live-calcium-imaging-virus-infected-human-intestinal-organoid

Live Calcium Imaging of Virus-Infected Human Intestinal Organoid Monolayers Using Genetically Encoded Calcium Indicators

Calcium signaling is an integral regulator of nearly every tissue. Within the intestinal epithelium, calcium is involved in the regulation of secretory ...

Baylor College of Medicine

Rotavirus causes severe diarrheal disease in children by broadly dysregulating intestinal homeostasis. However, the underlying mechanism(s) of rotavirus-induced dysregulation remains unclear. We found that rotavirus-infected cells produce paracrine signals that manifested as intercellular calcium waves (ICWs), observed in cell lines and human intestinal enteroids. Rotavirus ICWs were caused by the release of extracellular adenosine 5'-diphosphate (ADP) that activated P2Y1 purinergic receptors on neighboring cells. ICWs were blocked by P2Y1 antagonists or CRISPR-Cas9 knockout of the P2Y1 receptor. Blocking the ADP signal reduced rotavirus replication, inhibited rotavirus-induced serotonin release and fluid secretion, and reduced diarrhea severity in neonatal mice. Thus, rotavirus exploited paracrine purinergic signaling to generate ICWs that amplified the dysregulation of host cells and altered gastrointestinal physiology to cause diarrhea.

Rotavirus induces intercellular calcium waves through ADP signaling.

Cadaver dissection has long been hailed as a vital component of medical education. Although most physicians acknowledge positive impacts of cadaver dissection on their learning, they are less likely to will their bodies for anatomical dissection than the general public. This study aims to determine whether the proportion of medical students open to willed body donation changes after completing cadaver dissection.

Fewer medical students are open to body donation after dissecting human cadavers.

Viruses are among the most prevalent enteric pathogens. Although virologists historically relied on cell lines and animal models, human intestinal organoids (HIOs) continue to grow in popularity. HIOs are nontransformed, stem cell-derived, ex vivo cell cultures that maintain the cell type diversity of the intestinal epithelium. They offer higher throughput than standard animal models while more accurately mimicking the native tissue of infection than transformed cell lines. Here, we review recent literature that highlights virological advances facilitated by HIOs. We discuss the variations and limitations of HIOs, how HIOs have allowed for the cultivation of previously uncultivatable viruses, and how they have offered insight into tropism, entry, replication kinetics, and host-pathogen interactions. In each case, we discuss exemplary viruses and archetypal studies. We discuss how the speed and flexibility of HIO-based studies contributed to our knowledge of SARS-CoV-2 and antiviral therapeutics. Finally, we discuss the current limitations of HIOs and future directions to overcome these.

Gastrointestinal organoids in the study of viral infections.

Student-run clinics represent a unique medical education and healthcare delivery model powered largely by good intentions. These good intentions may produce questionable results, however, when juxtaposed with intense academic pressure to fill one's curriculum vitae with personal achievements, leadership roles and peer-reviewed publications. It becomes a legitimate ethical question whether student-run clinics consistently and materially enrich the care of underserved communities, or merely inspire a litany of rushed, short-term and low-quality projects that sidestep patient welfare or even cause brazen harm. As co-directors of HOMES Clinic, a student-managed clinic which offers free health and social services to people experiencing housing insecurity, we routinely encounter such well-intentioned but ethically questionable proposals. Here, we present four short case studies that dissect apart some of these common yet suspect assumptions underpinning student-run clinics. We then conclude with a rubric for reflective, calibrated action.

Turning good intentions into good outcomes: ethical dilemmas at a student-run clinic and a rubric for reflective action.

Nucleotides are potent extracellular signaling molecules during homeostasis, infection, and injury due to their ability to activate purinergic receptors. The nucleotide ATP activates P2X receptors (P2RXs), whereas the nucleotides ADP, ATP, UTP, and UDP-glucose selectively activate different P2Y receptors (P2RYs). Several studies have established crucial roles for P2 receptors during intestinal inflammatory and infectious diseases, yet the most extensive characterization of purinergic signaling has focused on immune cells and the central and enteric nervous systems. As epithelial cells serve as the first barrier against irritants and infection, we hypothesized that the gut epithelium may express multiple purinergic receptors that respond to extracellular nucleotide signals. Using the Human Protein Atlas and Gut Cell Survey, we queried single-cell RNA sequencing (RNAseq) data for the P2 purinergic receptors in the small and large intestines. In silico analysis reveals robust mRNA expression of P2RY1, P2RY2, P2RY11, and P2RX4 throughout the gastrointestinal tract. Human intestinal organoids exhibited a similar expression pattern with a prominent expression of P2RY1, P2RY2, and P2RX4, but this purinergic receptor repertoire was not conserved in T84, Caco2, and HT29 intestinal epithelial cell lines. Finally, P2YR1 and P2YR2 agonists elicited robust calcium responses in human intestinal organoids, but calcium responses were weaker or absent in the cell lines. These findings suggest that the gastrointestinal epithelia respond to extracellular purinergic signaling via P2RY1, P2RY2, P2RY11, and P2RX4 receptors and highlight the benefit of using intestinal organoids as a model of intestinal purinergic signaling. Several studies have revealed crucial roles for P2 receptors during inflammatory and infectious diseases, however, these have largely been demonstrated in immune cells and the enteric nervous system. Although epithelial cells serve as the first barrier against infection and inflammation, the role of purinergic signaling within the gastrointestinal tract remains largely unknown. This work expands our knowledge of purinergic receptor distribution and relative expression along the intestine.

J. Thomas Gebert

Alkek Center for Metagenomics and Microbiome Research,
Department of Molecular Virology and Microbiology,
Alkek Center for Metagenomics and Microbiome Research, Department of Molecular Virology and Microbiology

Baylor College of Medicine

Live Calcium Imaging of Virus-Infected Human Intestinal Organoid Monolayers Using Genetically Encoded Calcium Indicators

J. Thomas Gebert

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Alkek Center for Metagenomics and Microbiome Research,Department of Molecular Virology and Microbiology,Alkek Center for Metagenomics and Microbiome Research, Department of Molecular Virology and Microbiology

Baylor College of Medicine

Live Calcium Imaging of Virus-Infected Human Intestinal Organoid Monolayers Using Genetically Encoded Calcium Indicators

Alkek Center for Metagenomics and Microbiome Research,
Department of Molecular Virology and Microbiology,
Alkek Center for Metagenomics and Microbiome Research, Department of Molecular Virology and Microbiology