Islet-derived stellate-like cells as a novel source for islet neogenesis in chicks

Proteomic profiling of small extracellular vesicles derived from mouse pancreatic cancer and stellate cells: Role in pancreatic cancer

Small extracellular vesicles (sEVs) are cell-derived vesicles evolving as important elements involved in all stages of cancers. sEVs bear unique protein signatures that may serve as biomarkers. Pancreatic cancer (PC) records a very poor survival rate owing to its late diagnosis and several cancer cell-derived proteins have been reported as candidate biomarkers. However, given the pivotal role played by stellate cells (PSCs, which produce the collagenous stroma in PC), it is essential to also assess PSC-sEV cargo in biomarker discovery. Thus, this study aimed to isolate and characterise sEVs from mouse PC cells and PSCs cultured alone or as co-cultures and performed proteomic profiling and pathway analysis. Proteomics confirmed the enrichment of specific markers in the sEVs compared to their cells of origin as well as the proteins that are known to express in each of the culture types. Most importantly, for the first time it was revealed that PSC-sEVs are enriched in proteins (including G6PI, PGAM1, ENO1, ENO3, and LDHA) that mediate pathways related to development of diabetes, such as glucose metabolism and gluconeogenesis revealing a potential role of PSCs in pancreatic cancer-related diabetes (PCRD). PCRD is now considered a harbinger of PC and further research will enable to identify the role of these components in PCRD and may develop as novel candidate biomarkers of PC.

Role of Pancreatic Stellate Cell-Derived Exosomes in Pancreatic Cancer-Related Diabetes: A Novel Hypothesis

Pancreatic ductal adenocarcinoma (PDAC) is a devastating condition characterised by vague symptomatology and delayed diagnosis. About 30% of PDAC patients report a history of new onset diabetes, usually diagnosed within 3 years prior to the diagnosis of cancer. Thus, new onset diabetes, which is also known as pancreatic cancer-related diabetes (PCRD), could be a harbinger of PDAC. Diabetes is driven by progressive β cell loss/dysfunction and insulin resistance, two key features that are also found in PCRD. Experimental studies suggest that PDAC cell-derived exosomes carry factors that are detrimental to β cell function and insulin sensitivity. However, the role of stromal cells, particularly pancreatic stellate cells (PSCs), in the pathogenesis of PCRD is not known. PSCs are present around the earliest neoplastic lesions and around islets. Given that PSCs interact closely with cancer cells to drive cancer progression, it is possible that exosomal cargo from both cancer cells and PSCs plays a role in modulating β cell function and peripheral insulin resistance. Identification of such mediators may help elucidate the mechanisms of PCRD and aid early detection of PDAC. This paper discusses the concept of a novel role of PSCs in the pathogenesis of PCRD.

Screening and Identification of Key Genes for Activation of Islet Stellate Cell

Background

It has been demonstrated that activated islet stellate cells (ISCs) play a critical role in islet fibrogenesis and significantly contribute to the progression of type 2 diabetes mellitus. However, the key molecules responsible for ISCs activation have not yet been determined. This study aimed to identify the potential key genes involved in diabetes-induced activation of ISCs.

Method

Stellate cells were isolated from three 10-week-old healthy male Wistar rats and three Goto-Kakizaki (GK) rats. Cells from each rat were primary cultured under the same condition. A Genome-wide transcriptional sequence of stellate cells was generated using the Hiseq3000 platform. The identified differentially expressed genes were validated using quantitative real-time PCR and western blotting in GK rats, high fat diet (HFD) rats, and their controls.

Results

A total of 204 differentially expressed genes (DEGs) between GK. ISCs and Wistar ISCs (W.ISCs) were identified, accounting for 0.58% of all the 35,362 genes detected. After the Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses, the mRNA levels of these genes were further confirmed by real-time PCR in cultured ISCs. We then selected Fos, Pdpn, Bad as the potential key genes for diabetes-induced activation of ISCs. Finally, we confirmed the protein expression levels of FOS, podoplanin, and Bad by western blotting and immunofluorescence in GK rats, HFD rats, and their controls. The results showed that the expression level of FOS was significantly decreased, while podoplanin and Bad were significantly increased in GK.ISCs and HFD rats compared with controls, which were consistent with the expression of α-smooth muscle actin.

Conclusions

A total of 204 DEGs were found between the GK.ISCs and W.ISCs. After validating the expression of potential key genes from GK rats and HFD rats, Fos, Pdpn, and Bad might be potential key genes involved in diabetes-induced activation of ISCs.

A Transcriptional Sequencing Analysis of Islet Stellate Cell and Pancreatic Stellate Cell

BACKGROUND

Our previous studies have shown that islet stellate cell (ISC), similar to pancreatic stellate cell (PSC) in phenotype and biological characters, may be responsible for the islet fibrosis in type 2 diabetes. To further identify the differences between PSC and ISC and for better understanding of the physiological function of ISC, we employed genome-wide transcriptional analysis on the PSCs and ISCs of Wistar rats.

METHOD

PSCs and ISCs from each rat were primarily cultured at the same condition. Genome-wide transcriptional sequence of stellate cells was generated. The identified differentially expressed genes were validated using RT-PCR.

RESULTS

32 significant differentially expressed genes between PSCs and ISCs were identified. Moreover, collagen type 11a1 (COL11A1), was found to be expressed 2.91-fold higher in ISCs compared with PSCs, indicating that COL11A1 might be a potential key gene modulating the differences between PSC and ISC.

CONCLUSIONS

Our study identified and validated the differences between PSC and ISC in genome-wide transcriptional scale, confirming the assumption that ISC and PSC are similar other than identical. Moreover, our data might be instrumental for further investigation of ISC and islet fibrosis, and some differential expressed genes may provide an insight into new therapeutic targets for type 2 diabetes.

Isolation and characterization of human islet stellate cells

BACKGROUND AND AIMS

We have previously demonstrated that islet stellate cells (ISCs) exhibiting a similar phenotype to classical pancreatic stellate cells (PSCs) could be isolated from rat islets, where they may contribute to islet fibrosis in type 2 diabetes mellitus (T2DM). This study was designed to determine whether human islets also contain ISC.

MATERIALS AND METHODS

Using standard explants techniques, human ISCs were enriched from freshly isolated human islets. Immunofluorescence visualization of markers for PSCs(α-smooth muscle actin;α-SMA), desmin, vimentin, glial fibrillary acidic protein (GFAP) was used to characterize the human ISC. Cell counting kit-8 (CCK-8) was used to assess the proliferation of ISC. The wound-healing assay and the transwell migration were used to assess the migration capacity of ISC. Immunofluorescence against collagen typesI (col-I), collagen typesIII (col-III) and fibronectin (FN) was performed to identify extracellular matrix (ECM) component synthesized by ISC. Adipogenic and osteogenic differentiation were tried to detected stem cell potential.

RESULTS

In culture, ISC with triangular shape grow out from human islets. The passaged ISC expressed α-SMA, desmin, vimentin, GFAP and was positive for col-I, col-III and FN. The proliferation and migration ability of ISC was significantly slower than those of PSC. And both the human PSC and ISC were able to differentiate in vitro into adipocyte- and osteoblast-like cells.

CONCLUSION

Similar to our previous rat experiment, the current study shows that human islets also contain ISC which is phenotypically similar but not identical to human PSC.

Crosstalk Between Activated Myofibroblasts and β Cells in Injured Mouse Pancreas

OBJECTIVES

In injury conditions, myofibroblasts are induced to lay down matrix proteins and support the repair process. In this study, we investigated the role of myofibroblasts, particularly stellate cells, in the growth and regeneration of pancreatic β cells.

METHODS

We used both in vitro and in vivo approaches to address whether stellate cells may promote the growth of β cells.

RESULTS

Our experiments demonstrated that activated stellate cells support the proliferation of β cells in vitro. In vivo, mesenchymals surrounding the pancreatic islets are activated (induced to proliferate) in the islet regeneration model of Pten null mice. These mesenchymals display markers of pancreatic stellate cells, such as desmin and to a lesser extent, smooth muscle actin α. We have shown previously that targeted β-cell deletion of Pten lead to a significant increase in total islet mass. This phenotype was accompanied by an increase in peri-islet mitotic activity, particularly in islets injured by streptozotocin, a β cell-specific toxin.

CONCLUSIONS

Together with the in vitro observations, our data, here, suggest that that these mesenchymal cells may support the regeneration of the islets. Identifying how the communication occurs may provide clinically relevant mechanism for inducing β-cell regeneration.

In vitro reconstitution of pancreatic islets

The lack of transplantable pancreatic islets is a serious problem that affects the treatment of patients with type 1 diabetes mellitus. Beta cells can be induced from various sources of stem or progenitor cells, including induced pluripotent stem cells in the near future; however, the reconstitution of islets from β cells in culture dishes is challenging. The generation of highly functional islets may require three-dimensional spherical cultures that resemble intact islets. This review discusses recent advances in the reconstitution of islets. Several factors affect the reconstitution of pseudoislets with higher functions, such as architectural similarity, cell-to-cell contact, and the production method. The actual transplantation of naked or encapsulated pseudoislets and islet-like cell clusters from various stem cell sources is also discussed. Advancing our understanding of the methods used to reconstitute pseudoislets should expand the range of potential strategies available for developing de novo islets for therapeutic applications.

Isolation and characterization of islet stellate cells in rat

The central role of PSCs in pancreatic fibrogenesis is well established. However, the mechanism responsible for the islet fibrosis presenting in the late stage of T2DM has not been fully elucidated. This study was designed to determine whether the endocrine pancreatic islets contain cells resembling PSCs. PSCs were isolated from pancreas using standard explants techniques. A similar method was used to acquire ISCs. Adherent ISCs with a stellate, angular morphology migrated from the edge of cultured islets within 48 h of primary culture. ISCs contained fewer lipid droplets than equivalent PSCs, and their rapid disappearance accompanied by the increased expression of α-SMA suggested that ISCs were more rapidly activated than PSCs in vitro. They expressed α-SMA, vimentin, GFAP and were positive for ECM components col-I, col-III and FN, all of which are characteristics of classical PSCs. However, ISCs differed from PSCs by having reduced rates of proliferation and migration in vitro. Our in vitro study shows that isolated islets contain a population of stellate cells which are phenotypically similar but not identical to PSCs. In view of the established role of PSCs in pancreatic fibrosis, we suggest that these may contribute to islet fibrosis in T2DM.

Pancreatic progenitors: The shortest route to restore islet cell mass

The regenerative process of the pancreas is of interest because the main pathogenesis of diabetes mellitus is an inadequate number of insulin-producing β-cells. The functional mass of β-cells is decreased in most forms of diabetes, so replacing missing β-cells or triggering their regeneration may allow for improved diabetes treatment. Therefore, expansion of the β-cell mass from endogenous sources, either in vivo or in vitro, represents an area of increasing interest. The mechanism of islet regeneration remains poorly understood, but the identification of islet progenitor sources is critical for understanding β-cell regeneration. One potential source is the islet proper, via the de-differentiation, proliferation and redifferentiation of facultative progenitors residing within the islet. The new pancreatic islets derived from progenitor cells present within the ducts have been reported, but the existence and identity of the progenitor cells have been debated. In this mini-review, we focus primarily on pancreatic progenitors, which are islet progenitors capable of differentiating into insulin producing cells. We also emphasize the importance of pancreatic progenitors as a target for stem cell therapy for diabetes.