Tissue Maintenance Research Articles

Computational investigation of naturally occurring anticancer agents in regulating Hedgehog pathway proteins.

Embryonic development in humans is controlled by the Hedgehog pathway, which becomes inactive in mature tissues. Except for tissue maintenance and healing, activation of this pathway results in tumorigenesis with only a few exceptions. The drugs currently in use have shown no effectiveness in blocking the key proteins responsible for tumorigenesis. Therefore, it is crucial to find new inhibitors that can stop the abnormal activation of the pathway. A preliminary Insilco screening of naturally occurring compounds was carried out to identify potential inhibitors of the pathway. Docking of seventeen naturally occurring antitumorigenic compounds against the four key proteins of the regulatory proteins of the Hedgehog pathway using AutoDock v4.2.6 software was carried out. Liriodenine exhibited the strongest binding affinity towards three out of the four regulatory proteins (-7.61 kcal/mol with Smoothened, -8.14 kcal/mol with Patched-I, and -6.15 kcal/mol with Gli-II) of the Hedgehog pathway, whereas 2',4-dihydroxy-3-methoxychalcone displayed the highest binding affinity of -7.04 kcal/mol with the Sonic Hedgehog protein. Additional molecular dynamic simulation was conducted using Gromacs with Liriodenine and 2',4-dihydroxy-3-methoxy chalcone. Every protein-ligand complex underwent simulation using v5.1.4 software for a duration of 100 nanoseconds. The findings from the simulation indicate that Liriodenine and 2',4-dihydroxy-3-methoxy chalcone form a strong bond with their corresponding protein. Our findings show that the two aforementioned molecules have potential as new inhibitors of the pathway and should be further investigated in both invitro and in vivo experiments.

Fibrillarin homologs regulate translation in divergent cell lineages during planarian homeostasis and regeneration

Tissue homeostasis and regeneration involve complex cellular changes. The role of rRNA modification-dependent translational regulation in these processes remains largely unknown. Planarians, renowned for their ability to undergo remarkable tissue regeneration, provide an ideal model for the analysis of differential rRNA regulation in diverse cell types during tissue homeostasis and regeneration. We investigated the role of RNA 2’-O-methyltransferase, Fibrillarin (FBL), in the planarian Schmidtea mediterranea and identified two FBL homologs: Smed-fbl-1 (fbl-1) and Smed-fbl-2 (fbl-2). Both are essential for planarian regeneration, but play distinct roles: fbl-1 is crucial for progenitor cell differentiation, while fbl-2 is important for late-stage epidermal lineage specification. Different 2’-O-methylation patterns were observed upon fbl-1 and fbl-2 knockdown, suggesting their roles in translation of specific mRNA pools during regeneration. Ribo-seq analysis further revealed differing impacts of fbl-1 and fbl-2 knockdown on gene translation. These findings indicate divergent roles of the duplicate fbl genes in specific cell lineage development in planarians and suggest a role of rRNA modifications in translational regulation during tissue maintenance and regeneration.

MicroRNAs obtained from cervical swabs in predicting preterm birth

HIGHLIGHTS Increased expression of certain miRNAs in women experiencing preterm birth could be linked to various molecular pathways which contributes to preterm birth. miRNAs obtained from cervical swabs exhibit statistically significant difference in expression between women with term births and preterm births. ABSTRACT Objective: Identifying the risk of preterm birth is crucial for early intervention. miRNAs, small noncoding RNAs that regulate gene expression, play a key role in development and tissue maintenance. Under stress conditions, their regulatory functions become significant, linking them to disease states. Using miRNAs from cervical swabs as potential biomarkers could revolutionize preterm birth risk assessment. This systematic review examines current research on the effectiveness of cervical swab miRNAs in predicting and estimating preterm birth risks, aiming to enhance early detection and management strategies for preterm births. Materials and Methods: Using the PubMed database, 14 articles were obtained using the keywords “microRNA” and “preterm”. Reviews and unrelated studies were then excluded from both pooled articles, resulting in 4 articles included in the final review. Risk of bias were examined using the Newcastle Ottawa Scale. Sample characteristics, time of cervical swab collection, and results from each study were extracted for further analysis. Results: A total of 4 articles were included in this review. Various miRNAs were examined in and were generally successful in predicting preterm birth. miRNA-145, miRNA-199, miRNA-30, miRNA-21, and miRNA-181 family were examined by multiple studies and produced significant results in predicting preterm birth. Based on enrichment analysis, various miRNAs were found to be involved in several biomolecular signaling pathways leading to preterm birth, such as inflammation, chemokine and cytokine signaling pathway, and toll-like receptor signaling. Conclusion: miRNAs obtained from cervical swabs exhibit statistically significant difference in expression between women with term births and preterm births. Further studies are needed to improve the predicting power and accuracy of miRNAs in preterm births.

Senescence as a therapeutic target in cancer and age-related diseases.

Cellular senescence is a stress response that restrains the growth of aged, damaged or abnormal cells. Thus, senescence has a crucial role in development, tissue maintenance and cancer prevention. However, lingering senescent cells fuel chronic inflammation through the acquisition of a senescence-associated secretory phenotype (SASP), which contributes to cancer and age-related tissue dysfunction. Recent progress in understanding senescence has spurred interest in the development of approaches to target senescent cells, known as senotherapies. In this Review, we evaluate the status of various types of senotherapies, including senolytics that eliminate senescent cells, senomorphics that suppress the SASP, interventions that mitigate senescence and strategies that harness the immune system to clear senescent cells. We also summarize how these approaches can be combined with cancer therapies, and we discuss the challenges and opportunities in moving senotherapies into clinical practice. Such therapies have the potential to address root causes of age-related diseases and thus open new avenues for preventive therapies and treating multimorbidities.

Abstract 4116300: Valvular Abnormalities and Risk of Abdominal Aortic Aneurysm Associated with Fluoroquinolone Use; A Retrospective Cohort Study

Introduction: Fluoroquinolones (FQ) are efficacious antibiotics whose antimicrobial effect is achieved through bacterial DNA gyrase inhibition. However, there is evidence suggesting that FQ may cause impaired collagen synthesis and an increase in tissue collagen degradation. Collagen serves as a predominant structural constituent of the aortic wall and heart valves. These structures undergo tissue maintenance, which necessitates the regulated expression of MMPs and TGF-β. In this study, we hypothesized that prolonged usage of FQs may increase risk of valvular abnormalities and abdominal aortic aneurysm. Methods: We conducted a retrospective cohort study utilizing de-identified patient data from the TriNetX platform, an extensive electronic health records (EHR) system. The cohorts consisted of smoker patients who used FQs for more than two consecutive weeks, Cohort A, N= 352,215 and smoker patients without a history of FQ use, Cohort B, N=350,912. Propensity score matching balanced baseline characteristics between cohorts: age, sex, ethnicity, and comorbidities. Results: The risk of developing AAA among smokers with a history of FQ use was 1.222% while the risk was 0.806% among smokers without history of FQ use (P< 0.0001, 95% CI (0.63,0.691), Risk Ratio (RR)= 0.66). The risk of developing nonrheumatic (NR) aortic insufficiency among smokers with history of FQ use was 1.479% while smokers with no history of fluoroquinolone use had a 0.95% risk (P<<0.0001, 95% CI (0.616,0.67), RR= 0.643). The risk of developing NR mitral insufficiency in smokers with history of FQ use was 3.873% versus their smoker FQ naive counterparts risk of 2.317% (P< 0.0001, 95% CI (0.582,0.615), RR= 0.598). NR tricuspid insufficiency in smokers with FQ usage was also increased versus their smoker FQ naive counterparts at 3.089% and 1.758%, respectively (P< 0.0001, 95% CI (0.552,0.587), RR =0.569). Conclusions: This study uncovered a significant association between FQ use, risk of AAA, and NR-valvular insufficiencies among smokers. In particular, male smokers are at highest risk of developing AAA. This same population is at risk for prostatitis that would likely need treatment with FQs, further increasing their risk. Despite the efficacy of this class of antibiotics, caution is paramount when prescribing FQs in individuals who are actively smoking or have any connective tissue pathologies.

Regulation of the Intestinal Stem Cell Pool and Proliferation in Drosophila.

Understanding the regulation of somatic stem cells, both during homeostasis and in response to environmental challenges like injury, infection, chemical exposure, and nutritional changes, is critical because their dysregulation can result in tissue degeneration or tumorigenesis. The use of models such as the Drosophila and mammalian adult intestines offers valuable insights into tissue homeostasis and regeneration, advancing our knowledge of stem cell biology and cancer development. This review highlights significant findings from recent studies, unveiling the molecular mechanisms that govern self-renewal, proliferation, differentiation, and regeneration of intestinal stem cells (ISCs). These insights not only enhance our understanding of normal tissue maintenance but also provide critical perspectives on how ISC dysfunction can lead to pathological conditions such as colorectal cancer (CRC).

Zinc and its binding proteins: essential roles and therapeutic potential.

Zinc is an essential micronutrient that participates in a multitude of cellular and biochemical processes. It is indispensable for normal growth and the maintenance of physiological functions. As one of the most significant trace elements in the body, zinc fulfills three primary biological roles: catalytic, structural, and regulatory. It serves as a cofactor in over 300 enzymes, and more than 3000 proteins require zinc, underscoring its crucial role in numerous physiological processes such as cell division and growth, immune function, tissue maintenance, as well as synthesis protein and collagen synthesis. Zinc deficiency has been linked to increased oxidative stress and inflammation, which may contribute to the pathogenesis of a multitude of diseases, like neurological disorders and cancer. In addition, zinc is a key constituent of zinc-binding proteins, which play a pivotal role in maintaining cellular zinc homeostasis. This review aims to update and expand upon the understanding of zinc biology, highlighting the fundamental roles of zinc in biological processes and the health implications of zinc deficiency. This work also explores the diverse functions of zinc in immune regulation, cellular growth, and neurological health, emphasizing the need for further research to fully elucidate the therapeutic potential of zinc supplementation in disease prevention and management.

A novel ITGB8 transcript variant sustains ovarian cancer cell survival through genomic instability and altered ploidy on a mutant p53 background

BackgroundTranscript variants and protein isoforms are central to unique tissue functions and maintenance of homeostasis, in addition to being associated with aberrant states such as cancer, where their crosstalk with the mutated tumor suppressor p53 may contribute to genomic instability and chromosomal rearrangements. We previously identified several novel splice variants in ovarian cancer RNA-sequencing datasets; herein, we aimed to elucidate the biological effects of the Integrin Subunit Beta 8 variant (termed pITGB8-205).MethodsResolution of the full-length sequence of pITGB8-205 through rapid amplification of cDNA ends (RACE-PCR). Cell cycle analysis and karyotype studies were performed to further explore genomic instability. RNA-seq and proteomics analyses were used to identify the differential expression of the genes.ResultsThis full-length study revealed a unique 5’ sequence in pITGB8-205 that differed from the reported ITGB8-205 sequence, suggesting differential regulation of this novel transcript. Under a p53 mutant background, overexpression of pITGB8-205 triggered genetic instability reminiscent of oncogene-induced replicative stress with extensive abnormal mitoses and chromosomal and nuclear aberrations indicative of chromosomal instability, leading to near whole-genome duplication that imposes energy stress on cellular resources. Micronuclei and aneuploidy are striking features of pITGB8-205-overexpressing p53-mutant cells but are not enhanced in p53 wild-type (WT) cells. RNA-seq and proteomics analyses further suggested that p53 inactivation in ovarian cancer provides a permissive intracellular molecular niche for pITGB8-205 to mediate its effects on genomic instability. This observation is pivotal considering that most high-grade serous ovarian carcinoma (HGSC) tumors express mutant p53. The resulting aneuploid clones with enhanced self-renewal and survival capabilities disrupt clonal dominance under stress yet maintain a balance between replicative stress and prosurvival advantages.ConclusionpITGB8-205-overexpressing clones sustain ovarian tumor cell survival, achieve homeostasis and are formidable opponents of therapy.

Apoptotic extracellular vesicles carrying Mif regulate macrophage recruitment and compensatory proliferation in neighboring epithelial stem cells during tissue maintenance.

Apoptotic cells can signal to neighboring cells to stimulate proliferation and compensate for cell loss to maintain tissue homeostasis. While apoptotic cell-derived extracellular vesicles (AEVs) can transmit instructional cues to mediate communication with neighboring cells, the molecular mechanisms that induce cell division are not well understood. Here, we show that macrophage migration inhibitory factor (Mif)-containing AEVs regulate compensatory proliferation via ERK signaling in epithelial stem cells of larval zebrafish. Time-lapse imaging showed efferocytosis of AEVs from dying epithelial stem cells by healthy neighboring stem cells. Proteomic and ultrastructure analysis of purified AEVs identified Mif localization on the AEV surface. Pharmacological inhibition or genetic mutation of Mif, or its cognate receptor CD74, decreased levels of phosphorylated ERK and compensatory proliferation in the neighboring epithelial stem cells. Disruption of Mif activity also caused decreased numbers of macrophages patrolling near AEVs, while depletion of the macrophage lineage resulted in a reduced proliferative response by the epithelial stem cells. We propose that AEVs carrying Mif directly stimulate epithelial stem cell repopulation and guide macrophages to cell non-autonomously induce localized proliferation to sustain overall cell numbers during tissue maintenance.

One-Step Cartilage Repair of Full-Thickness Knee Chondral Lesions Using a Hyaluronic Acid–Based Scaffold Embedded With Bone Marrow Aspirate Concentrate: Long-term Outcomes After Mean Follow-up Duration of 14 Years

Background: One-step cell-based techniques of cartilage repair that lead to restoration of durable chondral tissue and long-term maintenance of joint function are cost-effective and ideal for routine use. Purposes: To examine the long-term clinical outcomes, after a mean follow-up duration of 14 years, of cartilage repair in the knee using a hyaluronic acid–based scaffold in association with bone marrow aspirate concentrate (HA-BMAC) and to evaluate the effect of age, lesion characteristics, and associated treatments on the outcome of this cartilage repair method. Study Design: Case series; Level of evidence, 4. Methods: Patients were followed prospectively for a mean duration of 14.0 years after undergoing treatment of knee full-thickness articular cartilage injury using HA-BMAC. Clinical evaluation consisted of the patient-reported scoring tools of the visual analog scale and the Knee injury and Osteoarthritis Outcome Score, which were completed preoperatively and at the time of final follow-up. Results: A total of 26 patients with a mean age of 48.3 years (17 male, 9 female) and median chondral lesion size of 6.6 cm2 (range, 1-27 cm2) were followed prospectively. There were 3 treatment failures, and 1 patient who underwent medial compartment unicompartmental arthroplasty 12 years after HA-BMAC treatment of patellar chondral injury. Of the 22 remaining patients, after a mean final follow-up duration of 14.0 years (range, 12-16 years), the median visual analog scale score of 0.6 was significantly decreased from the preoperative median score of 5.0 (P < .001). The median Knee injury and Osteoarthritis Outcome Score Pain (92), Symptoms (86), Activities of Daily Living (96), Sports (85), and Quality of Life (88) subscale values were all increased compared with the preoperative scores (P≤ .001). There was no correlation of clinical outcome score and body mass index. Conclusion: One-step cartilage repair of full-thickness chondral defects in the knee using an HA-BMAC led to successful long-term clinical outcomes and maintenance of joint junction after a mean follow-up duration of 14 years. Long-term clinical success in active, nonobese patients has been uniformly demonstrated across a wide range of patient ages and lesion types, including cases of multicompartment involvement, treatment of associated conditions, and large or bipolar chondral lesions.

Exceptional longevity of mammalian ovarian and oocyte macromolecules throughout the reproductive lifespan

The mechanisms contributing to age-related deterioration of the female reproductive system are complex, however aberrant protein homeostasis is a major contributor. We elucidated exceptionally stable proteins, structures, and macromolecules that persist in mammalian ovaries and gametes across the reproductive lifespan. Ovaries exhibit localized structural and cell-type-specific enrichment of stable macromolecules in both the follicular and extrafollicular environments. Moreover, ovaries and oocytes both harbor a panel of exceptionally long-lived proteins, including cytoskeletal, mitochondrial, and oocyte-derived proteins. The exceptional persistence of these long-lived molecules suggest a critical role in lifelong maintenance and age-dependent deterioration of reproductive tissues.

Exceptional longevity of mammalian ovarian and oocyte macromolecules throughout the reproductive lifespan.

The mechanisms contributing to age-related deterioration of the female reproductive system are complex, however aberrant protein homeostasis is a major contributor. We elucidated exceptionally stable proteins, structures, and macromolecules that persist in mammalian ovaries and gametes across the reproductive lifespan. Ovaries exhibit localized structural and cell-type-specific enrichment of stable macromolecules in both the follicular and extrafollicular environments. Moreover, ovaries and oocytes both harbor a panel of exceptionally long-lived proteins, including cytoskeletal, mitochondrial, and oocyte-derived proteins. The exceptional persistence of these long-lived molecules suggest a critical role in lifelong maintenance and age-dependent deterioration of reproductive tissues.

Paraptosis-A Distinct Pathway to Cell Death.

Cell death is a critical biological process necessary for development, tissue maintenance, and defense against diseases. To date, more than 20 forms of cell death have been identified, each defined by unique molecular pathways. Understanding these different forms of cell death is essential for investigating the pathogenesis of diseases such as cancer, neurodegenerative disorders, and autoimmune conditions and developing appropriate therapies. Paraptosis is a distinct form of regulated cell death characterized by cytoplasmic vacuolation and dilatation of cellular organelles like the mitochondria and endoplasmic reticulum (ER). It is regulated by several signaling pathways, for instance, those associated with ER stress, calcium overload, oxidative stress, and specific cascades such as insulin-like growth factor I receptor (IGF-IR) and its downstream signaling pathways comprising mitogen-activated protein kinases (MAPKs) and Jun N-terminal kinase (JNK). Paraptosis has been observed in diverse biological contexts, including development and cellular stress responses in neuronal, retinal, endothelial, and muscle cells. The induction of paraptosis is increasingly important in anticancer therapy, as it targets non-apoptotic stress responses in tumor cells, which can be utilized to induce cell death. This approach enhances treatment efficacy and addresses drug resistance, particularly in cases where cancer cells are resistant to apoptosis. Combining paraptosis-inducing agents with traditional therapies holds promise for enhancing treatment efficacy and overcoming drug resistance, suggesting a valuable strategy in anticancer therapy.

Sorted stem/progenitor epithelial cells of pubertal bovine mammary gland present limited potential to reconstitute an organised mammary epithelium after transplantation.

The development and maintenance of mammary gland tissue depend on the proliferation and differentiation of mammary stem and progenitor cells. Here, we investigated populations of mammary epithelial cells that are potential candidates for bovine mammary gland development using xenotransplantation into mice cleared mammary fat pad. Transplanted mammary explants from 17-month-old Holstein heifers developed outgrowths exhibiting the archetypal morphology and molecular marker distributions of the bovine gland. Xenotransplantation of sorted mammary epithelial cells (CD49fpos) into bovinised fat pads using inactivated bovine fibroblasts resulted in outgrowth developments with 50% take rate, but these lacked the ductal or alveolar epithelial structures of the normal mammary gland. Similar results were obtained with xenografts of candidate bovine mammary epithelial stem cells (CD49fhighCD24pos) or epithelial cells of the basal lineage (CD49fhighCD24neg) which also developed as clumps of cells surrounded by stromal stretches within the mouse adipose tissue. In conclusion, sorted cells showed compromised regenerative potential for epithelial morphogenesis. Further work is therefore needed to identify mammary stem/progenitor cells with full regenerative capabilities for biogenesis of normal mammary gland structure, with milk-secreting function.

Nature's Elixir for Cancer Treatment: Targeting Tumor-induced Neovascularization.

Angiogenesis, a multistep process, involves sprouting of new vessels from the pre-existing vessels in response to a stimulus in its microenvironment. Normally, angiogenesis is important for tissue maintenance and homeostasis, however it is also known to be associated with various pathologies, including cancer. Importantly, neovascularization is very crucial for tumors to grow and metastasize since it allows delivery of oxygen and nutrients as well as promotes tumor cell dissemination to distant sites. Activation of angiogenic switch is a consequence of imbalance in pro- as well as anti-angiogenic factors, that are immensely impacted by reactive oxygen species and epigenetic regulation. Several reports have suggested that angiogenic inhibitors significantly inhibit tumor growth. Therefore, anti-angiogenic therapy has gained substantial attention and has been considered a rational approach in cancer therapeutics. In this line, several anti- angiogenic drugs have been approved, however, their long term usage caused several side effects. In view of this, researchers switched to plant-based natural compounds for identifying safe and cost-effective anti-angiogenic drugs. Of note, various phytochemicals have been evaluated to reduce tumor growth by inhibiting tumor-induced angiogenesis. Moreover, the implication of nano-carriers to enhance the bioavailability of phytochemicals has proven to be more efficient anti-cancer agents. The present review highlights the existing knowledge on tumor-induced neovascularization and its regulation at the epigenetic level. Further, we emphasize the inhibitory effect of phytochemicals on tumor- induced angiogenesis that will open up new avenues in cancer therapeutics.

Chromatin remodeling in tissue stem cell fate determination.

Tissue stem cells (TSCs), which reside in specialized tissues, constitute the major cell sources for tissue homeostasis and regeneration, and the contribution of transcriptional or epigenetic regulation of distinct biological processes in TSCs has been discussed in the past few decades. Meanwhile, ATP-dependent chromatin remodelers use the energy from ATP hydrolysis to remodel nucleosomes, thereby affecting chromatin dynamics and the regulation of gene expression programs in each cell type. However, the role of chromatin remodelers in tissue stem cell fate determination is less well understood. In this review, we systematically discuss recent advances in epigenetic control by chromatin remodelers of hematopoietic stem cells, intestinal epithelial stem cells, neural stem cells, and skin stem cells in their fate determination and highlight the importance of their essential role in tissue homeostasis, development, and regeneration. Moreover, the exploration of the molecular and cellular mechanisms of TSCs is crucial for advancing our understanding of tissue maintenance and for the discovery of novel therapeutic targets.

A sustained calcium response mediated by IP3 receptor anchoring to the desmosome is essential for apoptotic cell elimination

Efficient elimination of apoptotic cells within epithelial cell sheets is crucial for preserving epithelial barrier integrity.1 It is well established that immediate neighbors of an apoptotic cell actively participate in its removal by enclosing it within a wall of actomyosin, pushing it out in a purse-string manner in a process called apical extrusion.2,3,4,5,6,7 Here, we found that sustained elevation of calcium ions in neighboring epithelial cells is necessary to generate the contractility required for apoptotic cell elimination. This phenomenon, which we call calcium response in effectors of apical extrusion (CaRE), highlights the disparate calcium dynamics within the epithelial sheet. Furthermore, we elucidate the essential role of desmosomes in CaRE. Specifically, we identify a subset of IP3 receptors within the endoplasmic reticulum that is recruited to the desmosome by K-Ras-induced actin-binding protein as the core component of this process. The interplay between these cellular structures heightens actomyosin contractility to drive apoptotic cell removal. Our findings underscore the physiological significance of integrating desmosomes with the endoplasmic reticulum in epithelial sheet homeostasis, shedding new light on cell-cell communication and tissue maintenance.

Anti-aging based on stem cell therapy: A scoping review.

Stem cells are present in the tissues and organs and remain in a quiescent and undifferentiated state until it is physiologically necessary to produce new descendant cells. Due to their multipotency property, mesenchymal stem cells have attracted considerable attention worldwide due to their immunomodulation and therapeutic function in tissue regeneration. Stem cells secrete components such as paracrine factors, extracellular vesicles, and exosomes which have been shown to have anti-inflammatory, anti-aging, reconstruction and wound healing potentials in many in vitro and in vivo models. The pluripotency and immunomodulatory features of stem cells could potentially be an effective tool in cell therapy and tissue repair. Aging affects the capacity for self-renewal and differentiation of stem cells, decreasing the potential for regeneration and the loss of optimal functions in organisms over time. Current progress in the field of cellular therapy and regenerative medicine has facilitated the evolution of particular guidelines and quality control approaches, which eventually lead to clinical trials. Cell therapy could potentially be one of the most promising therapies to control aging due to the fact that single stem cell transplantation can regenerate or substitute the injured tissue. To understand the involvement of stem cells not only in tissue maintenance and disease but also in the control of aging it is important to know and identify their properties, functions, and regulation in vivo, which are addressed in this review.

Abstract C072: Bmi1 expression is upregulated in response to injury/stress in the pancreas

Abstract Pancreatic homeostasis is regulated in part through epigenetic mechanisms that restrict or enable access of pancreatic lineage transcription factors to their target genes. These epigenetic protein cascades are also required for regeneration of the pancreas after injury. B-cell Moloney murine leukemia virus integration site 1 (Bmi1), a central protein in the Polycomb repressor complex 1 (PRC1), has been shown to be required for the regeneration of the pancreas after injury and its absence prevents pancreatic neoplasia in mice. Previous work also suggests that Bmi1 marks a subset of acinar cells contributing to pancreatic renewal and tissue maintenance. It remains unclear how Bmi1 expression levels are regulated in response to pancreatic stress and injury. Here we assess the baseline expression of Bmi1 in pancreatic tissue with a genetic reporter mouse model as well as changes in Bmi1 mRNA levels at different time points after the induction of pancreatitis in wild-type mice via RNA in situ hybridization (RNAscope). We also compare the ability of the murine pancreas to regenerate after acute pancreatitis in the presence and absence of Bmi1. Our data indicates that rather than a specific subpopulation, most, if not all, acinar cells in the pancreas express Bmi1 during their life and specific loss of Bmi1 in the pancreas impairs regeneration after acute pancreatitis. We also show an increase in Bmi1 mRNA levels within the pancreas shortly after the induction of acute pancreatitis which reduces as the pancreas resumes its normal histology. Altogether, our data indicate that Bmi1 expression is dynamic, responsive to injury and necessary for pancreatic homeostasis and regeneration. Citation Format: Nur Muhammad Renollet, Joyce K Thompson, Emily Wu, Osama Alkhalili, Nina Steele, Filip Bednar. Bmi1 expression is upregulated in response to injury/stress in the pancreas [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr C072.

Satellite cell dynamics during skeletal muscle hypertrophy.

Skeletal muscle stem cells (MuSCs) display distinct behavior crucial for tissue maintenance and repair. Upon activation, MuSCs exhibit distinct modes of division: symmetric division, facilitating either self-renewal or differentiation, and asymmetric division, which dictates divergent cellular fates. This review explores the nuanced dynamics of MuSC division and the molecular mechanisms governing this behavior. Furthermore, it introduces a novel phenomenon observed in a subset of MuSCs under hypertrophic stimuli termed division-independent differentiation. Insights into the underlying mechanisms driving this process are discussed, alongside its broader implications for muscle physiology.