Cell Transformation from One Type of Cell to Another

ScienceDaily (Oct. 5, 2011) — Researchers from the Haematopoietic Differentiation and Stem Cell Biology group at the Centre for Genomic Regulation (CRG), have described one of the mechanisms by which a cell (from the skin, for example) can be converted into another which is completely different (e.g., a neuron or hepatic cell). They have discovered that the cell transcription factor C/EBPa is a determinant factor in cell transdifferentiation.

Cell transformation a la carte.

This differentiation mechanism can be applied to any cells of an organism.

The scope of the study, published in the Proceedings of the National Academy of Sciences (PNAS), could profoundly influence the development of cell therapies.

In all tissues, stem cells specialise to produce very different cell types. This specialisation is, to a great extent, regulated by transcription factors, proteins responsible for activating or repressing the transcription of various genes. The study of these factors is essential for understanding how a stem cell is converted into a specialised cell as well as the reverse path, that is, how a specialised cell is converted into a stem cell. This process, which reveals all the steps of specialisation, is known as dedifferentiation.

This reversal of the cell differentiation process had already been described in skin cells by a group of Japanese researchers, and cases of skin cells being converted into cardiac cells, neurons and liver cells (hepatocytes) have been reported. However, until now it hadn't been possible to see if, during this process, the cell was reconverted into a stem cell for later specialisation, or if it simply transformed into another cell. This process of direct transformation is what is known as transdifferentiation.

Investigators from the CRG, led by Thomas Graf, research professor at the ICREA, have studied this process for years. In this research they used immune system cells and saw that it was possible to convert a leukocyte (white blood cell) into a macrophage (cells which engulf and digest any foreign particle), without the need to reconvert into a stem cell, that is, following the reverse specialisation pathway. The results of this research show that dedifferentiation and transdifferentiation are completely different processes.

The scope of these findings is currently restricted to the fields of research and academia, but they will be relevant for the development of treatments with cell therapy. The possibility of obtaining cells of any type at the moment that they are required is getting closer all the time.

'Back-Up System' Reduces Heart Disease Deaths, Research Finds

ScienceDaily (Oct. 5, 2011) — Small bypass vessels which act as a 'back-up system' for the heart's main arteries play a significant role in reducing the mortality of patients with coronary artery disease, according to new research.

The left figure shows a heart with well-developed natural bypass vessels (coronary collateral arteries), the right figure shows a heart with poorly developed natural bypass vessels, leading to a much larger area with lack of blood supply (grey) in case of a blockage.

Researchers from UCL, University of Bern, Yale University and other international collaborators examined the role of natural bypass vessels called coronary collaterals in patients with blocked arteries.

The study, published online in theEuropean Heart Journal, shows that patients with lots of these vessels have a 36% reduced risk of mortality, highlighting their importance as a therapeutic target.

Coronary collaterals are tiny, specialised blood vessels that connect the larger vessels in the heart. They can be thought of as the heart's 'back-up system' as they are essentially invisible until activated, when they can enlarge their diameters in order to carry significant blood flow and bypass blockages.

For many years, doctors believed that there were no connections between the main coronary arteries, and if one of these arteries got blocked patients would normally undergo bypass surgery or stenting. However, research is now building up concerning the importance of coronary collaterals.

This study pooled data from 12 studies enrolling 6,529 patients. Researchers compared patient survival rates in participants with a high number of natural bypass vessels with those with minimal bypass vessels. Survival rates were higher among those who had a higher number of well developed vessels, compared to those with fewer or no such vessels.

It is not yet clear why some people have better bypass networks than others, but scientists believe genes and lifestyle factors play an important role.

Lead author Dr Pascal Meier, a consultant at The Heart Hospital (part of University College Hospitals NHS Foundation Trust) and scientist at UCL Institute of Cardiovascular Science, commented: "When we see patients with a heart attack (clotted coronary artery), the damage caused to the heart varies greatly from person to person. One reason for this is because the 'back-up system' is better developed in some patients -- but our study is the first to clearly show a difference in mortality. We found that whether patients underwent stenting to open their blocked artery or were treated with medications only, they had improved survival if their natural bypass vessels were better developed.

"A growing body of research demonstrates that these vessels are protective and reduce mortality in patients with blocked coronary arteries. We should find means to promote these natural bypass vessels in order to improve outcomes for patients with heart disease."

Dr Christian Seiler, Professor of Cardiology at the University Hospital Bern and senior investigator of this study, said: "We know that regular physical activity can improve the natural bypass network. Recently, some small studies have examined possible ways of promoting natural bypass vessels, such as a treatment known as external counterpulsation (which imitates physical activity) and injections with a growth factor called G-CSF.

Our study adds weight to the increasing evidence that we should be focusing more of our efforts on identifying how we can better develop natural bypass vessels."

Dr Pascal Meier was appointed as a result of the Yale-UCL Collaborative and will continue to work closely with Yale scientists to develop new cardiovascular devices and treatments.

Immune Mechanism Blocks Inflammation Generated by Oxidative Stress

ScienceDaily (Oct. 5, 2011) — Conditions like atherosclerosis and age-related macular degeneration (AMD) -- the most common cause of blindness among the elderly in western societies -- are strongly linked to increased oxidative stress, the process in which proteins, lipids and DNA damaged by oxygen free radicals and related cellular waste accumulate, prompting an inflammatory response from the body's innate immune system that results in chronic disease.

Age-related macular degeneration (AMD) gradually destroys sharp, central vision. It is the most common cause of blindness among the elderly. There are two forms: dry AMD and the typically more severe and faster-acting wet AMD. In dry AMD, light-sensitive cells in the center of the retina slowly break down, obscuring central vision. In wet AMD, abnormal blood vessels grow under the retina, leak and disrupt vision. In this image, drusen -- yellowish deposits of cellular debris -- accumulate in a case of dry AMD. 

In the October 6, 2011 issue ofNature, researchers at the University of California, San Diego School of Medicine, as part of an international collaborative effort, identify a key protein that binds to a molecule generated by oxidative stress, blocking any subsequent inflammatory immune response. The scientists, led by senior author Christoph J. Binder, assistant adjunct professor of medicine at UC San Diego, principal investigator at the Center for Molecular Medicine of the Austrian Academy of Sciences and professor at the Medical University of Vienna, say their findings reveal important insights into how the innate immune system responds to oxidative stress and might be exploited to prevent and treat AMD and other chronic inflammatory diseases.

Specifically, Binder, Joseph L. Witztum, professor of medicine at UC San Diego, and colleagues in Austria, Germany, England and Maryland discovered that when lipids (fats) in cell membranes degrade through oxidative stress, they produce a number of reactive products, including a compound called malondialdehyde (MDA), which in turn modifies other molecules to create novel oxidation-specific epitopes, the part of antigens that draws the attention and inflammatory response of the innate immune system.

The researchers noted, in particular, that MDA attracted an immune system protein called complement factor H (CFH), which bound to it, effectively blocking the uptake of MDA-modified proteins by macrophages, a type of white blood cell charged with killing and eliminating foreign invaders and substances. In in-vivo experiments, the researchers reported that CFH neutralized the inflammatory effects of MDA in mice retinas, limiting the inflammatory response associated with AMD and other chronic diseases.

They also found that a specific mutation in the CFH protein, which is associated with a four-to-seven-fold greater risk of developing AMD, greatly diminished the ability of CFH to bind to MDA.

Binder said the findings further demonstrate the innate immune system's important but not fully appreciated "house-keeping function, defending against endogenous waste products and not just against foreign microbial products."

Beyond that, he said the distinctive, protective role of CFH represents a potential new therapeutic approach for treating AMD, heart disease and other chronic conditions. "This activity of CFH can be used for the development of neutralizing agents to mimic this function."

Funding for this study came, in part, from the Austrian Academy of Sciences, the Austrian Research Promotion Agency, the Austrian Science Fund, the National Institutes of Health, the Edward N. & Della L. Thorne Memorial Foundation Awards Program in AMD Research, the Wilmer Eye Institute, the Deutsche Forschugsgemeinschaft, the ProRetina Foundation, the Fondation Leducq, the Wynn-Gund Translational Research Acceleration Program, the National Neurovision Research Institute, the American Health Assistance Foundation and the European Commission.

Co-authors of the paper are David Weismann of the Austrian Academy of Sciences and the Medical University of Vienna; Karsten Hartvigsen, Austrian Academy of Sciences, Medical University of Vienna and UC San Diego; Nadine Lauer, Christine Skerka and Peter F. Zipfel, Freidrich Schiller University, Jena, Germany; Keiryn L. Bennett and Giulio Superti-Furga, Austrian Academy of Sciences; Hendrik P.N. Scholl, Marisol Cano and James T. Handa, Johns Hopkins University; Peter Charbel Issa, University of Oxford, United Kingdom; Hubert Brandstatter, Medical University of Vienna; and Sotirios Tsimikas, UC San Diego.

Rebooting the System: Immune Cells Repair Damaged Lung Tissues After Flu Infection

ScienceDaily (Oct. 5, 2011) — There's more than one way to mop up after a flu infection. Now, researchers from the Perelman School of Medicine at the University of Pennsylvania report in Nature Immunology that a previously unrecognized population of lung immune cells orchestrate the body's repair response following flu infection.

Immuno-fluorescence staining in mouse inflamed lung tissue showing activated airway epithelial cells (green), infiltrating macrophages (red) and cell nuclei (blue).

In addition to the looming threat of a deadly global pandemic, an estimated 200,000 people are hospitalized because of the flu and 36,000 die each year in the US, according to the Centers for Disease Control. However, many influenza-related deaths are not a direct result of the invading virus but instead are linked to the body's failure to effectively repair and restore lung tissues after it has been damaged by the virus. However, the processes that promote lung tissue repair have remained elusive.

In this new report, David Artis, PhD, associate professor of Microbiology; Laurel Monticelli, a PhD student in the Artis lab; and colleagues observed that flu-infected mice without a population of immune cells called innate lymphoid cells suffered poor lung function leading to eventual death. The team also found that those innate lymphoid cells produced a growth factor called amphiregulin. Infusion of innate lymphoid cells or amphiregulin to the lungs of infected mice normalized lung function, suggesting that the activation of these cells is central to tissue repair at lung surfaces.

Notably, the researchers found that innate lymphoid cells don't attack the virus per se, as other immune cells do; rather, they spur the proliferation of cells that line the lung, which aids in wound healing of the lung tissues that have been severely damaged as a result of the viral infection.

Based on these findings, this lung cell population could also promote wound healing following other respiratory infections and possibly drive tissue remodeling in situations of non-infectious lung injury and inflammation such as asthma, explains first author Monticelli.

In order to extend these studies to human health, Artis and his team collaborated with researchers at Columbia University to identify a population of innate lymphoid cells that is resident in healthy human lung tissue similar to the cells found in mice. These findings raise the possibility that these cells may also orchestrate lung tissue repair in humans and that targeting activation of innate lymphoid cells through amphiregulin or other proteins may speed tissue recovery in patients suffering from respiratory illnesses.

"The identification of innate lymphoid cells in the lung, and new studies from multiple research groups illuminating their previously unrecognized functions in diverse disease processes could help in the design of new drugs to prevent or better fight many common infectious or inflammatory diseases," concludes Artis.

In addition to Artis and Monticelli, co-authors include Gregory F. Sonnenberg, Michael C. Abt, Theresa Alenghat, Carly G.K. Ziegler, Travis A. Doering, Jill M. Angelosanto, Brian J. Laidlaw, Joshua M. Diamond, Ronald G. Collman and E. John Wherry, all from Penn; Cliff Y. Yang and Ananda W. Goldrath from the University of California, San Diego; and Taheri Sathaliyawala, Masaru Kubota, Damian Turner and Donna L. Farber from Columbia University.

HIV: Cell-Penetrating Peptides for Drug Delivery Act Like a Swiss Army Knife

ScienceDaily (Oct. 5, 2011) — Cell-penetrating peptides, such as the HIV TAT peptide, are able to enter cells using a number of mechanisms, from direct entry to endocytosis, a process by which cells internalize molecules by engulfing them.

Schematic: HIV TAT (blue) permeates membrane, interacts with cytoskeleton (green). 

Further, these cell-penetrating peptides, or CPPs, can facilitate the cellular transfer of various molecular cargoes, from small chemical molecules to nano-sized particles and large fragments of DNA. Because of this ability, CPPs hold great potential as in vitro and in vivo delivery vehicles for use in research and for the targeted delivery of therapeutics to individual cells.

But exactly how cell-penetrating peptides -- and particularly the HIV TAT peptide -- accomplish these tasks has so far been a mystery.

"The HIV TAT peptide is special. People discovered that one can attach almost anything to this peptide and it could drag it across the cell," said Gerard Wong, a professor of bioengineering and of chemistry and biochemistry at the UCLA Henry Samueli School of Engineering and Applied Science and the California NanoSystems Institute at UCLA. "So there are obvious beneficial drug-delivery and biotechnology applications."

In a new study published in Proceedings of the National Academy of Sciences, UCLA Engineering researchers, including Wong and bioengineering professors Timothy Deming and Daniel Kamei, identify how HIV TAT peptides can have multiple interactions with the cell membrane, the actin cytoskeleton and specific cell-surface receptors to produce multiple pathways of translocation under different conditions.

Moreover, because the researchers now understand how cell-penetrating peptides work, they say it is possible to formulate a general recipe for reprograming normal peptides into CPPs.

"Prior to this, people didn't really know how it all worked, but we found that the HIV TAT peptide is really kind of like a Swiss Army Knife molecule, in that it can interact very strongly with membranes, as well as with the cytoskeletons of cells," said Wong, the study's lead author. "The second part wasn't well appreciated by the field."

In addition to the membrane activity, researchers discovered that the HIV TAT peptide also creates its own binding site out of the membrane. This means the peptide can actually go through the membrane and induce the cytoskeleton directly to have an endocytotic event.

"We found that there are two channels of activity," Wong said. "Because of the peculiar sequence of HIV TAT, it's very good at being able to interact with membranes. Further, with the high-density packing of charged amino acids in the peptide, it can also interact very strongly with the cell's cytoskeleton, as well as its receptors."

In addition, the researchers noticed that small cargoes can be transferred directly, while cargoes larger than a few nanometers needed to be anchored to the membrane by the TAT peptide.

Deming, who specializes in synthetic methods, prepared the polypeptide samples for use in the experiments. Kamei, an expert in cellular trafficking, performed cell-based endocytosis experiments using inhibitor drugs and confocal microscopy to identify dominant mechanisms of endocytosis.

"This research is exciting because cell-penetrating peptides have been used in the area of drug delivery for some time," Kamei said. "Gaining any additional understanding of these delivery agents will help in future drug-carrier designs."

It is the group's hope that the new understanding gained from their study will be used to engineer new molecules that are more effective in delivering therapeutic agents.

"This collaboration was important because it combined expertise in the areas of synthesis, characterization and cellular trafficking to address a very relevant problem," Kamei said. "I definitely see more opportunity for combining these areas to tackle other problems in the growing field of biomaterials."