Activation of pancreatic-duct-derived progenitor cells during pancreas regeneration in adult rats

β-cell neogenesis: A rising star to rescue diabetes mellitus

BACKGROUND

Diabetes Mellitus (DM), a chronic metabolic disease characterized by elevated blood glucose, is caused by various degrees of insulin resistance and dysfunctional insulin secretion, resulting in hyperglycemia. The loss and failure of functional β-cells are key mechanisms resulting in type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM).

AIM OF REVIEW

Elucidating the underlying mechanisms of β-cell failure, and exploring approaches for β-cell neogenesis to reverse β-cell dysfunction may provide novel strategies for DM therapy.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Emerging studies reveal that genetic susceptibility, endoplasmic reticulum (ER) stress, oxidative stress, islet inflammation, and protein modification linked to multiple signaling pathways contribute to DM pathogenesis. Over the past few years, replenishing functional β-cell by β-cell neogenesis to restore the number and function of pancreatic β-cells has remarkably exhibited a promising therapeutic approach for DM therapy. In this review, we provide a comprehensive overview of the underlying mechanisms of β-cell failure in DM, highlight the effective approaches for β-cell neogenesis, as well as discuss the current clinical and preclinical agents research advances of β-cell neogenesis. Insights into the challenges of translating β-cell neogenesis into clinical application for DM treatment are also offered.

Development, regeneration, and physiological expansion of functional β-cells: Cellular sources and regulators

Pancreatic regeneration is a complex process observed in both normal and pathological conditions. The aim of this review is to provide a comprehensive understanding of the emergence of a functionally active population of insulin-secreting β-cells in the adult pancreas. The renewal of β-cells is governed by a multifaceted interaction between cellular sources of genetic and epigenetic factors. Understanding the development and heterogeneity of β-cell populations is crucial for functional β-cell regeneration. The functional mass of pancreatic β-cells increases in situations such as pregnancy and obesity. However, the specific markers of mature β-cell populations and postnatal pancreatic progenitors capable of increasing self-reproduction in these conditions remain to be elucidated. The capacity to regenerate the β-cell population through various pathways, including the proliferation of pre-existing β-cells, β-cell neogenesis, differentiation of β-cells from a population of progenitor cells, and transdifferentiation of non-β-cells into β-cells, reveals crucial molecular mechanisms for identifying cellular sources and inducers of functional cell renewal. This provides an opportunity to identify specific cellular sources and mechanisms of regeneration, which could have clinical applications in treating various pathologies, including in vitro cell-based technologies, and deepen our understanding of regeneration in different physiological conditions.

EZH2 inhibitors promote β-like cell regeneration in young and adult type 1 diabetes donors

β-cells are a type of endocrine cell found in pancreatic islets that synthesize, store and release insulin. In type 1 diabetes (T1D), T-cells of the immune system selectively destroy the insulin-producing β-cells. Destruction of these cells leads to a lifelong dependence on exogenous insulin administration for survival. Consequently, there is an urgent need to identify novel therapies that stimulate β-cell growth and induce β-cell function. We and others have shown that pancreatic ductal progenitor cells are a promising source for regenerating β-cells for T1D owing to their inherent differentiation capacity. Default transcriptional suppression is refractory to exocrine reaction and tightly controls the regenerative potential by the EZH2 methyltransferase. In the present study, we show that transient stimulation of exocrine cells, derived from juvenile and adult T1D donors to the FDA-approved EZH2 inhibitors GSK126 and Tazemetostat (Taz) influence a phenotypic shift towards a β-like cell identity. The transition from repressed to permissive chromatin states are dependent on bivalent H3K27me3 and H3K4me3 chromatin modification. Targeting EZH2 is fundamental to β-cell regenerative potential. Reprogrammed pancreatic ductal cells exhibit insulin production and secretion in response to a physiological glucose challenge ex vivo. These pre-clinical studies underscore the potential of small molecule inhibitors as novel modulators of ductal progenitor differentiation and a promising new approach for the restoration of β-like cell function.

Regeneration of Pancreatic Beta Cells by Modulation of Molecular Targets Using Plant-Derived Compounds: Pharmacological Mechanisms and Clinical Potential

Type 2 diabetes (T2D) is characterized by pancreatic beta-cell dysfunction, increased cell death and loss of beta-cell mass despite chronic treatment. Consequently, there has been growing interest in developing beta cell-centered therapies. Beta-cell regeneration is mediated by augmented beta-cell proliferation, transdifferentiation of other islet cell types to functional beta-like cells or the reprograming of beta-cell progenitors into fully differentiated beta cells. This mediation is orchestrated by beta-cell differentiation transcription factors and the regulation of the cell cycle machinery. This review investigates the beta-cell regenerative potential of antidiabetic plant extracts and phytochemicals. Various preclinical studies, including in vitro, in vivo and ex vivo studies, are highlighted. Further, the potential regenerative mechanisms and the intra and extracellular mediators that are of significance are discussed. Also, the potential of phytochemicals to translate into regenerative therapies for T2D patients is highlighted, and some suggestions regarding future perspectives are made.

Pharmacological inhibition of human EZH2 can influence a regenerative β-like cell capacity with in vitro insulin release in pancreatic ductal cells

BACKGROUND

Therapeutic replacement of pancreatic endocrine β-cells is key to improving hyperglycaemia caused by insulin-dependent diabetes . Whilst the pool of ductal progenitors, which give rise to the endocrine cells, are active during development, neogenesis of islets is repressed in the human adult. Recent human donor studies have demonstrated the role of EZH2 inhibition in surgically isolated exocrine cells showing reactivation of insulin expression and the influence on the H3K27me3 barrier to β-cell regeneration. However, those studies fall short on defining the cell type active in transcriptional reactivation events. This study examines the role of the regenerative capacity of human pancreatic ductal cells when stimulated with pharmacological inhibitors of the EZH2 methyltransferase.

RESULTS

Human pancreatic ductal epithelial cells were stimulated with the EZH2 inhibitors GSK-126, EPZ6438, and triptolide using a 2- and 7-day protocol to determine their influence on the expression of core endocrine development marker NGN3, as well as β-cell markers insulin, MAFA, and PDX1. Chromatin immunoprecipitation studies show a close correspondence of pharmacological EZH2 inhibition with reduced H3K27me3 content of the core genes, NGN3, MAFA and PDX1. Consistent with the reduction of H3K27me3 by pharmacological inhibition of EZH2, we observe measurable immunofluorescence staining of insulin protein and glucose-sensitive insulin response.

CONCLUSION

The results of this study serve as a proof of concept for a probable source of β-cell induction from pancreatic ductal cells that are capable of influencing insulin expression. Whilst pharmacological inhibition of EZH2 can stimulate secretion of detectable insulin from ductal progenitor cells, further studies are required to address mechanism and the identity of ductal progenitor cell targets to improve likely methods designed to reduce the burden of insulin-dependent diabetes.

Direct Reprogramming of Somatic Cells into Induced β-Cells: An Overview

The persistent shortage of insulin-producing islet mass or β-cells for transplantation in the ever-growing diabetic population worldwide is a matter of concern. To date, permanent cure to this medical complication is not available and soon after the establishment of lineage-specific reprogramming, direct β-cell reprogramming became a viable alternative for β-cell regeneration. Direct reprogramming is a straightforward and powerful technique that can provide an unlimited supply of cells by transdifferentiating terminally differentiated cells toward the desired cell type. This approach has been extensively used by multiple groups to reprogram non-β-cells toward insulin-producing β-cells. The β-cell identity has been achieved by various studies via ectopic expression of one or more pancreatic-specific transcription factors in somatic cells, bypassing the pluripotent state. This work highlights the importance of the direct reprogramming approaches (both integrative and non-integrative) in generating autologous β-cells for various applications. An in-depth understanding of the strategies and cell sources could prove beneficial for the efficient generation of integration-free functional insulin-producing β-cells for diabetic patients lacking endogenous β-cells.

Therapeutic Strategies Targeting Pancreatic Islet β-Cell Proliferation, Regeneration, and Replacement

Diabetes results from insufficient insulin production by pancreatic islet β-cells or a loss of β-cells themselves. Restoration of regulated insulin production is a predominant goal of translational diabetes research. Here, we provide a brief overview of recent advances in the fields of β-cell proliferation, regeneration, and replacement. The discovery of therapeutic targets and associated small molecules has been enabled by improved understanding of β-cell development and cell cycle regulation, as well as advanced high-throughput screening methodologies. Important findings in β-cell transdifferentiation, neogenesis, and stem cell differentiation have nucleated multiple promising therapeutic strategies. In particular, clinical trials are underway using in vitro-generated β-like cells from human pluripotent stem cells. Significant challenges remain for each of these strategies, but continued support for efforts in these research areas will be critical for the generation of distinct diabetes therapies.

A potential fate decision landscape of the TWEAK/Fn14 axis on stem and progenitor cells: a systematic review

Stem and progenitor cells (SPCs) possess self-remodeling ability and differentiation potential and are responsible for the regeneration and development of organs and tissue systems. However, the precise mechanisms underlying the regulation of SPC biology remain unclear. Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) acts on miscellaneous cells via binding to fibroblast growth factor-inducible 14 (Fn14) and exerts pleiotropic functions in the regulation of divergent stem cell fates. TWEAK/Fn14 signaling can regulate the proliferation, differentiation, and migration of multiple SPCs as well as tumorigenesis in certain contexts. Although TWEAK’s roles in modulating multiple SPCs are sparsely reported, the systemic effector functions of this multifaceted protein have not been fully elucidated. In this review, we summarized the fate decisions of TWEAK/Fn14 signaling on multiple stem cells and characterized its potential in stem cell therapy.

Magnetic Resonance Imaging of Transplanted Porcine Neonatal Pancreatic Cell Clusters Labeled with Exendin-4-Conjugated Manganese Magnetism-Engineered Iron Oxide Nanoparticles

Recently, we have shown that manganese magnetism-engineered iron oxide nanoparticles (MnMEIO NPs) conjugated with exendin-4 (Ex4) act as a contrast agent that directly trace implanted mouse islet β-cells by magnetic resonance imaging (MRI). Here we further advanced this technology to track implanted porcine neonatal pancreatic cell clusters (NPCCs) containing ducts, endocrine, and exocrine cells. NPCCs from one-day-old neonatal pigs were isolated, cultured for three days, and then incubated overnight with MnMEIO-Ex4 NPs. Binding of NPCCs and MnMEIO-Ex4 NPs was confirmed with Prussian blue staining in vitro prior to the transplantation of 2000 MnMEIO-Ex4 NP-labeled NPCCs beneath the left renal capsule of six nondiabetic nude mice. The 7.0 T MRI on recipients revealed persistent hypointense areas at implantation sites for up to 54 days. The MR signal intensity of the graft on left kidney reduced 62–88% compared to the mirror areas on the contralateral kidney. Histological studies showed colocalization of insulin/iron and SOX9/iron staining in NPCC grafts, indicating that MnMEIO-Ex4 NPs were taken up by mature β-cells and pancreatic progenitors. We conclude that MnMEIO-Ex4 NPs are excellent contrast agents for detecting and long-term monitoring implanted NPCCs by MRI.

On the Origin of Pancreatic Cancer: Molecular Tumor Subtypes in Perspective of Exocrine Cell Plasticity

Pancreatic ductal adenocarcinoma (PDAC) is a devastating type of cancer. While many studies have shed light into the pathobiology of PDAC, the nature of PDAC's cell of origin remains under debate. Studies in adult pancreatic tissue have unveiled a remarkable exocrine cell plasticity including transitional states, mostly exemplified by acinar to ductal cell metaplasia, but also with recent evidence hinting at duct to basal cell transitions. Single-cell RNA sequencing has further revealed intrapopulation heterogeneity among acinar and duct cells. Transcriptomic and epigenomic relationships between these exocrine cell differentiation states and PDAC molecular subtypes have started to emerge, suggesting different ontogenies for different tumor subtypes. This review sheds light on these diverse aspects with particular focus on studies with human cells. Understanding the "masked ball" of exocrine cells at origin of PDAC and leaving behind the binary acinar vs duct cell classification may significantly advance our insights in PDAC biology.

Stem/progenitor cells in normal physiology and disease of the pancreas

Though embryonic pancreas progenitors are well characterised, the existence of stem/progenitor cells in the postnatal mammalian pancreas has been long debated, mainly due to contradicting results on regeneration after injury or disease in mice. Despite these controversies, sequencing advancements combined with lineage tracing and organoid technologies indicate that homeostatic and trigger-induced regenerative responses in mice could occur. The presence of putative progenitor cells in the adult pancreas has been proposed during homeostasis and upon different stress challenges such as inflammation, tissue damage and oncogenic stress. More recently, single cell transcriptomics has revealed a remarkable heterogeneity in all pancreas cell types, with some cells showing the signature of potential progenitors. In this review we provide an overview on embryonic and putative adult pancreas progenitors in homeostasis and disease, with special emphasis on in vitro culture systems and scRNA-seq technology as tools to address the progenitor nature of different pancreatic cells.

Ngn3-Positive Cells Arise from Pancreatic Duct Cells

The production of pancreatic β cells is the most challenging step for curing diabetes using next-generation treatments. Adult pancreatic endocrine cells are thought to be maintained by the self-duplication of differentiated cells, and pancreatic endocrine neogenesis can only be observed when the tissue is severely damaged. Experimentally, this can be performed using a method named partial duct ligation (PDL). As the success rate of PDL surgery is low because of difficulties in identifying the pancreatic duct, we previously proposed a method for fluorescently labeling the duct in live animals. Using this method, we performed PDL on neurogenin3 (Ngn3)-GFP transgenic mice to determine the origin of endocrine precursor cells and evaluate their potential to differentiate into multiple cell types. Ngn3-activated cells, which were marked with GFP, appeared after PDL operation. Because some GFP-positive cells were aligned proximally to the duct, we hypothesized that Ngn3-positive cells arise from the pancreatic duct. Therefore, we next developed an in vitro pancreatic duct culture system using Ngn3-GFP mice and examined whether Ngn3-positive cells emerge from this duct. We observed GFP expressions in ductal organoid cultures. GFP expressions were correlated with Ngn3 expressions and endocrine cell lineage markers. Interestingly, tuft cell markers were also correlated with GFP expressions. Our results demonstrate that in adult mice, Ngn3-positive endocrine precursor cells arise from the pancreatic ducts both in vivo and in vitro experiments indicating that the pancreatic duct could be a potential donor for therapeutic use.

A new hypothetical model for pancreatic development based on change in the cell division orientation

Although lifelong renewal and additional compensatory growth in response to demand are undeniable facts, so far, no specific stem cells have been found for pancreatic cells. According to the consensus model, the development of pancreas results from the hierarchical differentiation of pluripotent stem cells towards the appearance of the first endocrine and exocrine cells at approximately 7.5 to 8th gestation week (GW) of human embryo. However, the primitive endocrine cells arising from the embryonic phase of development do not appear to be mature or fully functional. Asymmetric localization of cellular components, such as Numb, partition protein complexes (PAR), planar cell polarity components, and certain mRNAs on the apical and basal sides of epithelial cells, causes cellular polarization. According to our model, the equal distribution of cellular components during symmetric cell division yields similar daughter cells that are associated with duct expansion. In contrast, asymmetric cell division is associated with uneven distribution of cellular components among daughter cells, resulting in different fates. Asymmetric cell division leads to duct branching and the development of acinar and stellate cells by a daughter cell, as well as the development of islet progenitor cells through partial epithelial-to-mesenchymal transition (EMT) and delamination of another daughter cell. Recently, we have developed an efficient method to obtain insulin-secreting cells from the transdifferentiation of hESC-derived ductal cells inducing a partial EMT by treatment with Wnt3A and activin A in a hypoxic environment. Similar models can be offered for other tissues and organs such as mammary glands, lungs, prostate, liver, etc. This model may open a new horizon in the field of regenerative medicine and be useful in explaining the cause of certain abnormalities, such as the occurrence of certain cysts and tumors.

From hair to pancreas: transplanted hair follicle mesenchymal stem cells express pancreatic progenitor cell markers in a rat model of acute pancreatitis

Acute pancreatitis (AP) is commonly accompanied by intense pain and is associated with high mortality rates. However, the effectiveness of existing therapeutic approaches remains unsatisfactory. Stem cell therapy, which can promote the regeneration of damaged tissue and alleviate systemic inflammatory responses, has brought new possibility for patients suffering from AP. In particular, hair follicle-derived mesenchymal stem cells (HF-MSCs) are proposed as a suitable cell source for treating pancreatic diseases, but further research on their effectiveness, safety, and underlying mechanisms is warranted for clinical implementation. In this work, the therapeutic potential of HF-MSC transplantation was studied in an L-arginine-induced AP rat model. HF-MSCs were extracted from infant Sprague-Dawley (SD) rats, expanded in vitro, and detected by flow cytometry. HF-MSCs were labeled by PKH67 and transplanted into rats with AP via tail vein injection. Serum specimens were collected at 24 h, 48 h, and 72 h after transplantation, and the levels of amylase, lipase, and anti-inflammatory factors, namely interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), were analyzed. Pancreas samples were collected and assayed by immunofluorescence and immunohistochemistry 1 week after transplantation to monitor the differentiation of HF-MSCs and the functional recovery of the damaged pancreas. Intravenously delivered rat HF-MSCs spontaneously homed to the damaged pancreas and expressed pancreatic progenitor cell markers, relieved inflammation, and boosted pancreatic regeneration. These findings indicate that HF-MSC transplantation is a potentially effective treatment for AP.

Chemical pancreatectomy treats chronic pancreatitis while preserving endocrine function in preclinical models

Chronic pancreatitis affects over 250,000 people in the US and millions worldwide. It is associated with chronic debilitating pain, pancreatic exocrine failure, and high risk of pancreatic cancer and usually progresses to diabetes. Treatment options are limited and ineffective. We developed a new potential therapy, wherein a pancreatic ductal infusion of 1%-2% acetic acid in mice and nonhuman primates resulted in a nonregenerative, near-complete ablation of the exocrine pancreas, with complete preservation of the islets. Pancreatic ductal infusion of acetic acid in a mouse model of chronic pancreatitis led to resolution of chronic inflammation and pancreatitis-associated pain. Furthermore, acetic acid-treated animals showed improved glucose tolerance and insulin secretion. The loss of exocrine tissue in this procedure would not typically require further management in patients with chronic pancreatitis because they usually have pancreatic exocrine failure requiring dietary enzyme supplements. Thus, this procedure, which should be readily translatable to humans through an endoscopic retrograde cholangiopancreatography (ERCP), may offer a potential innovative nonsurgical therapy for chronic pancreatitis that relieves pain and prevents the progression of pancreatic diabetes.

Pancreatic β cell regeneration induced by clinical and preclinical agents

Diabetes, one of the most common chronic diseases in the modern world, has pancreatic β cell deficiency as a major part of its pathophysiological mechanism. Pancreatic regeneration is a potential therapeutic strategy for the recovery of β cell loss. However, endocrine islets have limited regenerative capacity, especially in adult humans. Almost all hypoglycemic drugs can protect β cells by inhibiting β cell apoptosis and dedifferentiation via correction of hyperglycemia and amelioration of the consequent inflammation and oxidative stress. Several agents, including glucagon-like peptide-1 and γ-aminobutyric acid, have been shown to promote β cell proliferation, which is considered the main source of the regenerated β cells in adult rodents, but with less clarity in humans. Pancreatic progenitor cells might exist and be activated under particular circumstances. Artemisinins and γ-aminobutyric acid can induce α-to-β cell conversion, although some disputes exist. Intestinal endocrine progenitors can transdeterminate into insulin-producing cells in the gut after FoxO1 deletion, and pharmacological research into FoxO1 inhibition is ongoing. Other cells, including pancreatic acinar cells, can transdifferentiate into β cells, and clinical and preclinical strategies are currently underway. In this review, we summarize the clinical and preclinical agents used in different approaches for β cell regeneration and make some suggestions regarding future perspectives for clinical application.

Pancreas Optical Clearing and 3-D Microscopy in Health and Diabetes

Although first described over a hundred years ago, tissue optical clearing is undergoing renewed interest due to numerous advances in optical clearing methods, microscopy systems, and three-dimensional (3-D) image analysis programs. These advances are advantageous for intact mouse tissues or pieces of human tissues because samples sized several millimeters can be studied. Optical clearing methods are particularly useful for studies of the neuroanatomy of the central and peripheral nervous systems and tissue vasculature or lymphatic system. Using examples from solvent- and aqueous-based optical clearing methods, the mouse and human pancreatic structures and networks will be reviewed in 3-D for neuro-insular complexes, parasympathetic ganglia, and adipocyte infiltration as well as lymphatics in diabetes. Optical clearing with multiplex immunofluorescence microscopy provides new opportunities to examine the role of the nervous and circulatory systems in pancreatic and islet functions by defining their neurovascular anatomy in health and diabetes.

Therapeutic Potentials of MicroRNAs for Curing Diabetes Through Pancreatic β-Cell Regeneration or Replacement

MicroRNAs are a type of noncoding RNAs that regulates the expression of target genes at posttranscriptional level. MicroRNAs play essential roles in regulating the expression of different genes involved in pancreatic development, β-cell mass maintenance, and β-cell function. Alteration in the level of miRNAs involved in β-cell function leads to the diabetes. Being an epidemic, diabetes threatens the life of millions of patients posing a pressing demand for its urgent resolve. However, the currently available therapies are not substantial to cure the diabetic epidemic. Thus, researchers are trying to find new ways to replenish the β-cell mass in patients with diabetes. One promising approach is the in vivo regeneration of β-cell mass or increasing the efficiency of β-cell function. Another clinical strategy is the transplantation of in vitro developed β-like cells. Owing to their role in pancreatic β-cell development, maintenance, functioning and their involvement in diabetes, overexpression or attenuation of different miRNAs can cause β-cell regeneration in vivo or can direct the differentiation of various kinds of stem/progenitor cells to β-like cells in vitro. Here, we will summarize different strategies used by researchers to investigate the therapeutic potentials of miRNAs, with focus on miR-375, for curing diabetes through β-cell regeneration or replacement.

The cellular origins of cancer with particular reference to the gastrointestinal tract

Stem cells or their closely related committed progenitor cells are the likely founder cells of most neoplasms. In the continually renewing and hierarchically organized epithelia of the oesophagus, stomach and intestine, homeostatic stem cells are located at the beginning of the cell flux, in the basal layer of the oesophagus, the isthmic region of gastric oxyntic glands and at the bottom of gastric pyloric-antral glands and colonic crypts. The introduction of mutant oncogenes such as KrasG12D or loss of Tp53 or Apc to specific cell types expressing the likes of Lgr5 and Mist1 can be readily accomplished in genetically engineered mouse models to initiate tumorigenesis. Other origins of cancer are discussed including 'reserve' stem cells that may be activated by damage or through disruption of morphogen gradients along the crypt axis. In the liver and pancreas, with little cell turnover and no obvious stem cell markers, the importance of regenerative hyperplasia associated with chronic inflammation to tumour initiation is vividly apparent, though inflammatory conditions in the renewing populations are also permissive for tumour induction. In the liver, hepatocytes, biliary epithelial cells and hepatic progenitor cells are embryologically related, and all can give rise to hepatocellular carcinoma and cholangiocarcinoma. In the exocrine pancreas, both acinar and ductal cells can give rise to pancreatic ductal adenocarcinoma (PDAC), although the preceding preneoplastic states are quite different: acinar-ductal metaplasia gives rise to pancreatic intraepithelial neoplasia culminating in PDAC, while ducts give rise to PDAC via. mucinous cell metaplasia that may have a polyclonal origin.

Beta cell identity changes with mild hyperglycemia: Implications for function, growth, and vulnerability

OBJECTIVE

As diabetes develops, marked reductions of insulin secretion are associated with very modest elevations of glucose. We wondered if these glucose changes disrupt beta cell differentiation enough to account for the altered function.

METHODS

Rats were subjected to 90% partial pancreatectomies and those with only mild glucose elevations 4 weeks or 10 weeks after surgery had major alterations of gene expression in their islets as determined by RNAseq.

RESULTS

Changes associated with glucose toxicity demonstrated that many of the critical genes responsible for insulin secretion were downregulated while the expression of normally suppressed genes increased. Also, there were marked changes in genes associated with replication, aging, senescence, stress, inflammation, and increased expression of genes controlling both class I and II MHC antigens.

CONCLUSIONS

These findings suggest that mild glucose elevations in the early stages of diabetes lead to phenotypic changes that adversely affect beta cell function, growth, and vulnerability.

Inadequate β-cell mass is essential for the pathogenesis of type 2 diabetes

For patients with type 1 diabetes, it is accepted among the scientific community that there is a marked reduction in β-cell mass; however, with type 2 diabetes, there is disagreement as to whether this reduction in mass occurs in every case. Some have argued that β-cell mass in some patients with type 2 diabetes is normal and that the cause of the hyperglycaemia in these patients is a functional abnormality of insulin secretion. In this Personal View, we argue that a deficient β-cell mass is essential for the development of type 2 diabetes. The main point is that there are enormous (≥10 fold) variations in insulin sensitivity and insulin secretion in the general population, with a very close correlation between these two factors for any individual. Although β-cell mass cannot be accurately measured in living patients, it is highly likely that it too is highly correlated with insulin sensitivity and secretion. Thus, our argument is that a person with type 2 diabetes can have a β-cell mass that is the same as a person without type 2 diabetes, but because they are insulin resistant, the mass is inadequate and responsible for their diabetes. Because the abnormal insulin secretion of diabetes is caused by dysglycaemia and can be largely reversed with glycaemic control, it is a less serious problem than the reduction in β-cell mass, which is far more difficult to restore.

Establishment of long-term serum-free culture for lacrimal gland stem cells aiming at lacrimal gland repair

BACKGROUND

Aqueous-deficient dry eye disease (ADDED) resulting from dysfunction of the lacrimal gland (LG) is currently incurable. Although LG stem/progenitor cell-based therapy is considered to be a promising strategy for ADDED patients, the lack of a reliable serum-free culture method to obtain enough lacrimal gland stem cells (LGSCs) and the basic standard of LGSC transplantation are obstacles for further research.

METHODS

Adult mouse LGSCs were cultured in Matrigel-based 3D culture under serum-free culture condition, which contained EGF, FGF10, Wnt3A, and Y-27632. LGSCs were continuously passaged over 40 times every 7 days, and the morphology and cell numbers were recorded. LGSCs were induced to differentiate to ductal cells by reducing Matrigel rigidity, while fetal bovine serum was used for the induction of acinar cells. RT-PCR or qRT-PCR analysis, RNA-sequence analysis, H&E staining, and immunofluorescence were used for characterization and examining the differentiation of LGSCs. LGSCs were allotransplanted into diseased LGs to examine the ability of repairing the damage. The condition of eye orbits was recorded using a camera, the tear production was measured using phenol red-impregnated cotton threads, and the engraftments of LGSCs were examined by immunohistochemistry.

RESULTS

We established an efficient 3D serum-free culture for adult mouse LGSCs, in which LGSCs could be continuously passaged for long-term expansion. LGSCs cultured from both the healthy and ADDED mouse LGs expressed stem/progenitor cell markers Krt14, Krt5, P63, and nestin, had the potential to differentiate into acinar or ductal-like cells in vitro and could engraft into diseased LGs and relieve symptoms of ADDED after orthotopic injection of LGSCs.

CONCLUSION

We successfully established an efficient serum-free culture for adult mouse LGSCs aiming at LG repair for the first time. Our approach provides an excellent theoretical and technical reference for future clinical research for ADDED stem cell therapy.

Stem Cells, Self-Renewal, and Lineage Commitment in the Endocrine System

The endocrine system coordinates a wide array of body functions mainly through secretion of hormones and their actions on target tissues. Over the last decades, a collective effort between developmental biologists, geneticists, and stem cell biologists has generated a wealth of knowledge related to the contribution of stem/progenitor cells to both organogenesis and self-renewal of endocrine organs. This review provides an up-to-date and comprehensive overview of the role of tissue stem cells in the development and self-renewal of endocrine organs. Pathways governing crucial steps in both development and stemness maintenance, and that are known to be frequently altered in a wide array of endocrine disorders, including cancer, are also described. Crucially, this plethora of information is being channeled into the development of potential new cell-based treatment modalities for endocrine-related illnesses, some of which have made it through clinical trials.

Pancreatic β cell regeneration: To β or not to β

Diabetes is a major worldwide health problem which results from the loss and/or dysfunction of pancreatic insulin-producing β cells in the pancreas. Therefore, there is great interest in understanding the endogenous capacity of β cells to regenerate under normal or pathological conditions, with the goal of restoring functional β cell mass in patients with diabetes. Here, we summarize the current status of β cell regeneration research, which has been broadly divided into three in vivo mechanisms: 1. proliferation of existing β cells; 2. neogenesis of β cells from adult ductal progenitors; and 3. transdifferentiation of other cell types into β cells. We discuss the evidence and controversies for each mechanism in mice and humans, as well as the prospect of using these approaches for the treatment of diabetes.

SIRT1 Activation Promotes β-Cell Regeneration by Activating Endocrine Progenitor Cells via AMPK Signaling-Mediated Fatty Acid Oxidation

Induction of β-cell regeneration from endogenous cells represents a highly promising strategy in stem cell-based treatment for patients with diabetes. Recently, calorie restriction has been shown to affect the regulation of tissue and cell regeneration, including β cells, via metabolic related mechanisms. Here, we examined the potential utility of sirtuin 1 (SIRT1), a calorie restriction mimetic, for stimulating β-cell regeneration and the underlying mechanisms of such stimulation. The present results showed that SIRT1 activation with SRT1720 promoted β-cell regeneration in streptozotocin (STZ)-induced β-cell-deficient neonatal rats. This beneficial effect involved enhanced activation of neurogenin3 (NGN3)-positive endocrine progenitors from pancreatic ductal cells, rather than an expansion of residual β cells. A dynamic expression profile of SIRT1 was observed in endocrine progenitors both during β-cell regeneration in neonatal rats and in the second transition phase of mouse pancreas development. Consistently, SRT1720 treatment upregulated endocrine progenitor differentiation in cultured pancreatic rudiments. Upregulation of NGN3 by SIRT1 activation was through stimulating AMP-activated protein kinase (AMPK) signaling-mediated fatty acid oxidation (FAO) in human pancreatic progenitor cells; AMPK inhibition abolished these effects. The present findings demonstrate a promotional effect of SIRT1 activation on β-cell restoration and endocrine progenitor differentiation that involves regulation of AMPK signaling-mediated FAO. Stem Cells 2019;37:1416-1428.

Pancreatic duct-like cell line derived from pig embryonic stem cells: expression of uroplakin genes in pig pancreatic tissue

The isolation of a cell line, PICM-31D, with phenotypic characteristics like pancreatic duct cells is described. The PICM-31D cell line was derived from the previously described pig embryonic stem cell-derived exocrine pancreatic cell line, PICM-31. The PICM-31D cell line was morphologically distinct from the parental cells in growing as a monolayer rather than self-assembling into multicellular acinar-like structures. The PICM-31D cells were propagated for over a year at split ratios of 1:3 to 1:10 at each passage without change in phenotype or growth rate. Electron microscopy showed the cells to be a polarized epithelium of cuboidal cells joined by tight junction-like adhesions at their apical/lateral aspect. The cells contained numerous mucus-like secretory vesicles under their apical cell membrane. Proteomic analysis of the PICM-31D's cellular proteins detected MUC1 and MUC4, consistent with mucus vesicle morphology. Gene expression analysis showed the cells expressed pancreatic ductal cell-related transcription factors such as GATA4, GATA6, HES1, HNF1A, HNF1B, ONECUT1 (HNF6), PDX1, and SOX9, but little or no pancreas progenitor cell markers such as PTF1A, NKX6-1, SOX2, or NGN3. Pancreas ductal cell-associated genes including CA2, CFTR, MUC1, MUC5B, MUC13, SHH, TFF1, KRT8, and KRT19 were expressed by the PICM-31D cells, but the exocrine pancreas marker genes, CPA1 and PLA2G1B, were not expressed by the cells. However, the exocrine marker, AMY2A, was still expressed by the cells. Surprisingly, uroplakin proteins were prominent in the PICM-31D cell proteome, particularly UPK1A. Annexin A1 and A2 proteins were also relatively abundant in the cells. The expression of the uroplakin and annexin genes was detected in the cells, although only UPK1B, UPK3B, ANXA2, and ANXA4 were detected in fetal pig pancreatic duct tissue. In conclusion, the PICM-31D cell line models the mucus-secreting ductal cells of the fetal pig pancreas.

Endogenous Pancreatic β Cell Regeneration: A Potential Strategy for the Recovery of β Cell Deficiency in Diabetes

Endogenous pancreatic β cell regeneration is a potential strategy for β cell expansion or neogenesis to treat diabetes. Regeneration can occur through stimulation of existing β cell replication or conversion of other pancreatic cells into β cells. Recently, various strategies and approaches for stimulation of endogenous β cell regeneration have been evaluated, but they were not suitable for clinical application. In this paper, we comprehensively review these strategies, and further discuss various factors involved in regulation of β cell regeneration under physiological or pathological conditions, such as mediators, transcription factors, signaling pathways, and potential pharmaceutical drugs. Furthermore, we discuss possible reasons for the failure of regenerative medicines in clinical trials, and possible strategies for improving β cell regeneration. As β cell heterogeneity and plasticity determines their function and environmental adaptability, we focus on β cell subtype markers and discuss the importance of research evaluating the characteristics of new β cells. In addition, based on the autoimmunologic features of type 1 diabetes, NOD/Lt-SCID-IL2rg null (NSG) mice grafted with human immune cells and β cells are recommended for use in evaluation of antidiabetic regenerative medicines. This review will further understand current advances in endogenous β cell regeneration, and provide potential new strategies for the treatment of diabetes focused on cell therapy.

Neurog3 misexpression unravels mouse pancreatic ductal cell plasticity

In the context of type 1 diabetes research and the development of insulin-producing β-cell replacement strategies, whether pancreatic ductal cells retain their developmental capability to adopt an endocrine cell identity remains debated, most likely due to the diversity of models employed to induce pancreatic regeneration. In this work, rather than injuring the pancreas, we developed a mouse model allowing the inducible misexpression of the proendocrine gene Neurog3 in ductal cells in vivo. These animals developed a progressive islet hypertrophy attributed to a proportional increase in all endocrine cell populations. Lineage tracing experiments indicated a continuous neo-generation of endocrine cells exhibiting a ductal ontogeny. Interestingly, the resulting supplementary β-like cells were found to be functional. Based on these findings, we suggest that ductal cells could represent a renewable source of new β-like cells and that strategies aiming at controlling the expression of Neurog3, or of its molecular targets/co-factors, may pave new avenues for the improved treatments of diabetes.

Biological processes and signal transduction pathways regulated by the protein methyltransferase SETD7 and their significance in cancer

Protein methyltransferases have been shown to methylate histone and non-histone proteins, leading to regulation of several biological processes that control cell homeostasis. Over the past few years, the histone-lysine N-methyltransferase SETD7 (SETD7; also known as SET7/9, KIAA1717, KMT7, SET7, SET9) has emerged as an important regulator of at least 30 non-histone proteins and a potential target for the treatment of several human diseases. This review discusses current knowledge of the structure and subcellular localization of SETD7, as well as its function as a histone and non-histone methyltransferase. This work also underlines the putative contribution of SETD7 to the regulation of gene expression, control of cell proliferation, differentiation and endoplasmic reticulum stress, which indicate that SETD7 is a candidate for novel targeted therapies with the aim of either stimulating or inhibiting its activity, depending on the cell signaling context.

Porcine Neonatal Pancreatic Cell Clusters Maintain Their Multipotency in Culture and After Transplantation

Ductal epithelium is primarily detected in porcine neonatal pancreatic cell clusters (NPCCs) bearing grafts, suggesting that transplants might exhibit progenitor-like phenotypes. Here we found that soon after NPCC isolation, PDX1⁺/insulin⁻ and SOX9⁺ pancreatic progenitor-like cells dramatically increased while dual-hormonal progenitor-like cells were routinely observed in NPCC culture. After transplantation (Tx), insulin⁺ cells increased and PDX1⁺ and SOX9⁺ cells gradually decreased in both non-diabetic (NDM) and streptozotocin-induced diabetic (DM) grafts over 2 months. Strikingly, a significantly higher percentage of insulin⁺ cells were detected in 9-day and 16-day, but not in 23-day, 30-day and 60-day grafts implying that hyperglycemia could only facilitate NPCC-derived β cells early post-Tx. A higher percentage of NPCC-derived β cells in early DM grafts was determined via an enhanced neogenic differentiation based on the detection of insulin⁺ cells budding out from PDX1⁺/SOX9⁺ epithelium. Interestingly, a drop in SOX9⁺ progenitor-like cells was detected 16 days post-Tx in DM grafts whilst PDX1⁺ cells do not show a significant difference until 60 days post-Tx between DM and NDM grafts, demonstrating that distinct progenitor-like populations fuel new β cells post-Tx. In conclusion, PDX1⁺/SOX9⁺ cells could be quickly activated after NPCC isolation, maintain their multipotency in culture and differentiate into new β cell post-Tx.

Heterogeneity of SOX9 and HNF1β in Pancreatic Ducts Is Dynamic

Pancreatic duct epithelial cells have been suggested as a source of progenitors for pancreatic growth and regeneration. However, genetic lineage-tracing experiments with pancreatic duct-specific Cre expression have given conflicting results. Using immunofluorescence and flow cytometry, we show heterogeneous expression of both HNF1β and SOX9 in adult human and murine ductal epithelium. Their expression was dynamic and diminished significantly after induced replication. Purified pancreatic duct cells formed organoid structures in 3D culture, and heterogeneity of expression of Hnf1β and Sox9 was maintained even after passaging. Using antibodies against a second cell surface molecule CD51 (human) or CD24 (mouse), we could isolate living subpopulations of duct cells enriched for high or low expression of HNF1β and SOX9. Only the CD24^high (Hnfβ^high/Sox9^high) subpopulation was able to form organoids.

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HNF1β and SOX9 are differentially expressed across the pancreatic ductal tree

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Their expression was dynamic and diminished significantly after replication

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Live subpopulations can be isolated using CD51 (human) and CD24 (mouse).

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Only the CD24^high (Hnfβ^high/Sox9^high) subpopulation was able to form organoids

Regenerating β cells of the pancreas - potential developments in diabetes treatment

INTRODUCTION

The etiology of diabetes is mainly attributed to insulin deficiency due to the lack of β cells (type 1), or to insulin resistance that eventually results in β cell dysfunction (type 2). Therefore, an ultimate cure for diabetes requires the ability to replace the lost insulin-secreting β cells. Strategies for regenerating β cells are under extensive investigation.

AREAS COVERED

Herein, the authors first summarize the mechanisms underlying embryonic β cell development and spontaneous adult β cell regeneration, which forms the basis for developing β cell regeneration strategies. Then the rationale and progress of each β cell regeneration strategy is reviewed. Current β cell regeneration strategies can be classified into two main categories: in vitro β cell regeneration using pluripotent stem cells and in vivo reprogramming of non-β cells into β cells. Each has its own advantages and disadvantages.

EXPERT OPINION

Regenerating β cells has shown its potential as a cure for the treatment of insulin-deficient diabetes. Much progress has been made, and β cell regeneration therapy is getting closer to a clinical reality. Nevertheless, more hurdles need to be overcome before any of the strategies suggested can be fully translated from bench to bedside.

Pancreatic and Islet Remodeling in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Knockout Ferrets

In cystic fibrosis (CF), there is early destruction of the exocrine pancreas, and this results in a unique form of diabetes that affects approximately half of adult CF individuals. An animal model of cystic fibrosis-related diabetes has been developed in the ferret, which progresses through phases of glycemic abnormalities because of islet remodeling during and after exocrine destruction. Herein, we quantified the pancreatic histopathological changes that occur during these phases. There was an increase in percentage ductal, fat, and islet area in CF ferrets over time compared with age-matched wild-type controls. We also quantified islet size, shape, islet cell composition, cell proliferation (Ki-67), and expression of remodeling markers (matrix metalloprotease-7, desmin, and α-smooth muscle actin). Pancreatic ducts were dilated with scattered proliferating cells and were surrounded by activated stellate cells, indicative of tissue remodeling. The timing of islet and duct proliferation, stellate cell activation, and matrix remodeling coincided with the previously published stages of glycemic crisis and inflammation. This mapping of remodeling events in the CF ferret pancreas provides insights into early changes that control glycemic intolerance and subsequent recovery during the evolution of CF pancreatic disease.

Pancreatic β Cell Regeneration as a Possible Therapy for Diabetes

Diabetes is the result of having inadequate supply of functional insulin-producing β cells. Two possible approaches for replenishing the β cells are: (1) replacement by transplanting cadaveric islets or β cells derived from human embryonic stem cells/induced pluripotent stem cells and (2) induction of endogenous regeneration. This review focuses on endogenous regeneration, which can follow two pathways: enhanced replication of existing β cells and formation of new β cells from cells not expressing insulin, either by conversion from a differentiated cell type (transdifferentiation) or differentiation from progenitors (neogenesis). Exciting progress on both pathways suggest that regeneration may have therapeutic promise.

Phenotypic plasticity in the pancreas: new triggers, new players

The pancreas has a very limited regenerative potential during homeostasis. Despite its quiescent nature, recent in vivo models suggest a certain degree of regeneration and cellular interconversion is possible within the adult pancreas. It has now become evident that cellular plasticity can be observed in essentially all cell types within the pancreas when provided with the right stress stimuli. In this review, we will focus on the latest findings uncovering phenotypic plasticity of different cell types in the pancreas, the molecular mechanisms behind such plasticity and how plasticity associated with pancreatic or non-pancreatic cells could be harnessed in the generation of new insulin-producing beta cells.

Cellular and molecular mechanisms coordinating pancreas development

The pancreas is an endoderm-derived glandular organ that participates in the regulation of systemic glucose metabolism and food digestion through the function of its endocrine and exocrine compartments, respectively. While intensive research has explored the signaling pathways and transcriptional programs that govern pancreas development, much remains to be discovered regarding the cellular processes that orchestrate pancreas morphogenesis. Here, we discuss the developmental mechanisms and principles that are known to underlie pancreas development, from induction and lineage formation to morphogenesis and organogenesis. Elucidating such principles will help to identify novel candidate disease genes and unravel the pathogenesis of pancreas-related diseases, such as diabetes, pancreatitis and cancer.

Phosphorylation of carboxypeptidase B1 protein regulates β-cell proliferation

A reduction in pancreatic islet β-cells leads to the onset of diabetes. Hence, the identification of the mechanisms inducing β-cell proliferation is important for developing a treatment course against the disease. It has been well established that post-translational modifications (PTMs) of proteins affect their functionality. In addition, PTMs have been suggested to play important roles in organ regeneration. Therefore, in this study, we investigated PTMs associated with pancreatic regeneration using two-dimensional electrophoresis. Four carboxypeptidase B1 (CPB1) proteins were identified at different isoelectric points, with the same molecular weight. The motif of CPB1 PTMs was identified by mass spectrophotometry, and the downregulation of CPB1 phosphorylation in pancreatectomy was confirmed. The dephosphorylation of CPB1 induced β-cell proliferation. We thus surmise that the altered PTM of CPB1 is associated with pancreatic regeneration.

Lacrimal Gland Repair after Short-term Obstruction of Excretory Duct in Rabbits

Aqueous tear-deficient dry eye is a multifactorial chronic disorder in which the lacrimal glands fail to produce enough tears to maintain a healthy ocular surface. The existence of lacrimal gland stem/progenitor cells was proposed in several species, yet their origin and characteristics are not very clear. Here, we investigated the presence of resident progenitor cells and their regenerative potential in a rabbit model with lacrimal gland main excretory duct ligation-induced injury. The ligation-injured lacrimal glands temporarily decreased in weight and had impaired tear secretion. Protein expression profiles and transcriptional profiles were obtained from injured tissue. Isolated lacrimal gland progenitor cells were tested and characterized by stem cell-related marker evaluation, single cell clonal assay and three-dimensional (3-D) culture. The results of our study indicate that lacrimal glands are capable of tissue repair after duct ligation-induced injury, likely involving resident stem/progenitor cells and epithelial-mesenchymal transitions. Lacrimal gland progenitor cells isolated from ligated tissue can differentiate in 3-D culture. The results provide further insights into lacrimal gland stem/progenitor cell physiology and their potential for treating severe cases of tear deficiency.

Phosphorylated mTOR Expression Profiles in Human Normal and Carcinoma Tissues

Mammalian target of rapamycin (mTOR) is a key controller of cell growth and proliferation in normal tissues and solid tumors. In the present study, an immunohistochemical analysis of the expression pattern of phosphorylated mTOR (p-mTOR) was performed in human normal fetal and adult tissues and various carcinoma tissues. p-mTOR expression showed tissue and cell type specificity in normal and cancer tissues. In normal fetal and adult tissues, p-mTOR staining was observed in the intestinal crypt, intrahepatic bile ductule, pancreatic duct, distal nephron of the kidney, umbrella cell of urothelium, mesothelial cell, and choroid plexus. In cancer tissues, p-mTOR expression was higher in adenocarcinoma than in other types of cancers, in metastatic cancer than in primary cancer, and in the forefront of the infiltrating cancer cells. These results suggest that p-mTOR is implicated not only in cell proliferation but also in tubular morphogenesis in normal and cancer tissues. In addition, mTOR activation appears to be associated with cancer cell invasion and migration in solid tumors.

Stem cells to restore insulin production and cure diabetes

BACKGROUND

The advancement of knowledge in the field of regenerative medicine is increasing the therapeutic expectations of patients and clinicians on cell therapy approaches. Within these, stem cell therapies are often evoked as a possible therapeutic option for diabetes, already ongoing or possible in the near future.

AIM

The purpose of this document is to make a point of the situation on existing knowledge and therapies with stem cells to treat patients with diabetes by focusing on some of the aspects that most frequently raise curiosity and discussion in clinical practice and in the interaction with the patient. In fact, at present there are no clinically approved treatments based on the use of stem cells for the treatment of diabetes, but several therapeutic approaches have already been evaluated or are being evaluated in clinical trials.

DATA SYNTHESIS

It is possible to identify three large potential application fields: 1) the reconstruction of the β cell mass; 2) the immunomodulation in type 1 diabetes (T1D); 3) the treatment of complications. In this study we will limit the discussion to approaches that have the potential for clinical translation, deliberately omitting aspects of basic biology and preclinical data. Also, we intentionally omit the treatment of the complications that will be the subject of a future document. Finally, an overview of the Italian situation regarding the storage of cord blood cells for the therapy of diabetes will be given.

17β-Estradiol Promotes Islet Cell Proliferation in a Partial Pancreatectomy Mouse Model

17β-Estradiol (E2) is a multifunctional steroid hormone in modulating metabolism in vivo. Previous studies have reported that E2 could promote insulin secretion and protect β cells from apoptosis. In this study, the partial pancreatectomy (PPx) model was used to study the role of E2 in islet cell proliferation. The animals were divided into four groups, including sham control, PPx model, E2, and E2 plus estrogen antagonist (E2 plus ICI) groups. In the E2 group, 5-bromo-2'-deoxyuridine- and Ki67-positive cells significantly increased after PPx, and the protein expression of forkhead transcription factor M1, cyclin A2, cyclin B1, and cyclin E2 also significantly increased in the isolated islets. The messenger RNA expression of cyclin A2 and cyclin B2 increased in E2 treatment group. Additionally, the effects of E2 on the PPx mice were partially blocked by estrogen antagonist ICI182,780. The results indicated that E2 significantly promoted islet cell proliferation in PPx model mice, and it upregulated the expression of cell cycle genes. In conclusion, E2 treatment is beneficial for islet cell proliferation in adult mice after PPx. A partial pancreatectomy in mice may be an attractive model for the study of islet cell proliferation.

Stem cells to replace or regenerate the diabetic pancreas: Huge potential & existing hurdles

Various stem cell sources are being explored to treat diabetes since the proof-of-concept for cell therapy was laid down by transplanting cadaveric islets as a part of Edmonton protocol in 2000. Human embryonic stem (hES) cells derived pancreatic progenitors have got US-FDA approval to be used in clinical trials to treat type 1 diabetes mellitus (T1DM). However, these progenitors more closely resemble their foetal counterparts and thus whether they will provide long-term regeneration of adult human pancreas remains to be demonstrated. In addition to lifestyle changes and administration of insulin sensitizers, regeneration of islets from endogenous pancreatic stem cells may benefit T2DM patients. The true identity of pancreatic stem cells, whether these exist or not, whether regeneration involves reduplication of existing islets or ductal epithelial cells transdifferentiate, remains a highly controversial area. We have recently demonstrated that a novel population of very small embryonic-like stem cells (VSELs) is involved during regeneration of adult mouse pancreas after partial-pancreatectomy. VSELs (pluripotent stem cells in adult organs) should be appreciated as an alternative for regenerative medicine as these are autologous (thus immune rejection issues do not exist) with no associated risk of teratoma formation. T2DM is a result of VSELs dysfunction with age and uncontrolled proliferation of VSELs possibly results in pancreatic cancer. Extensive brainstorming and financial support are required to exploit the potential of endogenous VSELs to regenerate the pancreas in a patient with diabetes.

Smad2/3 Linker Phosphorylation Is a Possible Marker of Pancreatic Stem/Progenitor Cells in the Regenerative Phase of Acute Pancreatitis

OBJECTIVES

The aims of this study are to characterize cell proliferation and differentiation during regeneration after pancreatitis and pancreatic buds during development to evaluate the role of Smad2/3, phosphorylated at the specific linker threonine residues (pSmad2/3L-Thr) in positive cells.

METHODS

Male C57BL/6 mice received hourly intraperitoneal injections of cerulein and were analyzed after induced pancreatitis. Pancreatitis-affected tissue sections and pancreatic buds were immunostained for pSmad2/3L-Thr, with other markers thought to be stem/progenitor markers of the pancreas.

RESULTS

pSmad2/3L-Thr immunostaining-positive cells increased as the pancreatitis progressed. The expression of pSmad2/3L-Thr was seen in acinar cells and ductlike tubular complexes. These results suggest that pSmad2/3L-Thr is expressed during acinar-ductal metaplasia. Immunohistochemical colocalization of pSmad2/3L-Thr with Ki67 was never observed. pSmad2/3L-Thr-positive cells may remain in an undifferentiated state. During the pancreatic development process, pSmad2/3L-Thr was expressed as other markers. pSmad2/3L-Thr develops in duct structure of the undifferentiated cell population in the last part of viviparity that acinar structure is formed clearly.

CONCLUSIONS

pSmad2/3L-Thr expression occurs during acinar-ductal metaplasia after pancreatitis and may represent the contribution of stem cells and/or progenitor cells to the differentiation of the pancreas.

Pancreatic β-cell regeneration: Facultative or dedicated progenitors?

The adult pancreas is only capable of limited regeneration. Unlike highly regenerative tissues such as the skin, intestinal crypts and hematopoietic system, no dedicated adult stem cells or stem cell niche have so far been identified within the adult pancreas. New β cells have been shown to form in the adult pancreas, in response to high physiological demand or experimental β-cell ablation, mostly by replication of existing β cells. The possibility that new β cells are formed from other sources is currently a point of major controversy. Under particular injury conditions, fully differentiated pancreatic duct and acinar cells have been shown to dedifferentiate into a progenitor-like state, however the extent, to which ductal, acinar or other endocrine cells contribute to restoring pancreatic β-cell mass remains to be resolved. In this review we focus on regenerative events in the pancreas with emphasis on the restoration of β-cell mass. We present an overview of regenerative responses noted within the different pancreatic lineages, following injury. We also highlight the intrinsic plasticity of the adult pancreas that allows for inter-conversion of fully differentiated pancreatic lineages through manipulation of few genes or growth factors. Taken together, evidence from a number of studies suggest that differentiated pancreatic lineages could act as facultative progenitor cells, but the extent to which these contribute to β-cell regeneration in vivo is still a matter of contention.

Involvement of Pancreatic Stellate Cells in Regeneration of Remnant Pancreas after Partial Pancreatectomy

Background and objectives

Mechanism of regeneration of remnant pancreas after partial pancreatectomy (PX) is still unknown. In this study, effect of siRNA against the collagen specific chaperone, HSP47, which inhibits collagen secretion from activated pancreas stellate cells (aPSCs), and induces their apoptosis, on regeneration of remnant pancreas was determined.

Methods

Pancreatectomy was performed according to established methods. Proliferation of cells was assessed by BrdU incorporation. Immunostaining of HSP47 was employed to identify PSCs. Progenitor cells were identified by SOX9 staining. Acinar cells were immunostained for amylase. Co-culture of acinar cells with aPSCs were carried out in a double chamber with a cell culture insert. siRNA HSP47 encapsulated in vitamin A-coupled liposome (VA-lip siRNA HSP47) was delivered to aPSCs by iv injection.

Results

In remnant pancreas of 90% PX rat, new areas of foci were located separately from duodenal areas with normal pancreatic features. After PX, BrdU uptake of acinar cells and islet cells significantly increased, but was suppressed by treatment with VA-lip siRNA HSP47. BrdU uptake by acinar cells was augmented by co-culturing with aPSCs and the augmentation was nullified by siRNA HSP47. BrdU uptake by progenitor cells in foci area was slightly enhanced by the same treatment. New area which exhibited intermediate features between those of duodenal and area of foci, emerged after the treatment.

Conclusion

aPSCs play a crucial role in regeneration of remnant pancreas, proliferation of acinar and islet cells after PX through the activity of secreted collagen. Characterization of new area emerged by siRNA HSP47 treatment as to its origin is a future task.

Adult human pancreas-derived cells expressing stage-specific embryonic antigen 4 differentiate into Sox9-expressing and Ngn3-expressing pancreatic ducts in vivo

Background

Tissue-specific stem/progenitor cells are found in various adult tissues and may have the capacity for lineage-specific differentiation, facilitating applications in autologous transplantation. Stage-specific embryonic antigen 4 (SSEA-4), an early embryonic glycolipid antigen, is expressed in cells derived from adult human pancreas exocrine tissue. Here, we examined the characteristics and lineage-specific differentiation capacity of SSEA-4⁺ cells.

Methods

Human adult partial pancreas tissues were obtained from different donors and cultured in vitro. SSEA-4⁺ and CA19-9⁺ cells were isolated from adult human pancreas exocrine cells using magnetic-activated cell sorting, and gene expression was validated by quantitative polymerase chain reaction. To confirm in-vivo differentiation, SSEA-4⁺ and CA19-9⁺ cells were transplanted into the dorsal subcutaneous region of mice. Finally, morphological features of differentiated areas were confirmed by immunostaining and morphometric analysis.

Results

SSEA-4-expressing cells were detected in isolated pancreas exocrine cells from adult humans. These SSEA-4⁺ cells exhibited coexpression of CA19-9, a marker of pancreatic duct cells, but not amylase expression, as shown by immunostaining and flow cytometry. SSEA-4⁺ cells exhibited higher relative expression of Oct4, Nanog, Klf4, Sox2, and c-Myc mRNAs than CA19-9⁺ cells. Pancreatic intralobular ducts (PIDs) were generated from SSEA-4⁺ or CA19-9⁺ cells in vivo at 5 weeks after transplantation. However, newly formed PIDs from CA19-9⁺ cells were less abundant and showed an incomplete PID morphology. In contrast, newly formed PIDs from SSEA-4⁺ cells were abundant in the transplanted area and showed a crowded morphology, typical of PIDs. Sox9 and Ngn3, key transcription factors associated with pancreatic development and regeneration, were expressed in PIDs from SSEA-4⁺ cells.

Conclusions

SSEA-4-expressing cells in the adult human pancreas may have the potential for regeneration of the pancreas and may be used as a source of stem/progenitor cells for pancreatic cell lineage-specific differentiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0422-0) contains supplementary material, which is available to authorized users.