Scientists Discover a Key Quality-Control Mechanism in DNA Replication

by Meagan Raeke

Illustration of the 55LCC complex. (Image: Courtesy of Cameron Baines/Phospho Biomedical Animation)

When cells in the human body divide, they must first make accurate copies of their DNA. The DNA replication exercise is one of the most important processes in all living organisms and is fraught with risks of mutation, which can lead to cell death or cancer. Now, findings from biologists from the Perelman School of Medicine and from the University of Leeds have identified a multiprotein “machine” in cells that helps govern the pausing or stopping of DNA replication to ensure its smooth progress. Illustration of the 55LCC complex. (Image: Courtesy of Cameron Baines/Phospho Biomedical Animation)

The discovery, published in Cell, advances the understanding of DNA replication, helps explain a puzzling set of genetic diseases, and could inform the development of future treatments for neurologic and developmental disorders.

“We’ve found what appears to be a critical quality-control mechanism in cells,” says senior co-corresponding author Roger Greenberg, the J. Samuel Staub, M.D. Professor in the department of Cancer Biology, director of the Penn Center for Genome Integrity, and director of basic science at the Basser Center for BRCA at Penn Medicine. “Trillions of cells in our body divide every single day, and this requires accurate replication of our genomes. Our work describes a new mechanism that regulates protein stability in replicating DNA. We now know a bit more about an important step in this complex biological process.”

Read the full story at Penn Medicine News.

Greenberg is a member of the Penn Bioengineering Graduate Group.

Bioengineers on the Brink of Breaching Blood-brain Barrier

by Nathi Magubane

From left: Emily Han, Rohan Palanki, Jacqueline Li, Michael Mitchell, Dongyoon Kim, and Marshall Padilla of Penn Engineering.

Imagine the brain as an air traffic control tower, overseeing the crucial and complex operations of the body’s ‘airport.’ This tower, essential for coordinating the ceaseless flow of neurological signals, is guarded by a formidable layer that functions like the airport’s security team, diligently screening everything and everyone, ensuring no unwanted intruders disrupt the vital workings inside.

However, this security, while vital, comes with a significant drawback: sometimes, a ‘mechanic’—in the form of critical medication needed for treating neurological disorders—is needed inside the control tower to fix arising issues. But if the security is too stringent, denying even these essential agents entry, the very operations they’re meant to protect could be jeopardized.

Now, researchers led by Michael Mitchell of the University of Pennsylvania are broaching this long-standing boundary in biology, known as the blood-brain barrier, by developing a method akin to providing this mechanic with a special keycard to bypass security. Their findings, published in the journal Nano Letters, present a model that uses lipid nanoparticles (LNPs) to deliver mRNA, offering new hope for treating conditions like Alzheimer’s disease and seizures—not unlike fixing the control tower’s glitches without compromising its security.

“Our model performed better at crossing the blood-brain barrier than others and helped us identify organ-specific particles that we later validated in future models,” says Mitchell, associate professor of bioengineering at Penn’s School of Engineering and Applied Science, and senior author on the study. “It’s an exciting proof of concept that will no doubt inform novel approaches to treating conditions like traumatic brain injury, stroke, and Alzheimer’s.”

Read the full story in Penn Today.

Arjun Raj Receives 2023-24 Heilmeier Award

by Olivia J. McMahon

Arjun Raj, Ph.D.

Arjun Raj, Professor in Bioengineering in Penn Engineering, has been named the recipient of the 2023-24 George H. Heilmeier Faculty Award for Excellence in Research for “pioneering the development and application of single-cell, cancer-fighting technologies.”

The Heilmeier Award honors a Penn Engineering faculty member whose work is scientifically meritorious and has high technological impact and visibility. It is named for the late George H. Heilmeier, a Penn Engineering alumnus and member of the School’s Board of Advisors, whose technological contributions include the development of liquid crystal displays and whose honors include the National Medal of Science and Kyoto Prize.

Raj, who also holds an appointment in Genetics in the Perelman School of Medicine, is a pioneer in the burgeoning field of single-cell engineering and biology. Powered by innovative techniques he has developed for molecular profiling of single cells, his scientific discoveries range from the molecular underpinnings of cellular variability to the behavior of single cells across biology, including in diseases such as cancer.

Raj will deliver the 2023-24 Heilmeier Lecture at Penn Engineering during the spring 2024 semester.

This story originally appeared in Penn Engineering Today.

Read more stories featuring Dr. Raj here.

Leveraging the Body’s Postal System to Understand and Treat Disease

by Nathi Magubane

Microwell device with a solution in the reservoir (Image: Courtesy of David E. Reynolds)

Akin to the packages sent from one person to another via an elaborate postal system, cells send tiny parcels that bear contents and packaging material that serve key purposes: To protect the contents from the outside world and to make sure it gets to the right place via a label with an address. 

These packages are known as extracellular vesicles (EVs)—lipid-bound molecules that serve a variety of regulatory and maintenance functions throughout the body. They assist in the removal of unwanted materials within the cell, and they transport proteins, aid in DNA and RNA transfer, and promote tumorigeneses in cancerous cells. 

Given their myriad roles, EVs have taken center stage for many researchers in the biomedical space as they have the potential to improve current methods of disease detection and treatment. The main challenge, however, is accurately identifying the molecular contents of EVs while also characterizing the EVs, which, unlike other cellular components that are more homogenous, have more heterogeneity.

Now, a team of researchers at the University of Pennsylvania has developed a novel platform, droplet-free double digital assay, for not only profiling individual EVs but also accurately discerning their molecular contents. The researchers took the digital assay, which quantifies the contents of a molecule via binary metric—a 1 corresponds to the presence of a molecule and a zero to the lack thereof—and applies it to the EV. The work is published in Advanced Science.

The team was led by Jina Ko, an assistant professor with appointments in the School of Engineering and Applied Science and Perelman School of Medicine. “Our method allows for highly accurate quantification of the individual molecules inside an EV,” Ko says . “This opens up many doors in the realm of early disease detection and treatment.”

The researchers first compartmentalized individual EVs utilizing a microwell approach to isolate the EVs. Next, they captured individual molecules within the EVs and amplified the signal for clarity. The team then was able to determine the expression levels of pivotal EV biomarkers with remarkable precision via fluorescence.

Read the full story in Penn Today.

Jina Ko is an assistant professor in the Department of Pathology and Laboratory Medicine in the Perelman School of Medicine and an assistant professor in the Department of Bioengineering in the School of Engineering and Applied Science at the University of Pennsylvania.

David Reynolds is a Ph.D. candidate in the Department of Bioengineering in Penn Engineering.

Other authors include, Menghan Pan, George Galanis, Yoon Ho Roh, Renee-Tyler T. Morales, Shailesh Senthil Kumar, and Su-Jin Heo of the Department of Bioengineering at Penn Engineering; Jingbo Yang and Xiaowei Xu of the Department of Pathology and Laboratory Medicine at Penn Medicine; and Wei Guo of the Department of Biology in the School of Arts & Sciences at Penn.

The research was supported by the National Institutes of Health: grants R00CA256353, R35 GM141832, and CA174523 (SPORE).

Harnessing Artificial Intelligence for Real Biological Advances—Meet César de la Fuente

by Eric Horvath

In an era peppered by breathless discussions about artificial intelligence—pro and con—it makes sense to feel uncertain, or at least want to slow down and get a better grasp of where this is all headed. Trusting machines to do things typically reserved for humans is a little fantastical, historically reserved for science fiction rather than science. 

Not so much for César de la Fuente, PhD, the Presidential Assistant Professor in Psychiatry, Microbiology, Chemical and Biomolecular Engineering, and Bioengineering in Penn’s Perelman School of Medicine and School of Engineering and Applied Science. Driven by his transdisciplinary background, de la Fuente leads the Machine Biology Group at Penn: aimed at harnessing machines to drive biological and medical advances. 

A newly minted National Academy of Medicine Emerging Leaders in Health and Medicine (ELHM) Scholar, among earning a host of other awards and honors (over 60), de la Fuente can sound almost diplomatic when describing the intersection of humanity, machines and medicine where he has made his way—ensuring multiple functions work together in harmony. 

“Biology is complexity, right? You need chemistry, you need mathematics, physics and computer science, and principles and concepts from all these different areas, to try to begin to understand the complexity of biology,” he said. “That’s how I became a scientist.”

Read the full story in Penn Medicine News.

Artificial Intelligence is Leveling Up the Fight Against Infectious Diseases

by

Image credit: NIAID

Artificial intelligence is a new addition to the infectious disease researcher’s toolbox. Yet in merely half a decade, AI has accelerated progress on some of the most urgent issues in medical science and public health. Researchers in this field blend knowledge of life sciences with skill in computation, chemistry and design, satisfying decades-long appeals for interdisciplinary tactics to treat these disorders and stop their spread.

Diseases are “infectious” when they are caused by organisms, including parasites, viruses, bacteria and fungi. People and animals can contract infectious diseases from their environments or food, or through interactions with one another. Some, but not all, are contagious.

Infectious diseases are an intractable global challenge, posing problems that continue to grow in severity even as science has offered a steady pace of solutions. The world continues to become more interconnected, bringing people into new kinds and levels of relation, and the climate crisis is throwing environmental and ecological networks out of balance. Diseases that were once treatable by drugs have become resistant, and new drug discovery is more costly than ever. Uneven resource distribution means that certain parts of the world are perennial hotspots for diseases that others never fear.

Cesar de la Fuente brings an expert eye to how AI has transformed infectious disease research in a recently published piece in Science with co-authors Felix Wong and James J. Collins from MIT.

Presidential Assistant Professor in the Department of Bioengineering and the Department of Chemical and Biomolecular Engineering at the University of Pennsylvania School of Engineering and Applied Science, with additional primary appointments in Psychiatry and Microbiology within the Perelman School of Medicine, de la Fuente brings a multifaceted perspective to his survey of the field.

In the paper, de la Fuente and co-authors assess the progress, limitations and promise of research in AI and infectious diseases in three major areas of inquiry: anti-infective drug discovery, infection biology, and diagnostics for infectious diseases.

Read more in Penn Engineering Today.

The Art and Science of Living-Like Architecture

by

Collaborators from Penn Engineering and the Stuart Weitzman School of Design have created “living-like” bioactive interior architecture designed to one day protect us from hidden airborne threats. The figure above demonstrates (A) design for support lattices for the team’s innovative bioactive sites, (B) a ribbon-like geometry for hanging and (C, D) how these structures may be integrated into indoor environments to biologically sense and react to air.

“This technology is not alive,” says Laia Mogas-Soldevila. “It is living-like.”

The distinction is an important one for the assistant professor at the Stuart Weitzman School of Design, for reasons both scientific and artistic. With a doctorate in biomedical engineering, several degrees in architecture, and a devotion to sustainable design, Mogas-Soldevila brings biology to everyday life, creating materials for a future built halfway between nature and artifice.

The architectural technology she describes is unassuming at first look: A freeze-dried pellet, small enough to get lost in your pocket. But this tiny lump of matter, the result of more than a year’s collaboration between designers, engineers and biologists, is a biomaterial that contains a “living-like” system.

When touched by water, the pellet activates and expresses a glowing protein, its fluorescence demonstrating that life and art can harmonize into a third and very different thing, as ready to please as to protect. Woven into lattices made of flexible natural materials promoting air and moisture flow, the pellets form striking interior design elements that could one day keep us healthy.

“We envision them as sensors,” explains Mogas-Soldevila. “They may detect pathogens, such as bacteria or viruses, or alert people to toxins inside their home. The pellets are designed to interact with air. With development, they could monitor or even clean it.”

For now, they glow, a triumphant first stop on the team’s roadmap to the future. The fluorescence establishes that the lab’s biomaterial manufacturing process is compatible with the leading-edge cell-free engineering that gives the pellets their life-like properties.

A rapidly expanding technology, cell-free protein expression systems allow researchers to manufacture proteins without the use of living cells.

Gabrielle Ho, Ph.D. candidate in the Department of Bioengineering and co-leader of the project, explains how the team’s design work came to be cell-free, a technique rarely explored outside of lab study or medical applications.

“Typically, we’d use living E. coli cells to make a protein,” says Ho. “E. coli is a biological workhorse, accessible and very productive. We’d introduce DNA to the cell to encourage expression of specific proteins. But this traditional method was not an option for this project. You can’t have engineered E. coli hanging on your walls.”

Cell-free systems contain all the components a living cell requires to manufacture protein —energy, enzymes and amino acids — and not much else. These systems are therefore not alive. They do not replicate, and neither can they cause infection. They are “living-like,” designed to take in DNA and push out protein in ways that previously were only possible using living cells.

“One of the nicest things about these materials not being alive,” says Mogas-Soldevila, “is that we don’t need to worry about keeping them that way.”

Unlike living cells, cell-free materials don’t need a wet environment or constant monitoring in a lab. The team’s research has established a process for making these dry pellets that preserves bioactivity throughout manufacturing, storage and use.

Bioactive, expressive and programmable, this technology is designed to capitalize on the unique properties of organic materials.

Mogas-Soldevila, whose lab focuses exclusively on biodegradable architecture, understands the value of biomaterials as both environmentally responsible and aesthetically rich.

“Architects are coming to the realization that conventional materials — concrete, steel, glass, ceramic, etc. — are environmentally damaging and they are becoming more and more interested in alternatives to replace at least some of them. Because we use so much, even being able to replace a small percentage would result in a significant reduction in waste and pollution.”

Her lab’s signature materials — biopolymers made from shrimp shells, wood pulp, sand and soil, silk cocoons, and algae gums — lend qualities over and above their sustainable advantages.

“My obsession is diagnostic, but my passion is playfulness,” says Mogas-Soldevila. “Biomaterials are the only materials that can encapsulate this double function observed in nature.”

This multivalent approach benefited from the help of Penn Engineering’s George H. Stephenson Foundation Educational Laboratory & Bio-MakerSpace, and the support of its director, Sevile Mannickarottu. In addition to contributing essential equipment and research infrastructure to the team, Mannickarottu was instrumental in enabling the interdisciplinary relationships that led the team to success, introducing Ho to the DumoLab Research team collaborators. These include Mogas-Soldevila, Camila Irabien, a Penn Biology major who provided crucial contributions to experimental work, and Fulbright design fellow Vlasta Kubušová, who co-led the project during her time at Penn and who will continue fueling the project’s next steps.

Read the full story in Penn Engineering Today.

César de la Fuente Named AIMBE Fellow

by

César de la Fuente
César de la Fuente

César de la Fuente, Presidential Assistant Professor in Psychiatry, Microbiology, Bioengineering and in Chemical and Biomolecular Engineering, has been named an American Institute for Medical and Biological Engineering (AIMBE) Fellow. The only faculty member inducted this year from the University of Pennsylvania, de la Fuente is one of the youngest members ever to have been selected as an AIMBE Fellow.

Election to the AIMBE College of Fellows is among the highest professional distinctions accorded to a medical and biological engineer, with AIMBE Fellows representing the top 2% of medical and biological engineers. College membership honors those who have made outstanding contributions to “engineering and medicine research, practice, or education” and to “the pioneering of new and developing fields of technology, making major advancements in traditional fields of medical and biological engineering, or developing/implementing innovative approaches to bioengineering education.”

Nominated and reviewed by peers and members of the College of Fellows, de la Fuente was elected Fellow “for the development of novel antimicrobial peptides designed using principles from computation, engineering and biology.”

A formal ceremony will be held during the AIMBE Annual Event in Arlington, Virginia on March 27, 2023, where de la Fuente will be inducted along with 140 colleagues who make up the AIMBE College of Fellows Class of 2023.

AIMBE Fellows are among the most distinguished medical and biological engineers, including 3 Nobel Prize laureates and 17 Fellows having received the Presidential Medal of Science and/or Technology and Innovation, along with 205 having been inducted into the National Academy of Engineering, 105 into the National Academy of Medicine and 43 into the National Academy of
Sciences.

This story was originally posted in Penn Engineering Today.

Read more stories featuring César de la Fuente here.

New Insights into the Mechanisms of Tumor Growth

by

3d render of cells secreting exosomes
A team of researchers led by the School of Arts & Science’s Wei Guo offers new insights into a mechanism that promotes tumor growth. “This information could be used to help clinicians diagnose cancers earlier in the future,” says Guo.

In many instances, the physical manifestation of cancers and the ways they are subsequently diagnosed is via a tumor, tissue masses of mutated cells and structures that grow excessively. One of the major mysteries in understanding what goes awry in cancers relates to the environments within which these structures grow, commonly known as the tumor microenvironment.

These microenvironments play a role in facilitating tumor survival, growth, and spread. Tumors can help generate their own infrastructure in the form of vasculature, immune cells, signaling molecules, and extracellular matrices (ECMs), three-dimensional networks of collagen-rich support scaffolding for a cell. ECMs also help regulate cellular communications, and in the tumor microenvironment ECMs can be a key promoter of tumor growth by providing structural support for cancerous cells and in modulating signaling pathways that promote growth.

Now, new research led by the School of Arts & Science’s Wei Guo and published in the journal Nature Cell Biology has bridged the complex structural interactions within the tumor microenvironment to the signals that trigger tumor growth. The researchers studied cancerous liver cells grown on ECMs of varying stiffness and discovered that the stiffening associated with tumor growth can initiate a cascade that increases the production of small lipid-encapsulated vesicles known as exosomes.

“Think of these exosomes as packages that each cell couriers out, and, depending on the address, they get directed to other cells,” says Ravi Radhakrishnan, professor of bioengineering in the School of Engineering and Applied Science and a co-author of the paper.

“By recording the number of packages sent, the addresses on these packages, their contents, and most importantly, how they’re regulated and generated, we can better understand the relationship between a patient’s tumor microenvironment and their unique molecular signaling signatures, hinting at more robust personalized cancer therapies,” Radhakrishnan says.

While studying exosomes in relation to tumor growth and metastasis has been well-documented in recent years, researchers have mostly focused on cataloging their characteristics rather than investigating the many processes that govern the creation and shuttling of exosomes between cells. As members of Penn’s Physical Sciences Oncology Center (PSOC), Guo and Radhakrishnan have long collaborated on projects concerning tissue stiffness. For this paper, they sought to elucidate how stiffening promotes exosome trafficking in cancerous intracellular signaling.

“Our lab previously found that high stiffness promotes the secretion of exosomes,” says Di-Ao Liu, co-first author of the paper and a graduate student in the Guo Lab. “Now, we were able to model the stiffening processes through experiments and identify molecular pathways and protein networks that cause this, which better links ECM stiffening to cancerous signaling.”

Read the full story in Penn Today.

New Single Cell Analysis Tool

by Nathi Magubane

Researchers at Penn and colleagues have developed a tool to analyze single cells that assesses both the patterns of gene activation within a cell and which sibling cells shared a common progenitor.

3D illustration of a cell held by a pipet and a needle
Arjun Raj of the School of Engineering and Applied Science and the Perelman School of Medicine, former postdoc Lee Richman, now of Brigham and Women’s Hospital, and colleagues have developed a new analysis tool that combines a cell’s unique gene expression data with information about the cell’s origins. The method can be applied to identify new cell subsets throughout development and better understand drug resistance.

Recent advances in analyzing data at the single-cell level have helped biologists make great strides in uncovering new information about cells and their behaviors. One commonly used approach, known as clustering, allows scientists to group cells based on characteristics such as the unique patterns of active or inactive genes or by the progeny of duplicating cells, known as clones, over several generations.

Although single-cell clustering has led to many significant findings, for example, new cancer cell subsets or the way immature stem cells mature into “specialized” cells, researchers to this point had not been able to marry what they knew about gene-activation patterns with what they knew about clone lineages.

Now, research published in Cell Genomics led by University of Pennsylvania professor of bioengineering Arjun Raj has resulted in the development of ClonoCluster, an open-source tool that combines unique patterns of gene activation with clonal information. This produces hybrid cluster data that can quickly identify new cellular traits; that can then be used to better understand resistance to some cancer therapies.

“Before, these were independent modalities, where you would cluster the cells that express the same genes in one lot and cluster the others that share a common ancestor in another,” says Lee Richman, first paper author and a former postdoc in the Raj lab who is now at Brigham and Women’s Hospital in Boston. “What’s exciting is that this tool allows you to draw new lines around your clusters and explore their properties, which could help us identify new cell types, functions, and molecular pathways.”

Researchers in the Raj Lab use a technique known as barcoding to assign labels to cells they are interested in studying, particularly useful for tracking cells, clustering data based on cells’ offspring, and following lineages over time. Believing they could parse more valuable information out of this data by incorporating the cell’s unique patterns of gene activation, the researchers applied ClonoCluster to six experimental datasets that used barcoding to track dividing cells’ offspring. Specifically, they looked at the development of chemotherapy resistance and of stem cells into specialized tissue types.

Read the full story in Penn Today.