Objective
Long-term islet transplantation outcomes for T1D are poor with low insulin independence rates and patients require increasing doses of insulin over time. Of concern are the high doses of anti-rejection drugs that are required to prevent the body rejecting the human islets that are obtained from a deceased donor. These high doses of anti-rejection drugs increase the risk of cancer and infection.
The main objective of our project is to improve islet transplantation outcomes including metabolic control as well as safety outcomes by reducing the amount of anti-rejection drugs given through co-delivering a cell therapy called a macrophage at the time of islet transplantation.
We have previously manufactured human macrophages as a cell therapy product for a different condition that has been proven to work safely and effectively in humans at our center.
Specifically we will determine:
If giving a specific sort of macrophage termed an alternatively activated macrophages (AAMs) with islets improves the long-term function of transplanted islets while simultaneously allowing a reduced dose of anti-rejection drug to be used.
We will perform macrophage plus islet transplants in diabetic mice directly into the liver to emulate what happens in humans. The dose of islets will not by itself cure the diabetes. However by giving macrophages as a co-therapy we hope that this will improve blood glucose control and even cure the diabetes in the mouse.
We will determine:
1. The best state of delivery e.g. AAMs and their effect on islet graft function (insulin secretion and glucose measurements performed in mice)
2. The effect of anti-rejection drugs on the macrophages’ behavior
3. Whether macrophage therapy allows a reduction in the anti-rejection medication and the mechanisms involved
4. Fine-tune numbers of macrophages to be delivered and their effect on islet graft function
5. Do an indepth examination of macrophages and the characteristics of the selected macrophages
The experiments will be confined to mice and the main readout of islet transplant success will be the amount of insulin the islet graft produces which will be measured at regular time points after the transplant for up to 16 weeks. We will also examine how the macrophages cause this improvement and will look at other cells and messengers that may be involved in this. A number of different mouse models will be used including those that receive islets from a donor mouse that is "mismatched" to the recipient - therefore emulating the human transplant, allowing us to test whether the dose of anti-rejection drugs can be lowered.
Impact: The results can be rapidly translated to humans in a subsequent study to improve human islet transplantation outcomes with a greater chance of insulin independence whilst reducing the dose of anti-rejection drugs required, therefore improving patient safety. In the future, we believe that this macrophage cell therapy could be applied to stem cell-derived islet transplantation to allow greater insulin independence rates for a longer period with decreased doses of anti-rejection drugs which again reduces the risk of infection and cancer in the transplant recipient.
Background Rationale
Background and Issues with Islet Transplantation: Transplantation of islets into the liver of someone with T1D can stabilize blood glucose control but rarely results in insulin independence. Islets from multiple donor pancreases are typically required to impact on blood glucose control and insulin independence is low. During the transplantation process, islets die because of inflammation (the body’s natural response to injury) and immune rejection and in the short and long-term islet function deteriorates due to anti-rejection drugs. Once islets are transplanted into the liver they do not have a blood supply and over a period of weeks, blood vessels develop between islets and liver forming an islet graft. More than 60% of transplanted islets die in the first 72 hours after a transplant. A major issue that limits the procedure is the need for high dose anti-rejection drugs which increase the risk of infection and cancer and limits the treatment to adults only.
If it was possible to give a treatment at the same time as the islets that reduced inflammation, lowered the risk of rejection of the islets from immune causes and which improved the rate at which islets formed a blood supply with the liver this would reduce islet death in this critical period. This strategy would lead to improved islet function and could also reduce the amount of anti-rejection drugs required.
Proposal: We propose to improve islet transplantation outcomes by transplanting a cell therapy called a macrophage which is a type of immune cell with islets at the time of islet transplant. A cell therapy is where cells are injected into a patient to improve an effect.
Macrophages originate from the bone marrow and are released into the bloodstream. These cells can take on different forms depending on what “cytokines” are present in the blood stream. Cytokines are chemical messengers released by cells of the immune system that help to regulate the body's response to infection and inflammation. Macrophages become biased and can change form according to these chemical messengers and they shift towards a certain type of behavior or response, which impacts on how they function in the body.
Rationale for Macrophage Therapy: Some macrophages are “alternatively activated" macrophages (AAM) and have properties which:
i) reduce inflammation
ii) help reduce immune rejection
iii) encourage blood vessel formation
iv) allow a reduction in the dose of antirejection drugs.
All these properties make it the ideal candidate for transplanting with islets and could reduce the number of islets that died at the time of transplant and improve the short and long-term function of the islets. It would also mean that the amount of anti-rejection drugs taken could be reduced improving patient safety.
Our team have previously manufactured AAMs from human bone marrow in high numbers in a specialized laboratory under strict conditions appropriate for humans. We have shown that they are safe and effective for other diseases.
The main objective of our project is to improve islet transplantation outcomes by co-delivering a macrophage cell therapy at the time of islet transplantation. A great strength of our project is that we have previously manufactured human macrophages for cell therapy products for a different condition that has been proven to work safely and effectively in humans. If successful we would therefore be in a position to translate our studies rapidly into humans.
Description of Project
Type 1 diabetes (T1D): T1D is a chronic disease that is projected to increase to 17.5 million in 2040. It is characterized by high blood glucose levels resulting from insulin deficiency and therapy mainly relies on insulin injections. Hypoglycemia or low blood glucose is common and occurs in 30% of people. Repeated episodes of hypoglycemia leads to severe hypoglycemia - a low blood glucose requiring external help and this is often associated with impaired awareness of hypoglycemia (IAH) an inability to sense when blood glucose readings are low. IAH impacts on life expectancy and quality of life and places a huge burden on the patient and their family.
Islet transplantation for T1D: the transplantation of insulin producing cells termed islets into the liver of someone with T1D is a recognized treatment worldwide targeted to people that suffer from hypoglycemia with IAH where treatment has been in intensified. It is effective and eliminates hypos, stabilizes blood glucose control, restores awareness of hypoglycemia and improves quality-of-life.
Problems with islet transplantation: Most patients wait over 1 year to be transplanted with islets from donated pancreases – a scarce resource; islets from more than 2 donor pancreases are required compounding the issue. The procedure rarely results in insulin independence. Islets do not have a blood supply when transplanted and over 60% islet loss is seen mainly because of inflammation and rejection. Blood vessel formation between the islets and implant site in the liver is very slow. Anti-rejection drugs are required which increases the risk of cancer and infection and impacts on graft function.
Macrophages as a cell therapy for islet transplantation: A cell therapy is a therapy in which cells are injected into a patient to achieve a beneficial therapeutic effect. Macrophages are cells which develop in the bone marrow and are then are released into the bloodstream. They exist in different forms including an activated form where they help reduce inflammation, fight immune rejection and promote blood vessel formation. Macrophages in contrast to islets can be grown in the laboratory. Our research team have already manufactured macrophages for humans as an off-the-shelf product meaning there is no reliance on obtaining donor tissue. Researchers in our group have given macrophages at our center in human trials for liver disease where they were proven to be safe, well tolerated and effective.
We propose that giving macrophages with islets will lead to better islet transplant outcomes, allowing reduced doses of anti-rejection drugs to be used.
Following an islet infusion we will test in diabetic mice the effects on blood glucose control of macrophages and will test the best route and dose to give the cells. If this co-therapy improves blood glucose control, then we will test that this improvement is still present with anti-rejection drugs. We will also test if the dose of these anti-rejection drugs can be decreased with the macrophages.
Long term vision:
In the near future this could be applied to human islet transplantation rapidly with a human macrophage product given at the same time as the islet transplant. This could decrease the loss of islets post-transplantation and lead to more people achieving insulin independence with islets from one donor pancreas. It would allow a reduction in the dose of anti-rejection drugs, improve the islets blood vessel formation to the surrounding tissue and allow more people to be transplanted as more pancreases would be available.
A major benefit in the future will be the administration of macrophages with stem-cell islets; this co-therapy would enable stem-cell derived islet grafts to achieve insulin independence for longer allowing a reduction in anti-rejection drugs, improving patient safety.
Anticipated Outcome
In all the experiments described below a diabetic mouse will be used and transplanted with a number of islets directly into the liver so as to emulate the human situation. The number of islets used is a marginal number and this number of islets would not by themselves cure the mouse of diabetes. If the co-therapy worked this could in combination with the islets cure the diabetes in the mouse. Different types of mouse models will be used to rigorously test the effectiveness of the macrophage co-therapy.
Our anticipated outcomes are:
1. That the AAM-macrophage when transplanted with islets into diabetic mice is associated with the greater insulin secretion and insulin independence rates versus those diabetic mice transplanted with the same number of islets alone - (with a number of islets selected to fall just short of a cure). We will also identify the best dose of the AAM to use at the time of transplant with islets into the liver.
2. The AAM-macrophage is unlikely to be affected by anti-rejection drugs tested under laboratory conditions in a dish with specific assays that test their behaviour/function. Following transplantation of AAM-macrophages with islets and standard doses of anti-rejection drugs (reflecting concentrations obtained in humans) in diabetic mice and run for up to 4 weeks - we would not expect any difference in function of the retrieved macrophage - consistent with the anti-rejection drugs having no effect on the behaviour of the macrophage.
3. We would expect that in the experiments where islets are transplanted with AAMs and anti-rejection drugs into the livers of diabetic mice, this would achieve a cure and, or, better insulin secretion versus islets alone.
4. A second dose of these macrophages given the following day after the transplant by an injection into the tail vein will prove even more effective than a single dose at improving islet graft function as measured by glucose and insulin concentrations.
5. Where two different mice strains are used with islets from one mouse strain transplanted into another diabetic mouse capable of mounting an appropriate and effective immune response, these experiments require the mice to be on anti-rejection drugs - if they are not on these drugs the islets would be rejected. Such a scenario allows us to test if mice given AAM-macrophages plus islets with low doses of anti-rejection drugs achieve the same sort of blood glucose control as those given islets with high doses of anti-rejection drugs. We anticipate that there will be no difference in glucose control and insulin concentrations at the end of these experiments between these 2 groups.
6. The above experiments will be repeated in an autoimmune mouse model of T1D and we would again anticipate that the dose of anti-rejection drugs can be lowered with a similar result seen as above.
7. We anticipate that the macrophage therapy may lead to an increase in certain immune cells that would promote good glucose control.
8. The AAM-macrophage plus islet transplant will be safe with no evidence of long-term liver injury.
If this therapy is effective, we believe the translation of macrophages to human islet transplantation subsequently is likely to be relatively straightforward since macrophages have already been made and used in humans for another disease indication at our center and so the production of a macrophage product from healthy donors that will be frozen, and kept ready to use on demand for human islet transplantation will be readily achievable.
Relevance to T1D
A macrophage therapy that was transplanted at the time of human islets into the liver of the person with T1D would improve human islet transplantation outcomes with islet transplants that functioned better for longer. It would also allow a reduction in the dose of anti-rejection drugs used which themselves are associated with an increased risk of infection and cancer and can also lead to higher glucose levels and islet grafts which do not function as well. Such a co-therapy could have a significant economic impact.
Specifically:
1. Less islets would be required to control blood glucose levels for each patient with T1D with more people achieving insulin independence.
2. More patients with T1D would achieve insulin independence from their islet transplants.
3. Transplants would work better for longer.
4. More pancreases for more people on the waiting list for islet transplantation – currently people are waiting more than a year for their transplant.
5. In the UK only 11% of all pancreases are used for transplantation purposes. There are multiple reasons why they are not acceptable for transplantation purposes: one reason is that the numbers of islets isolated need to be above 200,000. In the future it is possible that those pancreases that would have otherwise been fit for transplant but where slightly lower numbers were isolated, could be utilized in combination with macrophages.
6. Reduced doses of anti-rejection drugs could be used. This would mean that the risk of infection and cancer would decrease.
7. Reduced progression of complications including from eye disease and kidney disease with less admissions to hospital.
The major impact of this co-therapy however would be the effect it would have on people with T1D that were receiving stem cell derived islets in the future with a greater chance of insulin independence for a longer period of time as well as a reduction in the dose of anti-rejection drugs with a much better safety profile for patients.