Immunohistochemical study of the principal pancreatic islet of the toadfish, Halobatrachus didactylus (Pisces: Batrachoididae)

A Pro-Endocrine Pancreatic Islet Transcriptional Program Established During Development Is Retained in Human Gallbladder Epithelial Cells

BACKGROUND & AIMS

Pancreatic islet β-cells are factories for insulin production; however, ectopic expression of insulin also is well recognized. The gallbladder is a next-door neighbor to the developing pancreas. Here, we wanted to understand if gallbladders contain functional insulin-producing cells.

METHODS

We compared developing and adult mouse as well as human gallbladder epithelial cells and islets using immunohistochemistry, flow cytometry, enzyme-linked immunosorbent assays, RNA sequencing, real-time polymerase chain reaction, chromatin immunoprecipitation, and functional studies.

RESULTS

We show that the epithelial lining of developing, as well as adult, mouse and human gallbladders naturally contain interspersed cells that retain the capacity to actively transcribe, translate, package, and release insulin. We show that human gallbladders also contain functional insulin-secreting cells with the potential to naturally respond to glucose in vitro and in situ. Notably, in a non-obese diabetic (NOD) mouse model of type 1 diabetes, we observed that insulin-producing cells in the gallbladder are not targeted by autoimmune cells. Interestingly, in human gallbladders, insulin splice variants are absent, although insulin splice forms are observed in human islets.

CONCLUSIONS

In summary, our biochemical, transcriptomic, and functional data in mouse and human gallbladder epithelial cells collectively show the evolutionary and developmental similarities between gallbladder and the pancreas that allow gallbladder epithelial cells to continue insulin production in adult life. Understanding the mechanisms regulating insulin transcription and translation in gallbladder epithelial cells would help guide future studies in type 1 diabetes therapy.

Unique localization of disseminated pancreas in the oesophagus of catfish (clarias gariepinus) with reference to sexual dimorphism

BACKGROUND

The fish pancreas has been reported to be composed of two portions: compact and disseminated. However, little has been elucidated in catfish. The present study describes a unique localization of the disseminated pancreas in African catfish.

METHODS

The sections were obtained and used for either routine histological examination following staining with haematoxylin and eosin (H & E), periodic acid-Schiff's, or were subjected to immunohistochemical staining for detection of both insulin-producing β cells and glucagon-producing alpha cells.

RESULTS

Our investigation showed that the pancreas of catfish consisted of both compact and disseminated portions. The compact pancreas was embedded in the mesenteric adipose tissue between the spleen, stomach and liver. However, the disseminated one showed unique localization in the tunica adventitia of the middle portion of the oesophagus. The pancreas consisted of two portions, exocrine and endocrine. Furthermore, in both types of pancreas, the female showed a significantly higher ratio for the endocrine islet area/pancreatic tissue area than that of the male and also a significantly higher ratio for both insulin- and glucagon-positive area/islet area in the female pancreas (compact and disseminated) than that of the male.

IN CONCLUSION

The present study provides evidence on a unique localization of the disseminated pancreas in the oesophagus of catfish. Furthermore, we revealed sex-related difference in the endocrine portion in both pancreatic tissues with more development in the female. The study suggests that sex hormones could be contributed to such sexual dimorphism. However, further investigation is required to compare the degree of development during the spawning and resting seasons.

Expression profiling of the sex-related gene Dmrt1 in adults of the Lusitanian toadfish Halobatrachus didactylus (Bloch and Schneider, 1801)

Doublesex and mab-3 related transcription factor 1 (Dmrt1) gene is a widely conserved gene involved in sex determination and differentiation across phyla. To gain insights on Dmrt1 implication for fish gonad cell differentiation and gametogenesis development, its mRNA was isolated from testis and ovary from the Lusitanian toadfish (Halobatrachus didactylus). The cDNA from Dmrt1 was synthesized and cloned, whereas its quantitative and qualitative gene expression, as well as its protein immunolocalization, were analyzed. A main product of 1.38 kb, which encodes a protein of 295 aa, was reported, but other minority Dmrt1 products were also identified by RACE-PCR. This gene is predominantly expressed in testis (about 20 times more than in other organs or tissues), specially in spermatogonia, spermatocytes and spermatids, as well as in somatic Sertoli cells, indicating that Dmrt1 plays an important role in spermatogenesis. Although Dmrt1 transcripts also seem to be involved in oogenesis development, and it cannot be excluded that toadfish Dmrt1 could be functionally involved in other processes not related to sex.