Scott T. Magness

Background & Aims: Necrotizing enterocolitis (NEC) is a life-threatening disease of premature infants marked by inflammation, ischemia, mucosal injury, and, in advanced cases, necrosis extending into deeper layers of the intestinal wall. Because NEC affects specialized, interacting cells in a developing intestine, we used single-nucleus transcriptomics to build a transmural, cell-type-resolved map and nominate hypothesis-generating disease programs distinct from maturation. Methods: Full-thickness intestinal specimens from fetal/prenatal controls, acute NEC cases, and infant controls were analyzed by single-nucleus RNA sequencing (snRNA-seq). Fetal and infant samples served as developmental references. Analyses included cell annotation, NEC-versus-infant differential expression, gene ontology (GO), cross-lineage recurrence, cell death signatures, and developmental maturity. Results: We profiled 53,735 nuclei by snRNA-seq and resolved 34 epithelial, stromal, vascular, immune, neuronal, glial, and smooth muscle populations. We used a morphology-based nuclei scoring system for sample selection that predicted high-quality transcript recovery. NEC nuclei were represented across this cellular landscape, with recurrent gene-expression changes suggesting shared inflammatory recruitment, antimicrobial/redox defense, stress adaptation, complement/vascular activation, reduced homeostatic signaling, and cell death-associated regulation. Developmental maturity analysis identified fetal-like expression levels in subsets of NEC-regulated genes. Proliferative crypt populations exhibit DNA repair/cell-cycle programs with inflammatory, hypoxic, and ER-stress features, while absorptive enterocytes showed reduced digestive, transport, detoxification, and terminal villus-function programs. Secretory-lineage changes implicated goblet mucus-barrier responses with reduced glycosylation, trafficking, and hydration; enteroendocrine changes in epithelial defense, metabolic stress, and neural signaling; and Paneth cell retention of antimicrobial effector transcripts despite altered ER quality control, autophagy, and granule delivery in NEC. Non-epithelial programs implicated stromal Wnt/BMP niche loss, impaired lymphatic drainage/scavenging, macrophage cytokine activation with reduced clearance machinery, neuroglial circuit defects, and altered smooth muscle contraction-relaxation balance. Conclusions: This single nuclear intestinal cell atlas nominates multicellular programs that may govern NEC initiation, progression toward tissue destruction, and resolution toward functional recovery.

Background & Aims: Dynamic cell cycle control is critical for intestinal crypt maintenance and injury responses, yet genetic regulators driving these changes remain poorly defined. As reserve intestinal stem cells (rISCs) are often considered to be slowly-cycling and can resist replication-dependent injury, factors that restrain proliferation may confer cytoprotection. Here, we define SOX9 as a regulator of intestinal stem cell (ISC) cycling and injury resistance. Methods: Primary human ISCs were engineered to tune SOX9 levels, visualize cell cycle state, and manipulate cell cycle regulators. Using this system, we tested how SOX9 dosage impacts stemness, differentiation, proliferative recovery after SOX9 washout, and survival after 5-FU-mediated injury. Transcriptional analyses identified candidate links between SOX9 levels and cell cycle control, which were functionally tested using inducible INK4A (CDKN2A) and Cyclin D2 (CCND2) ISC lines. Results: SOX9 induction lengthens the cell cycle in a dose-dependent manner largely by elongating G1 phase through the INK4A-Rb pathway. The effects of high SOX9 levels repressing proliferation and stem cell activity are reversible. SOX9 induction protects against 5-FU toxicity. This protection is mimicked by INK4A overexpression or pharmacological G1 phase arrest and repressed by CCND2 induction. Conclusions: These findings identify SOX9-mediated G1 elongation as a reversible cytoprotective program that confers key functional properties associated with rISCs: proliferative restraint, retained stem cell potential, and resistance to replication-dependent injury. This positions G1 length as a potential determinant of which crypt cells survive injury to act as reserve stem cells.

Summary: The Planar Cell Polarity (PCP) complex regulates many diverse phenotypes. While recent literature has elucidated key mechanisms underlying PCP, a mechanistic understanding of how these components function as a system to drive polarity is lacking. Here, we develop a comprehensive multicellular mathematical model centered around key PCP phosphorylation events, directly simulating the protein interactions that drive PCP. Our model confirms key PCP phenotypes, including robust single-junction asymmetry and multicellular polarity alignment in the absence of extrinsic signals. It predicts unique roles for the two known positive feedback mechanisms and predicts that VANGL-mediated DVL phosphorylation may be an underappreciated negative feedback mechanism. To test model predictions, we employ transgenic primary human intestinal epithelium cultured on biomimetic planar-crypt microarrays (PCMs) as a new platform for studying PCP. Together, our model provides novel insights into the mechanisms that regulate PCP, while our experimental results highlight an unappreciated role for PCP in intestinal biology.

These studies validate an approach to identify and predict upstream regulation of restituting epithelium in a unique pig intestinal ischemic injury model. Identification of potential molecular mediators of restitution, such as CSF-1, will inform the development of targeted therapeutic interventions for the medical management of patients with ischemia-mediated intestinal injury.

This study refines a powerful translational pig model, defining an age-dependent relationship between enteric glia and the intestinal epithelium during intestinal ischemic injury and confirming an important role for enteric glial cell (EGC) activity in driving mucosal barrier restitution. This study suggests that targeting the enteric glial network could lead to novel interventions to improve recovery from intestinal injury in neonatal patients.

Background and Aims: The intestinal epithelium exhibits dynamic control of cell cycle phase lengths, yet no experimental platform exists for directly analyzing cell cycle phases in living human intestinal stem cells (ISCs). Here, we develop primary human ISC lines with two different reporter constructs to provide fluorescent readouts to analyze cell cycle phases in cycling ISCs. Methods: 3D printing was used to construct a collagen press for making chamber slides that support primary human ISC growth and maintenance within the working distance of a confocal microscope objective. The PIP-FUCCI fluorescent cell cycle reporter and a variant with H2A-mScarlet that allows for automated tracking of cell cycle phases (PIP-H2A) were used in human ISCs along with live imaging and EdU pulsing. An analysis pipeline combining free-to-use programs and publicly available code was compiled to analyze live imaging results. Results: Chamber slides with soft collagen pressed to a thickness of 0.3 mm concurrently support ISC cycling and confocal imaging. PIP-FUCCI ISCs were found to be optimal for snapshot analysis wherein all nuclei are assigned to a cell cycle phase from a single image. PIP-H2A ISCs were better suited for live imaging since constant nuclear signal allowed for more automated analysis. CellPose2 and TrackMate were used together to track cycling cells. Conclusions: We present two complete platforms for analyzing cell cycle phases in living primary human ISCs. The PIP-FUCCI construct allows for cell cycle phase assignment from one image of living cells, the PIP-H2A construct allows for semi-automated direct quantification of cell cycle phase lengths in human ISCs using our computational pipeline. These platforms hold great promise for future studies on how pharmaceutical agents affect the intestinal epithelium, how cell cycle is regulated in human ISCs, and more.