Explore the vast range of titles available.

Despite many potent biological activities, retinoids such as retinoic acid (RA) and retinal possess dose-related broad side effects. In this study, we show that this problem, which has been unsolvable for a long time, can be tackled through a controlled release strategy in which retinal is continuously delivered to the skin via sustained release from proretinal nanoparticles. The water dispersible proretinal nanoparticles are stable when kept in water at neutral pH and at room temperature for 8 months under light-proof conditions, and show sustained release of retinal into human synthetic sebum at a pH of 5. In the daily topical application tests performed for 4 weeks on rats' skin, the nanoparticles showed superior ability to increase epidermal thickness compared to RA and retinal, with no skin irritation observed for the proretinal particles, but severe skin irritation observed for RA and free retinal. When tested under occlusion conditions in human volunteers, insignificant skin irritation was observed for the proretinal nanoparticles. The 12-week, double-blind, split-face study on human volunteers indicates better antiaging efficacy of the particles as compared to the free RA.

▴ Alitretinoin is an endogenous retinoid and acts as a pan-agonist at retinoid receptors, binding with high affinity to both retinoic acid receptors and retinoid X receptors (RXR). Oral alitretinoin once daily is approved for use in patients with severe chronic hand eczema unresponsive to treatment with potent topical corticosteroids. ▴ In a large (n=1032), randomized, double-blind, placebo-controlled, multicentre study (BACH) of up to 24 weeks’ duration in adults with severe chronic hand eczema, significantly more patients in the alitretinoin 10 or 30mg/day groups than in the placebo group responded to treatment with clear/ almost clear hands, as assessed by the Physician Global Assessment (PGA) [primary endpoint]. ▴ In an extension phase of the BACH study, alitretinoin was effective in patients who relapsed after responding to initial treatment with the drug. Of patients who had responded to initial treatment with alitretinoin 30 mg/day, significantly more alitretinoin 30 mg/day than placebo recipients responded on the PGA with clear/almost clear hands during the extension phase (primary endpoint; 80% vs 8%). Of those who had responded to initial treatment with alitretinoin 10 mg/day, 48% of alitretinoin 10 mg/day and 10% of placebo recipients responded during the extension phase. ▴ Alitretinoin was generally well tolerated in clinical trials excluding pregnant women. The most common treatment-emergent adverse events and abnormal laboratory test results were consistent with those previously observed with other oral retinoids and RXR agonists.

Totipotent cells hold enormous potential for regenerative medicine. Thus, the development of cellular models recapitulating totipotent-like features is of paramount importance. Cells resembling the totipotent cells of early embryos arise spontaneously in mouse embryonic stem (ES) cell cultures. Such ‘2-cell-like-cells’ (2CLCs) recapitulate 2-cell-stage features and display expanded cell potential. Here, we used 2CLCs to perform a small-molecule screen to identify new pathways regulating the 2-cell-stage program. We identified retinoids as robust inducers of 2CLCs and the retinoic acid (RA)-signaling pathway as a key component of the regulatory circuitry of totipotent cells in embryos. Using single-cell RNA-seq, we reveal the transcriptional dynamics of 2CLC reprogramming and show that ES cells undergo distinct cellular trajectories in response to RA. Importantly, endogenous RA activity in early embryos is essential for zygotic genome activation and developmental progression. Overall, our data shed light on the gene regulatory networks controlling cellular plasticity and the totipotency program. High-throughput chemical screening identifies retinoic acid signaling as a regulatory pathway of 2-cell-like cell reprogramming and early mouse development.

Dietary vitamin A during pregnancy is required for the formation of secondary lymphoid organs of the developing embryo and affects the offspring’s immune competence in adulthood. Vitamin A needed for offspring immunity This comparison of pregnant mice on diets completely lacking vitamin A, and with low and high vitamin A content, reveals a role for maternal vitamin A metabolites — notably retinoic acid — in establishing innate immunity in the developing fetus. The vitamin is required for the formation of secondary lymphoid organs during embryonic development and affects the offspring's immune competence during adulthood. The impact of nutritional status during fetal life on the overall health of adults has been recognized 1 ; however, dietary effects on the developing immune system are largely unknown. Development of secondary lymphoid organs occurs during embryogenesis and is considered to be developmentally programmed 2 , 3 . Secondary lymphoid organ formation depends on a subset of type 3 innate lymphoid cells (ILC3) named lymphoid tissue inducer (LTi) cells 2 , 3 , 4 , 5 . Here we show that mouse fetal ILC3s are controlled by cell-autonomous retinoic acid (RA) signalling in utero , which pre-sets the immune fitness in adulthood. We found that embryonic lymphoid organs contain ILC progenitors that differentiate locally into mature LTi cells. Local LTi cell differentiation was controlled by maternal retinoid intake and fetal RA signalling acting in a haematopoietic cell-autonomous manner. RA controlled LTi cell maturation upstream of the transcription factor RORγt. Accordingly, enforced expression of Rorgt restored maturation of LTi cells with impaired RA signalling, whereas RA receptors directly regulated the Rorgt locus. Finally, we established that maternal levels of dietary retinoids control the size of secondary lymphoid organs and the efficiency of immune responses in the adult offspring. Our results reveal a molecular link between maternal nutrients and the formation of immune structures required for resistance to infection in the offspring.

The segmented body plan of vertebrates is established during somitogenesis, a well-studied process in model organisms; however, the details of this process in humans remain largely unknown owing to ethical and technical limitations. Despite recent advances with pluripotent stem cell-based approaches 1 – 5 , models that robustly recapitulate human somitogenesis in both space and time remain scarce. Here we introduce a pluripotent stem cell-derived mesoderm-based 3D model of human segmentation and somitogenesis—which we termed ‘axioloid’—that captures accurately the oscillatory dynamics of the segmentation clock and the morphological and molecular characteristics of sequential somite formation in vitro. Axioloids show proper rostrocaudal patterning of forming segments and robust anterior–posterior FGF–WNT signalling gradients and retinoic acid signalling components. We identify an unexpected critical role of retinoic acid signalling in the stabilization of forming segments, indicating distinct, but also synergistic effects of retinoic acid and extracellular matrix on the formation and epithelialization of somites. Comparative analysis demonstrates marked similarities of axioloids to the human embryo, further validated by the presence of a Hox code in axioloids. Finally, we demonstrate the utility of axioloids for studying the pathogenesis of human congenital spine diseases using induced pluripotent stem cells with mutations in HES7 and MESP2 . Our results indicate that axioloids represent a promising platform for the study of axial development and disease in humans. A 3D model of human segmentation and somitogenesis derived from induced pluripotent stem cells captures the oscillatory dynamics of the segmentation clock as well as morphological and molecular features of the developing embryonic axis and tail.

The development of functional neurons is a complex orchestration of multiple signaling pathways controlling cell proliferation and differentiation. Because the balance of antioxidants is important for neuronal survival and development, we hypothesized that ferroptosis must be suppressed to gain neurons. We find that removal of antioxidants diminishes neuronal development and laminar organization of cortical organoids, which is fully restored when ferroptosis is inhibited by ferrostatin-1 or when neuronal differentiation occurs in the presence of vitamin A. Furthermore, iron-overload-induced developmental growth defects in C. elegans are ameliorated by vitamin E and A. We determine that all-trans retinoic acid activates the Retinoic Acid Receptor, which orchestrates the expression of anti-ferroptotic genes. In contrast, retinal and retinol show radical-trapping antioxidant activity. Together, our study reveals an unexpected function of vitamin A in coordinating the expression of essential cellular gatekeepers of ferroptosis, and demonstrates that suppression of ferroptosis by radical-trapping antioxidants or by vitamin A is required to obtain mature neurons and proper laminar organization in cortical organoids. Neuronal development is tightly controlled by nutrients and antioxidants. Here, authors show that ferroptosis, a cell death modality driven by lipid peroxidation, is required to be suppressed by vitamin A or antioxidants to ensure proper neuronal development.

Purpose: To develop a simple pharmacodynamic (PD) assay for the evaluation of the bioequivalence of topically applied retinoid products. Methods: Daily applications of products containing tretinoin or adapalene were made to the forearms of human subjects for up to 21 days. Percutaneous absorption was enhanced through the use of polyethylene film occlusion (5 h). Pharmacologic activity was assessed through the daily measurement of three cutaneous responses intimately linked to retinoid-induced changes in epidermal differentiation: (1) erythema; (2) exfoliation (scaling/peeling), and (3) increased transepidermal water loss. Results: The PD model exhibited the sensitivity and specificity required to function as a bioequivalence surrogate. It was possible to differentiate between: (1) three concentrations of tretinoin in a commercial cream product line; (2) two concentrations of tretinoin in a commercial gel product line; (3) different vehicles (gel vs. cream) containing the same concentration of tretinoin, and (4) tretinoin and adapalene at the same concentration. The applicability of this model for bioequivalence testing was established by showing that it had sufficient power to determine that three test tretinoin cream products and two approved generic tretinoin gel products were equivalent to their corresponding reference products. Conclusions: A surrogate PD model to assess retinoid bioequivalence has been developed.

Pancreatic ductal adenocarcinoma is characterised by a dense desmoplastic stroma composed of stromal cells and extracellular matrix (ECM). This barrier severely impairs drug delivery and penetration. Activated pancreatic stellate cells (PSCs) play a key role in establishing this unique pathological obstacle, but also offer a potential target for anti-tumour therapy. Here, we construct a tumour microenvironment-responsive nanosystem, based on PEGylated polyethylenimine-coated gold nanoparticles, and utilise it to co-deliver all- trans retinoic acid (ATRA, an inducer of PSC quiescence) and siRNA targeting heat shock protein 47 (HSP47, a collagen-specific molecular chaperone) to re-educate PSCs. The nanosystem simultaneously induces PSC quiescence and inhibits ECM hyperplasia, thereby promoting drug delivery to pancreatic tumours and significantly enhancing the anti-tumour efficacy of chemotherapeutics. Our combination strategy to restore homoeostatic stromal function by targeting activated PSCs represents a promising approach to improving the efficacy of chemotherapy and other therapeutic modalities in a wide range of stroma-rich tumours. Stromal-tumour interactions play an important role in pancreatic cancer progression. Here, they describe the development of a tumour microenvironment-responsive gold nanoparticle system incorporating all- trans retinoic acid (ATRA) and siRNA against heat shock protein 47 (HSP47), for use in pancreatic cancer treatment.

Drugs that induce redifferentiation of cancer cells are efficient only in some subtypes of AML. The authors show that sensitivity to pro-differentiation drugs such as ATRA can be induced by co-treatment with epigenetic drugs. An inhibitor of histone demethylase, LSD1, safely used as an antidepressant in humans, reprograms AML cells and makes them sensitive to the effects of ATRA in vitro and in vivo , suggesting that epigenetic interventions can increase response to cancer treatments. Acute promyelocytic leukemia (APL), a cytogenetically distinct subtype of acute myeloid leukemia (AML), characterized by the t(15;17)-associated PML-RARA fusion, has been successfully treated with therapy utilizing all- trans -retinoic acid (ATRA) to differentiate leukemic blasts. However, among patients with non-APL AML, ATRA-based treatment has not been effective. Here we show that, through epigenetic reprogramming, inhibitors of lysine-specific demethylase 1 (LSD1, also called KDM1A), including tranylcypromine (TCP), unlocked the ATRA-driven therapeutic response in non-APL AML. LSD1 inhibition did not lead to a large-scale increase in histone 3 Lys4 dimethylation (H3K4 me2 ) across the genome, but it did increase H3K4 me2 and expression of myeloid-differentiation–associated genes. Notably, treatment with ATRA plus TCP markedly diminished the engraftment of primary human AML cells in vivo in nonobese diabetic (NOD)-severe combined immunodeficient (SCID) mice, suggesting that ATRA in combination with TCP may target leukemia-initiating cells. Furthermore, initiation of ATRA plus TCP treatment 15 d after engraftment of human AML cells in NOD-SCID γ (with interleukin-2 (IL-2) receptor γ chain deficiency) mice also revealed the ATRA plus TCP drug combination to have a potent anti-leukemic effect that was superior to treatment with either drug alone. These data identify LSD1 as a therapeutic target and strongly suggest that it may contribute to AML pathogenesis by inhibiting the normal pro-differentiative function of ATRA, paving the way for new combinatorial therapies for AML.

Three-dimensional (3D) organoids can serve as an in vitro platform to study cell–cell interactions, tissue development, and toxicology. Development of organoids with tissue architecture similar to testis in vivo has remained a challenge. Here, we present a microwell aggregation approach to establish multicellular 3D testicular organoids from pig, mouse, macaque, and human. The organoids consist of germ cells, Sertoli cells, Leydig cells, and peritubular myoid cells forming a distinct seminiferous epithelium and interstitial compartment separated by a basement membrane. Sertoli cells in the organoids express tight junction proteins claudin 11 and occludin. Germ cells in organoids showed an attenuated response to retinoic acid compared to germ cells in 2D culture indicating that the tissue architecture of the organoid modulates response to retinoic acid similar to in vivo. Germ cells maintaining physiological cell–cell interactions in organoids also had lower levels of autophagy indicating lower levels of cellular stress. When organoids were treated with mono(2-ethylhexyl) phthalate (MEHP), levels of germ cell autophagy increased in a dose-dependent manner, indicating the utility of the organoids for toxicity screening. Ablation of primary cilia on testicular somatic cells inhibited the formation of organoids demonstrating an application to screen for factors affecting testicular morphogenesis. Organoids can be generated from cryopreserved testis cells and preserved by vitrification. Taken together, the testicular organoid system recapitulates the 3D organization of the mammalian testis and provides an in vitro platform for studying germ cell function, testicular development, and drug toxicity in a cellular context representative of the testis in vivo. Summary Sentence Prepubertal testicular cells undergo in vitro morphogenesis and give rise to spherical organoids with testes-specific tissue architecture.