What Does This Do? Reprogramming Adult Cells to an Embryonic State

The myriad array of cell types that comprise the complex human anatomy is captivating in itself, but in my opinion, the realization that they find their roots in a single population of specialized cells is astounding. Stem cells, with the unique capacity to differentiate into mature cells and divide into identical copies without differentiating, undergo a tightly regulated developmental scheme during embryogenesis to eventually form a fully functional adult.

Although all of our fully matured cells are genetically the same, the differences in cellular functionality can be attributed to variations in gene expression. But what is a gene and what does it do?

A colony of induced pluripotent stem cells.  The colonies are grown on a feed layer which consists of mouse embryonic fibroblasts that help to maintain the stem cells in an undifferentiated state.

A colony of induced pluripotent stem cells. The colonies are grown on a feed layer which consists of mouse embryonic fibroblasts that help to maintain the stem cells in an undifferentiated state.

A molecular instruction manual or gene is a region of DNA; this gene encodes for the synthesis of proteins, which in turn become our functional molecular building blocks. There are many steps that regulate the degree of how our genetic code is transcribed and translated into protein, which are essential components in stem cell behavior.

Researchers are looking to harness the properties of stem cells for regenerative medicine applications. In addition to a steady decrease in donor organ supply as the population continues to age, complications commonly arise due to immune rejection post-surgical treatment. Through cellular therapy, stem cells can be used to replace diseased or damage tissues and organs, circumventing the current issues in surgically implanting donor organs.

Although the utilization of stem cells in a clinical setting sounds promising, both ethical and research concerns must be carefully considered. Looking through a research lens, stem cells can either be harvested from embryos or from adult sources with differing capacities to transform, namely embryonic sources can differentiate to any cell type known as pluripotency, while adult sources have limited potency.

In addition, ethical concerns arise in extracting stem cells from embryonic sources because the embryo is destroyed in the process. These challenges have led researchers to evaluate which key components directs a stem cells ability to differentiate, and if these factors can be used to coax mature cells to revert back to a stem like state with the ability to transform.

In 2012 Drs. Yamanaka and Gurdon were awarded the noble prize in Physiology and Medicine for their discoveries leading to the successful reprogramming of mature cells to stem cells by re-expressing key genes in their DNA. New techniques for controlling gene expression for inducing adult cell pluripotency are emerging with greater efficiencies, providing new strides in the success of regenerative medicine. In fact, I don’t think it’s too far fetched to imagine a day where we use our own cells for personalized disease treatment, thanks to the amazing abilities of genes, and the power to control their expression.

Quinton Smith is a second year graduate student conducting research under the advisement of Sharon Gerecht in the Department of Chemical and Biomolecular Engineering.

INBT engineers coax stem cells to diversify

Growing new blood vessels in the lab is a tough challenge, but a Johns Hopkins engineering team has solved a major stumbling block: how to prod stem cells to become two different types of tissue that are needed to build tiny networks of veins and arteries.

The team’s solution is detailed in an article appearing in the January 2013 print edition of the journal Cardiovascular Research. The article also was published recently in the journal’s online edition. The work is important because networks of new blood vessels, assembled in the lab for transplanting into patients, could be a boon to people whose circulatory systems have been damaged by heart disease, diabetes and other illnesses.

blood-vessel-3-72

Illustration by Maureen Wanjare

“That’s our long-term goal—to give doctors a new tool to treat patients who have problems in the pipelines that carry blood through their bodies,” said Sharon Gerecht, an assistant professor of chemical and biomolecular engineering who led the research team. “Finding out how to steer these stem cells into becoming critical building blocks to make these blood vessel networks is an important step.”

In the new research paper, the Gerecht team focused on vascular smooth muscle cells, which are found within the walls of blood vessels. Two types have been identified: synthetic smooth muscle cells, which migrate through the surrounding tissue, continue to divide and help support the newly formed blood vessels; and contractile smooth muscles cells, which remain in place, stabilize the growth of new blood vessels and help them maintain proper blood pressure.

To produce these smooth muscle cells, Gerecht’s lab has been experimenting with both National Institutes of Health-approved human embryonic stem cells and induced pluripotent stem cells. The induced pluripotent stem cells are adult cells that have been genetically reprogrammed to act like embryonic stem cells. Stem cells are used in this research because they possess the potential to transform into specific types of cells needed by particular organs within the body.

In an earlier study supervised by Gerecht, her team was able to coax stem cells to become a type of tissue that resembled smooth muscle cells but didn’t quite behave properly. In the new experiments, the researchers tried adding various concentrations of growth factor and serum to the previous cells. Growth factor is the “food’ that the cells consume; serum is a liquid component that contains blood cells.

“When we added more of the growth factor and serum, the stem cells turned into synthetic smooth muscle cells,” Gerecht said. “When we provided a much smaller amount of these materials, they became contractile smooth muscles cells.”

This ability to control the type of smooth muscle cells formed in the lab could be critical in developing new blood vessel networks, she said. “When we’re building a pipeline to carry blood, you need the contractile cells to provide structure and stability,” she added. “But in working with very small blood vessels, the migrating synthetic cells can be more useful.”

In cancer, small blood vessels are formed to nourish the growing tumor. The current work could also help researchers understand how blood vessels are stabilized in tumors, which could be useful in the treatment of cancer.

“We still have a lot more research to do before we can build complete new blood vessel networks in the lab,” Gerecht said, “but our progress in controlling the fate of these stem cells appears to be a big step in the right direction.”

In addition to her faculty appointment with Johns Hopkins’ Whiting School of Engineering, Gerecht is affiliated with the university’s Institute for NanoBioTechnology (INBT) and the Johns Hopkins Engineering in Oncology Center.

The lead author of the new Cardiovascular Research paper is Maureen Wanjare, a doctoral student in Gerecht’s lab who is supported both by the INBT, through a National Science Foundation Integrative Graduate Education and Research Traineeship, and by the NIH. Coauthors of the study are Gerecht and Frederick Kuo, who participated in the research as an undergraduate majoring in chemical and biomolecular engineering. The human induced pluripotent stem cells used in the study were provided by Linzhao Cheng, a hematology professor in the Johns Hopkins School of Medicine.

This research was supported by an American Heart Association Scientist Development Grant and NIH grant R01HL107938.

Original press release can be found here.

 

Engineered hydrogel helps grow new, scar-free skin

In early testing, this hydrogel, developed by Johns Hopkins researchers, helped improve healing in third-degree burns. Photo by Will Kirk/HomewoodPhoto.jhu.edu

Johns Hopkins researchers have developed a jelly-like material and wound treatment method that, in early experiments on skin damaged by severe burns, appeared to regenerate healthy, scar-free tissue.

In the Dec. 12-16 online Early Edition of Proceedings of the National Academy of Sciences, the researchers reported their promising results from mouse tissue tests. The new treatment has not yet been tested on human patients. But the researchers say the procedure, which promotes the formation of new blood vessels and skin, including hair follicles, could lead to greatly improved healing for injured soldiers, home fire victims and other people with third-degree burns.

The treatment involved a simple wound dressing that included a specially designed hydrogel—a water-based, three-dimensional framework of polymers. This material was developed by researchers at Johns Hopkins’ Whiting School of Engineering, working with clinicians at the Johns Hopkins Bayview Medical Center Burn Center and the Department of Pathology at the university’s School of Medicine.

Third-degree burns typically destroy the top layers of skin down to the muscle. They require complex medical care and leave behind ugly scarring. But in the journal article, the Johns Hopkins team reported that their hydrogel method yielded better results. “This treatment promoted the development of new blood vessels and the regeneration of complex layers of skin, including hair follicles and the glands that produce skin oil,” said Sharon Gerecht, an assistant professor of chemical and biomolecular engineering who was principal investigator on the study.

Guoming Sun, left, a postdoctoral fellow, and Sharon Gerecht, an assistant professor of chemical and biomolecular engineering, helped develop a hydrogel that improved burn healing in early experiments. Photo by Will Kirk/HomewoodPhoto.jhu.edu

Gerecht said the hydrogel could form the basis of an inexpensive burn wound treatment that works better than currently available clinical therapies, adding that it would be easy to manufacture on a large scale. Gerecht suggested that because the hydrogel contains no drugs or biological components to make it work, the Food and Drug Administration would most likely classify it as a device. Further animal testing is planned before trials on human patients begin. But Gerecht said, “It could be approved for clinical use after just a few years of testing.”

John Harmon, a professor of surgery at the Johns Hopkins School of Medicine and director of surgical research at Bayview, described the mouse study results as “absolutely remarkable. We got complete skin regeneration, which never happens in typical burn wound treatment.”

If the treatment succeeds in human patients, it could address a serious form of injury. Harmon, a coauthor of the PNAS journal article, pointed out that 100,000 third-degree burns are treated in U. S. burn centers like Bayview every year. A burn wound dressing using the new hydrogel could have enormous potential for use in applications beyond common burns, including treatment of diabetic patients with foot ulcers, Harmon said.

Guoming Sun, Gerecht’s Maryland Stem Cell Research Postdoctoral Fellow and lead author on the paper, has been working with these hydrogels for the last three years, developing ways to improve the growth of blood vessels, a process called angiogenesis. “Our goal was to induce the growth of functional new blood vessels within the hydrogel to treat wounds and ischemic disease, which reduces blood flow to organs like the heart,” Sun said. “These tests on burn injuries just proved its potential.”

Gerecht says the hydrogel is constructed in such a way that it allows tissue regeneration and blood vessel formation to occur very quickly. “Inflammatory cells are able to easily penetrate and degrade the hydrogel, enabling blood vessels to fill in and support wound healing and the growth of new tissue,” she said. For burns, the faster this process occurs, Gerecht added, the less there is a chance for scarring.

Originally, her team intended to load the gel with stem cells and infuse it with growth factors to trigger and direct the tissue development. Instead, they tested the gel alone. “We were surprised to see such complete regeneration in the absence of any added biological signals,” Gerecht said.

Sun added, “Complete skin regeneration is desired for various wound injuries. With further fine-tuning of these kinds of biomaterial frameworks, we may restore normal skin structures for other injuries such as skin ulcers.”

Gerecht and Harmon say they don’t fully understand how the hydrogel dressing is working. After it is applied, the tissue progresses through the various stages of wound repair, Gerecht said. After 21 days, the gel has been harmlessly absorbed, and the tissue continues to return to the appearance of normal skin.

The hydrogel is mainly made of water with dissolved dextran—a polysaccharide (sugar molecule chains). “It also could be that the physical structure of the hydrogel guides the repair,” Gerecht said. Harmon speculates that the hydrogel may recruit circulating bone marrow stem cells in the bloodstream. Stem cells are special cells that can grow into practically any sort of tissue if provided with the right chemical cue. “It’s possible the gel is somehow signaling the stem cells to become new skin and blood vessels,” Harmon said.

Additional co-authors of the study included Charles Steenbergen, a professor in the Department of Pathology; Karen Fox-Talbot, a senior research specialist from the Johns Hopkins School of Medicine; and physician researchers Xianjie Zhang, Raul Sebastian and Maura Reinblatt from the Department of Surgery and Hendrix Burn and Wound Lab. From the Whiting School’s Department of Chemical and Biomolecular Engineering, other co-authors were doctoral students Yu-I (Tom) Shen and Laura Dickinson, who is a Johns Hopkins Institute for NanoBioTechnology (INBT) National Science Foundation IGERT fellow. Gerecht is an affiliated faculty member of INBT.

The work was funded in part by the Maryland Stem Cell Research Fund Exploratory Grant and Postdoctoral Fellowship and the National Institutes of Health.

The Johns Hopkins Technology Transfer staff has filed a provisional patent application to protect the intellectual property involved in this project.

Related links:

Sharon Gerecht’s Lab

Johns Hopkins Burn Center

Johns Hopkins Institute for NanoBioTechnology

 

Story by Mary Spiro

Gerecht wins NSF CAREER Award for work in blood vessel formation

Sharon Gerecht (Photo:Will Kirk/JHU)

Sharon Gerecht, assistant professor in Chemical and Biomolecular Engineering at Johns Hopkins University, has been awarded the Faculty Early Career Development (CAREER) Award from the National Science Foundation. The $450,000 prize over five years will help Gerecht in her investigation into how hypoxia, or decreased oxygen, affects the development of blood vessels.

Gerecht’s interdisciplinary research brings together her expertise in stem cell and vascular biology with her background in engineering.  Gerecht said she hopes to discover the mechanisms and pathways involved in the formation of vascular networks, as they relate to embryonic development and diseases such as cancer.

Many medical conditions, such as cancer and heart disease, create areas of decreased oxygen or hypoxia in the spaces between cells. But oxygen is required to maintain normal tissue function by blood vessel networks, which bring nutrients to cells. Likewise, the differentiation of stem cells into more complex organs and structures needs a plentiful supply of oxygen from the vasculature to function.

Gerecht’s study will examine how low oxygen levels impact the growth factors responsible for promoting vascular networks. She also will study the growth of vascular networks in engineered hydrogels that mimic the physical attributes of the extracellular matrix, which is the framework upon which cells divide and grow. Finally, her laboratory will focus on discovering how stem cells differentiate to blood vessel cells and assemble into networks under hypoxic conditions.

She will conduct her research through her role as a project director at the Johns Hopkins Engineering in Oncology Center (EOC), a Physical Science-Oncology Center of the National Cancer Institute. Gerecht is also an associated faculty member of the Johns Hopkins Institute for NanoBioTechnology, which administers the EOC.

Gerecht earned her doctoral degree from Technion – Israel Institute of Technology followed by postdoctoral training at Massachusetts Institute of Technology. She joined the faculty of the Whiting School of Engineering at Johns Hopkins in 2007.

The prestigious CAREER award, given to faculty members at the beginning of their academic careers, is one of NSF’s most competitive awards and emphasizes high-quality research and novel education initiatives. It provides funding so that young investigators have the opportunity to focus more intently on furthering their research careers.

Story by Mary Spiro