Progressive loss and dysfunction of islet β-cells has not yet been solved in the treatment of diabetes. Regenerating protein (Reg) has been identified as a trophic factor which is demonstrated to be associated with pancreatic tissue regeneration. We previously produced recombinant Reg3α protein (rReg3α) and proved that it protects against acute pancreatitis in mice. Whether rReg3α protects islet β-cells in diabetes has been elusive. In the present study, rReg3α stimulated MIN6 cell proliferation and resisted STZ-caused cell death. The protective effect of rReg3α was also found in mouse primary islets. In BALB/c mice, rReg3α administration largely alleviated STZ-induced diabetes by the preservation of β-cell mass. The protective mechanism could be attributed to Akt/Bcl-2/-xL activation and GRP78 upregulation. Scattered insulin-expressing cells and clusters with small size, low insulin density, and exocrine distribution were observed and considered to be neogenic. In isolated acinar cells with wheat germ agglutinin (WGA) labeling, rReg3α treatment generated insulin-producing cells through Stat3/Ngn3 signaling, but these cells were not fully functional in response to glucose stimulation. Our results demonstrated that rReg3α resists STZ-induced β-cell death and promotes β-cell regeneration. rReg3α could serve as a potential drug for β-cell maintenance in anti-diabetic treatment.

Background: Over the past 40 years since the discovery of regenerating family proteins (Reg proteins), numerous studies have highlighted their biological functions in promoting cell proliferation and resisting cell apoptosis, particularly in the regeneration and repair of pancreatic islets and exocrine glands. Successively, short peptides derived from Reg3δ and Reg3α have been employed in clinical trials, showing favorable therapeutic effects in patients with type I and type II diabetes. However, continued reports have been limited, presumably attributed to the potential side effects. Methods: This review summarizes extensive research on Reg proteins over the past decade, combined with our own related studies, proposing that Reg proteins exhibit dimorphic effects. Results: The activity of Reg proteins is not as simplistic as previously perceived but shows auto-immunogenicity depending on different pathophysiological microenvironments. The immunogenicity of Reg proteins could recruit immune cells leading to an anti-tumor effect. Such functional diversity is correlated with their structural characteristics: the N-terminal region contributes to autoantigenicity, while the C-type lectin fragment near the C-terminal determines the trophic action. It should be noted that B-cell masking antigens might also reside within the C-type lectin domain. Conclusions: Reg proteins have dual functional roles under various physiological and pathological conditions. These theoretical foundations facilitate the subsequent development of diagnostic reagents and therapeutic drugs targeting Reg proteins.

Reg3A is upregulated in various cancers and considered a potential target for antitumor treatments. However, the effect of Reg3A in metastasis has been elusive. This study aims to disclose the role of Reg3A overexpression in hepatic metastasis of LoVo colon cancer cells. A stable cell line of LoVo cells overexpressing Reg3A (LoVo-luc-Reg3A), labeled with luc reporter gene, was constructed. Cell proliferation, apoptosis, migration, and invasion were determined using MTT, EdU, Hoechst's staining, flow cytometry, and transwell assays, respectively. Hepatic metastasis of LoVo-luc-Reg3A cells was investigated in BALB/c nude mice. Living bioluminescence imaging, histological examination, and mRNA sequencing (mRNA-seq) were performed to assess the metastatic efficiency and gene expression alteration. Reg3A content was determined by Western blotting and Enzyme-Linked Immunosorbent Assay. Cell attachment capacity was determined in the Matrigel culture. Reg3A overexpression did not promote LoVo cell proliferation or apoptosis, but facilitated cell migration and invasion. In the hepatic metastasis model, Reg3A overexpression increased the number of metastatic colonies. The result of mRNA-seq suggested 349 differentially expressed genes (DEGs) by Reg3A upregulation, many of which were related to colon adenocarcinoma tumorigenesis compared to normal colon tissue. Gene ontology enrichment assay indicated that the DEGs are mainly associated with cell adhesion, leukocyte regulation, extracellular matrix (ECM) remodeling, integrin binding, and STAT protein binding. Reg3A overexpression led to an enrichment of Reg3A protein in local tumor tissue of liver metastasis and ECM/intracellular space in ex vivo cultured cells. However, Reg3A concentration in serum and culture medium was relatively low. Reg3A overexpression also resulted in an increased number of cells that attach to Matrigel, which was attenuated by treatments of siRNA-Reg3A and single-chain variable fragment against Reg3A. Endogenous Reg3A overexpression facilitates hepatic metastasis of LoVo colon cancer cells. The prometastatic effect could be contributed by Reg3A enrichment in ECM, which alters the cell adhesion behavior.

Molecular analyses of individual cells with high resolution, specificity, and sensitivity can not only reveal cellular heterogeneity but also provide a better understanding of diseases and accelerate drug discoveries. Single-cell endoscopy is an advanced live-cell technique that relies on a smart endoscope that allows minimally invasive probing of the interiors of individual cells. Compared with other single-cell analysis techniques, single-cell endoscopy has shown great promise in applications such as flexible single-cell manipulation, ultrasensitive sensing, and precise intracellular delivery. In this review, we aim to map out the landscape of recent advances in single-cell endoscopy techniques by focusing on both fundamental considerations and significant progress over the past decade. Specifically, we summarize the predominant live-cell endoscopes, including their fabrication and characterization. Furthermore, a series of valuable intracellular molecular sensing events, such as nucleic acids, proteins, ions, etc., are introduced with a main emphasis on how single-cell endoscopy can solve these issues and what merits single-cell endoscopy can provide. Finally, we briefly outline the remaining challenges and directions for the future development of single-cell endoscopy techniques.