Hematopoiesis post anti-CD117 monoclonal antibody treatment in wild-type and Fanconi anemia settings.

Anti-CD117 monoclonal antibody (mAb) agents have emerged as exciting alternative conditioning strategies to traditional genotoxic irradiation or chemotherapy conditioning for both allogeneic and autologous gene-modified hematopoietic stem cell transplantation. Further, these agents are concurrently being explored in the treatment of mast cell disorders. Despite promising results in animal models and more recently in patients, the short-term and long-term effects of these treatments have not been fully explored. We conducted rigorous assessments to evaluate the effects of antagonistic anti-mCD117 mAb, ACK2, on hematopoiesis in wild-type (WT) and Fanconi Anemia (FA) mice. Importantly, we found no evidence of short-term DNA damage in either setting following this treatment suggesting that ACK2 does not induce immediate genotoxicity, providing crucial insights into its safety profile. Surprisingly, FA mice exhibited an increase in colony formation post-ACK2 treatment without accompanying DNA damage, indicating a potential targeting of hematopoietic stem cells (HSCs) and expansion of hematopoietic progenitor cells. Moreover, the long-term phenotypic and functional changes in hematopoietic stem and progenitor cells did not significantly differ between the ACK2-treated and control groups, in either setting, supporting that ACK2 does not adversely affect hematopoietic capacity. These finding underscore the safety of these agents when utilized as a short-course treatment in the conditioning context, as they did not induce significant changes in DNA damage amongst hematopoietic stem or progenitor cells. However, through a comparison of gene expression via single-cell RNA sequencing between untreated and treated mice, it was revealed that the ACK2 mAb, via c-Kit downregulation, effectively modulated the MAPK pathway with Fos down-regulation in WT and FA mice. Importantly, this modulation was achieved without causing prolonged disruptions. These findings validate the safety of the treatment and also enhance our understanding of its intricate mode of action at the molecular level.

Regulation of zebrafish fin regeneration by vitamin D signaling.

BACKGROUND: Vitamin D is an essential nutrient that has long been known to regulate skeletal growth and integrity. In models of major appendage regeneration, treatment with vitamin D analogs has been reported to improve aspects of zebrafish fin regeneration in specific disease or gene misexpression contexts, but also to disrupt pattern in regenerating salamander limbs. Recently, we reported strong mitogenic roles for vitamin D signaling in several zebrafish tissues throughout life stages, including epidermal cells and osteoblasts of adult fins. To our knowledge, molecular genetic approaches to dissect vitamin D function in appendage regeneration have not been described. RESULTS: Using a knock-in GFP reporter for the expression of the vitamin D target gene and negative regulator cyp24a1, we identified active vitamin D signaling in adult zebrafish fins during tissue homeostasis and regeneration. Transgenic expression of cyp24a1 or a dominant-negative vitamin D receptor (VDR) inhibited regeneration of amputated fins, whereas global vitamin D treatment accelerated regeneration. Using tissue regeneration enhancer elements, we found that local enhancement of VDR expression could improve regeneration with low doses of a vitamin D analog. CONCLUSIONS: Vitamin D signaling enhances the efficacy of fin regeneration in zebrafish.

Vitamin D Stimulates Cardiomyocyte Proliferation and Controls Organ Size and Regeneration in Zebrafish.

Attaining proper organ size during development and regeneration hinges on the activity of mitogenic factors. Here, we performed a large-scale chemical screen in embryonic zebrafish to identify cardiomyocyte mitogens. Although commonly considered anti-proliferative, vitamin D analogs like alfacalcidol had rapid, potent mitogenic effects on embryonic and adult cardiomyocytes in vivo. Moreover, pharmacologic or genetic manipulation of vitamin D signaling controlled proliferation in multiple adult cell types and dictated growth rates in embryonic and juvenile zebrafish. Tissue-specific modulation of vitamin D receptor (VDR) signaling had organ-restricted effects, with cardiac VDR activation causing cardiomegaly. Alfacalcidol enhanced the regenerative response of injured zebrafish hearts, whereas VDR blockade inhibited regeneration. Alfacalcidol activated cardiac expression of genes associated with ErbB2 signaling, while ErbB2 inhibition blunted its effects on cell proliferation. Our findings identify vitamin D as mitogenic for cardiomyocytes and other cell types in zebrafish and indicate a mechanism to regulate organ size and regeneration.

Lamellar projections in the endolymphatic sac act as a relief valve to regulate inner ear pressure.

The inner ear is a fluid-filled closed-epithelial structure whose function requires maintenance of an internal hydrostatic pressure and fluid composition. The endolymphatic sac (ES) is a dead-end epithelial tube connected to the inner ear whose function is unclear. ES defects can cause distended ear tissue, a pathology often seen in hearing and balance disorders. Using live imaging of zebrafish larvae, we reveal that the ES undergoes cycles of slow pressure-driven inflation followed by rapid deflation. Absence of these cycles in lmx1bb mutants leads to distended ear tissue. Using serial-section electron microscopy and adaptive optics lattice light-sheet microscopy, we find a pressure relief valve in the ES comprised of partially separated apical junctions and dynamic overlapping basal lamellae that separate under pressure to release fluid. We propose that this lmx1-dependent pressure relief valve is required to maintain fluid homeostasis in the inner ear and other fluid-filled cavities.

Protective Effects of Glycyrrhizic Acid and 18ß-Glycyrrhetinic Acid against Cisplatin-Induced Nephrotoxicity in BALB/c Mice.

The clinical use of antineoplastic drug cisplatin (CP) is commonly complicated by nephrotoxic side effects that limit its application and therapeutic efficiency. This study used a model of CP-induced renal injury in male BALB/c mice to investigate the protective effects of the active components of licorice, glycyrrhizic acid (GA), and 18ß-glycyrrhetinic acid (18ßGA) against CP-induced nephrotoxicity, and the chemoprotectant, amifostine, was used as a control. Oral administration of GA or 18ßGA significantly reduced CP-induced increases in the levels of blood urea nitrogen, creatinine, and lactate dehydrogenase. Hematoxylin and eosin staining revealed that GA and 18ßGA delayed the progression of renal injury, including tubular necrosis, hyaline casts, and tubular degeneration in response to CP exposure. Oxidative status and inflammatory responses in CP-treated mice were restored to near-normal levels by treatment with GA or 18ßGA. These protective effects might be associated with upregulation of nuclear factor E2-related protein (Nrf2) and downregulation of nuclear factor-κ-light-chain-enhancer of activated B cells (NF-κB) in the kidney. Notably, we demonstrated that GA and 18ßGA rendered renal cells resistant to CP-induced HMGB1 cytoplasmic translocation and release. These findings suggest that GA and 18ßGA might be act as the chemoprotectants against CP-induced nephrotoxicity.