Root causes: Bioelectronics to restore organ function

by Kim Roth

The work of Assistant Professor Tim Bruns has been recognized with a highly competitive National Science Foundation Faculty Early Career Development (CAREER) Award. The five-year award will fund Bruns’ winning proposal, “Modeling dorsal root ganglia: Electrophysiology of microelectrode recording and stimulation.”

Bruns directs the U-M Peripheral Neural Engineering and Urodynamics (pNEURO) Lab, which develops bioelectronic interfaces with the peripheral nervous system to understand systems-level neurophysiology as well as to restore autonomic organ function. Dorsal root ganglia (DRG), which lie near the spinal cord and contain the cells of multiple, converging peripheral sensory nerves, have been an important focus of his research.

“Many peripheral nerves are small and hard to access, so when we’re trying to learn about these sensory systems, recording and decoding signals from the DRG can simplify the process while still giving us important clues about what’s happening,” Bruns says.

But electrodes used to record signals from or stimulate DRG have shortcomings that lessen the efficacy of current and potential therapies and slow research efforts. With the CAREER Award, Bruns will study and model the anatomy and behavior of neurons in the DRG to better understand how they interact with electrodes and, ultimately, improve upon existing technology.

Mapping DRG

While many researchers have examined individual nerve cells in the DRG, Bruns is one of the first to study their arrangement, electrical behavior, and interactions at a systems level within the DRG.

In work recently published in Journal of Neuroscience Methods, Bruns and lab members found concentrations of nerve cells in different areas of the DRG and demonstrated a novel way to quantify their patterns and distribution.

Through collaborations with U-M Electrical Engineering and Computer Science faculty, his team is using the findings to develop improved microelectrodes, including a new, flexible, non-penetrating thin-film array that better matches the shape of the DRG and may reach more neurons with better long-term viability than current devices.

Student Zachariah Sperry demonstrates a novel thin-film electrode array that is being developed in collaboration with Electrical Engineering researchers. Bruns’ lab members have worked with slugs to validate use of the electrode, and examine slug neural activity, prior to focused testing in our large-animal bladder focused experiments. Photo by Marcin Szczepanski/Multimedia Director and Senior Producer, University of Michigan, College of Engineering

Toward restored bladder function

In the case of bladder dysfunction, sensory neuron signals recorded from particular DRG can help researchers and clinicians learn more about the bladder’s state. The DRG also can serve as a target for nerve stimulation therapies, including closed-loop systems that provide electrostimulation when bladder pressure approaches a critical threshold.

Bruns’ team is studying the effectiveness of new algorithms to estimate bladder pressure from DRG signals and also has demonstrated the use of microelectrodes to monitor and modulate lower urinary tract behavior from DRG signals and DRG stimulation, both in animal models. These are the first long-term, behavioral experiments examining bladder function at DRG, providing a clearer path towards clinical relevance.

Tim Bruns, Assistant Professor of Biomedical Engineering at Michigan Engineering and his students observe the buccal mass of an aplysia Californica (sea slug) moving. From left are Ahmed Jiman, Aileen Ouyang, Tim Bruns and Zachariah Sperry. Photo by Marcin Szczepanski/Multimedia Director and Senior Producer, University of Michigan, College of Engineering

Improving sexual dysfunction

Some patients using existing bladder pacemakers to improve bladder function have reported improvements in sexual function, too. Bruns and colleagues in the U-M Medical School believe neurostimulation may hold promise as a potential treatment for female sexual dysfunction (FSD). In pre-clinical research, his lab has found that peripheral nerve stimulation can increase vaginal blood flow, a proxy for assessing sexual arousal.

“In terms of importance, these are quality of life issues and incredibly important to patients, yet few researchers are working in these areas,” says Bruns. In collaboration with a urogynecologist in the U-M Medical School, Bruns recently conducted a patient survey to assess interest in neuromodulation for FSD. Over 700 respondents in Michigan completed the survey.

“…These are quality of life issues and incredibly important to patients, yet few researchers are working in these areas”Tim Bruns

The team now is leading an active clinical study that runs through early 2018. All three women who have completed the study so far had significant improvement in the Female Sexual Function Index, an assessment tool to gauge key aspects of sexual function in women.

Controlling blood glucose

In a small, exploratory study of kidney neuromodulation to control blood glucose, researchers in Bruns’ lab have found that stimulation in particular ranges can prevent the organs from reabsorbing sugar and boost glucose excretion from the body. The early findings are laying a foundation for further work to develop potential non-pharmacologic approaches to treating diabetes.

“FSD may affect up to 40 percent of adult women; millions of men and women suffer from bladder control issues; and diabetes affects nearly 10 percent of the U.S. population,” Bruns notes. “As we better understand how nerves control the ways in which our organs function and as we develop new interfaces for interacting with neurons, we’re finding more and more opportunities to improve quality of life for these, and other, patient populations – there’s so much we can do, especially when we work closely with clinicians.

“As we better understand how nerves control the ways in which our organs function and as we develop new interfaces for interacting with neurons, we’re finding more and more opportunities to improve quality of life for these, and other, patient populations”Tim Bruns

Bruns’ DRG work is funded by National Science Foundation CAREER Award 1653080, National Institutes of Health NIBIB SPARC grant U18EB021760, and Craig H. Neilsen Foundation grant 314980.

For more information on the FSD clinical trial, visit https://clinicaltrials.gov/ct2/show/NCT02692417 or contact Bruns at bruns@umich.edu

Tim Bruns wins NSF CAREER Award

U-M BME assistant professor Tim Bruns has received a prestigious National Science Foundation Faculty Early Career Development (CAREER) Award. Bruns leads the Peripheral Neural Engineering and Urodynamics Lab (pNEURO Lab) in Biomedical Engineering. The group is interested in developing interfaces with the peripheral nervous system to restore function and to examine systems-level neurophysiology, primarily focusing on organ function.  Bruns will use his award to study and model the behavior of neurons within dorsal root ganglia (DRG), unique structures next to the spinal cord that contain converging sensory nerves. This work will inform research and development of novel microelectrodes designed to record and stimulate DRG. Research in this area could lead to the restoration of nerve function for a wide range of disorders.

One Lab, Three Approaches to Restoring Ovarian Function Ariella Shikanov

By Aimee Balfe

BME Assistant Professor Ariella Shikanov has just received an NSF CAREER award to help fund one of the three approaches her lab is taking to help restore ovarian function in women and girls undergoing treatment for cancer and autoimmune disease that is toxic to the ovaries.

While physicians can freeze a woman’s eggs, allowing her to later have a biologically related child, the process isn’t suitable for some patients, including young girls. It also doesn’t address the issue of ovaries’ endocrine function. “Ovaries are not only about making babies,” says Shikanov, “they also produce estrogen, progesterone, and other hormones that are very important for the health of a woman’s bones, cardiovascular system, and skin.”

“Ovaries are not only about making babies…they also produce estrogen, progesterone, and other hormones that are very important for the health of a woman’s bones, cardiovascular system, and skin.” Shikanov

They’re also essential for enabling girls to go through puberty. Girls who’ve lost ovarian function require synthetic hormones, whose long-term use carries a health risk. In addition, the dosage has to be just right. Too little and the girls won’t grow sufficiently. Too much and the bones’ growth plates close prematurely. Without optimal dosing, the girls are at increased risk for various bone, cardiovascular, and metabolic problems like diabetes and obesity.

The Path to U-M

shikanovShikanov would become captivated by this issue and begin down a road that would lead her from the Hebrew University in Jerusalem to U-M via a postdoctoral fellowship in the lab of Lonnie Shea. Then at Northwestern, and now U-M’s William and Valerie Hall Chair and Professor of BME, Shea had been working on ovarian tissue engineering and needed a postdoc with expertise in polymer synthesis and hydrogel development. Shikanov, a medicinal chemist by training, had the right skill set.

“He told me, ‘Don’t worry; you’ll learn about reproduction,’” she says. Over the next four years, she found herself doing surgeries in mice, looking for ways to make ovarian tissue transplantation more successful, and developing synthetic culture environments for ovarian follicles – the structures that contain immature eggs and are essential to endocrine function.

The latter offered an intriguing engineering challenge. “We had to design a hydrogel that would be soft enough not to kill an ovarian follicle, but rigid enough to support its 3D structure as it matures and expands 100 times in volume,” she says. “It also had to be physiologic, allowing the diffusion of nutrients and oxygen.”

“We had to design a hydrogel that would be soft enough not to kill an ovarian follicle, but rigid enough to support its 3D structure as it matures and expands 100 times in volume” Shikanov

She was deep in this work when U-M announced a cluster-hire position in reproductive biomaterials that precisely matched her expertise. She was hired in 2012, launching a lab that would address ovarian function through three distinct but mutually reinforcing projects.

The Projects

Restoring endocrine function in girls

Shikanov’s first project aims to restore endocrine function in girls with damaged ovaries, allowing them to undergo physiologic puberty. She is developing an implant that encapsulates donor ovarian tissue in an immunoisolating hydrogel. Injected under the skin, it won’t restore fertility but would stimulate the production of estrogen at this critical time.

“Puberty starts in the brain,” says Shikanov. “The hypothalamus secretes a hormone, which stimulates the pituitary gland to secrete follicular stimulating hormone, which tells the ovarian tissue to secrete estrogen. Then the estrogen goes back to the brain, controlling things through a finely tuned loop. This is what allows us to go through puberty, and this why it is so important to have a healthy and functioning ovarian tissue that we aim to engineer.”

With a grant from The Hartwell Foundation, her lab has already demonstrated in mice that the process works and that its longevity is determined by the number of follicles implanted. She plans to move to larger animal models before testing the product in humans.

Understanding how ovarian follicles develop

Shikanov’s second project, for which she won her CAREER award, aims to understand the cell signaling involved in the development of ovarian follicles so she can design better culture systems for harvested tissue.

Harvesting of immature ovarian follicles holds promise for restoring fertility when a woman can’t freeze her eggs – either because she doesn’t have time to undergo ovarian stimulation prior to starting treatment or because she has a hormone-driven cancer where stimulation would be inappropriate. The problem has been getting follicles to survive and mature in culture.

The reason for this, says Shikanov, is that follicles’ essential signaling networks are poorly understood. “Right now, we know that follicles grow best when they’re co-cultured with other follicles and stem cells, but we don’t know why.”

She hopes to remedy this through mechanistic studies of folliculogenesis. Using transcription factor reporters, metabolomics, and systems biology, she aims to reveal the identity, timing and activity pattern of secreted growth factors and transcription factors that allow follicles to grow.

During the project, she plans to continue collaborating with Lonnie Shea, as well as with BME computational modeling expert David Sept, new faculty member Kelly Arnold, and U-M’s metabolomics core, MRC2.

She will start the experimental work in mice, but hopes to move to human tissue in a matter of years. “I want to get to the point where I can take one follicle and say, if I add this list of factors at these concentrations in this timing sequence, I will be able to grow the follicle without adding other follicles or cells,” she says.

Designing an artificial ovary
engineering-ovary
Her final project is the design of an artificial ovary. This involves encapsulating the smallest, primordial follicles in a synthetic polymer that mimics the ovaries’ natural environment with the goal of restoring both fertility and endocrine function. She expects that her mechanistic studies will offer substantial insights to this work.

Shikanov says her research is extremely gratifying, and she enjoys introducing it to young people, especially women, through camps and programs for middle and high schoolers. In addition, her lab is always seeking talented postdocs interested in learning more about biomaterials in reproductive sciences. She can be contacted at shikanov@umich.edu.