Insulin-Producing Beta Cell Subtypes May Impact Diabetes Treatment


Researchers from the Oregon Stem Cell Center in Portland, Oregon have demonstrated the existence of at least four separate subtypes of human insulin-producing beta cells that may be important in the understanding and treatment of diabetes.

“This study marks the first description of several different kinds of human insulin producing beta cells,” said Markus Grompe of the Oregon Stem Cell Center at Oregon Health Science University. “Some of the cells are better at releasing insulin than others, whereas others may regenerate quicker. Therefore, it is possible that people with different percentages of the subtypes are more prone to diabetes. Further understanding of cell characteristics could be the key to uncovering new treatment options, as well as the reason why some people are diabetic and others are not.”

Diabetes mellitus affects more than 29 million people in the United States. There are two main types of diabetes mellitus, type I and type II. Type I diabetes mellitus is caused by insufficient production of insulin. Type II diabetes mellitus is caused by insulin resistance or the inability of the body to properly respond to the insulin produced by the body. Type I diabetes mellitus results from dysfunction or loss of insulin producing beta cells in the endocrine portion of the pancreas. Insulin is a hormone that helps the body keep normal blood sugar levels, and incorporate sugar in the bloodstream into cells to grow and repair tissues. Previously, only a single variety of beta cell was known to exist. However, using human pancreatic islets, or clusters of up to 4,000 cells, Grompe and colleagues identified a method to identify and isolate four distinct types of beta cells. They also found that hundreds of genes were differently expressed between cell subtypes and that these distinct beta cell subtypes produced different amounts of insulin.

All type 2 diabetics had abnormal percentages of the subtypes, suggesting a possible role in the disease process. Additional research is needed to determine how different forms of diabetes – and other diseases – affect the new cell subtypes, as well as how researchers may take advantage of these differences for medical treatment.

This work was published in: Craig Dorrell et al., “Human islets contain four distinct subtypes of β cells,” Nature Communications, 2016; 7: 11756 DOI: 10.1038/ ncomms11756.

Directly Reprogramming Gut Cells into Beta Cells to Treat Diabetes


Type 1 diabetes mellitus results from destruction of insulin-producing beta cells in the pancreas. Diabetics have to give themselves routine shots of insulin. The hope that stem cells offer is the production of cells that can replace the lost beta cells. “We are looking for ways to make new beta cells for these patients to one day replace daily insulin injections,” says Ben Stanger, MD, PhD, assistant professor of Medicine in the Division of Gastroenterology, Perelman School of Medicine at the University of Pennsylvania.

Some diabetics have had beta cells from cadavers transplanted into their bodies to replace the missing beta cells. Such a procedure shows that replacement therapy is, in principle possible. Therefore, transplanting islet cells to restore normal blood sugar levels in type 1 diabetics could treat and even cure disease. Unfortunately, transplantable islet cells are in short supply, and stem cell-based approaches have a long way to go before they reach the clinic. However, Stanger and his colleagues have tried a different strategy for treating type 1 diabetes. “It’s a powerful idea that if you have the right combination of transcription factors you can make any cell into any other cell. It’s cellular alchemy,” comments Stanger.

New research from Stanger and a postdoctoral fellow in his laboratory, Yi-Ju Chen that was published in Cell Reports, describes the production of new insulin-making cells in the gut of laboratory animals by introducing three new transcription factors. This experiment raises the prospect of using directly reprogrammed adult cells as a source for new beta cells.

In 2008, Stanger and others in Doug Melton’s laboratory used three beta-cell reprogramming factors (Pdx1, MafA, and Ngn3, collectively called PMN) to convert pancreatic acinar cells (the cells in the pancreas that secrete enzymes rather than hormones) into cells that had many of the features of pancreatic beta cells.

Following this report, the Stanger and his team set out to determine if other cells types could be directly reprogrammed into beta cells. “We expressed PMN in a wide spectrum of tissues in one-to-two-month-old mice,” says Stanger. “Three days later the mice died of hypoglycemia.” It was clear that Stanger and his crew were on to something. Further work showed that some of the mouse cells were making way too much extra insulin and that killed the mice.

When the dead mice were autopsied, “we saw transient expression of the three factors in crypt cells of the intestine near the pancreas,” explained Stanger.

They dubbed these beta-like, transformed cells “neoislet” cells. These neoislet cells express insulin and show outward structural features akin to beta cells. These neoislets also respond to glucose and release insulin when exposed to glucose. The cells were also able to improve hyperglycemia in diabetic mice.

Stanger and his co-workers also figured out how to turn on the expression of PMN in only the intestinal crypt cells to prevent the deadly whole-body hypoglycemia side effect that first killed the mice.

In culture, the expression of PMN in human intestinal ‘‘organoids,’ which are miniature intestinal units grown in culture, also converted intestinal epithelial cells into beta-like cells.

“Our results demonstrate that the intestine could be an accessible and abundant source of functional insulin-producing cells,” says Stanger. “Our ultimate goal is to obtain epithelial cells from diabetes patients who have had endoscopies, expand these cells, add PMN to them to make beta-like cells, and then give them back to the patient as an alternate therapy. There is a long way to go for this to be possible, including improving the functional properties of the cells, so that they more closely resemble beta cells, and figuring out alternate ways of converting intestinal cells to beta-like cells without gene therapy.”

This is hopefully a grand start to what might be a cure for type 1 diabetes.

Priming Cocktail for Cardiac Stem Cell Grafts


Approximately 700,000 Americans suffer a heart attack every year and stem cells have the potential to heal the damage wrought by a heart attack. Stem cells therapy has tried to take stem cells cultured in the laboratory and apply them to damaged tissues.

In the case of the heart, transplanted stem cells do not always integrate into the heart tissue. In the words of Jeffrey Spees, Associate Professor of Medicine at the University of Vermont, “many grafts simply didn’t take. The cells would stick or would die.”

To solve this problem, Spees and his colleagues examined ways to increase the efficiency of stem cell engraftment. In his experiments, Spees and others used mesenchymal stem cells from bone marrow. Mesenchymal stem cells are also called stromal cells because they help compose the spider web-like filigree within the bone marrow known as “stroma.” Even though the stroma does not make blood cells, it supports the hematopoietic stem cells that do make all blood cells.  Here is a picture of bone marrow stroma to give you an idea of what it looks like:

Immunohistochemistry-Paraffin: Bone marrow stromal cell antigen 1 Antibody [NBP2-14363] Staining of human smooth muscle shows moderate cytoplasmic positivity in smooth muscle cells.
Immunohistochemistry-Paraffin: Bone marrow stromal cell antigen 1 Antibody [NBP2-14363] Staining of human smooth muscle shows moderate cytoplasmic positivity in smooth muscle cells.
Stromal cells are known to secrete a host of molecules that protect injured tissue, promote tissue repair, and support the growth and proliferation of stem cells.

Spees suspected that some of the molecules made by bone marrow stromal cells could enhance the engraftment of stem cells patches in the heart. To test this idea, Spees and others isolated proteins from the culture medium of bone marrow stem cells grown in the laboratory and tested their ability to improve the survival and tissue integration of stem cell patches in the heart.

Spees tenacity paid off when he and his team discovered that a protein called “Connective tissue growth factor” or CTGF plus the hormone insulin were in the culture medium of these stem cells. Furthermore, when this culture medium was injected into the heart prior to treating them with stem cells, the stem cell patches engrafted at a higher rate.

“We broke the record for engraftment,” said Spees. Spees and his co-workers called their culture medium from the bone marrow stem cells “Cell-Kro.” Cell-Kro significantly increases cell adhesion, proliferation, survival, and migration.

Spees is convinced that the presence of CTGF and insulin in Cell-Kro have something to do with its ability to enhance stem cell engraftment. “Both CTGF and insulin are protective,” said Spees. “Together they have a synergistic effect.”

Spees is continuing to examine Cell-Kro in rats, but he wants to take his work into human trials next. His goal is to use cardiac stem cells (CSCs) from humans, which already have a documented ability to heal the heart after a heart attack. See here, here, and here.

“There are about 650,000 bypass surgeries annually,” said Spees. “These patients could have cells harvested at their first surgery and banked for future application. If they return for another procedure, they could then receive a graft of their own cardiac progenitor cells, primed in Cell-Kro, and potentially re-build part of their injured heart.”

Human Stem Cells Elucidate the Mechanisms of Beta-Cell Failure in Diabetes


Wolfram syndrome is a rare form of diabetes characterized by high blood sugar levels that result from insufficient levels of the hormone insulin.  The chronically high blood sugar levels cause degeneration of the optic nerve, leading to progressive vision loss (optic atrophy).  Wolfram syndrome patients often also have abnormal pituitary glands that release abnormally low levels of the hormone vasopressin (also known as antidiuretic hormone or ADH), which causes hearing loss caused by changes in the inner ear (sensorineural deafness), urinary tract problems, reduced amounts of the sex hormone testosterone in males (hypogonadism), or neurological or psychiatric disorders.

Diabetes mellitus is typically the first symptom of Wolfram syndrome, usually diagnosed around age 6. Nearly everyone with Wolfram syndrome who develops diabetes mellitus requires insulin replacement therapy. Optic atrophy is often the next symptom to appear, usually around age 11. The first signs of optic atrophy are loss of color vision and peripheral (side) vision. Over time, the vision problems get worse, and people with optic atrophy are usually blind within approximately 8 years after signs of optic atrophy first begin.

Mutations in the WFS1 gene cause more than 90 percent of the cases of Wolfram syndrome type 1.  The WFS1 gene encodes a protein called wolframin that regulates the amount of calcium in cells.  A proper calcium balance is important for a whole host of cellular processes, including cell-to-cell communication, the tensing (contraction) of muscles, and protein processing.  Wolframin protein is found in many different tissues, such as the pancreas, brain, heart, bones, muscles, lung, liver, and kidneys.  Inside cells, wolframin is in the membrane of a cell structure called the endoplasmic reticulum that is involved in protein production, processing, and transport. Wolframin is particularly important in the pancreas, where it helps process proinsulin into mature hormone insulin, the hormone that helps control blood sugar levels.

WFS1 gene mutations lead to the production of a sub-functional versions of wolframin.  As a result, calcium levels within cells are not properly regulated and the endoplasmic reticulum does not work correctly.  When the endoplasmic reticulum does not have enough functional wolframin, the cell triggers its own cell death (apoptosis).  In the pancreas, the cells that make insulin (beta cells) die off, which causes diabetes mellitus.  The gradual loss of cells along the optic nerve eventually leads to blindness, and the death of cells in other body systems likely causes the various signs and symptoms of Wolfram syndrome type 1.

A certain mutation in the CISD2 gene also causes Wolfram syndrome type 2. The CISD2 gene provides instructions for making a protein that is in the outer membrane of cell structures called mitochondria,the energy-producing centers of cells.  Even though the function of the CISD2 protein is unknown, CISD2 mutations produce nonfunctional CISD2 protein that causes mitochondria to eventually break down. This accelerates the onset of cell death.  Cells with high energy demands such as nerve cells in the brain, eye, or gastrointestinal tract are most susceptible to cell death due to reduced energy, and people with mutations in the CISD2 gene have ulcers and bleeding problems in addition to the usual Wolfram syndrome features.

Some people with Wolfram syndrome do not have an identified mutation in either the WFS1 or CISD2 gene. The cause of the condition in these individuals is unknown.

Now that you have a proper introduction to Wolfram syndrome, scientists from the New York Stem Cell Foundation and Columbia University Medical Center have produce induced pluripotent stem cells (iPSCs) from skin samples provided by Wolfram syndrome patients.  All of the patients who volunteered for this study were recruited from the Naomi Berrie Diabetes Center and had childhood onset diabetes and required treatment with injected insulin, and all had vision loss.  Control cell lines that did not have mutations in WFS1 were obtained from Coriell Research for Medical Research.

These skin samples contained cells known as fibroblasts and these were reprogrammed into induced pluripotent stem cells.  In order to show that these cells were truly iPSCs, this group implanted them underneath the kidney capsule of immuno-compromised mice, and they formed the teratoma tumors so characteristic of these cells.

When these iPSCs were differentiated into insulin-secreting pancreatic beta cells, Linshan Shang and her colleagues discovered that the beta cells made from cells that did not come from Wolfram syndrome patients secreted normal levels of insulin.  However, those beta cells made from iPSCs derived from Wolfram patients failed to secrete normal quantities of insulin either in culture or when transplanted into the bodies of laboratory animals.  Further investigations of these cells showed these beta cells showed elevated levels of stress in the endoplasmic reticulum as a result of an accumulation of unfolded proteins.

What on earth is endoplasmic reticulum protein-folding stress?  First some cell biology.  When the cell needs to make a protein that will be secreted, embedded in a membrane or vesicle. that protein begins its life on ribosomes (protein synthesis factories of the cell) in the cytoplasm, but later those ribosomes are dragged to a cellular structure called the endoplasmic reticulum.  While on the surface of the endoplasmic reticulum, the ribosome completes the synthesis of the protein and extrudes the protein into the interior of the endoplasmic reticulum or embeds the protein into the endoplasmic reticulum membrane.  From there, the protein is trafficked in a vesicle to another subcellular structure called the Golgi apparatus, were it undergoes further modification, and from the Golgi apparatus, the protein goes to the membrane, secretory vesicle or other places.

If the proteins in the endoplasmic reticulum cannot fold properly, they clump and build up inside the endoplasmic reticulum, and this induces the ERAD or Endoplasmic Reticulum-Associated Protein Degradation response.  The players in the ERAD response are shown below.  As you can see, this response is rather complicated, but if it fails to properly clear the morass of unfolded proteins in the endoplasmic reticulum, then the cell will undergo programmed cell death.

ERAD Response

However, this research team did not stop there.  When they treated the cultured beta cells made from cells taken from Wolfram syndrome patients with a chemical called 4-phenyl butyric acid, the stress on the cells was relieved and the cells survived.  This experiment shows that relieving this unfolded protein stress is a potential target for clinical intervention.

“These cells represent an important mechanism that causes beta-cell failure in diabetes.  This human iPS cell model represents a significant step forward in enabling the study of this debilitating disease and the development of new treatments,” said Dieter Egli, the principal investigator of the study, and senior research fellow at the New York Stem Cell Foundation.

Because all forms of diabetes mellitus ultimately result from an inability of the pancreatic beta cells to provide sufficient quantities of insulin in response to a rise in blood sugar concentrations, this Wolfram patient stem cell model enables an analysis of a more specific pathway that leads to beta-cell failure in more prevalent forms of diabetes.  Furthermore, this strategy enables the testing of strategies to restore beta-cell function that may be applicable to all types of diabetes.

Susan L. Solomon of the New York Stem Cell Foundation, said, “Using stem cell technology, we were able to study a devastating condition to better understand what causes the diabetes syndromes as well as discover possible new drug targets.”

Rudolph L. Leibel, a professor of diabetes research and co-author of this study, said, “This report highlights again the utility of close examination of rare disorders as a path to elucidating more common ones.  Our ability to create functional insulin-producing cells using stem cell techniques on skin cells from patients with Wolfram’s syndrome has helped to uncover the role of ER stress in the pathogenesis of diabetes.  The use of drugs that reduce such stress may prove useful in the prevention and treatment of diabetes.”

The ERAD response seems to play a role in the survival of insulin-producing beta cells in both type 1 and type 2 diabetes.  The ERAD response opposes the stress of the immune assault in type 1 diabetes and the metabolic stress of high blood glucose levels in both types of diabetes.  When the ERAD response fails, cell death ensues and this reduces the number of insulin-producing cells.

Isolation of Pancreatic Stem Cells


There has been a robust debate as to whether or not the pancreas has a stem cell population. Several studies suggested that the pancreatic duct cells could differentiate into hormone-secreting pancreatic cells. Unfortunately, when the cells of the pancreatic duct are marked, they clearly never contribute to regeneration of the pancreas. According to an article that appeared in the journal Developmental Cell by Oren Ziv, Benjamin Glaser, and Yuval Dor entitled “The Plastic Pancreas,” tying off the pancreatic duct kills off the acinar cells, but it leads to a large increase in the number of hormone-secreting beta cells. Something seems to be contributing cells to the adult pancreas. However when lineage studies tried to confirm that the pancreatic duct cells formed the new cells, it failed to find any connection between the new cells in the pancreas and the duct.

Pancreas

Recent experiments from Chris Wright’s lab suggest that the acinar cells are a population of progenitor cells that divide and differentiate into different kinds of pancreatic cell types after injury to the pancreas. A similar result was observed in work by Desai and others. If that’s not odd enough for you, another set of experiments from Pedro Herrera research group has shown once all the insulin-secreting beta cells are killed off, the adjacent glucagon-secreting cells transdifferentiate into insulin-secreting beta cells. Therefore, something interesting is afoot in the pancreas.

All these experiments were done with rodents. Whether or not they are transferable to human remains uncertain. Nevertheless, a fascinating paper in EMBO Journal from Hans Clevers lab at the Hubrecht Institute, Utrecht, Netherlands haws succeeded in culturing pancreatic precursor cells.

Here’s how they did it. Clevers and his crew took the pancreatic duct of mice and partially tied it off. In order to stem cells from the digestive tract to grow, they must upregulate a signaling pathway called the “Wnt” pathway. The Wnt pathway is quiet in the pancreas, but one the pancreas is injured, the Wnt pathway swings into gear and the cells begin to divide.

When Clevers and company dropped pancreatic duct tissue into culture, Wnt signaling activity soared and the cells grew into a mini-organ (organoid) that resembled and tiny pancreas in a culture dish. In fact, a single cell taken from the pancreatic duct could be cultured into an organoid.

Establishment of the pancreas organoids from adult pancreatic ducts. (A) Scheme representing the isolation method of the pancreatic ducts and the establishment of the pancreatic organoid culture. The pancreatic ducts were isolated from adult mouse pancreas after digestion, handpicked manually and embedded in matrigel. Twenty-four hours after, the pancreatic ducts closed and generated cystic structures. After several days in culture, the cystic structures started folding and budding. (B) Representative serial DIC images of a pancreatic organoid culture growing at the indicated time points. Magnifications: × 10 (days 0, 2, 4, 6, and 8) and × 4 (day 10 onwards). (C) Growth curves of pancreas cultures originated from isolated pancreatic ducts cultured as described in Materials and methods. Note that the cultures followed an exponential growth curve within each time window analysed. Graphs illustrate the number of cells counted per well at each passage from passages P1–P3 (left), P5–P7 (middle) and P10–P12 (right). The doubling time (hours) is indicated in each graph. Data represent mean±s.e.m., n=2. (D) Representative DIC images of XGAL staining in WT (left), Axin2-LacZ (middle) and Lgr5-LacZ (right) derived pancreas organoids.
Establishment of the pancreas organoids from adult pancreatic ducts. (A) Scheme representing the isolation method of the pancreatic ducts and the establishment of the pancreatic organoid culture. The pancreatic ducts were isolated from adult mouse pancreas after digestion, handpicked manually and embedded in matrigel. Twenty-four hours after, the pancreatic ducts closed and generated cystic structures. After several days in culture, the cystic structures started folding and budding.  (B) Representative serial DIC images of a pancreatic organoid culture growing at the indicated time points. Magnifications: × 10 (days 0, 2, 4, 6, and 8) and × 4 (day 10 onwards). (C) Growth curves of pancreas cultures originated from isolated pancreatic ducts cultured as described in Materials and methods. Note that the cultures followed an exponential growth curve within each time window analysed. Graphs illustrate the number of cells counted per well at each passage from passages P1–P3 (left), P5–P7 (middle) and P10–P12 (right). The doubling time (hours) is indicated in each graph. Data represent mean±s.e.m., n=2. (D) Representative DIC images of XGAL staining in WT (left), Axin2-LacZ (middle) and Lgr5-LacZ (right) derived pancreas organoids.

This experiment shows that there are techniques for growing unlimited quantities of pancreatic cells.  The therapeutic possibilities of this technology is tremendous.  In Clever’s own words, “We have found a way to activate the Wnt pathway to produce an unlimited expansion of pancreatic stem cells isolated from mice.  By changing the growth conditions we can select two different fates for the stem cells and generate large numbers of either hormone-producing beta cells or pancreatic duct cells.”

Can this work with human pancreatic duct cells?  That is the $64,000 question.   Clevers and his groups will almost certainly try to answer this questions next.  If Clevers and his crew can get this to work, then the possibilities are vast indeed.

Stem Cells Analyze the Cause and Treatment of Diabetes


A research group that is part of the New York Stem Cell Foundation or NYSCF has generated patient-specific beta cells (the cells that secrete insulin in the pancreas), and these cultured beta cells accurately recapitulate the features of maturity-onset diabetes of the young or MODY.

In this research, NYSCF scientists and researchers from the Naomi Berrie Diabetes Center of Columbia University used skin cells from MODY patients to produce induced pluripotent stem cells (iPSCs) that were differentiated in the culture dish to form insulin-secreting pancreatic beta cells (if that sounds like a lot of work that’s because it is).

Other laboratories have succeeded in generating beta cells from embryonic stem cells and iPSCs, but questions remain as to whether or not these cells accurately recapitulate genetically-acquired forms of diabetes mellitus.

Senior co-author of this study, Dieter Egli, a senior research fellow at NYSCF, said: “We focused on MODY, a form of diabetes that affects approximately one in 10,000 people. While patients and other models have yielded important clinical insights into this disease, we were particularly interested in its molecular aspects – how specific genes can affect responses to glucose by the beta cell.”

MODY is a genetically inherited form of diabetes mellitus, and the most common form of MODY, type 2, results from mutations in the glucokinase or GCK gene. Glucokinase is a liver-specific enzyme and it adds a phosphate group to sugar so that the sugar can be broken down to energy by means of a series of reactions known as “glycolysis.” Glucokinase catalyzes the first step of glycolysis in the liver and in pancreatic beta cells. Mutations in GCK increase the sugar concentration in order for GCK to properly metabolize sugar, and this increases blood sugar levels and increases the risk for vascular complications.

The steps of the enzymatic pathway glycolysis, which is used by cells to degrade sugar to energy.
The steps of the enzymatic pathway glycolysis, which is used by cells to degrade sugar to energy.

MODY patients are usually misdiagnosed as type 1 or type 2 diabetics, but proper diagnosis can greatly alter the treatment of this disease. Correctly diagnosing MODY can also alert family members that they too might be carriers or even susceptible to this disease.

NYSCF researchers worked with skin cells from two patients from the Berrie Center who had type 2 MODY. After reprogramming these skin cells to become iPSCs, they differentiated the cells into beta cells, These cells had the impaired GCK activity, but in order to compare them to something, the NYSCF group also made iPSCs with a genetically engineered version of GCK that was impaired in the same way as the GCK gene in these two patients, and another cell line with normal versions of the GCK gene. They used these iPSCs to make cultured beta cells.

“Our ability to create insulin-producing cells from skin cells, and then to manipulate the GCK gene in these cells using recently developed molecular methods, made it possible to definitely test several critical aspects of the utility of stem cells for the study of human disease,” said Haiqing Hua, lead author of this paper and a postdoctoral fellow in the Division of Molecular Genetics.

The beta cells made from these iPSCs were transplanted into mice and these mice were given an oral glucose tolerance test. An oral glucose tolerance test is used to diagnose diabetes mellitus. The patient fasts for 12 hours and then is given a concentrated glucose concentration (4 grams per kilogram body weight), which the patient drinks and then the blood glucose level is examined at 30-minute intervals. The blood glucose levels of diabetic patients will rise and only go down very sluggishly whereas the blood glucose levels of a nondiabetic patient will rise and then decrease as their pancreatic beta cells start to make insulin. Insulin signals cells to take up glucose and utilize it, which lowers the blood glucose levels. A reading of over 200 milligrams per deciliters

When mice with the transplanted beta cells made from iPSCs were given oral glucose tolerance tests, the beta cells from MODY patients   showed decreased sensitivity to glucose.  In other words, even in the presence of high blood sugar levels, the beta cells made from iPSCs that came from MODY patients secreted little insulin.  However, high levels of amino acids, which are the precursors of proteins, also induces insulin secretion, and in this case, beta cells from MODY patients secreted sufficient quantities of insulin.

When the iPSCs made from cells taken from MODY patients were subjected to genetic engineering techniques that repaired the defect in the GCK gene, these iPSCs differentiated into beta cells that responded normally to high blood glucose levels and secreted insulin when the blood glucose levels rose.

By making beta cells from MODY patients and then correcting the genetic defect in them and returning them to normal glucose sensitivity, NYSCF scientists showed that this type of diagnosis could lead to cures for MODY patients.

“These studies provide a critical proof-of-principle that genetic characteristics of patient-specific insulin-producing cells can be recapitulated through use of stem cell techniques and advanced molecular biological manipulation.  This opens up strategies for the development of new approaches to the understanding, treatment, and, ultimately, prevention of more common types of diabetes,” said Rudolph Leibel of the Columbia University Medical Center.

No Evidence of Regeneration of Insulin-Making Cells in the Pancreas


Type 1 diabetics and severe type 2 diabetics show reduction of insulin secretion as a result of destruction of the specific cells in the pancreas that produce insulin. These cells, the so-called beta cells, suffer destruction from the patient’s immune system (type 1 diabetes) or from overwork (type 2 diabetes). The holy grail of diabetes treatment is the regeneration of lost beta cells.

pancreas beta cells

Several reports have marshaled evidence that the pancreatic beta cells do regenerate, but the constant assault by the immune system eventually destroys all the beta cells. Other reports have argued that a stem cell population in the ductal system of the pancreas can replenish the beta cells. Thus, augmenting beta cell regeneration seemed to be simply a matter of employing the already-present regenerative properties of the pancreas.

Unfortunately, a recent study seems to put the kibosh on any hope that the pancreatic beta cells regenerate. This new study was published in the Journal of Clinical Investigation. In this paper, researchers at Children’s Hospital of Pittsburgh report were unable to find signs of new beta cell production in several common models of pancreatic injury (see Xiao, X., et al. 2013. No evidence for beta-cell neogenesis in murine adult pancreas. J Clin Invest., 123(5):2207-17).

“Overall, the paper puts one more nail in what was already becoming an increasingly tight coffin for what had been the prevailing hypothesis about β-cell neogenesis in adult mice,” said Fred Levine, who studies β-cell regeneration at Sanford Burnham Medical Research Institute in La Jolla, California and was not involved in the study. Still, Levine cautions that this negative result does not completely rule out adult regeneration of β-cells in other injury models.

To detect the formation of new beta cells, George Gittes and his colleagues used an old cell tracking method, but applied it in a different manner. They used two fluorescent tags in transgenic mice: a red tag that targets a protein in the cell membrane of most cells in the body, except for insulin producing cells, and a green tag that only tagged pancreatic beta cells. Gittes team looked for cells that turned on their insulin genes for the first time during a 40–48 hour window. The cells, therefore, would express both tags and, as a result, appeared yellow.

The yellow transition was detected in embryonic mice, where neogenesis (new beta cell production) is expected to occur. But when the researchers examined adult cells, they saw no yellow cells—meaning no evidence of neogenesis. They repeated this experiment in several common models of pancreatic damage. For example, the pancreatic duct ligation model (PDL damages other pancreatic cell types but not β-cells. The absence of detectable neogenesis in these models “puts pressure on us to find models in which there is neogenesis,” said Gittes. But he remains “very confident” that there are other models in which neogenesis occurs.

In fact, several models not tested in this paper have shown evidence of neogenesis, including one of Gittes’ own. In 2011, in which his team found evidence of neogenesis in a mice who beta cells were engineered to express diphtheria toxin receptors, that led to their death (see Criscimanna, A., et al. 2011. Duct cells contribute to regeneration of endocrine and acinar cells following pancreatic damage in adult mice. Gastroenterology, 141(4):1451-62). In 2010, two other research groups, including one headed by Levine, also demonstrated neogenesis in adult mice through trandifferentiation of preexisting α-cells in pancreatic islets into β-cells (Thorel, F., et al. 2010. Conversion of adult pancreatic alpha-cells to beta-cells after extreme beta-cell loss. Nature,464(7292):1149-54 and Chung, C.H., et al. 2010. Pancreatic β-cell neogenesis by direct conversion from mature α-cells. Stem Cells, 28(9):1630-8).

“Overall, I believe that the pathway by which β-cell regeneration occurs…is likely to vary depending on the stimulus for regeneration,” said Levine. Therefore, the current work does not rule out neogenesis, even from duct cells, in other models. “I would argue that the old cliché, ‘Absence of evidence is not evidence of absence’ should be kept in mind when evaluating studies like this.”