying predictive factors of premature delivery. We have now developed a pipeline and the analytical framework to integrate the single-cell analysis of immune signaling networks by mass cytometry and proteomic profiling of secreted serum factors with the precise phenotyping of pregnancy-related clinical outcomes. In a pilot, cross-sectional study of non-pregnant women, we identified candidate immune signatures that differentiated women with a history of preterm or term pregnancies (Gaudilliere B et al. Cytometry A, 2015). Longitudinal studies in pregnant patients are ongoing to validate these findings.
Our laboratory focuses on developing non-narcotic cardiac-safe pain therapeutics and other next generation therapeutics for anesthetic and analgesic care. Further, in order to provide overall better anesthetic care for our patients, we are also examining how common genetic polymorphisms in our patient population we care for may alter anesthetic and analgesic effects of the medications we administer and the post-operative course.
In order to optimize analgesics and limit side-effects, we are also interested in investigating the mechanism of how the nociceptive and cardioprotective signaling pathways are linked. This involves studying the role of nociceptors in cardiac protection and continued interest examining the mechanism of how opioids and volatile anesthetics protect tissue from ischemia-reperfusion injury.
Dr. Heifets directs both clinical and basic neuroscience research programs. His work bridges neuroscience, psychiatry and anesthesiology in pursuit of highly effective, safe and scalable treatment strategies for psychiatric disease. The nexus of these fields, and the focus of his research group, is the emerging class of rapid-acting psychiatric therapies, like ketamine, MDMA and psilocybin, which can trigger profound and lasting changes in nervous system function, behavior, and therapeutic outcomes. Through parallel human and animal experiments, his group is deconstructing the neural mechanisms responsible for these compounds’ neuroplastic potential, and working to develop more precise therapeutic strategies. Major projects in his research group include:
1) defining the neural circuitry responsible for MDMA’s prosocial therapeutic effects using brain-wide activity mapping and mouse behavioral models
2) unraveling the effect of “set and setting” for psychedelics and MDMA through brain imaging and behavioral analysis
3) using anesthetic drugs and induction of dream states to test the relationship between psychedelic experiences and therapeutic outcomes
4) testing new indications for psilocybin and MDMA, including a trial of psilocybin therapy for chronic low back pain, and MDMA for OCD, in close partnership with investigators at Stanford, UCSF and UC Berkeley.
Our research group collaborates extensively with investigators at Stanford in the departments of Anesthesiology, Perioperative and Pain Medicine; Psychiatry and Behavioral Sciences; and Radiology, and with research groups at UCSF, UC Berkeley and UC Irvine.
My laboratory is interested in finding new strategies to promote neuronal survival and improve functional outcome following brain injury. The brain consists of several different cell types, the most abundant of which are astrocytes, specialized glial cells that play a vital role in regulating neuronal signaling and homeostasis. All cells depend on mitochondrial function for both normal physiologic functioning and in response to injury; currently we are utilizing microRNAs to simultaneously target multiple pathways that regulate mitochondrial function in both neurons and astrocytes in order to promote cell survival subsequent to noxious stimuli, such as ischemia-reperfusion injury. We employ several in vivo and in vitro techniques, including live cell fluorescent imaging, to assess the cellular response to injury.
Our mission is to do the best clinically-informed basic science to advance our understanding of the neuroimmune contribution to chronic pain in a thoughtful manner with our patients always in mind.
In order to further understand the mechanisms that contribute to the transition from acute to chronic pain, we use a variety of approaches that span behavioral to cellular. We are particularly excited about techniques that can be translated to humans including live animal imaging and whole cell mass cytometry.
We are leading the way with two potentially revolutionary approaches to the treatment of chronic pain, namely transplantation and gene therapy. In the first approach, cells taken from the adrenal gland are transplanted on top of the spinal cord through a spinal needle. These cells make and secrete numerous natural analgesic substances, acting like a pump to produce a constant inhibition of pain. Unlike a pump however, these cells are alive, meaning that they keep making and secreting the analgesic chemicals for months.
The primary problems in gene therapy have been the targeting of the right cells, and the duration of the desired effect. We have used a highly modified herpes simplex virus (the kind that causes cold sores) to carry analgesic genes into the pain sensing cells. Because herpes viruses stay in these cells for the life of the host naturally, we should obtain very long lasting analgesic effects using these treatments. Thus, we are making use of the natural proclivity of herpes for entering and staying in the very cells we are interested in. In this way, we target pain treatment to painful areas, and only painful areas. These new approaches to therapy could revolutionize the treatment of chronic pain.