Biology subjects

Klein, O. D.

Publications and source records attributed to Klein, O. D..

5 recordsLinked to original sources

bioRxiv2018

LRH-1 Mitigates Intestinal Inflammatory Disease by Maintaining Epithelial Homeostasis and Cell Survival

Epithelial dysfunction and loss of intestinal crypts are defining features of inflammatory bowel disease (IBD). However, current therapies primarily target the immune system and not the epithelium. The nuclear receptor LRH-1 encoded by Nr5a2 is expressed in intestinal epithelium and is thought to contribute to epithelial renewal. Here we investigate how loss and gain of LRH-1 impacts the intestinal epithelium in healthy and inflammatory conditions. Knocking out LRH-1 in murine intestinal organoids reduces Notch signaling, increases crypt cell death and weakens the epithelial barrier. Loss of LRH-1 also distorts the cellular composition of the epithelium, resulting in an expansion of Paneth and goblet cells, and a decrease in enteroendocrine cells. Human LRH-1 (hLRH-1) not only rescues epithelial integrity, but when overexpressed, mitigates inflammatory damage in mouse and human intestinal organoids, including those from IBD patients. Finally, hLRH-1 greatly reduces disease severity in a mouse model of T cell-mediated colitis. Together with the failure of a ligand-incompetent hLRH-1 mutant to protect against TNF-damage, these findings provide compelling evidence that hLRH-1 mediates epithelial homeostasis and is an attractive target for intestinal disease.

cell biology↗

bioRxiv2018

Diverse progenitor cells preserve salivary gland ductal architecture after radiation induced damage

The ductal system of the salivary gland has long been postulated to be resistant to radiation-induced damage, a common outcome incurred by head and neck cancer patients receiving radiotherapy. Yet, whether the ducts are capable of regenerating after genotoxic injury, or if damage to ductal cells induces lineage plasticity, as has been reported in other organ systems, remains unknown. Here, we show that two ductal progenitor populations marked by KRT14 and KIT exclusively maintain non-overlapping ductal compartments after radiation exposure but do so through distinct cellular mechanisms. KRT14+ progenitor cells are fast cycling cells that proliferate in response to radiation-induced damage in a sustained manner and divide asymmetrically to produce differentiated cells of the larger granulated ducts. Conversely, KIT+ cells are long lived progenitors for the intercalated ducts that undergo few cell divisions either during homeostasis or after gamma radiation, thus maintaining ductal architecture in the near absence of cell turnover. Together, these data illustrate the regenerative capacity of the salivary ducts and highlight the heterogeneity in the damage responses used by salivary progenitor cells to maintain tissue architecture.\n\nSummary StatementThe salivary gland ductal network is maintained during homeostasis and after genotoxic injury by diverse progenitors that respond differentially to radiation induced damage.

developmental biology↗

bioRxiv2018

SOX2 Regulation by Hedgehog Signaling Controls Adult Lingual Epithelium Homeostasis

The adult tongue epithelium is continuously renewed from epithelial progenitor cells, and this process relies on intact Hedgehog (HH) signaling. In mice, inhibition of the HH pathway using Smoothened antagonists (HH pathway inhibitors or HPIs) leads to taste bud loss over a span of several weeks. Previously, we demonstrated that overexpression of Sonic Hedgehog (SHH) in lingual epithelial progenitors induces formation of ectopic taste buds accompanied by locally increased SOX2 expression, consistent with the hypothesis that taste bud differentiation depends on SOX2 downstream of HH. To test this idea, we inhibited HH signaling by treating SOX2-GFP mice with HPI and found a rapid and drastic decline in SOX2-GFP expression in taste progenitors and taste buds. Using a conditional Cre-lox system to delete Sox2, we found that loss of SOX2 blocks differentiation of both taste buds and non-taste epithelium that comprises the majority of the tongue surface; progenitor cells increase in number at the expense of differentiated taste cells and lingual keratinocytes. In contrast to the normal pattern of basally restricted proliferation, dividing cells are overabundant, disorganized and present in suprabasal epithelial layers in Sox2 deleted tongues. Additionally, SOX2 loss in taste progenitors leads non-cell autonomously to rapid loss of taste bud cells via apoptosis, dramatically shortening taste cell lifespans. Finally, when Sox2 is conditionally deleted in mice with constitutive overexpression of SHH, ectopic taste buds fail to form and endogenous taste buds disappear; instead, robust hyperproliferation takes over the entire lingual epithelium. In sum, our experiments suggest that SOX2 functions downstream of HH signaling to regulate lingual epithelium homeostasis.

developmental biology↗

bioRxiv2017

The actin cytoskeleton governs apical mitosis and daughter cell dispersion in intestinal epithelia

Cell proliferation is critical for maintaining the absorptive, protective and regenerative functions of the small intestine throughout adulthood. Interphase nuclei are positioned near the basal surface of the intestinal epithelium, but during mitosis, chromosomes are located apically. The molecular basis for apical-basal DNA positioning and its consequences for tissue homeostasis are poorly understood. Here, we image and pharmacologically perturb these behaviors in live murine intestinal organoids. We find that apical and basal DNA movements occur as a result of mitosis-coupled actin rearrangements that alter the basolateral shape of dividing cells, while the apical cell surface remains confined by cell-cell contacts that persist throughout mitosis. Strikingly, these polarized shape changes allow neighboring cells to insert between nascent daughters, intermingling cells of different lineages. In summary, polarized rearrangements of the actin cytoskeleton govern the mitotic behavior of intestinal epithelial cells and lead to interspersion of cell lineages.

cell biology↗

bioRxiv2017

Tissue Folding by Mechanical Compaction of the Mesenchyme

Many tissues fold during development into complex shapes. Engineering this process in vitro would represent an important advance for tissue engineering. We use embryonic tissue explants, finite element modeling, and 3D cell patterning techniques to show that a mechanical compaction of the ECM during mesenchymal condensation can drive tissue folding along programmed trajectories. The process requires cell contractility, generates strains at nearby tissue interfaces, and causes specific patterns of collagen alignment around and between condensates. Aligned collagen fibers support elevated tensions that promote the folding of interfaces along paths that can be predicted by finite element modeling. We demonstrate the robustness and versatility of this strategy for sculpting tissue interfaces by directing the morphogenesis of a variety of folded tissue forms from engineered patterns of mesenchymal condensates. These studies provide insight into the active mechanical properties of the embryonic mesenchyme and establish entirely new strategies for more robustly directing tissue morphogenesis ex vivo, without genetic engineering.

bioengineering↗