Islet cell transplantation

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Islet cell transplantation
Langerhanssche Insel.jpg
Microscopic image of an islet of Langerhans (lighter area) surrounded by exocrine pancreas tissue (darker staining).
MeSHD016381

Islet transplantation is the transplantation of isolated islets from a donor pancreas into another person. It is an experimental treatment for type 1 diabetes mellitus. Once transplanted, the islets begin to produce insulin, actively regulating the level of glucose in the blood.

Islets are usually infused into the person's liver.[1] If the cells are not from a genetically identical donor the person's body will recognize them as foreign and the immune system will begin to attack them as with any transplant rejection. To prevent this immunosuppressant drugs are used. Recent studies have shown that islet transplantation has progressed to the point that 58% of the people in one study were insulin independent one year after the operation.[2]

In the period from 1999 to 2004, 471 people with type 1 diabetes have received islet transplants at 43 institutions worldwide.[3]

History[edit]

The concept of islet transplantation is not new.[4] Investigators as early as the English surgeon Charles Pybus (1882–1975) attempted to graft pancreatic tissue to cure diabetes. Most, however, credit the recent era of islet transplantation research to Paul Lacy's studies dating back more than three decades. In 1967, Lacy's group described a novel collagenase-based method (later modified by Dr. Camillo Ricordi, then working with Dr. Lacy) to isolate islets, paving the way for future in vitro and in vivo islet experiments.[5] Subsequent studies showed that transplanted islets could reverse diabetes in both rodents and non-human primates.[6][7] In a summary of the 1977 Workshop on Pancreatic Islet Cell Transplantation in Diabetes, Lacy commented on the feasibility of “islet cell transplantation as a therapeutic approach [for] the possible prevention of the complications of diabetes in man”.[8] Improvements in isolation techniques and immunosuppressive regimens ushered in the first human islet transplantation clinical trials in the mid-1980s. The first successful trial of human islet allotransplantation resulting in long-term reversal of diabetes was performed at the University of Pittsburgh in 1990.[9] Yet despite continued procedural improvements, only about 10% of islet recipients in the late 1990s achieved euglycemia (normal blood glucose). In 2000, Dr. James Shapiro and colleagues published a report describing seven consecutive people who achieved euglycemia following islet transplantation using a steroid-free protocol and large numbers of donor islets, since referred to as the Edmonton protocol.[10] This protocol has been adapted by islet transplant centers around the world and has greatly increased islet transplant success.

Goals[edit]

The goal of islet transplantation is to infuse enough islets to control the blood glucose level removing the need for insulin injections. For an average-size person (70 kg), a typical transplant requires about one million islets, isolated from two donor pancreases. Because good control of blood glucose can slow or prevent the progression of complications associated with diabetes, such as nerve or eye damage, a successful transplant may reduce the risk of these complications. But a transplant recipient will need to take immunosuppressive drugs that stop the immune system from rejecting the transplanted islets.

Newer studies have focused their attention towards reducing severe hypoglycemic events, a life-threatening state in type 1 diabetes, rather than focus on removing the need for insulin injections entirely [11][12].

Procedure[edit]

The process of islet transplantation (illustration by Giovanni Maki).

Researchers use a mixture of highly purified enzymes (Collagenase) to isolate islets from the pancreas of a deceased donor. Collagenase solution is injected into the pancreatic duct which runs through the head, body and tail of the pancreas. Delivered this way, the enzyme solution causes distension of the pancreas, which is subsequently cut into small chunks and transferred into so-called Ricordi's chamber, where digestion takes place until the islets are liberated and removed from the solution. Isolated islets are then separated from the exocrine tissue and debris in a process called purification.

During the transplant, a radiologist uses ultrasound and radiography to guide placement of a catheter through the upper abdomen and into the portal vein of the liver. The islets are then infused through the catheter into the liver. The person will receive a local anesthetic. If a person cannot tolerate local anesthesia, the surgeon may use general anesthesia and do the transplant through a small incision. Possible risks of the procedure include bleeding or blood clots.

It takes time for the islets to attach to new blood vessels and begin releasing insulin. The doctor will order many tests to check blood glucose levels after the transplant, and insulin may be needed until control is achieved.

Immunosuppression[edit]

The Edmonton protocol uses a combination of immunosuppressive drugs, including daclizumab (Zenapax), sirolimus (Rapamune) and tacrolimus (Prograf). Daclizumab is given intravenously right after the transplant and then discontinued. Sirolimus and tacrolimus, the two main drugs that keep the immune system from destroying the transplanted islets, must be taken for life.

Limitations[edit]

While significant progress has been made in the islet transplantation field,[13] many obstacles remain that currently preclude its widespread application. Two of the most important limitations are the currently inadequate means for preventing islet rejection, and the limited supply of islets for transplantation. Current immunosuppressive regimens are capable of preventing islet failure for months to years, but the agents used in these treatments are expensive and may increase the risk for specific malignancies and opportunistic infections. In addition, and somewhat ironically, the most commonly used agents (like calcineurin inhibitors and rapamycin) are also known to impair normal islet function and/or insulin action. Further, like all medications, the agents have other associated toxicities, with side effects such as oral ulcers, peripheral edema, anemia, weight loss, hypertension, hyperlipidemia, diarrhea and fatigue.[14] Perhaps of greatest concern to the person and physician is the harmful effect of certain widely employed immunosuppressive agents on renal function. For the person with diabetes, renal function is a crucial factor in determining long-term outcome, and calcineurin inhibitors (tacrolimus and ciclosporin) are significantly nephrotoxic. Thus, while some people with a pancreas transplant tolerate the immunosuppressive agents well, and for such people diabetic nephropathy can gradually improve, in other people the net effect (decreased risk due to the improved blood glucose control, increased risk from the immunosuppressive agents) may worsen kidney function. Indeed, Ojo et al. have published an analysis indicating that among people receiving other-than-kidney allografts, 7%–21% end up with renal failure as a result of the transplant and/or subsequent immunosuppression.[15]

References[edit]

  1. ^ Lakey JR, Burridge PW, Shapiro AM (September 2003). "Technical aspects of islet preparation and transplantation". Transplant International. 16 (9): 613–32. doi:10.1111/j.1432-2277.2003.tb00361.x. PMID 12928769.
  2. ^ Close NC, Hering BJ, Eggerman TL (March 2005). "Results from the inaugural year of the Collaborative Islet Transplant Registry". Transplantation Proceedings. 37 (2): 1305–8. doi:10.1016/j.transproceed.2004.12.117. PMID 15848704.
  3. ^ Shapiro AM, Lakey JR, Paty BW, Senior PA, Bigam DL, Ryan EA (May 2005). "Strategic opportunities in clinical islet transplantation". Transplantation. 79 (10): 1304–7. doi:10.1097/01.TP.0000157300.53976.2A. PMID 15912095.
  4. ^ Piemonti L, Pileggi A (2013). "25 Years of the Ricordi Automated Method for Islet Isolation" (PDF). CellR4. 1 (1): 8–22.
  5. ^ Lacy PE, Kostianovsky M (January 1967). "Method for the isolation of intact islets of Langerhans from the rat pancreas". Diabetes. 16 (1): 35–9. doi:10.2337/diab.16.1.35. PMID 5333500.
  6. ^ Kemp CB, Knight MJ, Scharp DW, Lacy PE, Ballinger WF (August 1973). "Transplantation of isolated pancreatic islets into the portal vein of diabetic rats". Nature. 244 (5416): 447. doi:10.1038/244447a0. PMID 4200461.
  7. ^ Scharp DW, Murphy JJ, Newton WT, Ballinger WF, Lacy PE (January 1975). "Transplantation of islets of Langerhans in diabetic rhesus monkeys". Surgery. 77 (1): 100–5. PMID 122797.
  8. ^ Lacy PE (April 1978). "Workshop on Pancreatic Islet Cell Transplantation in Diabetes sponsored by the National Institute of Arthritis, Metabolism, and Digestive Diseases and held at the National Institutes of Health in Bethesda, Maryland, on November 29 and 30, 1977". Diabetes. 27 (4): 427–9. doi:10.2337/diab.27.4.427. PMID 416985.
  9. ^ Tzakis AG, Ricordi C, Alejandro R, Zeng Y, Fung JJ, Todo S, Demetris AJ, Mintz DH, Starzl TE (August 1990). "Pancreatic islet transplantation after upper abdominal exenteration and liver replacement". Lancet. 336 (8712): 402–5. doi:10.1016/0140-6736(90)91946-8. PMC 2972674. PMID 1974944.
  10. ^ Shapiro AM, Lakey JR, Ryan EA, Korbutt GS, Toth E, Warnock GL, Kneteman NM, Rajotte RV (July 2000). "Islet transplantation in seven patients with type 1 diabetes mellitus using a glucocorticoid-free immunosuppressive regimen". The New England Journal of Medicine. 343 (4): 230–8. doi:10.1056/NEJM200007273430401. PMID 10911004.
  11. ^ Hering BJ, Clarke WR, Bridges ND, Eggerman TL, Alejandro R, Bellin MD, Chaloner K, Czarniecki CW, Goldstein JS, Hunsicker LG, Kaufman DB, Korsgren O, Larsen CP, Luo X, Markmann JF, Naji A, Oberholzer J, Posselt AM, Rickels MR, Ricordi C, Robien MA, Senior PA, Shapiro AM, Stock PG, Turgeon NA (July 2016). "Phase 3 Trial of Transplantation of Human Islets in Type 1 Diabetes Complicated by Severe Hypoglycemia". Diabetes Care. 39 (7): 1230–40. doi:10.2337/dc15-1988. PMC 5317236. PMID 27208344.
  12. ^ Gerber PA, Hochuli M, Benediktsdottir BD, Zuellig RA, Tschopp O, Glenck M, de Rougemont O, Oberkofler C, Spinas GA, Lehmann R (January 2018). "Islet transplantation as safe and efficacious method to restore glycemic control and to avoid severe hypoglycemia after donor organ failure in pancreas transplantation". Clinical Transplantation. 32 (1): e13153. doi:10.1111/ctr.13153. PMID 29140547.
  13. ^ Robertson RP (February 2004). "Islet transplantation as a treatment for diabetes - a work in progress". The New England Journal of Medicine. 350 (7): 694–705. doi:10.1056/NEJMra032425. PMID 14960745.
  14. ^ Hirshberg B, Rother KI, Digon BJ, Lee J, Gaglia JL, Hines K, Read EJ, Chang R, Wood BJ, Harlan DM (December 2003). "Benefits and risks of solitary islet transplantation for type 1 diabetes using steroid-sparing immunosuppression: the National Institutes of Health experience". Diabetes Care. 26 (12): 3288–95. doi:10.2337/diacare.26.12.3288. PMID 14633816. Full text
  15. ^ Ojo AO, Held PJ, Port FK, Wolfe RA, Leichtman AB, Young EW, Arndorfer J, Christensen L, Merion RM (September 2003). "Chronic renal failure after transplantation of a nonrenal organ". The New England Journal of Medicine. 349 (10): 931–40. doi:10.1056/NEJMoa021744. PMID 12954741.