Tag Archives: paul browne

The Basel Declaration: Standing up for Medical Progress

Top European scientists have pledged to engage in more public dialogue, openness, and education about animal research. Concerned about threats to the future of medical research, the scientists met recently and drafted a declaration that affirms commitment to responsible research and animal welfare and calls for increased effort to facilitate public understanding of the essential role that animal studies play in contributing to scientific and medical progress.  The call for “trust, transparency, and communication on animal research” was adopted by the first Basel conference “Research at a Crossroads” November 29th.  The Declaration can be found here, along with an invitation to sign up to it.

Prof. Michael Hengartner, Prof. Dieter Imboden and Prof. Stefan Treue sign the declaration

The Declaration underscores the importance of a wide range of animal research, from basic research that seeks to understand fundamental biological processes, to applied research that seeks to turn such knowledge into new medical treatments, and the critical ongoing need for this work:

“Over the last 100 years biomedical research has contributed substantially to our understanding of biological processes and thus to an increase in life expectancy and improvement in the quality of life of humans and animals. However, the list of challenges and new opportunities remains long.

Without research using animals, it will not be possible to overcome the social and humanitarian challenges posed by these problems. Despite new and refined alternative methods, animal experiments will remain essential in the foreseeable future for biomedical research.”

The Declaration makes clear that:

“Biomedical research in particular cannot be separated into ‘basic’ and ‘applied’ research; it is a continuum stretching from studies of fundamental physiological processes to an understanding of the principles of disease and the development of therapies.”

A Nature report on the meeting and an accompanying editorial highlight the crucial considerations underlying the scientists’ call for action, including not only the actions of extremists, but also the broad consequences of failing to build understanding of animal research:

Biomedical scientists in Germany perceive a separate crisis — increasing legislative restrictions that make it more difficult to carry out animal experiments. Hearing little to the contrary from researchers themselves, the public tends to assume that animal experiments are an unnecessary evil, so politicians respond with more restrictions.”

That problem was a major motivation for the Basel Declaration — drafted and signed at a meeting in Basel, Switzerland, last week (see page 742). Its signatories pledge to engage in open debate with the public about their work on animal experiments, to stress the high ethical standards to which they adhere and to explain why they have to do it. They intend, for example, to visit local schools or to mention that their research used animals when speaking to the press about new results.”

Such efforts have already yielded dividends; the Nature report notes how a determined effort over the past decade by scientists in the United Kingdom to inform the public about the reality of animal research resulted in greatly increased support for it.

Speaking of Research applauds this effort and joins in urging others not only to sign on to the declaration, but also to act on the pledge to continue to increase efforts in outreach, education, and engagement.

In fact, there are many groups and sources for information and conversation to which scientists can turn to for advice on outreach. They include advocacy groups and collaborative networks such as Understanding Animal Research, Americans for Medical Progress, States United for Biomedical Research, and the Foundation for Biomedical Research. They also include scientific societies such as the American Physiological Society, Society for Neuroscience, American Association of Laboratory Animal Science, and the Federation of American Societies for Experimental Biology.  Many academic institutions have actively built outreach and education programs that offer good models for others.

Speaking of Research also offers information, tools and support for those who choose to contribute to public discussion of animal research.  There are many resources and avenues to support individuals who want to learn more and identify a range of effective ways to contribute to the public discussion of animal research.

Before we finish we’d like to draw your attention to an excellent example of the importance of basic animal research, Christina Agapakis writes on the Oscillator blog about a fascinating study which used gene therapy to restore vision in blind mice.  This news comes only a few weeks after scientists in Germany reported that they had used a vision chip containing 1,500 light-sensitive elements to partially restore sight in patients who were blind due to damage to the light-sensitive cells in their eyes.  In an open access paper published in Proceedings of the Royal Society B, the team who carried out this important clinical study highlight the importance of in vivo studies in rats, cats, and pigs, and in vitro studies using isolated chicken retinas, in establishing both the theoretical basis for this study, and subsequently in determining the safety of the implant they developed. These advances in vision research suggest that devices available to help blind people see in the 21st century will soon eclipse those that Star Trek predicted for the 24th century!

This is of course exactly the kind of groundbreaking biomedical research that the Basel declaration seeks to defend.

Allyson J. Bennett, Ph.D*. and Paul Browne, Ph.D.

Speaking of Research

*The views expressed on this blog post are mine alone and do not necessarily reflect the views of my employer, Wake Forest University Health Sciences.

 

Bob Edwards wins 2010 Nobel Prize for developing IVF: Thank the mice, rabbits, hamsters…

Professor Robert G. Edwards of the University of Cambridge has long been recognized as one of the pioneers of reproductive medicine. His most famous accomplishment, along with surgeon Patrick Steptoe*, came in 1978 with the birth of Louise Joy Brown, the first baby born through in-vitro fertilization.  This achievement has now been recognized by the Nobel Assembly who awarded him the Nobel Prize in Physiology or Medicine 2010 for “the development of in vitro fertilization”.

As Dario discussed in an article for this blog a few months ago the development of IVF by Bob Edwards depended on basic and applied research undertaken in rabbits and hamsters by pioneers including Gregory Pincus and Min Chueh Chang, who identified the essential conditions required for IVF.

In advanced information accompanying today’s announcement the Nobel Assembly notes the importance of this research in laying the foundations for the development of human IVF by Bob Edwards and Patrick Steptoe, and also discusses how Bob Edwards’ own extensive research on the reproductive biology of mice – and animal research he and his colleagues conducted in a variety of species while working on IVF – aided progress. In particular the Nobel Assembly highlights how his experience with mice in enabled Bob Edwards to solve a critical problem that was preventing successful IVF, by developing a way to harvest human egg cells at the optimal stage of their maturation prior to in vitro fertilization.

Professor Robert Edwards, Nobel Laureate and IVF pioneer

Without the decades of careful animal research undertaken by Bob Edwards, Gregory Pincus, Min Chueh Chang, and scores of their colleagues it is unlikely that IVF would ever have become a reality.

We heartily congratulate Professor Edwards on his Nobel Prize, an award that recognizes his outstanding contribution to a medical advance that has brought joy to hundreds of thousands of families around the world.

* Sadly Patrick Steptoe died in 1988 and therefore could not share the Nobel Prize with Robert Edwards.

Paul Browne

Animal research: At the forefront of modern medicine

Several reports in the news over the past week have highlighted yet again the importance of animal research to medical advances.

The BBC reports that gene therapy has been used successfully to treat a patient with severe β-thalassemia.  β-thalassemia is an inherited disorder caused by mutations in the β-globin chain of haemoglobin that lead to ineffective production of red blood cells and profound anaemia, and currently bone-marrow transplant is the only effective long term treatment for severe β-thalassemia. Unfortunately suitable donors are not easy to find, and in their absence patients depend on frequent blood transfusions that in turn lead to problems due to iron overload.  Against this background the news that this disease may be treated by gene therapy in the future is most welcome.

The team of scientists and doctors led by Dr. Philippe Leboulch, of Harvard Medical School in Boston, used a lentiviral vector, based on elements of the HIV virus, to insert copies of a functioning β-globin gene into the patient’s haematopoietic stem cells (HSCs), and then transplanted the modified HSCs back into the patient. Lentiviral vectors have become popular in gene therapy in recent years, indeed last year we discussed the use of a similar vector to treat the brain disorder X-linked adrenoleukodystrophy, and this popularity is due mainly to their improved safety compared to other vectors.  Early trials of gene therapy for X-linked severe combined immunodeficiency (X-SCID) were called into question when several patients developed leukemia when the retroviral vector used integrated into a location in the genome that activated an oncogene – though ultimately the treatment was of  great benefited to most patients – and research comparing retroviral vectors with lentiviral vectors in mice found that the latter had a much lower tendency to activate oncogenes and promote tumor growth (1).

As Dr. Leboulch and colleagues point out in their Nature Biotechnology paper (2) reporting this work, research on mice was not confined to evaluating the safety of the lentiviral vector. Years of work went into developing and refining the β–globin lentiviral vector in mouse models of β-thalassemia and sickle-cell disease (also caused by a mutation in the β-globin gene) before it was ready to test in a human patient.

Lentiviral vectors have proven capable of transferring these elaborate structures with fidelity and high titres (5, 6). Hence, several mouse models of the β-haemoglobinopathies have been corrected, long-term, by ex vivo transduction of haematopoietic stem cells (HSCs) with β-globin lentiviral vectors (5, 6, 7, 8, 9, 10). These advances have prompted the prudent initiation of a human clinical trial.

Such research is now bearing fruit, and it is hard to disagree with gene therapy expert Professor Adrian Trasher, quoted by the BBC as saying:

The good news is that technology is advancing rapidly, and it shouldn’t be too long before diseases such as thalassaemia can be reliably and safely treated in this way.

Another report from the BBC provides hope for the many thousands of patients on waiting on organ transplant lists; speaking at the British Science Festival Professor Steve Sacks announced  the development of a treatment using the drug mirococept to protect the transplanted organ from attack by the immune system , a technique that could potentially double the length of time it survives in the recipient before a new organ is required.  Currently transplanted organs last for about 10 years, and patients requiring replacement organs make up about 20% of those on the waiting lists. A small clinical trial of the technique indicates that is safe and a larger trial is now planned. Mirocosept works by blocking the activation of the complement system, a complex set of approximately 20 interacting enzymes and regulatory proteins found in the blood plasma and body fluids. The complement system plays a key role in fighting infection, but its activation is also a key early event in organ rejection.  Mirococept consists of a complement inhibitor peptide attached to a second peptide that allows it to attach to cell membranes, thus enabling it to remain on the surface of the transplanted organ and prevent complement activation.

The human Heart, washing with mirococept may prolong its life after transplant.

Mirococept itself was initially developed for the treatment of rheumatoid arthritis and ischaemia and reperfusion injury, after basic research in mice and rats demonstrated that the complement system played a major early role in activating the inflammatory response that is characteristic of these conditions, identified the key components involved in this response, and showed that blocking complement activation in several animal models could reduce tissue damage (3,4). Mirococept targets complement inhibition to specific tissues concentrating it where it is needed most and avoiding a more general inhibition that could leave the body vulnerable to infection, and performed well in animal models or arthritis, organ transplant, and ischemia and reperfusion injury (4,5). On the back of these promising results Mirococept has been taken into human trails for rheumatoid arthritis and organ transplant, where as we have seen it has proven to be a safe and reliable treatment. Larger trials to evaluate the efficacy of Mirococept are now underway for rheumatoid arthritis and being planned for organ transplants.

The shortage of organs for transplant is a major challenge, and many approaches are being considered to increase the supply, I have written previously of tissue engineering to build new organs but it will be years before this technology is in widespread use. Until then I would urge you all to sign up as an organ donor, it only takes a few minutes and you might just save several lives.

Our final story comes from the Autism Science Foundation, who write that a new drug named arbaclofen (STX209) improved the social interaction of autistic children, reducing tantrums and agitation, in an early clinical trial.  Unlike existing medications that treat specific symptoms of autism arbaclofen acts to correct an imbalance in the levels of two neurotransmitters, glutamate and GABA,  in the brains of autistic children.  This new approach comes from studies of a mouse model of fragile X syndrome, a common inherited form of mental impairment and a cause of some cases of autism, which demonstrated that excessive activation of group I metabotropic glutamate receptor played an important role in the disorder, as discussed in an overview on the Seaside Therapeutics website. STX209 acts to reduce the excessive levels of glutamate released in the brain and therefore reduce activation of the group I metabotropic glutamate receptor, an approach which worked well in a mouse model of fragile X syndrome.

Mice, a valuable resource in autism research. Image courtesy of Understanding Animal Research.

At a time when the parents of autistic children are bombarded with ineffective, ethically dubious, or downright dangerous “cures”, the development of a treatment that is both safe and effective is very welcome, lets just hope that it works as well in larger trials.

So once again this week the medical news is full of exciting developments that depended on basic and applied  medical research in animals, which is exactly the kind of work that Speaking of Research exists to support!

Paul Browne

1)      Montini E. et al. “Hematopoietic stem cell gene transfer in a tumor-prone mouse model uncovers low genotoxicity of lentiviral vector integration” Nature Biotechnology Volume 24, Pages 687-696 (2006) doi:10.1038/nbt1216

2)      Cavazzana-Calvo M. et al. “Transfusion independence and HMGA2 activation after gene therapy of human β-thalassaemia” Nature Volume 467, Pages 318–322 (2010) doi:10.1038/nature09328

3)      Sahu A. and Lambris J.D. “Complement inhibitors: a resurgent concept in anti-inflammatory therapeutics.” Immunopharmacology Volume 49, Pages 133-148 (2000) PubMed:10904113

4)      Souza G.D. “APT070 (Mirococept), a membrane-localised complement inhibitor, inhibits inflammatory responses that follow intestinal ischaemia and reperfusion injury.” Br J Pharmacol. 2005  145(8): 1027–1034.  doi:10.1038/sj.bjp.0706286

5)      Smith R.A.  “Targeting anticomplement agents.” Biochem Soc Trans. Vol.30(6), Pages 1037-1041 (2002) PubMed:12440967

Heart failure breakthrough: animal research paved the way!

Heart failure, where the heart is unable to maintain a sufficient blood flow to supply the body’s needs, is a leading cause of death, especially among the over 65’s. Half of all chronic heart failure patients die within four years of diagnosis. It can have a number of causes, for example damage to heart tissue after a heart attack, and leads to a variety of problems in patients. Fatigue and muscle weakness are common as the muscles receive insufficient oxygen, and because waste products cannot be removed from tissues quickly enough fluid can build up in the lungs and other parts of the body, often the legs and abdomen. The extra strain placed on the heart as it tries to maintain adequate blood pressure can lead to further damage to the heart and ultimately cardiac arrest.

Ivabradine can lower the heart rate while maintaining a normal blood pressure - good news for heart failure patients. Image courtesy of the CDC Public Health Image Library.

In heart failure the rate at which the heart beats is often increased, and group of scientists led by Karl Svedberg and Michael Komajda set up the SHIfT study, to evaluate whether a drug called Ivabradine, which lowers the heart rate, could reduce risk of death or hospitalization in a group of patients who had heart failure accompanied by an elevated resting heart rate.  Significantly fewer patients taking Ivabradine in addition to their existing treatments required hospital admission during the course of the study, compared to a control group who were given a placebo in addition to their existing treatment. The most striking outcome was that Ivabradine cut the risk of death by 26%.

So what is Ivabradine, and where does it come from?

Ivabradine slows the heart rate by inhibiting an electrical current known as the If current* which is a major regulator of the activity of the sinoatrial node – better known as the pacemaker. Inhibiting the If current slows the generation of the electrical impulses by the sinoatrial node that trigger heart contraction, and therefore slows the heart rate itself. Ivabradine, then known as S16257, was first developed in the early 1990’s when it was found to be able to block the If current in-vitro in sinoatrial node tissue from rabbits and guinea pigs, and slowed the generation of electrical impulses in a manner that was safer than other bradycardic drugs (1). Ivabradine was then evaluated in live rats and dogs, where it safely reduced the heart rate, and moreover did so without reducing the blood pressure (2,3). While beta-blockers such as Propranolol can reduce the heart rate they also lower the blood pressure – indeed they are used to treat hypertension – and hence are not suitable for many patients, so the development of a drug that could reduce heart rate without affecting blood pressure was very welcome.

Following the successful animal studies Ivabradine entered human clinical trials and in 2005 was approved for the treatment of angina pectoris. In angina pectoris the heart muscle receives too little oxygen, a problem exacerbated by a fast heart beat that increases the need for oxygen, so lowering of the heart rate by Ivabradine reduced oxygen demand and prevents angina attacks. The success of Ivabradine in the treatment of angina pectoris in turn led to its evaluation in heart failure.

The successful outcome of SHIfT study is a major boost to the development of better treatment regimes for heart failure, and if it is confirmed by further clinical trials will improve and prolong the lives of many heart failure patients.

* Hence the name of the SHIfT study – Systolic Heart failure treatment with the If inhibitor ivabradine Trial

Paul Browne

1) Thollon C. et al. “Electrophysiological effects of S 16257, a novel sino-atrial node modulator, on rabbit and guinea-pig cardiac preparations: comparison with UL-FS 49.” Br J Pharmacol. Volume 112(1), Pages 37-42 (1994) PubMedCentral:PMC1910295

2) Gardiner S.M. et al. “Acute and chronic cardiac and regional haemodynamic effects of the novel bradycardic agent, S16257, in conscious rats.”  Br J Pharmacol. Volume 115(4):579-586 (1995) PubMedCentral:PMC1908496

3) Simon L. et al. “Coronary and hemodynamic effects of S 16257, a new bradycardic agent, in resting and exercising conscious dogs.”  J Pharmacol Exp Ther. Volume 275(2), Pages 659-666 (1995) PubMed:7473152

Mice, rats, and the secrets of the genome.

It’s just over a decade since the completion of the first working draft of the human genome was announced, and seven years since the publication of the complete sequence, but in that short time the impact of this new knowledge on all areas medical research has been immense. Sequencing the human genome was a huge achievement, but having got the sequence an even greater task confronts scientists – working out what it all means.  To do this scientists have studied the natural variations that exist between individuals, and have also sequenced the genomes of a wide variety of species, some closely related to us, others separated from us by hundreds of millions of years of evolution. Scientists can analyze the similarities and differences between the genes of different species, and examine how changes to the structure or regulation of these genes are reflected in physiology.  In many cases it is also possible to use genetic modification to study the function of conserved genes in other species in ways that are just not possible, for technical and/or ethical reasons, in humans. A study published a couple of weeks ago in the scientific journal Nature provides an excellent example of how animal research contributes to our understanding of the human genome.

Blood flowing through the heart, but the cholesterol building up in an artery can cause a heart attack. Image courtesy of the British Heart Foundation

As the cost of technology such as DNA microarrays has fallen genome-wide association studies (GWAS) have become an increasingly popular way of examining the relationship between genetic differences between individuals and particular diseases. In a GWAS the whole genome of many individuals is screened for variations, and then any association between those variations and particular phenotypes or diseases is determined.  Tanya M. Teslovich and colleagues (1)  analysed the genomes of over 100,000 people who had been enrolled in 46 separate clinical studies, and identified 95 genes that have variants associated with increases in blood lipid (fat and cholesterol) levels.  One of the problems with GWAS studies is that while they are often good at identifying genes that are associated with a disease, they are not so good at identifying which genetic variations actually cause disease, or explaining how the genetic variations contribute to disease.  This is where Tanya Teslovich and colleagues scored highly; they were able to show that 14 of the 95 lipid-associated genes were also associated with the development of coronary artery disease, supporting the proposition that elevated blood lipids contribute to coronary artery disease. They also found that overall the effect of the variants was additive, the more risk variants of these 95 genes you have the greater your chance of having elevated blood lipids.

So that established that the gene variants were associated with elevated blood lipids, but to use that information to develop new treatments you need to know how the particular gene affects lipid levels. As you might expect many of the 95 genes identified were already known from previous studies to be involved in the regulation of blood lipids, and in several cases their precise role has been thoroughly studied. However, several of the genes had not been implicated in regulating blood lipids before, and the team decided to use genetically modified mice to investigate their function.  They injected viral vectors into the liver of the mice that contained either an extra copy of the gene being studied, to increase expression of the gene, or a short-hairpin RNA, to target the gene for knockdown via RNAi. This allowed them to discover that one gene, GALNT2, decreases levels of high-density lipoprotein cholesterol (HDLC), the so-called “good cholesterol”, while two other genes, Ttc39b and Ppp1r3b, increase  HDLC.

Another associated paper (2) in the same issue of Nature takes the analysis even further. Several studies, including the GWAS performed by Tanya M. Teslovich and colleagues, had demonstrated that variations in a particular region of chromosome 1 known as 1p13 were associated with high levels of Low-density lipoprotein “bad” cholesterol (LDLC) in the blood and heart disease, but that these variations were not within the coding sequence of any genes, so they would not affect the structure of any proteins. They first show through genetic studies of human subjects and human liver tissue culture that variations at 1p13 affect the expression of several genes –  and hence the amount of protein produced by those genes – and that one particular variation creates a binding site for the transcription factor C/EBP. Transcription factors are proteins that regulate the expression of genes, and this particular site altered the levels of a gene named SORT1. But what does SORT1 do? To answer this they again turned to GM mice, using virus vectors that specifically reduced or increased the levels of SORT1 in the mouse liver. Reducing or eliminating SORT1 expression in the mouse liver led to a reduction in the levels of LDLC in the blood, and that this was found to be due to SORT1 regulating the production of very-low-density lipoprotein (VLDL), a precursor to low-density lipoprotein, in the liver. As a result of this work a whole new pathway for the regulation of blood lipids has been uncovered, one that may offer new opportunities to scientists developing treatments for hypercholesterolemia.

As a BBC news report indicates, the identification of these genes and the elucidation of their function may aid the development of better diagnostic tools to identify those at risk of heart disease, and ultimately the development of better treatments.

These studies illustrate how important animal models, particularly GM mice, are to efforts to decode the human genome. As the biosciences move towards a more systems based approach to biology, one where knowledge of how networks of genes interact to produce a particular physiological or clinical outcome is applied to areas such as toxicology, the information that studies of GM animals can yield will become increasingly important. This importance has not gone unrecognized by the wider scientific community, the 2007 Nobel Prize in Medicine was awarded to Mario Capecchi, Sir Martin  Evans, and Oliver Smithies for their discoveries of  “ principles for introducing specific gene modifications in mice by the use of embryonic stem cells”.

With this in mind let’s turn briefly to another GM animal that’s been in the news lately – the rat.  While GM mice have become a mainstay of modern scientific research the rat has lagged behind, which is a shame since the larger size, longer lifespan, and more complex behavior of rats make them more effective animal models than mice for studying many human diseases, particularly neurological conditions. The lack of GM rats was due to the difficulty in growing rat embryonic stem cells (ESCs) in culture, a necessary first step in the most common methods of producing GM animals. Last year Matthew Evans wrote an article for the Pro-Test blog discussing how scientists at the University of Cambridge and the University of Southern California had developed a method for growing rat ESCs in culture, and how this achievement paved the way for the production of transgenic rats. Last week the same group of scientists announced that they had employed this method to produce GM rats whose p53 gene, a key tumor suppressor that is defective in several cancers, was deleted.

The humble lab rat, now available in GM. Image courtesy of Understanding Animal Research.

This is not the first time GM rats have been produced, as for the past few years scientists have been able to use zinc finger nucleases to knock-out rat genes. Zinc fingers, so called because one or more zinc ions stabilizes the finger like structure, are found in many proteins, allowing them to bind specifically to a structure within a cell, such as a particular DNA sequence. Scientists found that they could produce artificial zinc fingers that recognize particular genes, and then join a nuclease to that zinc finger so that it cuts out the target gene. This method, discussed in more detail in this excellent article by Elie Dolgin, allows scientists to knock-out genes in rat embryos. The downside of the zinc finger nuclease technique can only be used to knock-out genes, whereas the ESC method is more flexible – it can also be used to add extra copies of a gene, or to delete genes in specific tissues or stages of development.

It is now clear that the rat is joining the mouse at the forefront of the GM revolution in medicine, and that has to be great news for medical science and the patients that depend on it.

Paul Browne

1)      Teslovich T.M. et al. “Biological, clinical and population relevance of 95 loci for blood lipids” Nature Volume 466, Pages 707-713 (2010) DOI:10.1038/nature09270

2)      Musunuru K. et al. “From noncoding variant to phenotype via SORT1 at the 1p13 cholesterol locus” Nature Volume 466, Pages 714–719 (2010) DOI:10.1038/nature09266

Hopping rabbits herald breakthrough in tissue engineering

A team of NIH-funded scientists and veterinarians at Columbia University, the University of Missouri, Clemson University, and the Medical University of South Carolina, have this week announced a significant advance in tissue engineering, for the first time they have used cutting–edge tissue engineering technology to produced a moving joint, in this case the hip, in rabbits.  A press release on the NIH website discusses the work in some detail, and those with a subscription can read the original research article in the Lancet.  This is not the first paper to describe the production of bone or cartilage using tissue engineering, but it is the first time that the two tissues have been regenerated together to produce a moveable joint, and represents a significant step forward in terms of the complexity of tissue that can now be engineered.

Rabbits are a popular experimental model for the study of bone repair and regeneration; the structure of their bones is very similar to that seen in larger animals including humans, for example unlike some smaller rodents they have structures known as  Haversian canals that affect bone growth and repair, while their size allows more complex surgery than is possible with smaller rodents.

Tissue engineering techniques we have discussed previously, such as the artificial trachea and lung involved seeding a scaffold, were created by stripping cells from donor tissue, seeding with stem cells, and then allowing the cells to grow in vitro to produce a functioning organ. The technique reported this week differs in that the scaffold was made from an artificial bio-polymer, and rather than implant stem cells into the scaffold and growing the tissue in vitro, they coated the scaffolds with the growth factor known as TGFβ3 and then implanted it into the rabbits. TGFβ3 attracts bone and cartilage precursor cells to the scaffold, where they multiply and after a few weeks have formed a functioning joint.  When they compared scaffolds coated with TGFβ3 to bare scaffolds, they observed that more precursor cells were recruited to the scaffold when TGFβ3 was present, and that the rabbits transplanted with TGFβ3-coated scaffolds moved more easily when assessed one to two months after surgery, indeed the joints were able to support the weight of the rabbits without any limping.

Rabbits play an important role in medical research. Image courtesy of Understanding Animal Research.

This technique is significantly simpler than those approaches that require stem cell seeding and in vitro growth prior to transplant, and might be especially useful for younger hip transplant patients, individuals aged 65 or younger. Younger patients would be expected to recover more quickly, have fewer co-morbidities that would be aggravated by staying in bed for a prolonged time to allow the tissue to regenerate, and would benefit more from not having to have hip operations every 10-15 years as is currently the case with metal hip joints.  For more elderly patients metal hip joints are likely to remain the best option.

So does this technique replace that used in the tissue engineering studies we have previously discussed? Well, the answer is no, for some applications either approach might work, but for others, for example the trachea, artery and lung transplants, the tissue needs to be capable of functioning immediately following transplant. One aspect that is being evaluated elsewhere is the use of biopolymer scaffolds, which are being used with stem cells to produce replacement blood vessels, and may provide a more flexible and reliable alternative to the use of decellularized tissue.

It’s an interesting development, and one that again highlights how quickly things are happening in the field of tissue engineering. Of course it will be some time before clinical trials in humans start, before then this technique must be evaluated in a larger animal, probably a pig, to determine whether tissue regeneration on the scaffold is rapid and effective enough in a model of comparable sizes to humans. Only if these tests are successful will this technique warrant evaluation in a human clinical trial.

Paul Browne

Microbicide gel cuts HIV infection rates…thank the monkeys!

There was exciting news on Monday when it was announced at an international AIDS conference in Vienna that microbicide gel had dramatically reduced the transmission of HIV in a Phase 2 clinical trial involving 889 women in South Africa.  If confirmed by  larger phase 3 trials this gel will offer millions of women a way to protect themselves against this dread disease that blights communities around the world.

Dr Abdool Karim explains how to use a microbicide gel applicator. Image courtesy of CAPRISA.

Unlike previous microbicide gels that failed to offer significant protection against HIV infection this gel included the anti-retroviral drug tenofovir. Regular readers of this blog may recognize tenofovir, it was discussed in an article on the role of non-human primate research in developing HIV prophylaxis by virologist Dr. Koen Van Rompay that we posted last year.  Dr. Van Rompay’s article looked at the use of oral tenofovir in pre- and post-exposure prophylaxis rather than its use in a microbicide gel.

So did the research on preventing SIV transmission in monkeys influence the decision to use tenofovir in this microbicide gel? You betcha! In the first report of a Phase 1 trial of this tenofovir-containing microbicide gel published in 2006 (1) the authors state that the success of tenofovir in preventing SIV infection on monkeys – the same research discussed by Dr. Van Rompay – was a deciding factor when they took this gel into clinical trials.

‘Tenofovir gel, 9-[(R)-9-(2-phosphonylmethoxyprophyl) propyl]adenine monohydrate, a nucleotide reverse transcriptase inhibitor, has demonstrated ability to inhibit retroviral replication in animals and humans, and it has been well tolerated when used orally, as tenofovir disoproxil fumarate, (tenofovir DF; Viread) [16–20]. Tenofovir DF has been approved for treatment of HIV-1 infection and is increasingly used as part of therapeutic regimens for HIV-positive individuals [21]. Tenofovir has been proven to be effective in blocking the transmission of SIV in animal models when given as pre- or postexposure prophylaxis systemically or when applied as an intravaginal gel [22–25]. Tenofovir bisphosphate, the active intracellular moiety, has a very long intracellular half-life (> 72 h), which could allow for more convenient, coitally independent intravaginal use [26]. Given the data showing animal protection with tenofovir gel, and the extensive human safety data with oral tenofovir in HIV-positive patients, the HIV Prevention Trials Network (HPTN) decided to assess the safety and tolerability of tenofovir gel in HIV-negative and HIV-positive women and their male sexual partners (HPTN 050).’

The above passage also mentions that they tested whether the microbicide gel containing tenofovir could prevent vaginal SIV transmission in monkeys*, and the finding that it could drove their subsequent decision to take the gel into clinical trials.  This was an important decision, a review of HIV microbicide gels published in the journal Science (2) two years ago pointed out the failure to evaluate other microbicide gels in monkey models of HIV transmission allowed these gels to proceed into clinical trials where they subsequently failed.  It is notable that the microbicide PRO 2000, also evaluated in monkeys, is the only other microbicide to demonstrate an ability (albeit less dramatic) to prevent HIV infection in clinical trials.

So what now? Well the tenofovir containing gel will go on into larger phase 3 trials to further evaluate its ability to prevent HIV infection in women. In the meantime following a study showing that it can prevent the transmission of rectal SIV transmission in macaques (3) this gel is now in phase 1 safety trials in men.

This is welcome news after years of disappointment, and further evidence that where HIV is concerned there can be no shortcuts; all therapies whether microbicide gels or vaccines must be thoroughly evaluated in stringent animal models before being taken to human clinical trials. Perhaps now we can start to turn realism into optimism.

In other news this week, Americans for Medical progress have announced the 2010 Michael D. Hayre Fellows in Public Outreach. Neuroscientists Elizabeth Burnett and Scott Dobrin will use the fellowship grant to develop their project “Speaking Honestly – Animal Research Education (SHARE)”, which is designed to guide educators in leading classroom discussions on the humane use of animals in research in an engaging and interactive manner. We wish them the very best as they follow in the footsteps of the first Hayre fellow, Speaking of Research founder Tom Holder.

* Unfortunately this study was never published in the scientific literature, this is something that sometimes happens with pre-clinical studies performed by biotechnology and pharmaceutical companies…usually because they wish to keep the work confidential for commercial reasons…and is a source of great frustration to people like me who write about this work!

Paul Browne

1)      Mayer K.H. et al. “Safety and tolerability of tenofovir vaginal gel in abstinent and sexually active HIV-infected and uninfected women.” AIDS. volume 20(4), pages 543-551 (2006), DOI:10.1097/01.aids.0000210608.70762.c3.

2)      Grant R.M. “Whither or wither microbicides?”  Science. Volume 321(5888), pages 532-534 (2008), PubMed Central:PMC2835691.

3)      Cranage M. et al. “Prevention of SIV Rectal Transmission and Priming of T Cell Responses in Macaques after Local Pre-exposure Application of Tenofovir Gel” PLoS Med. Volume 5(8):e157(2008) DOI:10.1371/journal.pmed.0050157