Objective
The proposed research program focuses on two major objectives. The first objective focuses on the engineered muscle tissue to be implanted as a flap. For this, an engineered muscle tissue capable of secreting molecules that have the ability to attract regulating and suppressing immune cells will be created. The second objective aims to confirm the establishment of immune regulated environment within the engineered muscle tissue flap. Normal mice will be transplanted with the engineered tissue as a flap. Upon connection between the engineered muscle tissue with the body blood supply, the presence of immune regulating and suppressing cells will be studied by taking out the implanted engineered muscle tissue flap and analyzing its immune cell profile. Then, the normal mice will be transplanted with donor islets into the engineered flap, and the islets survival will be studied. If successful, the donor islets will survive and remain intact without any signs of immune attack such as inflammation.
Background Rationale
Islet transplantation using donor islets has the potential to cure T1D. However, it is currently hampered by the need for more optimal transplantation site, and by the need to protect the implanted islets from immune attack using medications that need to be taken for life. A more optimal transplantation site will provide the islets with persistent blood supply for nutrition and oxygen supply, and will shield them from immune attack, making anti-rejection drug administration redundant.
The immune system has a natural ability to regulate itself and prevent deleterious immune attack. The human body has several sites that are able to tolerate the introduction of donor tissues without eliciting an immune attack. These are called immune privileged sites. Immune cells called T regulating cells (Tregs) are responsible for the immune privilege. Islet transplantation into such sites was suggested. However, it was found to be insufficient and may not be enough to support long term protection of donor islets from immune attack, indicating that additional immune regulation may be required. Additional known natural mechanisms to escape immune attack are those of cancer tumors. Cancer tumors were shown to secrete molecules capable of recruitment of a combination of immune suppressive and regulating cells such as myeloid-derived suppressive cells / macrophages, neutrophils, Tregs, and dendritic cells. These molecules are responsible for the entrance of such immune cells to the tumor, providing it the ability to prevent immune attack and survive. This project aims to exploit these natural mechanisms of the immune system to regulate itself.
Among the current accepted islet transplantation sites is the muscle (intra-muscular transplantation), and it was shown to have many advantages. But, it required creation of new blood vessels within the muscle, and elicited immune attack on the transplanted donor islets. In addition, muscle contraction can affect blood supply and impair the islets function. Based on our expertise in muscle tissue engineering , and in engineering muscle tissue flap we suggest to overcome these intramuscular transplantation limitations by creating engineered muscle tissue flap as a more optimal site for donor islet transplantation. The engineered muscle tissue flap will harness the natural capacity of the immune system to regulate itself and escape immune attack. This will be achieved by engineering the muscle cells of the engineered muscle tissue to secrete molecules attracting a combination of regulating and suppressing immune cells.
Description of Project
Islet transplantation using donor islets has the potential to cure T1D. However, it is currently hampered by the need for more optimal transplantation site providing persistent blood supply to the islets, and by the need to protect the implanted islets from immune attack using medications that need to be taken for life. This project offers an alternative, more optimal islet transplantation site in which the donor implanted islets are provided with persistent blood supply and therefore can stay functional in the body for years. In addition, this transplantation site will shield the implanted islets from immune attack, and will eliminate the need for medications preventing it.
The suggested alternative islet transplantation site is an engineered muscle tissue flap composed of cells obtained from the patient. Proper tissue function in the body requires arterial fresh blood supply of oxygen and nutrition, together with venous drainage of waste and carbon dioxide produced by the cells of the tissue. The engineered muscle flap will be created using tissue engineering techniques. An engineered muscle tissue will be created in the lab and will contain a network of engineered blood capillaries. This engineered tissue will then be given a persistent body blood supply by connecting it to an artery and vein of the body. The engineered blood capillaries within the engineered tissue will connect to the artery and vein of the body, creating a flap with excellent blood supply. Its advantage stems from the persistent blood supply from the body, that can instantly support the engraftment of the implanted islets. We believe that preventing the immune cells from attacking the implanted islets can be achieved by harnessing the natural capacity of the immune system to regulate itself and attenuate its reactions. This immune system regulation is performed by suppressing and regulating immune cells. We aim to attract these regulating immune cells to the engineered muscle flap. This will create a locally immune regulated environment. For immune cells to enter the engineered flap, it should be connected to the lymphatics. Therefore, the engineered tissue will also contain engineered lymphatic vessels that will connect to the body lymphatic vessels. To attract the regulating and suppressing immune cells, the engineered muscle tissue flap will contain muscle cells that are able to secrete molecules that have the ability to attract such immune cells. A two-step procedure for islet transplantation is suggested: first creating the engineered muscle flap with local immune regulation, then injection of islets into the engineered flap. The strategy of the engineered muscle flap is relevant not only for the transplantation of donor islets but also for transplantation of islets from the same person. In newly T1D diagnosed patients, not all islets are immune attacked at once, and for a short period there are still functioning islets. Transplantation of these still functioning islets to the suggested transplantation site will shield them from the autoimmune attack and will allow them stay function for many more years.
Anticipated Outcome
The suggested alternative islet transplantation site in the form of an engineered muscle tissue flap is expected to provide donor islets transplanted within it a persistent blood supply (oxygen and nutrition as well as waste products removal). In addition, it will shield the donor islets from immune attack. The strategy proposed will eventually promote islet transplantation as it is expected to eliminate the long-term anti-rejection drugs burden, and to support better the islet long-term function. Such a progress has the potential to lead to improvement in quality of life.
Relevance to T1D
Islet transplantation using donor islets has the potential to cure T1D. However, it is currently hampered by the need for more optimal transplantation site, and by the need to protect the implanted islets from immune attack using medications that need to be taken for life. This project offers a more optimal transplantation site in which the donor implanted islets can stay functional in the body for years. In addition, this transplantation site will shield the implanted islets from immune attack, and will eliminate the need for medications preventing it.
T1D involves autoimmune attack on the insulin producing cells in the pancreas. These cells are part of the pancreatic islets. The strategy of the suggested transplantation site has the potential to address this autoimmune attack. In newly T1D diagnosed patients, not all beta cells are immune attacked at once, and for a short period there are still functioning islets. Transplantation of these still functioning islets to the suggested transplantation site will shield them from the autoimmune attack and will allow them stay function for many more years.