While kidney transplantation is the least expensive and most effective solution in kidney pathologies, unlike dialysis, in France nearly 20,000 people are waiting to receive a new kidney. This figure is due in particular to a lack of compatibility of blood groups between the donor and the recipient. Recently, British researchers succeeded in altering the blood type of three kidneys from deceased donors. This extraordinary advance in transplantation could pave the way for a considerable increase in the number of organs available to applicants, and in particular to those with rarer blood types.
Kidney transplantation, when possible, prolongs and improves patient comfort in the event of ultimate failure of kidney function (renal failure). It makes it possible to stop chronic dialysis, an invasive and restrictive therapy. In France, there are between 3500 and 3700 kidney transplants per year.
But the waiting time for obtaining a graft is variable and depends on the blood group. 31% of patients are transplanted in the first year of registration, 39% between 1 and 3 years, and 15% after 5 years. Indeed, the kidney of a person with blood group A cannot be transplanted to a person with blood group B, nor vice versa. In 2021a bioartificial kidney gave hope of overcoming the shortage of compatible organs.
Recently, researchers at the University of Cambridge succeeded in modifying the blood type of three kidneys from deceased donors, to make them O universal. This unprecedented and exceptional breakthrough will allow more transplants to be carried out, because blood group O can be used for people of any other blood group. The researchers’ work should be published soon in the journal British Journal of Surgery.
Molecular scissors in action to remove blood markers
Professor Mike Nicholson and PhD student Serena MacMillan used a normothermic infusion machine. It is a device that connects to a human kidney to pass oxygenated blood through the organ to better preserve it for future use. Specifically, the researchers used it to pass blood infused with an enzyme through the deceased patient’s kidney.
Serena MacMillan says in a communiqué : « Our confidence was really boosted after applying the enzyme to a piece of human kidney tissue and seeing very quickly that the antigens were cleared. After that, we knew the process was feasible, and we just had to expand the project to apply the enzyme to full-sized human kidneys. ».
You should know that, in our body, all the vessels are lined with receptors (called “markers”), which are specific to group A or B. The enzyme used in the study acted like “molecular scissors” to remove blood group markers that line the blood vessels of the kidney. This technique automatically made the organ blood group O in just a few hours, because this group has no specific markers, unlike A and B.
This is how this conversion to the “universal” O blood group eliminates the problems of compatibility and rejection. Indeed, when organs are rejected by the body, after transplantation, it is often these markers that are involved. Professor of transplant surgery, Nicholson, explains: “ The reason is that you have antigens and markers on your cells which can be either A or B. Your body naturally produces antibodies against those you don’t have. ».
Next, the Cambridge team will have to study how the newly modified type O kidney will react to a patient’s usual blood type in their normal blood supply. The infusion machine gives them the opportunity to test this modality before human clinical trials. In effect, they can perfuse this type O kidney with different types of blood and monitor how it will react, simulating the transplant process in the body.
Mike Nicholson, professor of transplant surgery at the University of Cambridge, is working on a perfusing kidney. © Kidney Research UK / PA
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Mike Nicholson, professor of transplant surgery at the University of Cambridge, is working on a perfusing kidney. © Kidney Research UK / PA
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Mike Nicholson, professor of transplant surgery at the University of Cambridge, is working on a perfusing kidney. © Kidney Research UK / PA
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Mike Nicholson, professor of transplant surgery at the University of Cambridge, is working on a perfusing kidney. © Kidney Research UK / PA
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This project is funded by the charity Kidney Research UK, as the disparities in access to kidney transplants across the Channel are exacerbated compared to France, even if the country is not spared. Dr Aisling McMahon, Director of Research at Kidney Research UK, says: “ The research Mike and Serena are undertaking is potentially groundbreaking. It’s incredibly impressive to see the progress the team has made in such a short time. […] As an organization, we are committed to funding research that transforms treatments and tackles health inequities ».
Indeed, people from minority ethnic groups often have to wait much longer for a transplant because blood type matches with available organs are rarer.
Overcome inequalities of access
In the Anglo-Saxon literature, the link between socioeconomic status and the results of the transplant has been widely studied using different social determinants depending on the study. Racial origin is frequently studied and used as a marker of socioeconomic inequalities. In France, more than 20,000 people are waiting for a transplant. Incompatibility of blood groups regularly prevents a transplant from being carried out, particularly in connection with the ethnic origin of the patients.
Indeed, a study published by INED and Science Po Paris, in June 2016, was interested in the social inequalities that may exist in the allocation of a transplant. The authors explain that blood group B (9% of the French population) is much more frequent among populations originating from certain areas of Africa, which are also confronted with an increased prevalence and a more rapid progression of renal insufficiency. . They add : ” It can be assumed that patients of immigrant origin from these populations, whose level of education is lower on average, represent a significant proportion of group B patients awaiting a transplant. ».
This is a global problem, the studies published on the subject across the Channel, across the Atlantic, in Brazil, in Germany, in Hungary, in Australia or in New Zealand ” all conclude that there are strong social disparities according to income, level of education and ethnic origin. Low socioeconomic status is associated with increased incidence of kidney disease, more frequent progression to end-stage, inadequate dialysis treatment, reduced access to transplantation, plus all the effects of poorer health “, recall the researchers.
In conclusion, this technique of converting blood groups to create a universal kidney could increase the supply of kidneys available for transplantation, especially among minority ethnic groups who are less likely to match the majority of donated kidneys. With such a change, it is possible to transplant this universal organ to a patient of group A or group B, without any restrictions. Serena MacMillan concludes: It’s very exciting to think about how this could potentially impact so many lives. ».