Biology subjects

Hebrok, M.

Publications and source records attributed to Hebrok, M..

5 recordsLinked to original sources

bioRxiv2026

MAFA drives pancreatic islet maturation through coordination of cell growth, metabolic maturation, and resilience to stress.

Stem cell-derived islets (SC-islets) are a promising source for replacing the loss of insulin-secreting {beta} cells in insulin-dependent diabetes patients, but compared to their primary human counter parts, SC-islets are considered functionally immature and do not immediately regulate blood glucose after transplantation. To better understand the molecular underpinnings of {beta} cell maturation, we genetically engineered human pluripotent stem cells (hPSCs) to control the induction of the {beta} cell-maturing transcription factor MAFA or a MAFA S64F mutant variant associated with premature {beta} cell aging and senescence in SC-islets. We employ a combination of in vitro assays, multi-omics analyses, and murine in vivo transplantation studies to demonstrate that MAFA remodeling of the SC-islet transcriptional landscape promotes SC-islet biogenesis and metabolic maturation giving rise to greater SC-islet resilience and insulin secretory capacity. Parallel MAFA S64F studies highlight the importance for compensatory mechanisms for sustaining accelerated oxidative metabolism and enhanced insulin secretion without inducing intracellular stress responses and islet dysfunction. Overall, these results reveal MAFA-governed transcriptional changes that drive SC-islet functional maturation, which provides the foundation for maturing SC-islets in vitro, preserving {beta} cell integrity, and improving SC-islet cell replacement therapies.

cell biology↗

bioRxiv2024

nSMase2-mediated exosome secretion shapes the tumor microenvironment to immunologically support pancreatic cancer

The pleiotropic roles of nSMase2-generated ceramide include regulation of intracellular ceramide signaling and exosome biogenesis. We investigated the effects of eliminating nSMase2 on early and advanced PDA, including its influence on the microenvironment. Employing the KPC mouse model of pancreatic cancer, we demonstrate that pancreatic epithelial nSMase2 ablation reduces neoplasia and promotes a PDA subtype switch from aggressive basal-like to classical. nSMase2 elimination prolongs survival of KPC mice, hinders vasculature development, and fosters a robust immune response. nSMase2 loss leads to recruitment of cytotoxic T cells, N1-like neutrophils, and abundant infiltration of anti-tumorigenic macrophages in the pancreatic preneoplastic microenvironment. Mechanistically, we demonstrate that nSMase2-expressing PDA cell small extracellular vesicles (sEVs) reduce survival of KPC mice; PDA cell sEVs generated independently of nSMase2 prolong survival of KPC mice and reprogram macrophages to a proinflammatory phenotype. Collectively, our study highlights previously unappreciated opposing roles for exosomes, based on biogenesis pathway, during PDA progression. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=189 SRC="FIGDIR/small/614610v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@b6e6d1org.highwire.dtl.DTLVardef@1ebb41eorg.highwire.dtl.DTLVardef@17e4275org.highwire.dtl.DTLVardef@3d31f1_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2022

Species-specific roles for the MAFA and MAFB transcription factors in regulatingislet β cell identity

Type 2 diabetes (T2D) is associated with compromised identity of insulin-producing pancreatic islet beta ({beta}) cells, characterized by inappropriate production of other islet cell-enriched hormones. Here we examined how hormone misexpression was influenced by the MAFA and MAFB transcription factors, closely related proteins that maintain islet cell function. Mice specifically lacking MafA in {beta} cells demonstrated broad, population-wide changes in hormone gene expression with an overall gene signature closely resembling islet gastrin (Gast)-positive cells generated under conditions of chronic hyperglycemia and obesity. A human {beta} cell line deficient in MAFB, but not one lacking MAFA, also produced a gastrin (GAST)-positive gene expression pattern. In addition, GAST was detected in human T2D {beta} cells with low levels of MAFB. Moreover, evidence is provided that human MAFB can directly repress GAST gene transcription. These results support a novel, species-specific role for MafA and MAFB in maintaining adult mouse and human {beta} cell identity, respectively, by repressing expression of Gast/GAST and other non-{beta} cell hormones.

cell biology↗

bioRxiv2022

Multiplexed microfluidic platform for stem-cell derived pancreatic islet β cells

Stem-cell derived {beta} cells offer an alternative to primary islets for biomedical discoveries as well as a potential surrogate for islet transplantation. The expense and challenge of obtaining and maintaining functional stem-cell derived {beta} cells calls for a need to develop better high-content and high-throughput culture systems. Microphysiological systems (MPS) are promising high-content in vitro platforms, but scaling for high-throughput screening and discoveries remain a challenge. Traditionally, simultaneous multiplexing of liquid handling and cell loading poses a challenge in the design of high-throughput MPS. Furthermore, although MPS for islet beta culture/testing have been developed, studies on multi-day culture of stem-cell derived {beta} cells in MPS have been limited. We present a scalable, multiplexed islet beta MPS device that incorporates microfluidic gradient generators to parallelize fluid handling for culture and test conditions. We demonstrated the viability and functionality of the stem-cell derived enriched {beta} clusters (eBCs) for a week, as assessed by the ~2 fold insulin release by the clusters to glucose challenge. To show the scalable multiplexing for drug testing, we demonstrated the exhaustion of eBC insulin reserve after long term exposure to logarithmic concentration range of glybenclamide. The MPS cultured eBCs also revealed a glycolytic bottleneck as inferred by insulin secretion responses to metabolites methyl succinate and glyceric acid. Thus, we present an innovative culture platform for eBCs with a balance of high-content and high-throughput characteristics.

bioengineering↗

bioRxiv2020

Single cell transcriptome analysis defines novel heterogeneity within the pancreatic ductal tree

Lineage tracing using genetically engineered mouse models is an essential tool for investigating cell-fate decisions of progenitor cells and biology of mature cell types, with relevance to physiology and disease progression. To study disease development, an inventory of an organs cell types and understanding of physiologic function is paramount. Here, we performed single-cell RNA sequencing to examine heterogeneity of murine pancreatic duct cells, pancreatobiliary cells, and intrapancreatic bile duct cells. We describe an epithelial-mesenchymal transitory axis in our three pancreatic duct subpopulations and identify SPP1 as a regulator of this fate decision as well as human duct cell de-differentiation. Our results further identify functional heterogeneity within pancreatic duct subpopulations by elucidating a role for Geminin in accumulation of DNA damage in the setting of chronic pancreatitis. Our findings implicate diverse functional roles for subpopulations of pancreatic duct cells in maintenance of duct cell identity and disease progression and establish a comprehensive road map of murine pancreatic duct cell, pancreatobiliary cell, and intrapancreatic bile duct cell homeostasis. SIGNIFICANCEMurine models are extensively used for pancreatic lineage tracing experiments and investigation of pancreatic disease progression. Here, we describe the transcriptome of murine pancreatic duct cells, intrapancreatic bile duct cells, and pancreatobiliary cells at single cell resolution. Our analysis defines novel heterogeneity within the pancreatic ductal tree and supports the paradigm that more than one population of pancreatic duct cells harbors progenitor capacity. We identify and validate unique functional properties of subpopulations of pancreatic duct cells including an epithelial-mesenchymal transcriptomic axis and roles in chronic pancreatic inflammation.

bioinformatics↗