Are You Getting the Right Match?

In the UK, there has been a big increase in the number of patients requiring transplants over the last decade or so. In fact, this pattern can be reflected worldwide. In order to understand why we need more donors to accommodate the continual increase in patients requiring transplantation of solid organs, its useful to know how we determine matches between donors and patients. "Solid" organs as you could infer, relate to organs that are in a solid state. Examples of these include the kidneys, pancreas, heart and lungs. It is widely accepted that it isn't easy to find compatibility between donor and recipient straight away - there must be biological compatibility of two types. The first is the well-known ABO blood group system. There are four different groups that an individual can fall into: A, B, AB, and O. Each group signifies the types of antigen present on the surface an erythrocyte, or red blood cell. Antigens are proteins on the plasma membrane of a cell, giving it its own 'identity'. This is essential in the multiple processes of the immune response, for example. A person identified with an 'A' type blood group has only 'A' type antigens on the cell surface membranes of red blood cells. However they will also have 'Anti-B' antibodies circulating in their blood plasma. The converse is true for those with a 'B' blood group. If someone were to have AB however, they would have both types of antigen on the cell surface membranes of red blood cells. Therefore no antibodies acting against these antigens would be circulating in their blood plasma. Now, those with type 'O' blood group are seen to be rarer than those with other blood groups, but it means as a donor you would be 'compatible' with any recipient of any blood type. For this blood type, no ABO antigens are present on the membranes of red blood cells, but the serum of these individuals will contain the 'Anti-A' and 'Anti-B' antibodies.

Chart showing the differences in cell type, antibodies and antigens present in individuals with different blood groups (Source: Wikipedia )

To illustrate this, let us consider a potential liver transplant between a donor with blood group O and recipient with blood group B. The donor has red blood cells with no ABO antigens, so when mixed with blood (and plasma) containing red blood cells with the B antigen and therefore 'Anti-A' antibodies, there will be no immune response. After all, the antibodies are not able to form an antigen-antibody complex.

Most people will be aware of the ABO blood group system; however there is another factor that always needs to be considered by doctors before carrying out any surgeries involving organ transplantation. This is what is known as the human leucocyte antigen (HLA) system. All cells known to contain nuclei in the body possess these protein complexes on their cell surface membranes. Therefore it is useful to know that red blood cells do not have these antigens as they have no nuclei, no genetic material encased. HLA types are inherited from both parents, and 'research has shown that the fewer the number of mismatches between donor and recipient HLA, the less likely it is that the organ will be rejected post-transplantation'. This is why it has become increasingly imperative for doctors to screen individuals for this type of antigen so that matches between patients and potential donors can be confirmed. A patients HLA type can be confirmed by a series of tests. The polymerase chain reaction (to create multiple copies of DNA) followed by gel electrophoresis (allows the scientist to visualise the result) being one of the more notable methods.

After the HLA type has been confirmed, the patient's serum is analysed to 'screen for the antibody profile'. Firstly, the serum is 'mixed with microbeads that have multiple HLAs on their surface'. This essentially serves to identify antibodies that are targeted at particular donor HLAs, using a fluorescent marker. This is needed as there is always a possibility that the recipient could have developed antibodies against a particular HLA in the past, whether it be pregnancy, previous transplants, or blood transfusions. These are known as 'sensitisation events'.

In addition to this, another test is carried out, involving mixing of recipient serum with donor cells. This is primarily to see if there is any immunological reaction to the donor cells, thus proving whether a donor is in fact compatible with the patient. The donor cells are those with nuclei, so scientists can test whether the HLAs of the donor form an antigen-antibody complex with antigens present in the patient's serum. 'Complement' molecules are also added which help to destroy cells (by lysis) that have their HLA antigens bound to patient antibodies. To see whether a reaction has occurred or not, a visualisation stain is applied, dead cells staining red, and live cells staining green.

Not only is it important to choose the right donor, but selecting viable organs for surgical use is also vital. Donors can either be living or deceased, but living donors 'are generally family members or close friends of the patient'. That isn't to say all are, of course, as altruistic donors are on the rise - these people are willing to donate an organ without knowing who will receive it in due course. Kidney donation is by far the most common transplantation from live donors. In fact, 'in the UK, 2732 out of 3740 transplants performed in 2011 were kidney transplants'. Donations from the deceased however can be divided into two sub-groups: those who are pronounced brain dead (DBD), or those with circulatory death (DCD). DCD is when the heart has completely stopped beating and thus there is no circulation flow throughout the body. DBD donors have organs 'kept alive' by a ventilator, with a constant blood supply in place.

A patient can be found to have their donated organs rejected by their own immune system at several possible stages after surgery:

Hyperacute: Rejection occurs immediately, even within a few minutes of transplantation. Surgeons would need to work quickly to remove the donor organ completely from the body. Nowadays, hyperacute rejection is very rare.

Accelerated acute: Rejection could happen within a few days to a week after surgery. The rejection may be due to the fact the patient has experienced a sensitisation event in the past, which produced the relevant antibodies.

Acute: Rejection occurs within the first 6 months of surgery, and is mainly due to a few mismatches in HLAs between the donor and the patient. This sort of rejection can be brought under control with certain immunosuppresant drugs that are specific to the recipient.

Chronic: Rejection could even occur after 6 months from the point of surgery and mainly due to repeated episodes of acute rejection. This is the main problem facing patients with transplants - some patients will be required to take immunosuppresive drugs for the vast duration of their life.


With a population as ethnically diverse as the UK, it has become increasingly difficult for those of minor ethnic origins to receive the right matches for organ donation, although overall there is a big gap between the numbers requiring transplants and willing donors.Those of Black and Asian origin have been known to have 'uncommon HLA types'. Many countries, such as Spain, Belgium, France and the USA have implemented an 'opt-out' scheme nationwide. This means it is presumed you give consent for your organs to be donated, unless you state otherwise. In the UK, the public's view may be changing on whether we should carry on with our current system in order to meet the piling demand for organs across all ages, all backgrounds, and all ethnicities.


Credit to Steven Jervis, clinical scientist at the Manchester Transplantation Laboratory who wrote for the Biological Sciences Review (Volume 24, Number 1)

"Dead Heart" Transplant - World First in Cardiac Surgery

In Australia this month, surgeons have managed to resuscitate a heart from circulatory death and use it for transplant in patients with 'end-stage heart failure'. Prior to this, hearts used for transplant were only sourced from brain-dead patients but whose hearts were still beating. Some have heralded this as a 'paradigm shift' in organ transplantation. The heart was able to be revived using what has been  dubbed as the 'heart-in-a-box' machine (the OCS - Organ Care System). Now the machine is commercially available to hospitals in Europe and Australia for clinical use. Usually, a beating heart is kept iced for a long period of time, however this machine is claimed to be a 'portable, warm perfusion, monitoring machine'. As of now, St. Vincent's Hospital Heart Lung Transplant Unit in Australia has transplanted two patients using this technique. However it is important to note that the OCS has already been used and approved for other types of transplantation such as the liver, kidneys and lungs. Up until now, it has proved difficult to repeat the same technique on 'dead' hearts.

The benefits of this new technique prove essential - the maximum possible number of donor hearts available will inevitably increase. In fact, it is estimated that 30% more lives could be saved with the introduction of this technique. Professor Peter MacDonald, Medical Director of the St Vincent's Heart Transplant Unit has said "this is a timely breakthrough. In all our years, our biggest hinderance has been the limited availability of donor organs". With regards to the OCS machine, portability is useful if it is needed in various departments in a hospital. It would also mean ease of transportation nationwide, or even worldwide.

 

Top: OCS "Heart-in-a-box" machine (TransMedics)

Above: OCS machine maintaining liver for transplant (BBC)

Interestingly however, this isn't the first time that this idea of using a dead heart donor has been experimented. Professor Kumud Dhital perfumed both of the operations in Austrailia says that "It is interesting to note that DCD hearts were utilised for the first wave of human heart transplants in the 1960's with the donor and recipient in adjacent operating theatres. This co-location of donor and recipient is extremely rare in the current era leading us to rely solely on brain dead donors -- until now".

The recovery of patients is even more astounding. Michelle Gribilas, 57, was the first patient to be treated with the surgery. Before the operation she was suffering from congenital [end-stage] heart failure. Two months after the procedure, she told the BBC: "Now I'm a different person altogether. I feel like I'm 40 years old - I'm very lucky". Senior cardiac nurse at the British Heart Foundation, Maureen Talbot, added "without this development, [patients] may still be waiting for a donor heart".


Credit to the BBC for their article 'Surgeons transplant heart that had stopped beating', published 24th October 2014. More on the subject can be found here.

Credit to St Vincent's Health Australia, whose story was published in ScienceDaily on October 24th 2014. The original article can be found here.

BBC Documentary: Pain, Pus and Poison - Part 1

Over the last 150 years or so, the story of the advancements of drugs, treatment, and techniques in medicine has developed at a great pace. Dr Michael Mosley recently presented a trilogy of documentaries for the BBC, telling tales of the beginnings of anaesthesia and the birth of the antibiotic era. In part one of the series, he focused on man's pursuit to free pain. It begins where you may not expect - the poppy. From this rather innocent-looking plant, a resin was extracted and given the name opium. Dissolved in alcohol, the medicine was called laudanum. Morphine, the drug we are familiar today with unprecedented properties in alleviating excruciating pain, was formerly discovered by 19th century pharmacist Friedrich Sertürner. Morphine works by blocking nerve endings associated with pain at the site of pain and in the brain. The direct blockage of these signals proves morphine very effective. Eventually isolating the active ingredients in raw opium, he had managed to obtain a substance that could now be quantified and measured for ease of administration. This fact is often underestimated about drugs - simply by being able to measure out a quantity of a substance offers a huge element of control and indeed safety. It was considered back then that medicines which originated from plant sources were alkaloids, containing the suffix -ine in their name. Hence we are familiar with morphine, whose former name was morphium. According to Dr Moseley, these alkaloids were considered 'our first real medicines'. Dr Walter Sneader, Former Head of Pharmacy at the University of Strathcylde says that the discovery of morphine was 'the single most important event that has ever occurred in drug discovery - far more important than the introduction of penicillin, in terms of advancing the science'. Sertürner then went on to isolate many more alkaloid chemicals, some of which include caffeine, nicotine and quinine. Another well known alkaloid that was discovered was cocaine. Ironically enough, at the point of introduction in industry this compound dissolved in alcohol was approved by the Pope himself. The famous neurologist Sigmund Freud went on to investigate more into the properties of cocaine.



Although these alkaloids were a start, these weren't considered potent enough to be effective in the operating theatre. Sir Humphrey Davy saw nitrous oxide as a potential drug for use in surgery, however surgeons still went on to attempt operations on people who were unfortunately, fully awake. It was only until William Morton and the introduction of ether as a gaseous anaesthetic agent, that anaesthesia started to advance rapidly. To read more on the subject of William Morton's discovery, visit my post, 'The History of Anaesthesia'.

After this remarkable discovery, chemists from all around the world began to experiment with various substances, coal tar notably being one of the 'more unlikely places'. Chemist and presenter Andrea Sella, mentions that using coal tar was able to open 'a whole new library of starting materials'. Some of the most iconic drugs in today's world were a product of this seemingly unpromising raw material, aspirin and heroin just to name a couple. In the 20th century, many more drugs with anaesthetic properties were developed. However it wasn't just anaesthetics; the world's first sleeping pill was discovered, chloral hydrate which became very popular. The barbiturates were another group of drugs that had the ability to put people to sleep. Sodium thiopental was one of the more notable ones, the 'truth drug' so given the name for it's use in interrogation, is featured in the documentary.

Now in the 21st century, we have made great strides in the development of even more effective and safer drugs for use in surgery, prescription, and treatment of diseases. It has come to a point where we can, with suitable starting materials such as simple molecules, develop any molecule we want to. This means we can develop any drug we want to. A surge in technological advances in the last few decades has supplemented our understanding of anaesthesia and how pain is managed.


Credit to the BBC for their medical documentary trilogy, 'Pain, Pus and Poison', broadcasted in September 2014.

Repairing Damaged Heart Tissue With Embryonic Stem Cells

Heart disease is now considered the most common cause of death in the UK, according to the BBC. This pressing issue has initiated research projects to find the best treatments, long-lasting treatments that involve the regeneration of heart tissue. Experiments back in 2005 involved deliberately inducing heart attacks in 18 sheep in order to test the potential of embryonic stem cells from mice. Research prior to this revealed that attempting to use stem cells from the patient would prove futile as adult stem cells do not have the capacity to differentiate into heart (cardiac) tissue. If this was possible, this would undoubtedly be a desirable solution as the patient's own cells are being used, reducing the risk of rejection.

Therefore embryonic stem cells have been labelled the next hope in the regeneration of damaged heart tissue. The experiment back in 2005 involved separating the sheep into two groups, one the control, the other being given 'multiple injections' of the embryonic stem cells [from mice] after a rest period of two weeks. These cells had been given growth factors to trigger them into developing into cardiac cells. Five sheep from this group were also given immunosuppressants in case there is an issue of rejection. Tagging the stem cells with 'fluorescent proteins' helped scientists to track their progress of colonisation, which was successful after one month. As anticipated, the cells were effective in regenerating the heart tissue in the non-control group, replacing the scarred tissue. In fact, the scientists were able to measure the heart's effectiveness to pump blood from the left ventricle. In the control group, blood ejection rate decreased by an average of 6.6%, whilst it was raised by 10% in the group given stem cell treatment.

By this data, the treatment seems very effective, however only 18 sheep were used in this set of experiments and embryonic stem cells of mice were used. Nevertheless the fact that this technique works in principle gives hope of new treatments involving stem cells. What was more encouraging for the scientists, is that there was no evidence of an attempt of rejection by the immune systems of sheep that were administered immunosuppressant drugs. However geneticist Robin Lovell-Badge, researcher at the National Institute for Medical Research, London, says that there is a "need to be cautious. Other tissues might reject the stem cells". He also pointed out that the sheep were only monitored for one month after the investigation. Side effects to the treatment or rejection could well occur further down the line - this is another implication for human trials.

Since these experiments, another study at the University of Washington Institute for Stem Cell and Regenerative Medicine also found success in the use of embryonic stem cells to regenerate tissue, this time in monkeys. The study summary stated that the stem cells "assembled muscle fibres and began to beat in synchrony with macaque (monkey) heart cells". What was interesting is that this time, human embryonic stem cells were used. The findings were published 30th April 2014 in Nature. 

Above: Green areas depict newly transplanted stem cells forming a graft with the primates original cardiac muscle cells (red). Full credit to the University of Washington

Credit is given to Anna Gosline, writer for New Scientist. Article can be found here. Original study findings can be found in The Lancet (Volume 336, pg 1005). 

University of Washington findings report can be found at ScieneDaily here.

World First In Organ Transplantation

Recently in September, it has been revealed that a woman in Sweden gave birth to a baby boy, only possible with a womb transplantation. This pivotal event in medical science has given hope to thousands of women around the globe who are unable to conceive. Some cancer treatments and birth defects are a couple pf the reasons why women have this problem. The donor of the uterus was a friend of the 36-year old, who was in her 60's at the time of transplantation. The birth was successful, however premature at 36 weeks, the baby weighing in at 1.8kg (3.9lb). Prior to the birth, the unidentified couple underwent IVF treatment in order to produce 11 embryos. These were frozen until the point of transplantation at the University of Gothenburg. As with the vast majority of organ transplants of today, the woman was given immunosuppressant drugs before the transplant, in order to reduce the risk of rejection by her own immune system.

After the transplant, doctors were then able to select an embryo from the ones frozen to implant into the new uterus. However this was only after a period of a year. In the short period before the birth, the baby was said to have developed an abnormal heart beat, hence the premature birth, however now the baby's condition is said to be 'normal'. However complications with this sort of transplant don't just stop there. If the couple were to have a second child, they would need to consider the fact that the immunosuppressant drugs can be 'damaging in the long term'. It would be considered that if they decide not to have a second child, then removing the transplanted womb would be a necessary precaution.

There have been several fails attempts at womb transplants, whether it be due to the organ becoming diseased, or birth resulting in miscarriages. Now, Professor Mats Brannstrom, who led the surgical team expressed relief and happiness in response to the success. In fact it has emerged that two more women will be receiving womb tranplants by the end of this year; suregons in the UK will be choosing 5 patients out of 60 who will undergo this potenially life changing opeation, according to the Sunday Times.

"Our success is based on more than 10 years of intensive animal research and surgical training". Despite the success however there are still concerns about the 'safety and effectiveness of the invasive procure', according to the BBC. This breakthrough is somewhat comparable to the leap in medical science that IVF allowed over 30 years ago. The Chairman of the British Fertility Society, Dr Allan Pacey said the operation "feels like a step change", however he is aware that it will need to be proved repeatable, reliable, and safe in the future for many more patients.


Credit to Oliver Moody, for his article 'More womb transplant babies on the way' which can be found here.
Additional credit to James Gallagher, Health Correspondent for the BBC, for his article 'First womb transplant baby born', which can be accessed here

Obesity And Its Expensive Relationship WIth The NHS...

Recently, the NHS chief executive Simon Stevens issued a statement to the public at the Public Health England conference in Coventry, which is held each year. In the light of an on-going obesity epidemic, he believes that "Obesity is the new smoking". Describing the disease as a "slow-motion car crash", he, along with thousands across the country, recognise that the costs involved in treating obesity has risen year on year to a point where it'll become unsustainable without raises taxes.

Basic statistics reveal how vast the problem is: 25% of adults and over 20% of children are considered obese. I encourage you to see my other article, 'Fat!', for more interesting statistics.

By many, obesity is considered a disease of all age groups, which makes the numbers affected much larger. Tackling the issue therefore proves an expensive task, as currently the government spends around £9bn every year on treatments.

Stevens added that Britain would be 'piling on the pounds in terms of future taxes'.

Percentage of men and women obese from 1993 - 2009 (BBC article)

However its important to appreciate that obesity isn't just an isolated disease. In the majority of cases, obesity will inevitably lead onto other complications including cancer, diabetes and heart disease. Treating people for these additional problems will only increase the overall cost of treatment. At present, the most common direct treatment for obesity (especially those morbidly or severely obese) is bariatric surgery. There are two main types - gastric band and gastric bypass. A gastric band uses a restriction of stomach size, so than when food is ingested, less is required to make you feel 'full'. The alternative method is a gastric bypass, 'where your digestive system is re-routed past most of your stomach'. This gives the effect of digesting less food, having a similar psychological effect to a gastric band. Despite the obvious benefits, patients are always made aware of the potential complications to their health post-surgery. Internal bleeding or deep vein thrombosis (DVT) are just a named couple. Generally however, patients are enrolled onto a 'rigourous and lifelong plan', including regular exercise and a monitored diet, according to NHS Choices.

However this measure may only be considered suitable for those whose life is at risk and require emergency intervention. Those who register as 'overweight' on the BMI scale, are currently not legible for bariatric surgery.

But how can the nationwide problem be tackled? According to the BBC, one of the future proposals would be to increase spending on 'lifestyle intervention programmes' rather than bariatric and similar surgery. This will be a step forward in combating obesity in the long term. Surgery could be considered a relatively short-term solution. 

Credit to Nick Triggle, BBC Health correspondent, for his article published which can be read here. Also the full speech by CEO Simon Stevens can be read here.

The Small Guys That Help Regulate Protein Synthesis

If you have an interest in cellular biology, the chances are you've come across the different types of nucleic acids that are used to code for proteins and control certain activities of the cell. However, what might be new to you is the existence of MicroRNA or miRNA, in its common notation. Essentially these are regular strands of RNA but very small - in fact a regular sized RNA molecule may be around 100 times longer than the average length miRNA. As miRNA are single stranded, the molecules tend to quite flexible, in contrast to the well known rigid DNA double helix molecule. Originally, scientists tended to believe that in eukaryotic cells at least, there were only two types of RNA: ribosomal RNA and messenger RNA. At first, miRNA were seen to be RNA that were too insignificant to have any real function, they were considered free clumps of nucleotides in short.

Now the importance of miRNA molecules has been realised, thanks to cutting edge research on a particular type of nematode worm - specifically Caenorhabditis elegans. In 1993, the first miRNA identified was named lin-4. What scientists found is that somehow, these minute molecules prevent the development of the larvae. 

After these baby steps into this field of research, the year 2000 saw the discovery of the miRNA molecule let-7. This was found to 'regulate development in C.elegans'. What was more significant however, was that this molecule could be found in all animal and plant cells. But what do we mean by 'regulate development'? This particular miRNA molecule is found to be responsible for controlling aspects of the cell cycle and cell differentiation. But healthy functioning cells doesn't rely on a single miRNA molecule - many different molecules working together ensure cellular processes go on as intended.

But how do miRNA's work?

In an average human cell, over 1000 different miRNA molecules can be found. Each of these specific strands seek to target a particular RNA molecule. With over 60% of RNA molecules being targeted by miRNAs, it could be said that controlling protein synthesis is a very organised and vast operation. What is important to note, is that miRNA molecules are encoded by genes, a lot like proteins in fact. It follows that these genes are present in the cell's DNA.

To synthesise miRNA, firstly one long strand of specially structured RNA is manufactured from miRNA genes. These could be considered the precursors of miRNA (Pri-miRNA) and are subsequently lysed by enzymes and transported from the nucleus, into the cytoplasm. Any two different  miRNAs can align through regular RNA-RNA hydrogen bonded base-pairing. However in some parts, there may be some non-complementary base pairing which would lead to bulges from the molecule. Using specific enzymes, the hydrogen bonds can be broken to leave two separate miRNA molecules which can go on to target their designated RNA molecule.

Due to inconsistencies in base pairing with an mRNA molecule, miRNAs have been found to inhibit protein synthesis by preventing the ribosome translating the RNA molecule. But another way miRNA's function is that they can achieve complete complementary base pairing with an mRNA molecule. Specific degrading enzymes can then recognise this situation and destroy the miRNA-mRNA complex, preventing the protein ever being synthesised.

(Two examples of pri-miRNA - sequences in red represent 'mature' miRNA. Notice there are bulges where there is no complementary base pairing - WIkipedia - microRNA)

Extended research has shown that 'malfunction of miRNAs is implicated in some liver diseases, diseases of the nervous system, cardiovascular disease, cancer and obesity'. One example given in the September issue of the Biological Sciences Review is miRNAs affecting normal nervous function. Individuals with mental retardation sometimes have whats called "fragile X syndrome", where as implied, the X chromosome tends to break easily. In association with this, it has been found that in the nerve cells of these individuals, miRNA molecules have prevented the synthesis of an essential protein by binding with mRNA.

Even miRNA has been believed to be the culprit in some cancers. It isn't always bad that an miRNA molecule binds to RNA - some miRNAs suppress tumour growth whilst others promote it.

At present, it may be difficult to see how miRNAs can be used to treat disease, but I believe there is no doubt that it could one day be widely use to diagnose them. Cancers are a good example. It has been observed that particular concentrations of a miRNA can correlate with different rates of growth of malignant tumours. From miRNA analysis, it may be possible for doctors to predict the best treatment options for patients.

However this does't mean treatment isn't possible! According to Professor Sheila Graham of the University of Glasgow, new research has revealed the potential of "miRNA sponges" in cells. These are non-functioning RNA molecules that "mop up" specific miRNA molecules so that they can't interrupt the synthesis of essential proteins.



Credit to Professor Sheila Graham for her article 'MicroRNAs - small players in big diseases' published in the Biological Sciences Review (Volume 27, Number 1).