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Pancreatic cancer occurs in the head of the pancreas in about half the patients and leads to bile duct obstruction.
Pancreatic cancer - double duct sign showing stricture (narrowing) of bile and pancreatic ducts.
Although ERCP is a safe procedure, it has a small but finite risk of triggering pancreatitis i.e. In patients who are very deeply jaundiced, surgery is not safe and the jaundice must be relieved by stenting. Images by courtesy of Dr Anthony Lopez, Consultant Radiologist and CEO of The Imaging Clinic.
Pancreatic delta cell: A type of cell in the pancreas (the organ of the digestive system located behind the stomach). Hormones of the Pancreasdelta cells, which secrete somatostatin, and gamma cells, which secrete pancreatic polypeptide. For decades, diabetes researchers have been searching for ways to replace the insulin-producing cells of the pancreas that are destroyed by a patient's own immune system.
Diabetes is actually a group of diseases characterized by abnormally high levels of the sugar glucose in the bloodstream. Each year, approximately 1,300 people with type 1 diabetes receive whole-organ pancreas transplants. Over the past several years, doctors have attempted to cure diabetes by injecting patients with pancreatic islet cells—the cells of the pancreas that secrete insulin and other hormones. More recently, James Shapiro and his colleagues in Edmonton, Alberta, Canada, have developed an experimental protocol for transplanting islet cells that involves using a much larger amount of islet cells and a different type of immunosuppressant therapy. If the success of the Edmonton protocol can be duplicated, many hurdles still remain in using this approach on a wide scale to treat diabetes. Before discussing cell-based therapies for diabetes, it is important to understand how the pancreas develops. In humans, the pancreas develops as an outgrowth of the duodenum, a part of the small intestine.
During fetal development, new endocrine cells appear to arise from progenitor cells in the pancreatic ducts.
Following birth and into adulthood, the source of new islet cells is not clear, and some controversy exists over whether adult stem cells exist in the pancreas. In developing a potential therapy for patients with diabetes, researchers hope to develop a system that meets several criteria.
Isolated beta cells, as well as islet clusters with lower-than-normal amounts of non-beta cells, do not release insulin in this biphasic manner.
Several groups of researchers are investigating the use of fetal tissue as a potential source of islet progenitor cells. Many researchers have focused on culturing islet cells from human adult cadavers for use in developing transplantable material. These investigators report that these cells do not produce as much insulin as normal islets, but it is within an order of magnitude. Another promising source of islet progenitor cells lies in the cells that line the pancreatic ducts. Susan Bonner-Weir and her colleagues reported last year that when ductal cells isolated from adult human pancreatic tissue were cultured, they could be induced to differentiate into clusters that contained both ductal and endocrine cells. Bonner-Weir and her colleagues are working with primary cell cultures from duct cells and have not established cells lines that can grow indefinitely. Some researchers question whether the ductal cells are indeed undergoing a dedifferentiation or whether a subset of stem-like or islet progenitors populate the pancreatic ducts and may be co-cultured along with the ductal cells. Ammon Peck of the University of Florida, Vijayakumar Ramiya of Ixion Biotechnology in Alachua, FL, and their colleagues [13, 14] have also cultured cells from the pancreatic ducts from both humans and mice. The discovery of methods to isolate and grow human embryonic stem cells in 1998 renewed the hopes of doctors, researchers, and diabetes patients and their families that a cure for type 1 diabetes, and perhaps type 2 diabetes as well, may be within striking distance.
Since their discovery three years ago, several teams of researchers have been investigating the possibility that human embryonic stem cells could be developed as a therapy for treating diabetes. Last year, researchers in Spain reported using mouse embryonic stem cells that were engineered to allow researchers to select for cells that were differentiating into insulin-producing cells [19]. Manfred Ruediger of Cardion, Inc., in Erkrath, Germany, is using the approach developed by Soria and his colleagues to develop insulin-producing human cells derived from embryonic stem cells. Recently Ron McKay and his colleagues described a series of experiments in which they induced mouse embryonic cells to differentiate into insulin-secreting structures that resembled pancreatic islets [10].
According to McKay, this system is unique in that the embryonic cells form a functioning pancreatic islet, complete with all the major cell types.
Recent research has also provided more evidence that human embryonic cells can develop into cells that can and do produce insulin. More recently, Itskovitz-Eldor and his Technion colleagues further characterized insulin-producing cells in embryoid bodies [1]. Taken together, these results indicate that the development of a human embryonic stem cell system that can be coaxed into differentiating into functioning insulin-producing islets may soon be possible. Ultimately, type 1 diabetes may prove to be especially difficult to cure, because the cells are destroyed when the body's own immune system attacks and destroys them. Before any cell-based therapy to treat diabetes makes it to the clinic, many safety issues must be addressed (see Chapter 10. But before any kind of human islet-precursor cells can be used therapeutically, a renewable source of human stem cells must be developed. If an endoscopist is unable to stent a narrowing in the bile duct at ERCP then the radiologist will attempt to stent this through a puncture of the liver by the technique of PTC. Within the pancreas, the delta cells are located in areas called the islets of Langerhans. For years, researchers have painstakingly dissected this complicated disease caused by the destruction of insulin producing islet cells of the pancreas.
This excess glucose is responsible for most of the complications of diabetes, which include blindness, kidney failure, heart disease, stroke, neuropathy, and amputations. People with type 1 diabetes must take insulin several times a day and test their blood glucose concentration three to four times a day throughout their entire lives. After a year, 83 percent of these patients, on average, have no symptoms of diabetes and do not have to take insulin to maintain normal glucose concentrations in the blood.
However, the requirement for steroid immunosuppressant therapy to prevent rejection of the cells increases the metabolic demand on insulin-producing cells and eventually they may exhaust their capacity to produce insulin. In a recent study, they report that [17], seven of seven patients who received islet cell transplants no longer needed to take insulin, and their blood glucose concentrations were normal a year after surgery. In mammals, the pancreas contains three classes of cell types: the ductal cells, the acinar cells, and the endocrine cells. The cells of both the exocrine system—the acinar cells—and of the endocrine system—the islet cells—seem to originate from the ductal cells during development.
Many researchers maintain that some sort of islet stem cell can be found intermingled with ductal cells during fetal development and that these stem cells give rise to new endocrine cells as the fetus develops.
Some researchers believe that islet stem cell-like cells can be found in the pancreatic ducts and even in the islets themselves.
Ideally, stem cells should be able to multiply in culture and reproduce themselves exactly. Instead insulin is released in an all-or-nothing manner, with no fine-tuning for intermediate concentrations of glucose in the blood [5, 18].
For example, using mice, researchers have compared the insulin content of implants from several sources of stem cells—fresh human fetal pancreatic tissue, purified human islets, and cultured islet tissue [2]. Although differentiated beta cells are difficult to proliferate and culture, some researchers have had success in engineering such cells to do this.
The major problem in dealing with these cells is maintaining the delicate balance between growth and differentiation.
Some researchers believe that multipotent (capable of forming cells from more than one germ layer) stem cells are intermingled with mature, differentiated duct cells, while others believe that the duct cells themselves can undergo a differentiation, or a reversal to a less mature type of cell, which can then differentiate into an insulin-producing islet cell. Over the course of three to four weeks in culture, the cells secreted low amounts of insulin when exposed to low concentrations of glucose, and higher amounts of insulin when exposed to higher glucose concentrations.
If ductal cells die off but islet precursors proliferate, it is possible that the islet precursor cells may overtake the ductal cells in culture and make it appear that the ductal cells are dedifferentiating into stem cells.
Last year, they reported that pancreatic ductal epithelial cells from adult mice could be cultured to yield islet-like structures similar to the cluster of cells found by Bonner-Weir. He and his colleagues have discovered a population of stem-like cells within both the adult pancreas islets and pancreatic ducts. In theory, embryonic stem cells could be cultivated and coaxed into developing into the insulin-producing islet cells of the pancreas.
Recent studies in mice show that embryonic stem cells can be coaxed into differentiating into insulin-producing beta cells, and new reports indicate that this strategy may be possible using human embryonic cells as well. Bernat Soria and his colleagues at the Universidad Miguel Hernandez in San Juan, Alicante, Spain, added DNA containing part of the insulin gene to embryonic cells from mice. By using this method, the non-insulin-producing cells will be killed off and only insulin-producing cells should survive.
McKay and his colleagues started with embryonic stem cells and let them form embryoid bodies—an aggregate of cells containing all three embryonic germ layers.

The cells assemble into islet-like structures that contain another layer, which contains neurons and is similar to intact islets from the pancreas [11]. Last year, Melton, Nissim Benvinisty of the Hebrew University in Jerusalem, and Josef Itskovitz-Eldor of the Technion in Haifa, Israel, reported that human embryonic stem cells could be manipulated in culture to express the PDX-1 gene, a gene that controls insulin transcription [16]. The researchers found that embryonic stem cells that were allowed to spontaneously form embryoid bodies contained a significant percentage of cells that express insulin. This autoimmunity must be overcome if researchers hope to use transplanted cells to replace the damaged ones. Although many progenitor cells have been identified in adult tissue, few of these cells can be cultured for multiple generations.
In addition, if a procedure is carried out to place a stent or to open the biliary sphincter from within, there is a tiny risk of bleeding or perforation, which may require surgery to repair. By puncturing the liver under ultrasound guidance, a wire may be passed into the duodenum through the liver and a stent railroaded across the strictured part of the bile duct. Surgery to drain the abscess and remove dead tissue is often needed. Outlook (Prognosis) How the person does depends on how severe the infection is. Despite progress in understanding the underlying disease mechanisms for diabetes, there is still a paucity of effective therapies.
Each year, diabetes affects more people and causes more deaths than breast cancer and AIDS combined. Type 1 diabetes, also known as juvenile-onset diabetes, typically affects children and young adults. Frequent monitoring is important because patients who keep their blood glucose concentrations as close to normal as possible can significantly reduce many of the complications of diabetes, such as retinopathy (a disease of the small blood vessels of the eye which can lead to blindness) and heart disease, that tend to develop over time. The deleterious effect of steroids is greater for islet cell transplants than for whole-organ transplants.
Islet cells used in transplants are obtained from cadavers, and the procedure requires at least two cadavers per transplant.
The endocrine cells produce the hormones glucagon, somatostatin, pancreatic polypeptide (PP), and insulin, which are secreted into the blood stream and help the body regulate sugar metabolism. During development these endocrine cells emerge from the pancreatic ducts and form aggregates that eventually form what is known as Islets of Langerhans. The pancreas is located in the abdomen, adjacent to the duodenum (the first portion of the small intestine). Ductal cells can be distinguished from endocrine cells by their structure and by the genes they express.
Others maintain that the ductal cells can differentiate into islet precursor cells, while others hold that new islet cells arise from stem cells in the blood.
Therefore, many researchers believe that it will be preferable to develop a system in which stem or precursor cell types can be cultured to produce all the cells of the islet cluster in order to generate a population of cells that will be able to coordinate the release of the appropriate amount of insulin to the physiologically relevant concentrations of glucose in the blood.
They found that insulin content was initially higher in the fresh tissue and purified islets. For example, Fred Levine and his colleagues at the University of California, San Diego, have engineered islet cells isolated from human cadavers by adding to the cells' DNA special genes that stimulate cell proliferation.
Cells that proliferate well do not produce insulin efficiently, and those that do produce insulin do not proliferate well. The researchers have determined by immunochemistry and ultrastructural analysis that these clusters contain all of the endocrine cells of the islet [4]. According to the researchers, it might be possible in principle to do a biopsy and remove duct cells from a patient and then proliferate the cells in culture and give the patient back his or her own islets. According to Bonner-Weir, both dedifferentiated ductal cells and islet progenitor cells may occur in pancreatic ducts.
Using a host of islet-cell markers they identified cells that produced insulin, glucagon, somatostatin, and pancreatic polypeptide.
These cells do not express the marker typical of ductal cells, so they are unlikely to be ductal cells, according to Habener. With a ready supply of cultured stem cells at hand, the theory is that a line of embryonic stem cells could be grown up as needed for anyone requiring a transplant.
The insulin gene was linked to another gene that rendered the mice resistant to an antibiotic drug.
This is important in ensuring that undifferentiated cells are not implanted that could give rise to tumors [15]. They then selected a population of cells from the embryoid bodies that expressed the neural marker nestin (see Appendix B.
Mouse embryonic stem cells were derived from the inner cell mass of the early embryo (blastocyst) and cultured under specific conditions. Several research groups are trying to apply McKay's results with mice to induce human embryonic stem cells to differentiate into insulin-producing islets. In these experiments, researchers cultured human embryonic stem cells and allowed them to spontaneously form embryoid bodies (clumps of embryonic stem cells composed of many types of cells from all three germ layers).
Based on the binding of antibodies to the insulin protein, Itskovitz-Eldor estimates that 1 to 3 percent of the cells in embryoid bodies are insulin-producing beta-islet cells. Many researchers believe that at least initially, immunosuppressive therapy similar to that used in the Edmonton protocol will be beneficial. A major consideration is whether any precursor or stem-like cells transplanted into the body might revert to a more pluripotent state and induce the formation of tumors.
Embryonic stem cells show the greatest promise for generating cell lines that will be free of contaminants and that can self renew.
Functional beta-cell mass after transplantation of human fetal pancreatic cells: differentiation or proliferation? PDX-1 and cell-cell contact act in synergy to promote d-cell development in a human pancreatic endocrine precursor cell line.
Differentiation of Embryonic Stem Cells to Insulin-Secreting Structures Similiar to Pancreatic Islets.
Effects of eight growth factors on the differentiation of cells derived from human embryonic stem cells. Islet transplantation in seven patients with type 1 diabetes mellitus using a glucocorticoid-free immunosuppressive regimen. Diminished fraction of blockable ATP-sensitive K+ channels in islets transplanted into diabetic mice. Insulin-secreting cells derived from embryonic stem cells normalize glycemia in streptozotocininduced diabetic mice. Multipotential nestin-positive stem cells isolated from adult pancreatic islets differentiate ex vivo into pancreatic endocrine, exocrine, and hepatic phenotypes.
In particular, tumours that arise in the body and tail of the pancreas may be difficult to see on ultrasound. The problems with this procedure include bleeding and leakage of bile from the punctured liver. For years investigators have been making slow, but steady, progress on experimental strategies for pancreatic transplantation and islet cell replacement. Diabetes is the seventh leading cause of death in the United States today, with nearly 200,000 deaths reported each year. Diabetes develops when the body's immune system sees its own cells as foreign and attacks and destroys them.
People with type 2 diabetes can often control their blood glucose concentrations through a combination of diet, exercise, and oral medication. To prevent the body from rejecting the transplanted pancreas, patients must take powerful drugs that suppress the immune system for their entire lives, a regimen that makes them susceptible to a host of other diseases.
As a result, less than 8 percent of islet cell transplants performed before last year had been successful. The islet cells must be immunologically compatible, and the tissue must be freshly obtained—within eight hours of death. The acinar cells are part of the exocrine system, which manufactures digestive enzymes, and ductal cells from the pancreatic ducts, which connect the acinar cells to digestive organs. A cross-section of the pancreas shows the islet of Langerhans which is the functional unit of the endocrine pancreas.
For example, ductal cells typically express a gene known as cytokeratin-9 (CK-9), which encodes a structural protein. Researchers are using several approaches for isolating and cultivating stem cells or islet precursor cells from fetal and adult pancreatic tissue. Stem cells should also be able to differentiate in vivo to produce the desired kind of cell. However, with time, insulin concentration decreased in the whole tissue grafts, while it remained the same in the purified islet grafts. However, because once such cell lines that can proliferate in culture are established, they no longer produce insulin. According to the researchers, the major issue is developing the technology to be able to grow large numbers of these cells that will reproducibly produce normal amounts of insulin [9]. This would work with patients who have type 1 diabetes and who lack functioning beta cells, but their duct cells remain intact. Instead, they express a marker called nestin, which is typically found in developing neural cells.

By growing the cells in the presence of an antibiotic, only those cells that were activating the insulin promoter were able to survive. However, some researchers believe that it will be important to engineer systems in which all the components of a functioning pancreatic islet are allowed to develop. The embryoid bodies were then treated with various growth factors, including nerve growth factor. The researchers also found that cells in the embryoid bodies express glut-2 and islet-specific glucokinase, genes important for beta cell function and insulin secretion.
A potential advantage of embryonic cells is that, in theory, they could be engineered to express the appropriate genes that would allow them to escape or reduce detection by the immune system.
These risks would seemingly be lessened if fully differentiated cells are used in transplantation. However, most researchers agree that until a therapeutically useful source of human islet cells is developed, all avenues of research should be exhaustively investigated, including both adult and embryonic sources of tissue. Now, researchers have turned their attention to adult stem cells that appear to be precursors to islet cells and embryonic stem cells that produce insulin.
The American Diabetes Association estimates that nearly 16 million people, or 5.9 percent of the United States population, currently have diabetes.
As a result, the islet cells of the pancreas, which normally produce insulin, are destroyed. Type 2 diabetes often progresses to the point where only insulin therapy will control blood glucose concentrations. Many hospitals will not perform a pancreas transplant unless the patient also needs a kidney transplant. Because of the shortage of organ donors, these requirements are difficult to meet and the waiting list is expected to far exceed available tissue, especially if the procedure becomes widely accepted and available.
The hormones released from each type of islet cell have a role in regulating hormones released from other islet cells. Beta islet cells, on the other hand, express a gene called PDX-1, which encodes a protein that initiates transcription from the insulin gene. In addition, several new promising studies indicate that insulin-producing cells can be cultivated from embryonic stem cell lines. For diabetes therapy, it is not clear whether it will be desirable to produce only beta cells—the islet cells that manufacture insulin—or whether other types of pancreatic islet cells are also necessary. When cultured islets were implanted, however, their insulin content increased over the course of three months. The cell lines are further engineered to express the beta islet cell gene, PDX-1, which stimulates the expression of the insulin gene. However, the autoimmune destruction would still be a problem and potentially lead to destruction of these transplanted cells [3].
Before transplantation, they could be placed into nonimmunogenic material so that they would not be rejected and the patient would avoid the devastating effects of immunosuppressant drugs. Using a sophisticated five-stage culturing technique, the researchers were able to induce the cells to form islet-like clusters that resembled those found in native pancreatic islets. Cells with markers consistent with islet cells were selected for further differentiation and characterization. The researchers found that both untreated embryoid bodies and those treated with nerve growth factor expressed PDX-1. Although the researchers did not measure a time-dependent response to glucose, they did find that cells cultured in the presence of glucose secrete insulin into the culture medium. Others have suggested that a technology should be developed to encapsulate or embed islet cells derived from islet stem or progenitor cells in a material that would allow small molecules such as insulin to pass through freely, but would not allow interactions between the islet cells and cells of the immune system. In the absence of insulin, glucose cannot enter the cell and glucose accumulates in the blood. That is because the risk of infection due to immunosuppressant therapy can be a greater health threat than the diabetes itself.
Further, islet cell transplant recipients face a lifetime of immunosuppressant therapy, which makes them susceptible to other serious infections and diseases.
In the human pancreas, 65 to 90 percent of islet cells are beta cells, 15 to 20 percent are alpha-cells, 3 to 10 percent are delta cells, and one percent is PP cells.
Beta cells are located adjacent to blood vessels and can easily respond to changes in blood glucose concentration by adjusting insulin production. Studies by Bernat Soria and colleagues, for example, indicate that isolated beta cells—those cultured in the absence of the other types of islet cells—are less responsive to changes in glucose concentration than intact islet clusters made up of all islet cell types. The researchers concluded that precursor cells within the cultured islets were able to proliferate (continue to replicate) and differentiate (specialize) into functioning islet tissue, but that the purified islet cells (already differentiated) could not further proliferate when grafted. Such cell lines have been shown to propagate in culture and can be induced to differentiate to cells, which produce insulin. Type 2 diabetes patients might benefit from the transplantation of cells expanded from their own duct cells since they would not need any immunosuppression.
However, depending upon the growth factors added, the cells can differentiate into different types of cells, including liver, neural, exocrine pancreas, and endocrine pancreas, judged by the markers they express, and can be maintained in culture for up to eight months [20]. There is also some evidence that differentiated cells derived from embryonic stem cells might be less likely to cause immune rejection (see Chapter 10. Cells cultured in the presence of low concentrations of glucose differentiated and were able to respond to changes in glucose concentration by increasing insulin secretion nearly sevenfold.
The cells responded to normal glucose concentrations by secreting insulin, although insulin amounts were lower than those secreted by normal islet cells (see Figure 7.2.
When these cells (in purple) were grown in culture, they spontaneously formed three-dimentional clusters similar in structure to normal pancreatic islets. Embryonic stem cells prior to formation of the aggregated embryoid bodies did not express PDX-1. The researchers concluded that embryoid bodies contain a subset of cells that appear to function as beta cells and that the refining of culture conditions may soon yield a viable method for inducing the differentiation of beta cells and, possibly, pancreatic islets. Such encapsulated cells could secrete insulin into the blood stream, but remain inaccessible to the immune system. Type 2 diabetes, also called adult-onset diabetes, tends to affect older, sedentary, and overweight individuals with a family history of diabetes.
But if a patient is also receiving a new kidney and will require immunosuppressant drugs anyway, many hospitals will perform the pancreas transplant. Insulin facilitates uptake of glucose, the main fuel source, into cells of tissues such as muscle.
Islet cell clusters typically respond to higher-than-normal concentrations of glucose by releasing insulin in two phases: a quick release of high concentrations of insulin and a slower release of lower concentrations of insulin. Importantly, the researchers found, however, that it was also difficult to expand cultures of fetal islet progenitor cells in culture [7]. When transplanted into immune-deficient mice, the cells secrete insulin in response to glucose. However, many researchers believe that if there is a genetic component to the death of beta cells, then beta cells derived from ductal cells of the same individual would also be susceptible to autoimmune attack. The researchers then implanted the cells into the spleens of diabetic mice and found that symptoms of diabetes were reversed. Because expression of the PDX-1 gene is associated with the formation of beta islet cells, these results suggest that beta islet cells may be one of the cell types that spontaneously differentiate in the embryoid bodies. The researchers are currently investigating whether these cells will reverse diabetes in an experimental diabetes model in mice [6, 8]. Although having a replenishable supply of insulin-producing cells for transplant into humans may be a long way off, researchers have been making remarkable progress in their quest for it. When the cells were injected into diabetic mice, they survived, although they did not reverse the symptoms of diabetes.
As depicted in the chart, the pancreatic islet-like cells showed an increase in release of insulin as the glucose concentration of the culture media was increased. The researchers now think that nerve growth factor may be one of the key signals for inducing the differentiation of beta islet cells and can be exploited to direct differentiation in the laboratory. This is called insulin resistance and the result is the same as with type 1 diabetes—a build up of glucose in the blood. The resulting pancreas is a combination of a lobulated, branched acinar gland that forms the exocrine pancreas, and, embedded in the acinar gland, the Islets of Langerhans, which constitute the endocrine pancreas.
Extremely high concentrations of glucose may require that more insulin be released quickly, while intermediate concentrations of glucose can be handled by a balance of quickly and slowly released insulin. While some researchers have pursued the research on embryonic stem cells, other researchers have focused on insulin-producing precursor cells that occur naturally in adult and fetal tissues. When the pancreatic islet-like cells were implanted in the shoulder of diabetic mice, the cells became vascularized, synthesized insulin, and maintained physical characteristics similar to pancreatic islets. Complementing these findings is work done by Jon Odorico of the University of Wisconsin in Madison using human embryonic cells of the same source.
In preliminary findings, he has shown that human embryonic stem cells can differentiate and express the insulin gene [12].

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