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Imaging the pancreas: new aspects on lobular development and adult constitution
Umeå University, Faculty of Medicine, Umeå Centre for Molecular Medicine (UCMM).
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The mouse pancreas is a mixed exocrine and endocrine glandconsisting of three lobular compartments: the splenic, duodenal and gastric lobes. During embryogenesis, the pancreas forms from two progenitor populations located on the dorsal and ventral side of the primitive gut tube. These anlagen are brought in close proximity as the gut elongates and rotates, and fuse to form a single organ. The splenic and duodenal lobes develop from the dorsal and ventral anlagen, respectively.

In the adult pancreas, exocrine tissue secretes digestive enzymes intothe gut lumen to support nutrient uptake. The endocrine Islets of Langerhans are scattered throughout the exocrine tissue and aid in regulation of energy homeostasis through the secretion of hormones. One of the key players in energy homeostasis is the pancreatic ß-cell, which is the most abundant cell type of the islets. The β-cells regulates blood glucose levels through the action of insulin. Conditions where this regulation does not function properly are gathered under the common name of Diabetes mellitus.

Type 1 diabetes (T1D) is characterized by insulin deficiency due to autoimmune destruction of the ß-cells. Using recently developed protocols for optical projection tomography (OPT) whole-organ imaging, we have revealed new spatial and quantitative aspects on ß-cell mass dynamics and immune infiltration during the course of T1D development in the non-obese diabetic (NOD) mouse model. We show that although immune infiltration appears to occur asynchronously throughout the organ, smaller islets, mainly located in the periphery of the organ, preferentially loose their ß-cells during early stages of disease progression. Larger islets appear more resistant to the autoimmune attack and our data indicate the existence of a compensatory proliferative capacity within these islets. We also report the appearance of structures resembling tertiary lymphoid organs (TLOs) in association with the remaining islets during later phases of T1D progression.

OPT has already proven to be a useful tool for assessments of ß-cellmass in the adult mouse pancreas. However, as with other techniques, previous protocols have relied on a tedious degree of manual postivacquisition editing. To further refine OPT-based assessment of pancreatic ß-cell mass distribution in the murine pancreas, we implemented a computational statistical approach, Contrast-Limited Adaptive Histogram Normalisation (CLAHE), to the OPT projection data of pancreata from C57Bl/6 mice. This methodology provided increased islet detection sensitivity, improved islet morphology and diminished subjectivity in thresholding for reconstruction and quantification. Using this approach, we could report a substantially higher number of islets than previously described for this strain and provide evidence of significant differences in islet mass distribution between the pancreatic lobes. The gastric lobe stood out in particular and contained a 75% higher islet density as compared to the splenic lobe.

Although the development of the early pancreatic buds has been relatively well studied, later morphogenetic events are less clear and information regarding the formation of the gastric lobe has largely been missing. Using OPT we have generated a quantitative three-dimensional road map of pancreatic morphogenesis in the mouse. We show that the gastric lobe forms as a perpendicular outgrowth fromthe stem of the dorsal pancreas at around embryonic day (e) 13.5, which grows into a mesenchymal domain overlaying the pyloric sphincter and proximal part of the glandular stomach. By analyzing mutant mice with aberrant spleen development, we further demonstrate that proper formation of the gastric lobe is dependent on the initial formation of the closely positioned spleen, indicating a close interplay between pancreatic and splenic mesenchyme during development. Additionally, we show that the expression profile of markers for pancreatic multipotent progenitors within the pancreas is heterogenous with regards to lobular origin. Altogether, our studies regarding the morphogenesis and adult constitution of the mouse pancreas recognize lobular heterogeneities that add important information for future interpretations of this organ.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2011. , 50 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1471
Keyword [en]
Type 1 diabetes, ß-cell mass, tertiary lymphoid organs, biomedical imaging, optical projection tomography, morphogenesis, pancreas development, gastric lobe, spleen development.
National Category
Other Basic Medicine Medical Genetics
Research subject
Medical Genetics; Developmental Neurosciences; Molecular Medicine
Identifiers
URN: urn:nbn:se:umu:diva-50601ISBN: 978-91-7459-341-9 (print)OAI: oai:DiVA.org:umu-50601DiVA: diva2:465786
Public defence
2012-01-20, Betula, Analysvägen 1, By 6M, Vån 1, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2011-12-22 Created: 2011-12-15 Last updated: 2011-12-22Bibliographically approved
List of papers
1. Quantification and 3-D imaging of the insulitis-induced destruction of β-cells in murine type 1 diabetes
Open this publication in new window or tab >>Quantification and 3-D imaging of the insulitis-induced destruction of β-cells in murine type 1 diabetes
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2010 (English)In: Diabetes, ISSN 0012-1797, E-ISSN 1939-327X, Vol. 59, no 7, 1756-1764 p.Article in journal (Refereed) Published
Abstract [en]

Objective: The aim of this study was to refine the information regarding the quantitative and spatial dynamics of infiltrating lymphocytes and remaining beta-cell volume during the progression of type 1 diabetes in the NOD mouse model of the disease.

Research design and methods: Using an ex vivo technique, optical projection tomography (OPT), we quantified and assessed the 3D spatial development and progression of insulitis and beta-cell destruction in pancreas from diabetes prone NOD and non-diabetes prone congenic NOD.H-2b mice between 3 and 16 weeks of age.

Results: Together with results showing the spatial dynamics of the insulitis process we provide data of beta-cell volume distributions down to the level of the individual islets and throughout the pancreas during the development and progression of type 1 diabetes. Our data provide evidence for a compensatory growth potential of the larger insulin(+) islets during the later stages of the disease around the time point for development of clinical diabetes. This is in contrast to smaller islets, which appear less resistant to the autoimmune attack. We also provide new information on the spatial dynamics of the insulitis process itself, including its apparently random distribution at onset, the local variations during its further development, and the formation of structures resembling tertiary lymphoid organs at later phases of insulitis progression.

Conclusions: Our data provides a powerful tool for phenotypic analysis of genetic and environmental effects on type 1 diabetes etiology as well as for evaluating the potential effect of therapeutic regimes.

Keyword
pancreas, mouse, mice
National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:umu:diva-33656 (URN)10.2337/db09-1400 (DOI)000279615100025 ()20393145 (PubMedID)
Available from: 2010-04-30 Created: 2010-04-30 Last updated: 2017-12-12Bibliographically approved
2. An improved protocol for optical projection tomography imaging reveals lobular heterogeneities in pancreatic islet and β-cell mass distribution
Open this publication in new window or tab >>An improved protocol for optical projection tomography imaging reveals lobular heterogeneities in pancreatic islet and β-cell mass distribution
2011 (English)In: Islets, ISSN 1938-2014, Vol. 3, no 4, 204-208 p.Article in journal (Refereed) Published
Abstract [en]

Optical projection tomography (OPT) imaging is a powerful tool for three-dimensional imaging of gene and protein distribution patterns in biomedical specimens. We have previously demonstrated the possibility, by this technique, to extract information of the spatial and quantitative distribution of the islets of Langerhans in the intact mouse pancreas. In order to further increase the sensitivity of OPT imaging for this type of assessment, we have developed a protocol implementing a computational statistical approach: contrast limited adaptive histogram equalization (CLAHE). We demonstrate that this protocol significantly increases the sensitivity of OPT imaging for islet detection, helps preserve islet morphology and diminish subjectivity in thresholding for tomographic reconstruction. When applied to studies of the pancreas from healthy C57BL/6 mice, our data reveal that, at least in this strain, the pancreas harbors substantially more islets than has previously been reported. Further, we provide evidence that the gastric, duodenal and splenic lobes of the pancreas display dramatic differences in total and relative islet and β-cell mass distribution. This includes a 75% higher islet density in the gastric lobe as compared to the splenic lobe and a higher relative volume of insulin producing cells in the duodenal lobe as compared to the other lobes. Altogether, our data show that CLAHE substantially improves OPT based assessments of the islets of Langerhans and that lobular origin must be taken into careful consideration in quantitative and spatial assessments of the pancreas.

Place, publisher, year, edition, pages
Austin: Landes Bioscience, 2011
Keyword
Animals, Cell Size, Computational Biology/*methods, Female, Image, Enhancement/methods, Imaging, Three-Dimensional/methods, Insulin-Secreting Cells/*cytology, Islets of Langerhans/*anatomy & histology, Mice, Mice, Inbred C57BL, Organ Size, Pancreas/anatomy & histology, Pancreas, Exocrine/anatomy & histology, Reproducibility of Results, Tomography, Optical/*methods
National Category
Endocrinology and Diabetes
Research subject
Molecular Medicine
Identifiers
urn:nbn:se:umu:diva-50597 (URN)10.4161/isl.3.4.16417 (DOI)21633198 (PubMedID)
Available from: 2011-12-15 Created: 2011-12-15 Last updated: 2011-12-22Bibliographically approved
3. Impaired spleen formation perturbs morphogenesis of the gastric lobe of the pancreas
Open this publication in new window or tab >>Impaired spleen formation perturbs morphogenesis of the gastric lobe of the pancreas
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2011 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 6, e21753- p.Article in journal (Refereed) Published
Abstract [en]

Despite the extensive use of the mouse as a model for studies of pancreas development and disease, the development of the gastric pancreatic lobe has been largely overlooked. In this study we use optical projection tomography to provide a detailed three-dimensional and quantitative description of pancreatic growth dynamics in the mouse. Hereby, we describe the epithelial and mesenchymal events leading to the formation of the gastric lobe of the pancreas. We show that this structure forms by perpendicular growth from the dorsal pancreatic epithelium into a distinct lateral domain of the dorsal pancreatic mesenchyme. Our data support a role for spleen organogenesis in the establishment of this mesenchymal domain and in mice displaying perturbed spleen development, including Dh +/-, Bapx1-/- and Sox11-/-, gastric lobe development is disturbed. We further show that the expression profile of markers for multipotent progenitors is delayed in the gastric lobe as compared to the splenic and duodenal pancreatic lobes. Altogether, this study provides new information regarding the developmental dynamics underlying the formation of the gastric lobe of the pancreas and recognizes lobular heterogeneities regarding the time course of pancreatic cellular differentiation. Collectively, these data are likely to constitute important elements in future interpretations of the developing and/or diseased pancreas.

Place, publisher, year, edition, pages
San Francisco, CA: Public Library of Science, 2011
Keyword
Animals, Homeodomain Proteins/genetics/metabolism, Immunohistochemistry, In Situ Hybridization, Mice, Morphogenesis/*physiology, Pancreas/*embryology/metabolism, SOXC, Transcription Factors/genetics/metabolism, Spleen/*embryology/metabolism, Transcription Factors/genetics/metabolism
National Category
Medical Genetics
Research subject
Molecular Medicine
Identifiers
urn:nbn:se:umu:diva-50598 (URN)10.1371/journal.pone.0021753 (DOI)21738788 (PubMedID)
Available from: 2011-12-15 Created: 2011-12-15 Last updated: 2017-12-08Bibliographically approved

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