Long-term culture of human pancreatic slices as a model to study real-time islet regeneration

The culture of live pancreatic tissue slices is a powerful tool for the interrogation of physiology and pathology in an in vitro setting that retains near-intact cytoarchitecture. However, current culture conditions for human pancreatic slices (HPSs) have only been tested for short-term applications, which are not permissive for the long-term, longitudinal study of pancreatic endocrine regeneration. Using a culture system designed to mimic the physiological oxygenation of the pancreas, we demonstrate high viability and preserved endocrine and exocrine function in HPS for at least 10 days after sectioning. This extended lifespan allowed us to dynamically lineage trace and quantify the formation of insulin-producing cells in HPS from both non-diabetic and type 2 diabetic donors. This technology is expected to be of great impact for the conduct of real-time regeneration/developmental studies in the human pancreas.

Pancreas tissue slices from organ donors enable in situ analysis of type 1 diabetes pathogenesis

In type 1 diabetes (T1D), autoimmune destruction of pancreatic β cells leads to insulin deficiency and loss of glycemic control. However, knowledge about human pancreas pathophysiology in T1D remains incomplete. To address this limitation, we established a pancreas tissue slice platform of donor organs with and without diabetes, facilitating the first live cell studies of human pancreas in T1D pathogenesis to our knowledge. We show that pancreas tissue slices from organ donors allow thorough assessment of processes critical for disease development, including insulin secretion, β cell physiology, endocrine cell morphology, and immune infiltration within the same donor organ. Using this approach, we compared detailed pathophysiological profiles for 4 pancreata from donors with T1D with 19 nondiabetic control donors. We demonstrate that β cell loss, β cell dysfunction, alterations of β cell physiology, and islet infiltration contributed differently to individual cases of T1D, allowing insight into pathophysiology and heterogeneity of T1D pathogenesis. Thus, our study demonstrates that organ donor pancreas tissue slices represent a promising and potentially novel approach in the search for successful prevention and reversal strategies of T1D.

Temporal Analysis of Amylase Expression in Control, Autoantibody-Positive, and Type 1 Diabetes Pancreatic Tissues

Within the human pancreas, exocrine and endocrine cells control secretion of digestive enzymes and production of hormones to maintain metabolic homeostasis, respectively. While the vast majority of type 1 diabetes research efforts have focused on endocrine function and autoimmunity, recent studies identified a series of unique features (e.g., reduced weight and volume, increased density of leukocytes) within the exocrine pancreas in this disease, but the mechanisms underlying these aberrancies are unknown. Therefore, we histologically assessed amylase, insulin, glucagon, lipase, and/or trypsinogen in 78 organ donor pancreata from birth through adulthood in control subjects and those at various stages of type 1 diabetes. While amylase-positive (AMY⁺) acinar cells were detectable in pancreata from all study groups, tissues from individuals >2 years of age contained clusters of acinar cells devoid of amylase (AMY^-). A majority of these AMY^- cell clusters localized proximal to islets (i.e., peri-islet). Additionally, most AMY^- clusters were positive for the exocrine enzymes lipase and trypsinogen. Interestingly, type 1 diabetes pancreata displayed significant reductions in the frequency of these AMY^- cell clusters. These results support a contribution of the islet-acinar axis in pancreatic development and underscore a potential role for the exocrine pancreas in the pathogenesis of type 1 diabetes.

Hospital time prior to death and pancreas histopathology: implications for future studies

AIMS/HYPOTHESIS

Diabetes research studies routinely rely upon the use of tissue samples from human organ donors. It remains unclear whether the length of hospital stay prior to organ donation affects the presence of cells infiltrating the pancreas or the frequency of replicating beta cells.

METHODS

To address this, 39 organ donors without diabetes were matched for age, sex, BMI and ethnicity in groups of three. Within each group, donors varied by length of hospital stay immediately prior to organ donation (<3 days, 3 to <6 days, or ≥6 days). Serial sections from tissue blocks in the pancreas head, body and tail regions were immunohistochemically double stained for insulin and CD45, CD68, or Ki67. Slides were electronically scanned and quantitatively analysed for cell positivity.

RESULTS

No differences in CD45⁺, CD68⁺, insulin⁺, Ki67⁺ or Ki67⁺/insulin⁺ cell frequencies were found when donors were grouped according to duration of hospital stay. Likewise, no interactions were observed between hospitalisation group and pancreas region, age, or both; however, with Ki67 staining, cell frequencies were greater in the body vs the tail region of the pancreas (∆ 0.65 [unadjusted 95% CI 0.25, 1.04]; p = 0.002) from donors <12 year of age. Interestingly, frequencies were less in the body vs tail region of the pancreas for both CD45⁺ cells (∆ -0.91 [95% CI -1.71, -0.10]; p = 0.024) and insulin⁺ cells (∆ -0.72 [95% CI -1.10, -0.34]; p < 0.001).

CONCLUSIONS/INTERPRETATION

This study suggests that immune or replicating beta cell frequencies are not affected by the length of hospital stay prior to donor death in pancreases used for research.

DATA AVAILABILITY

All referenced macros (adopted and developed), calculations, programming code and numerical dataset files (including individual-level donor data) are freely available on GitHub through Zenodo at https://doi.org/10.5281/zenodo.1034422.

Persistence of Pancreatic Insulin mRNA Expression and Proinsulin Protein in Type 1 Diabetes Pancreata

The canonical notion that type 1 diabetes (T1D) results following a complete destruction of β cells has recently been questioned as small amounts of C-peptide are detectable in patients with long-standing disease. We analyzed protein and gene expression levels for proinsulin, insulin, C-peptide, and islet amyloid polypeptide within pancreatic tissues from T1D, autoantibody positive (Ab+), and control organs. Insulin and C-peptide levels were low to undetectable in extracts from the T1D cohort; however, proinsulin and INS mRNA were detected in the majority of T1D pancreata. Interestingly, heterogeneous nuclear RNA (hnRNA) for insulin and INS-IGF2, both originating from the INS promoter, were essentially undetectable in T1D pancreata, arguing for a silent INS promoter. Expression of PCSK1, a convertase responsible for proinsulin processing, was reduced in T1D pancreata, supportive of persistent proinsulin. These data implicate the existence of β cells enriched for inefficient insulin/C-peptide production in T1D patients, potentially less susceptible to autoimmune destruction.

Continuing education for health professionals

Although continuing education in the health professions is an important endeavor, it has been largely neglected in the professional literature. Few studies have been done on (a) conceptual models to guide the design and implementation of continuing education and (b) the use of such models in continuing education. To fill this gap, two such models are described in this article: (a) instructional development and (b) community development. Combining and using these models can lead to more effective continuing education with more enduring effects. Principles to guide the implementation of these models are presented. An arthritis continuing education project based on the instructional and community development models is used to illustrate these principles. This continuing education project focused on occupational and physical therapists in clinical practice.