Tag: biomechanics

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Understanding the Physics of Kidney Development

Abstract image of tubules repelling each other and shifting around.
The model of tubule packing developed by the Hughes Lab shows the tubules repelling each other and shifting around.

A recent study by Penn Bioengineering researchers sheds new light on the role of physics in kidney development. The kidney uses structures called nephrons and tubules to filter blood and pass urine to the bladder. Nephron number is set at birth and can vary over an order of magnitude (anywhere from 100,000 to over a million nephrons in an individual kidney). While the reasons for this variability remain unclear, low numbers of nephrons predispose patients to hypertension and chronic kidney disease. 

Now, research published in Developmental Cell led by Alex J. Hughes, Assistant Professor in the Department of Bioengineering, demonstrates a new physics-driven approach to better visualize and understand how a healthy kidney develops to avoid organizational defects that would impair its function. While previous efforts have typically approached this problem using molecular genetics and mouse models, the Hughes Lab’s physics-based approach could link particular types of defects to this genetic information and possibly highlight new treatments to prevent or fix congenital defects.

During embryonic development, kidney tubules grow and the tips divide to make a branched tree with clusters of nephron stem cells surrounding each branch tip. In order to build more nephrons, the tree needs to grow more branches. To keep the branches from overlapping, the kidney’s surface grows more crowded as the number of branches increase. “At this point, it’s like adding more people to a crowded elevator,” says Louis Prahl, first author of the paper and Postdoctoral Fellow in the Hughes Lab. “The branches need to keep rearranging to accommodate more until organ growth stops.”

To understand this process, Hughes, Prahl and their team investigated branch organization in mouse kidneys as well as using computer models and a 3D printed model of tubules. Their results show that tubules have to actively restructure – essentially divide at narrower angles – to accommodate more tubules. Computer simulations also identified ‘defective’ packing, in which the simulation parameters caused tubules to either overlap or be forced beneath the kidney surface. The team’s experimentation and analysis of published studies of genetic mouse models of kidney disease confirmed that these defects do occur.

This study represents a unique synthesis of different fields to understand congenital kidney disease. Mathematicians have studied geometric packing problems for decades in other contexts, but the structural features of the kidney present new applications for these models. Previous models of kidney branching have approached these problems from the perspective of individual branches or using purely geometric models that don’t account for tissue mechanics. By contrast, The Hughes Lab’s computer model demonstrates the physics of how tubule families interact with each other, allowing them to identify ‘phases’ of kidney organization that either relate to normal kidney development or organizational defects. Their 3D printed model of tubules shows that these effects can occur even when one sets the biology aside.

Hughes has been widely recognized for his research in the understanding of kidney development. This new publication is the first fruit of his 2021 CAREER Award from the National Science Foundation (NSF) and he was recently named a 2023 Rising Star by the Cellular and Molecular Bioengineering (CMBE) Special Interest Group. In 2020 he became the first Penn Engineering faculty member to receive the Maximizing Investigators’ Research Award (MIRA) from the National Institutes of Health (NIH) for his forward-thinking work in the creation of new tools for tissue engineering.

Pediatric nephrologists have long worked to understand the cause of these childhood kidney defects. These efforts are often confounded by a lack of evidence for a single causative mutation. The Hughes Lab’s approach presents a new and different application of the packing problem and could help answer some of these unsolved questions and open doors to prevention of these diseases. Following this study, Hughes and his lab members will continue to explore the physics of kidney tubule packing, looking for interesting connections between packing organization, mechanical stresses between neighboring tubule tips, and nephron formation while attempting to copy these principles to build stem cell derived tissues to replace damaged or diseased kidney tissue. Mechanical forces play an important role in developmental biology and there is much scope for Hughes, Prahl and their colleagues to learn about these properties in relation to the kidney.

Read “The developing murine kidney actively negotiates geometric packing conflicts to avoid defects” in Developmental Cell.

Other authors include Bioengineering Ph.D. students and Hughes Lab members John Viola and Jiageng Liu.

This work was supported by NSF CAREER 2047271, NIH MIRA R35GM133380, Predoctoral Training Program in Developmental Biology T32HD083185, and NIH F32 fellowship DK126385.

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Penn Bioengineering Celebrates Five Researchers on Highly Cited Researchers 2021 List

The Department of Bioengineering is proud to announce that five of our faculty have been named on the annual Highly Cited Researchers™ 2021 list from Clarivate:

Dani Bassett, Ph.D.

Dani S. Bassett, J. Peter Skirkanich Professor in Bioengineering and in Electrical and Systems Engineering
Bassett runs the Complex Systems lab which tackles problems at the intersection of science, engineering, and medicine using systems-level approaches, exploring fields such as curiosity, dynamic networks in neuroscience, and psychiatric disease. They are a pioneer in the emerging field of network science which combines mathematics, physics, biology and systems engineering to better understand how the overall shape of connections between individual neurons influences cognitive traits.

Robert D. Bent Chair
Jason Burdick, Ph.D.

Jason A. Burdick, Robert D. Bent Professor in Bioengineering
Burdick runs the Polymeric Biomaterials Laboratory which develops polymer networks for fundamental and applied studies with biomedical applications with a specific emphasis on tissue regeneration and drug delivery. The specific targets of his research include: scaffolding for cartilage regeneration, controlling stem cell differentiation through material signals, electrospinning and 3D printing for scaffold fabrication, and injectable hydrogels for therapies after a heart attack.

César de la Fuente, Ph.D.

César de la Fuente, Presidential Assistant Professor in Bioengineering and Chemical & Biomedical Engineering in Penn Engineering and in Microbiology and Psychiatry in the Perelman School of Medicine
De la Fuente runs the Machine Biology Group which combines the power of machines and biology to prevent, detect, and treat infectious diseases. He pioneered the development of the first antibiotic designed by a computer with efficacy in animals, designed algorithms for antibiotic discovery, and invented rapid low-cost diagnostics for COVID-19 and other infections.

Carl June, M.D.

Carl H. June, Richard W. Vague Professor in Immunotherapy in the Perelman School of Medicine and member of the Bioengineering Graduate Group
June is the Director for the Center for Cellular Immunotherapies and the Parker Institute for Cancer Therapy and runs the June Lab which develops new forms of T cell based therapies. June’s pioneering research in gene therapy led to the FDA approval for CAR T therapy for treating acute lymphoblastic leukemia (ALL), one of the most common childhood cancers.

Vivek Shenoy, Ph.D.

Vivek Shenoy, Eduardo D. Glandt President’s Distinguished Professor in Bioengineering, Mechanical Engineering and Applied Mechanics (MEAM), and in Materials Science and Engineering (MSE)
Shenoy runs the Theoretical Mechanobiology and Materials Lab which develops theoretical concepts and numerical principles for understanding engineering and biological systems. His analytical methods and multiscale modeling techniques gain insight into a myriad of problems in materials science and biomechanics.

The highly anticipated annual list identifies researchers who demonstrated significant influence in their chosen field or fields through the publication of multiple highly cited papers during the last decade. Their names are drawn from the publications that rank in the top 1% by citations for field and publication year in the Web of Science™ citation index.

Bassett and Burdick were both on the Highly Cited Researchers list in 2019 and 2020.

The methodology that determines the “who’s who” of influential researchers draws on the data and analysis performed by bibliometric experts and data scientists at the Institute for Scientific Information™ at Clarivate. It also uses the tallies to identify the countries and research institutions where these scientific elite are based.

David Pendlebury, Senior Citation Analyst at the Institute for Scientific Information at Clarivate, said: “In the race for knowledge, it is human capital that is fundamental and this list identifies and celebrates exceptional individual researchers who are having a great impact on the research community as measured by the rate at which their work is being cited by others.”

The full 2021 Highly Cited Researchers list and executive summary can be found online here.

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Penn Bioengineering Alumna Cynthia Reinhart-King is President Elect of BMES

Dr. Cynthia Reinhart-King, Engineering, BME, Photo by Joe Howell

Penn Bioengineering alumna Cynthia Reinhart-King, Cornelius Vanderbilt Professor of Engineering and Professor of Biomedical Engineering at Vanderbilt University, was elected the next President of the Biomedical Engineering Society (BMES), the largest professional society for biomedical engineers. Her term as president-elect started at the annual BMES meeting in October 2021.

Reinhart-King graduated with her Ph.D. from Penn Bioengineering in 2006. She studied in the lab of Daniel Hammer, Alfred G. and Meta A. Ennis Professor in Bioengineering and Chemical and Biomolecular Engineering as a Whitaker Fellow and went on to complete postdoctoral training as an Individual NIH NRSA postdoctoral fellow at the University of Rochester. Prior to joining Vanderbilt, she was on the faculty of Cornell University and received tenure in the Department of Biomedical Engineering. The Reinhart-King lab at Vanderbilt “uses tissue engineering, microfabrication, novel biomaterials, model organisms, and tools from cell and molecular biology to study the effects of mechanical and chemical changes in tissues during disease progression.”

Reinhart-King gave the 2019 Grace Hopper Distinguished Lecture, sponsored by the Department of Bioengineering. This lecture series recognizes successful women in engineering and seeks to inspire students to achieve at the highest level. She is a recipient of numerous prestigious awards, including the Rita Schaffer Young Investigator Award in 2010, an NSF CAREER Award, and the Mid-Career Award in 2018 from BMES.

In a Q&A on the BMES Blog, Reinhart-King said that:

“BMES is facing many challenges, like many societies, as we deal with the hurdles associated with COVID-19 and inequities across society. We must continue to address those challenges. However, we are also in a terrific window of having robust membership, many members who are eager to get involved with the society’s activities, and a national lens on science and scientists. One of my goals will be to identify and create opportunities for our members to help build the reach of the society and its member.”

Read “Cynthia Reinhart-King is president-elect of the Biomedical Engineering Society” in Vanderbilt News.

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Student Research Highlight: Colin Huber

Colin Huber, Ph.D. student

Colin Huber, a Ph.D. candidate in Bioengineering studying head impact biomechanics and concussion in sports at the Center for Injury Research and Prevention (CIRP) at the Children’s Hospital of Philadelphia (CHOP), recently published “Variations in Head Impact Rates in Male and Female High School Soccer” in Medicine & Science in Sports & Exercise with colleagues from CHOP’s Minds Matter Concussion Frontier Program and the CIRP.

Colin’s paper, the goal of which was to compare “to compare head impact exposure rates (head impacts/exposure period) in male and female high school soccer by using multiple methodological approaches,” was recently profiled in the Penn Engineering Research & Innovation Newsletter.

Read the full story in the ADRO Newsletter.

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BE/MEAM Seminar: “Microbes in Biomechanics” (Christopher J. Hernandez)

Speaker: Christopher J. Hernandez, Ph.D.
Professor, Sibley School of Mechanical and Aerospace Engineering, Cornell University
Adjunct Scientist, Hospital for Special Surgery

Date: Thursday, February 4, 2021
Time: 3:00-4:00 PM EST
Zoom – check email for link or contact ksas@seas.upenn.edu

Title: “Microbes in Biomechanics”

This seminar is jointly hosted by the Department of Bioengineering and the Department of Mechanical Engineering and Applied Mechanics.

Abstract:

The idea that mechanical stresses influence the growth and form of organs and organisms originated in the 1800s and is the basis for the modern study of biomechanics and mechanobiology. Biomechanics and mechanobiology are well studied in eukaryotic systems, yet eukaryotes represent only a small portion of the diversity and abundance of life on Earth. Bacteria exhibit broad influences on human health (as both pathogens and as beneficial components of the gut microbiome) and processes used in biotechnology and synthetic biology. Over the past eight years my group has explored mechanobiology within individual bacteria and the effects of changes in the composition of commensal bacterial communities on the biomechanics in the musculoskeletal system.

The ability of the bacteria to not only resist mechanical loads (biomechanics) but also to respond to changes in the mechanical environment (mechanobiology) is necessary for survival. Here I describe a novel microfluidic platform used to explore the biomechanics and mechanobiology of individual, live bacteria. I discuss work from my group demonstrating that mechanical stress within the bacterial cell envelope can influence the assembly and function of multicomponent efflux pumps used by bacteria to resist toxins and antibiotics. Additionally, I share some of our more recent work showing that mechanical stress and strain within the bacterial cell envelope can stimulate a bacterial two-component system controlling gene expression. Our findings demonstrate that bacteria, like mammalian cells, have mechanosensitive systems that are key to survival.

In musculoskeletal disease, bacteria are commonly viewed as sources of infection. However, in the past decade the studies by my group and others have suggested that commensal bacteria – the microbiome – can modulate the pathogenesis of musculoskeletal disorders. My group is among the first to study the effects of the gut microbiome on orthopaedic disorders. Here I provide an introduction to the microbiome and current concepts of how modifications to the gut microbiome could influence the musculoskeletal system. Specifically, I discuss studies from my group which are the first to demonstrate that the gut microbiome influences bone biomechanics and the development of infection of orthopaedic implants.

Bio:

Dr. Hernandez is Professor in the Sibley School of Mechanical and Aerospace Engineering at Cornell University and is an Adjunct Scientist at the Hospital for Special Surgery. Dr. Hernandez is a Fellow of the American Institute for Medical and Biological Engineering (AIMBE), the American Society of Mechanical Engineers (ASME), and the American Society for Bone and Mineral Research (ASBMR). He is the 2018 recipient of the Fuller Albright Award for Scientific Excellence from the American Society for Bone and Mineral Research. He has served on the Board of Directors of the Orthopaedic Research Society and the American Society for Bone and Mineral Research. His laboratory’s research currently focuses on the effects of the microbiome on bone and joint disorders, periprosthetic joint infection and the biomechanics and mechanobiology of bacteria.

hernandezresearch.com

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Brianne Connizzo Appointed Assistant Professor at Boston University

by Mahelet Asrat

Brianne Connizzo, PhD

The Department of Bioengineering is proud to congratulate alumna Brianne Connizzo, PhD on her appointment as a tenure-track Assistant Professor in the Department of Biomedical Engineering in the College of Engineering at Boston University. Connizzo’s appointment will begin in January 2021, after completing her work as a postdoctoral researcher in Biological Engineering at MIT under the supervision of Alan J. Grodzinsky, ScD, Professor of Biological, Electrical, and Mechanical Engineering.

Connizzo got her BS in Engineering Science from Smith College (the first all women’s engineering program in the country) where she graduated in 2010 with highest honors. During her time there, she worked in the laboratory of Borjana Mikic, Rosemary Bradford Hewlett 1940 Professor of Engineering. While working in the lab, she explored the role of myostatin deficiency on Achilles tendon biomechanics and built mechanical testing fixtures for submerged testing of biological tissues. Connizzo continued along this path during her graduate studies in Bioengineering at Penn while working with Louis J. Soslowsky, Fairhill Professor in Orthopaedic Surgery and Professor in Bioengineering, at the McKay Orthopaedic Research Laboratory. Her thesis work focused on the dynamic re-organizations of collagen during tendon loading in the rotator cuff, developing a novel AFM-based method for measuring collagen fibril sliding along the way. During her time at Penn, Connizzo also served as the Social Chair for the Graduate Association of Bioengineers (GABE) and the Graduate Student Engineering Group (GSEG), both of which play a vital role in representing graduate students across the School of Engineering and Applied Sciences. She completed her PhD in Bioengineering in 2015 and then pursued her postdoctoral studies at MIT, focusing on fluid flow during compressive loading and developing novel explant culture models to explore real-time extracellular matrix turnover. For her work she was awarded both an NIH F32 postdoctoral fellowship and the NIH K99/R00 Pathway Independence Award, which are just a few of her long list of impressive accomplishments.

Although Connizzo’s interests in soft tissue mechanobiology span development, injury, and disease, her more recent work has targeted how aging influences tendon function and biology. With a fast-growing active and aging population, she believes that identifying the cause and contributors of age-related changes is critical to finding treatments and therapies that could prevent tendon disease, and thus improve overall population healthspan and quality of life. The primary objectives of the Connizzo Lab at Boston University will be to harness novel in vitro and in vivo models to study cell-controlled extracellular matrix remodeling and tissue biomechanics and to better understand normal tendon maintenance and the initiation of tendon damage in the context of aging.

“I am so grateful to have had the guidance of my mentors and peers at Penn during my doctoral studies, and even more thankful that many of those relationships remain a significant part of my support system to this day,” Connizzo says. “I’m really looking forward to this next chapter — to all the successes and failures in pursuing the science, to building a community at BU and in my own laboratory, and to supporting the next generation of brilliant young scientists.”

Congratulations Dr. Connizzo from everyone at Penn Bioengineering!