Discovery

What medical scientists are realizing more and more is that this mysterious connectedness applies not only to interactions among humans, but to the inner workings of their bodies – a biological tapestry of intricately woven parts and processes that sets the course for health and, when things go wrong, for disease.

In 2001, the findings of a breakthrough Ohio State University cancer study energized cancer researchers throughout the world. It also caught the attention of heart, spine and lung researchers closer to home. Today, biomedical researchers from multiple specialties at Ohio State are working together to define the role inflammation plays in the progression of numerous diseases and conditions.

In the 1946 movie “It’s a Wonderful Life,” a guardian angel describes the sometimes overlooked way in which each person’s life affects so many others.

What medical scientists are realizing more and more is that this mysterious connectedness applies not only to interactions among humans, but to the inner workings of their bodies – a biological tapestry of intricately woven parts and processes that sets the course for health and, when things go wrong, for disease.

Scientists at The Ohio State University Medical Center increasingly marvel at how it all fits together, and at how processes leading to cancer may also figure into maladies such as vascular disease, pulmonary fibrosis and spinal cord injury.

It follows, then, that research pertaining to one discipline can sometimes be extended to others. A cadre of Ohio State scientists is exploring this concept in relation to what is known as the body’s microenvironment, the area surrounding a tumor or other diseased or injured tissue.

“When we start looking at how the body responds to illness or injury, we find a lot of redundancy in the molecular pathways and cell processes for cancer and other diseases,” says Clay Marsh, MD, who directs the Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, and is also a member of Ohio State’s Comprehensive Cancer Center (OSUCCC). For example, Marsh says, inflammation – a protective or reparative reaction to disease or injury – plays a big role in cancer and many disorders.

“So we’re adapting our understanding of what happens with cells and chemical reactions involved with inflammation to learn how we can manipulate the repair or healing process in cancer and diseases outside of cancer,” he says. “We believe these disease models can be leveraged to help our basic understanding of health and disease.”

They are particularly interested in how the microenvironment and its biological conditions interact with, and thus influence, the disease or injury site, and vice versa.

It Started with Cancer

Mouse mammary tumor viewed through fluorescent light. Green areas show regions of tumor death.

In articles published subsequently in the journals Human Molecular Genetics and Nature Genetics, the scientists described their model as “paradigm shifting” because, previously, genetic mutations leading to breast cancer had been thought to occur only in epithelial cells, or cells that line or cover an organ, and not in stromal cells. They based their new model on laboratory evidence that mutations occur first in the epithelium and are followed by corresponding changes in the stroma.

Led by principal investigator Michael Ostrowski, PhD, and Gustavo Leone, PhD, the scientists in 2004 received a five-year, $8.6 million grant from the National Cancer Institute to further study the role of the tumor microenvironment in breast cancer progression.

“We’re taking a more holistic approach,” says Ostrowski, professor and chair of the Department of Molecular and Cellular Biochemistry and co-leader of the OSUCCC’s Molecular Biology and Cancer Genetics Program. “Instead of focusing just on the cells that make up the tumor itself, we’re examining the different components that contribute to the disease and how theymight be used for better diagnosis and treatment.”

Scientists know that the tumor microenvironment contains many types of cells, a meshwork of fibers and proteins and assorted chemical signals that keep cells functioning normally. But they need to better understand how these elements change as tumors develop and metastasize, interacting with the stroma and being influenced by it in return. Ostrowski notes that certain reparative hallmarks of the normal microenvironment, such as inflammation and fibrosis – the formation of fibrous or scar tissue – are meant to heal but can contribute to disease when they go wrong.

Similar Process in the Heart and Lungs
“Fibroblasts, or the cells that cause scarring in order to repair damaged tissue, can start behaving abnormally so that the process of fibrosis starts but has no end – it gets stuck in the ‘on’ mode,” he explains. “A lot of pulmonary fibrosis is similar to cancer metastasis. If we can see the differences between lung fibrosis and lung cancer, we might gain insight about their causes and possible cures.”

“Manipulating host-tumor reactions may be important in preventing or reversing cancer, and in re-establishing normal control mechanisms in the affected tissues or organs,” Marsh says. “Other human diseases share many mechanisms with cancer, including alterations in the host microenvironment to attempt to repair organ injury and retain organ function. It’s becoming better recognized that signals released and contained within tissue sites direct the immune system to respond and can determine host outcome.”

Consequently, he says, scientists at Ohio State are interfacing advanced mouse models of disease with human tissue to study the microenvironment in cancer and other diseases. This includes the role of the immune system (and immune cells known as macrophages) in pulmonary fibrosis and in vascular diseases such as atherosclerosis.

“Inflammatory cells are like soldiers in the body that respond to signals in the microenvironment of blood vessel walls and play a critical role in the physiology of atherosclerosis,” says Sanjay Rajagopalan, MD, the John Wolfe Professor of Medicine and Radiology in the Division of Cardiovascular Medicine. “These interactions provide insight as to how the plaque progresses and takes on vulnerable characteristics. The microenvironment in a blood vessel wall also can determine future cardiovascular events such as heart attack.”

Rajagopalan says microenvironment interactions with blood vessels and fat tissue are also important in type 2 diabetes. “The No. 1 problem diabetes patients have is their risk for heart attack and stroke, so what happens within the microenvironment of fat and blood vessel walls is of utmost importance,” he adds, noting that diabetes can magnify the process of atherosclerosis.

“What we study are the pathways by which inflammatory cells of the immune system home in on afflicted areas of the blood vessels and fat so we can understand the microenvironment in which these cells influence other cell types,”Rajagopalan says. “These inflammatory cells can arrive and wreak havoc; it’s an exaggeration of a normal defense mechanism that goes awry. When the inflammatory process goes wrong or is excessive, it actually contributes to diseases such as atherosclerosis and diabetes.”

He has two large grants from the National Institutes of Health. One is to study mouse models of inflammation in atherosclerosis. The other is to explore mechanisms in blood vessels and fat tissue in relation to diabetes.

Marsh and colleagues are interested in pulmonary fibrosis, an incurable disease that involves the inexorable deposition of scar tissue in the lung that ultimately replaces enough normal tissue that the lungs can’t send oxygen to the bloodstream. Marsh says the exact cause is unknown, “although it’s clear that there is repetitive injury from some source.” Scientists think there also may be a genetic component.

Marsh says an inflammatory response to the injury leads to scarring in this disease, “so in some ways it’s like a nonhealing wound to the lungs.” Regarding an NIH-funded study to learn how inflammatory cells respond to lung injury and contribute to scarring, he says, “We’ve identified that white blood cells called macrophages are important in the ongoing injury and scar-tissue buildup in the lungs, and we’ve identified factors that cause these cells to go to the lungs so we can try to disrupt them.”

In a study funded by Battelle, he and colleagues are analyzing the genetics of patients with pulmonary fibrosis to define molecular targets for improving outcomes. “Both of these basicscience studies use lung tissue and blood cells from human patients as well as from mouse models,” he notes.

A Role in Spinal Injury Repair

Inflammatory monocytes interacting with the endothelium, a thin layer of cells that line the inside of blood vessels, as viewed through a variety of fluorescent methods.

“The body has common overlapping mechanisms in response to tissue pathology or injury,” says Phillip Popovich, PhD, the Ray Poppleton Research Chair and director of Ohio State’s Center for Brain and Spinal Cord Repair. “Spinal cord injury also prompts a complex interaction between macrophages and resident cells of the nervous system – neurons and glial cells – to create a microenvironment not unlike that described by Dr.Marsh in the nonhealing lung.”

Popovich says macrophages (and other immune cells) that enter the injured spinal cord are pre-programmed to defend the resident cells from infection, but since most forms of spinal cord injury are not associated with infections at the lesion site, these immune cells may be unnecessary and could cause additional damage. But he points out that, as these cells interact with cells and factors in the microenvironment, they can be stimulated to repair injured tissue.

In separate grant studies funded by the NIH and the Craig T. Neilsen Foundation, Popovich and others are using rodent models that mimic the most common types of human spinal cord injuries. They hope tomodify the lesionmicroenvironment to stimulate macrophage-mediated repair rather than destruction.

“If we can see the differences between lung fibrosis and lung cancer, we might gain insight about their causes and possible cures.” Inflammatory monocytes interacting with the endothelium, a thin layer of cells that line the inside of blood vessels, as viewed through a variety of fluorescent methods.

He points to the bond between his studies and those of scientists like Ostrowski, Leone, Marsh and Rajagopalan. “The macrophage or immune response enters the microenvironment in all pathology or injury, so the beauty of all this research is that we may be able to translate it across many disciplines. We’d be manipulating or harnessing a natural process within the body to promote healing, as opposed to using drugs that may have toxic effects and whose total impact on the body is unknown.”

The others agree.

Turning on the Lights

Microphages (pictured in AC as green, yellow and red cells) are immune cells that can be stimulated to produce either inflammatory or anti-inflammatory proteins. By changing the microenvironment of a spinal cord injury (Figs. D-F), researchers can alter the level of the inflammatory, or antiinflammatory, response of the microphages at the lesion site.

“And if we can identify more than one target, we can do combined therapy aimed at multiple sources, making it harder for diseases like cancer to evade.”

Marsh says microenvironment research also may someday help physicians move from reactive treatment of disease to prediction and prevention of these same diseases.

“Ultimately, these studies are about collaborating to understand the interconnectedness of processes that have fallen out of balance in and around the disease or injury site,” he says. “By restoring the balance, perhaps we can transition people back to health. In the future, our goal is to detect these alterations in the patient before the clinical manifestations of the disease are expressed, and to prevent the clinical disease from occurring.”

from left: Michael Ostrowski, PhD; Gustavo Leone, PhD; Sanjay Rajagopalan, MD; Phillip Popovich, PhD; Clay Marsh, MD