Rapid mechanosensitive migration and dispersal of newly divided mesenchymal cells aid their recruitment into dermal condensates.

Embryonic mesenchymal cells are dispersed within an extracellular matrix but can coalesce to form condensates with key developmental roles. Cells within condensates undergo fate and morphological changes and induce cell fate changes in nearby epithelia to produce structures including hair follicles, feathers, or intestinal villi. Here, by imaging mouse and chicken embryonic skin, we find that mesenchymal cells undergo much of their dispersal in early interphase, in a stereotyped process of displacement driven by 3 hours of rapid and persistent migration followed by a long period of low motility. The cell division plane and the elevated migration speed and persistence of newly born mesenchymal cells are mechanosensitive, aligning with tissue tension, and are reliant on active WNT secretion. This behaviour disperses mesenchymal cells and allows daughters of recent divisions to travel long distances to enter dermal condensates, demonstrating an unanticipated effect of cell cycle subphase on core mesenchymal behaviour.

Losartan controls immune checkpoint blocker-induced edema and improves survival in glioblastoma mouse models.

Immune checkpoint blockers (ICBs) have failed in all phase III glioblastoma trials. Here, we found that ICBs induce cerebral edema in some patients and mice with glioblastoma. Through single-cell RNA sequencing, intravital imaging, and CD8+ T cell blocking studies in mice, we demonstrated that this edema results from an inflammatory response following antiprogrammed death 1 (PD1) antibody treatment that disrupts the blood-tumor barrier. Used in lieu of immunosuppressive corticosteroids, the angiotensin receptor blocker losartan prevented this ICB-induced edema and reprogrammed the tumor microenvironment, curing 20% of mice which increased to 40% in combination with standard of care treatment. Using a bihemispheric tumor model, we identified a "hot" tumor immune signature prior to losartan+anti-PD1 therapy that predicted long-term survival. Our findings provide the rationale and associated biomarkers to test losartan with ICBs in glioblastoma patients.

Clinical and molecular effects of oral CCR4 antagonist RPT193 in atopic dermatitis: A Phase 1 study.

BACKGROUND: RPT193 is an orally administered small molecule antagonist of the human C-C motif chemokine receptor 4 (CCR4) that inhibits the migration and downstream activation of T-helper Type 2 (Th2) cells. We investigated single- and multiple-ascending doses of RPT193 in healthy subjects, and multiple doses of RPT193 in subjects with moderate-to-severe atopic dermatitis (AD). METHODS: This was a first-in-human randomized, placebo-controlled Phase 1a/1b monotherapy study (NCT04271514) to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and CCR4 surface receptor occupancy in eligible healthy subjects and subjects with moderate-to-severe AD. Clinical efficacy and skin biomarker effects of RPT193 monotherapy were assessed as exploratory endpoints in AD subjects. RESULTS: In healthy (n = 72) and AD subjects (n = 31), once-daily RPT193 treatment was generally well tolerated, with no serious adverse events reported and all treatment-emergent adverse events reported as mild/moderate. In AD subjects, numerically greater improvements in clinical efficacy endpoints were observed with RPT193 monotherapy versus placebo up to the end of the treatment period (Day 29), with statistically significant improvement, compared to Day 29 and placebo, observed 2 weeks after the end of treatment (Day 43) on several endpoints (p < .05). Moreover, significant changes in the transcriptional profile were seen in skin biopsies of RPT193-treated versus placebo-treated subjects at Day 29, which were also significantly correlated with improvements in clinical efficacy measures. CONCLUSIONS: To our knowledge, this is the first clinical study with an oral CCR4 antagonist that showed clinical improvement coupled with modulation of the cutaneous transcriptomic profile in an inflammatory skin disease.

Dendritic cell paucity in mismatch repair-proficient colorectal cancer liver metastases limits immune checkpoint blockade efficacy.

Liver metastasis is a major cause of mortality for patients with colorectal cancer (CRC). Mismatch repair-proficient (pMMR) CRCs make up about 95% of metastatic CRCs, and are unresponsive to immune checkpoint blockade (ICB) therapy. Here we show that mouse models of orthotopic pMMR CRC liver metastasis accurately recapitulate the inefficacy of ICB therapy in patients, whereas the same pMMR CRC tumors are sensitive to ICB therapy when grown subcutaneously. To reveal local, nonmalignant components that determine CRC sensitivity to treatment, we compared the microenvironments of pMMR CRC cells grown as liver metastases and subcutaneous tumors. We found a paucity of both activated T cells and dendritic cells in ICB-treated orthotopic liver metastases, when compared with their subcutaneous tumor counterparts. Furthermore, treatment with Feline McDonough sarcoma (FMS)-like tyrosine kinase 3 ligand (Flt3L) plus ICB therapy increased dendritic cell infiltration into pMMR CRC liver metastases and improved mouse survival. Lastly, we show that human CRC liver metastases and microsatellite stable (MSS) primary CRC have a similar paucity of T cells and dendritic cells. These studies indicate that orthotopic tumor models, but not subcutaneous models, should be used to guide human clinical trials. Our findings also posit dendritic cells as antitumor components that can increase the efficacy of immunotherapies against pMMR CRC.

KLB dysregulation mediates disrupted muscle development in intrauterine growth restriction.

Intrauterine growth restriction (IUGR) is a leading cause of neonatal morbidity and mortality in humans and domestic animals. Developmental adaptations of skeletal muscle in IUGR lead to increased risk of premature muscle loss and metabolic disease in later life. Here, we identified ß-Klotho (KLB), a fibroblast growth factor 21 (FGF21) co-receptor, as a novel regulator of muscle development in IUGR. Using the pig as a naturally-occurring disease model, we performed transcriptome-wide profiling of fetal muscle (day 90 of pregnancy) from IUGR and normal-weight (NW) littermates. We found that, alongside large-scale transcriptional changes comprising multiple developmental, tissue injury and metabolic gene pathways, KLB was increased in IUGR muscle. Moreover, FGF21 concentrations were increased in plasma in IUGR fetuses. Using cultures of fetal muscle progenitor cells (MPCs), we showed reduced myogenic capacity of IUGR compared to NW muscle in vitro, as evidenced by differences in fusion indices and myogenic transcript levels, as well as mechanistic target of rapamycin (mTOR) activity. Moreover, transfection of MPCs with KLB small interfering RNA promoted myogenesis and mTOR activation, whereas treatment with FGF21 had opposite and dose-dependent effects in porcine and also in human fetal MPCs. In conclusion, our results identify KLB as a novel and potentially critical mediator of impaired muscle development in IUGR, through conserved mechanisms in pigs and humans. Our data shed new light onto the pathogenesis of IUGR, a significant cause of lifelong ill-health in humans and animals. KEY POINTS: Intrauterine growth restriction (IUGR) is associated with large-scale transcriptional changes in developmental, tissue injury and metabolic gene pathways in fetal skeletal muscle. Levels of the fibroblast growth factor 21 (FGF21) co-receptor, ß-Klotho (KLB) are increased in IUGR fetal muscle, and FGF21 concentrations are increased in IUGR fetal plasma. KLB mediates a reduction in muscle development through inhibition of mechanistic target of rapamycin signalling. These effects of KLB on muscle cells are conserved in pig and human, suggesting a vital role of this protein in the regulation of muscle development and function in mammals.

Lipid-Polymer Hybrid "Particle-in-Particle" Nanostructure Gene Delivery Platform Explored for Lyophilizable DNA and mRNA COVID-19 Vaccines.

SARS-CoV-2 has led to a worldwide pandemic, catastrophically impacting public health and the global economy. Herein, a new class of lipid-modified polymer poly (ß-amino esters) (L-PBAEs) is developed via enzyme-catalyzed esterification and further formulation of the L-PBAEs with poly(d,l-lactide-coglycolide)-b-poly(ethylene glycol) (PLGA-PEG) leads to self-assembly into a "particle-in-particle" (PNP) nanostructure for gene delivery. Out of 24 PNP candidates, the top-performing PNP/C12-PBAE nanoparticles efficiently deliver both DNA and mRNA in vitro and in vivo, presenting enhanced transfection efficacy, sustained gene release behavior, and excellent stability for at least 12 months of storage at -20 °C after lyophilization without loss of transfection efficacy. Encapsulated with spike encoded plasmid DNA and mRNA, the lipid-modified polymeric PNP COVID-19 vaccines successfully elicit spike-specific antibodies and Th1-biased T cell immune responses in immunized mice even after 12 months of lyophilized storage at -20 °C. This newly developed lipid-polymer hybrid PNP nanoparticle system demonstrates a new strategy for both plasmid DNA and mRNA delivery with the capability of long-term lyophilized storage.

Feather arrays are patterned by interacting signalling and cell density waves.

Feathers are arranged in a precise pattern in avian skin. They first arise during development in a row along the dorsal midline, with rows of new feather buds added sequentially in a spreading wave. We show that the patterning of feathers relies on coupled fibroblast growth factor (FGF) and bone morphogenetic protein (BMP) signalling together with mesenchymal cell movement, acting in a coordinated reaction-diffusion-taxis system. This periodic patterning system is partly mechanochemical, with mechanical-chemical integration occurring through a positive feedback loop centred on FGF20, which induces cell aggregation, mechanically compressing the epidermis to rapidly intensify FGF20 expression. The travelling wave of feather formation is imposed by expanding expression of Ectodysplasin A (EDA), which initiates the expression of FGF20. The EDA wave spreads across a mesenchymal cell density gradient, triggering pattern formation by lowering the threshold of mesenchymal cells required to begin to form a feather bud. These waves, and the precise arrangement of feather primordia, are lost in the flightless emu and ostrich, though via different developmental routes. The ostrich retains the tract arrangement characteristic of birds in general but lays down feather primordia without a wave, akin to the process of hair follicle formation in mammalian embryos. The embryonic emu skin lacks sufficient cells to enact feather formation, causing failure of tract formation, and instead the entire skin gains feather primordia through a later process. This work shows that a reaction-diffusion-taxis system, integrated with mechanical processes, generates the feather array. In flighted birds, the key role of the EDA/Ectodysplasin A receptor (EDAR) pathway in vertebrate skin patterning has been recast to activate this process in a quasi-1-dimensional manner, imposing highly ordered pattern formation.

RPW8/HR repeats control NLR activation in Arabidopsis thaliana.

In many plant species, conflicts between divergent elements of the immune system, especially nucleotide-binding oligomerization domain-like receptors (NLR), can lead to hybrid necrosis. Here, we report deleterious allele-specific interactions between an NLR and a non-NLR gene cluster, resulting in not one, but multiple hybrid necrosis cases in Arabidopsis thaliana. The NLR cluster is RESISTANCE TO PERONOSPORA PARASITICA 7 (RPP7), which can confer strain-specific resistance to oomycetes. The non-NLR cluster is RESISTANCE TO POWDERY MILDEW 8 (RPW8) / HOMOLOG OF RPW8 (HR), which can confer broad-spectrum resistance to both fungi and oomycetes. RPW8/HR proteins contain at the N-terminus a potential transmembrane domain, followed by a specific coiled-coil (CC) domain that is similar to a domain found in pore-forming toxins MLKL and HET-S from mammals and fungi. C-terminal to the CC domain is a variable number of 21- or 14-amino acid repeats, reminiscent of regulatory 21-amino acid repeats in fungal HET-S. The number of repeats in different RPW8/HR proteins along with the sequence of a short C-terminal tail predicts their ability to activate immunity in combination with specific RPP7 partners. Whether a larger or smaller number of repeats is more dangerous depends on the specific RPW8/HR autoimmune risk variant.

Hierarchical patterning modes orchestrate hair follicle morphogenesis.

Two theories address the origin of repeating patterns, such as hair follicles, limb digits, and intestinal villi, during development. The Turing reaction-diffusion system posits that interacting diffusible signals produced by static cells first define a prepattern that then induces cell rearrangements to produce an anatomical structure. The second theory, that of mesenchymal self-organisation, proposes that mobile cells can form periodic patterns of cell aggregates directly, without reference to any prepattern. Early hair follicle development is characterised by the rapid appearance of periodic arrangements of altered gene expression in the epidermis and prominent clustering of the adjacent dermal mesenchymal cells. We assess the contributions and interplay between reaction-diffusion and mesenchymal self-organisation processes in hair follicle patterning, identifying a network of fibroblast growth factor (FGF), wingless-related integration site (WNT), and bone morphogenetic protein (BMP) signalling interactions capable of spontaneously producing a periodic pattern. Using time-lapse imaging, we find that mesenchymal cell condensation at hair follicles is locally directed by an epidermal prepattern. However, imposing this prepattern's condition of high FGF and low BMP activity across the entire skin reveals a latent dermal capacity to undergo spatially patterned self-organisation in the absence of epithelial direction. This mesenchymal self-organisation relies on restricted transforming growth factor (TGF) ß signalling, which serves to drive chemotactic mesenchymal patterning when reaction-diffusion patterning is suppressed, but, in normal conditions, facilitates cell movement to locally prepatterned sources of FGF. This work illustrates a hierarchy of periodic patterning modes operating in organogenesis.

Targeting CXCR4-dependent immunosuppressive Ly6Clow monocytes improves antiangiogenic therapy in colorectal cancer.

Antiangiogenic therapy with antibodies against VEGF (bevacizumab) or VEGFR2 (ramucirumab) has been proven efficacious in colorectal cancer (CRC) patients. However, the improvement in overall survival is modest and only in combination with chemotherapy. Thus, there is an urgent need to identify potential underlying mechanisms of resistance specific to antiangiogenic therapy and develop strategies to overcome them. Here we found that anti-VEGFR2 therapy up-regulates both C-X-C chemokine ligand 12 (CXCL12) and C-X-C chemokine receptor 4 (CXCR4) in orthotopic murine CRC models, including SL4 and CT26. Blockade of CXCR4 signaling significantly enhanced treatment efficacy of anti-VEGFR2 treatment in both CRC models. CXCR4 was predominantly expressed in immunosuppressive innate immune cells, which are recruited to CRCs upon anti-VEGFR2 treatment. Blockade of CXCR4 abrogated the recruitment of these innate immune cells. Importantly, these myeloid cells were mostly Ly6Clow monocytes and not Ly6Chigh monocytes. To selectively deplete individual innate immune cell populations, we targeted key pathways in Ly6Clow monocytes (Cx3cr1-/- mice), Ly6Chigh monocytes (CCR2-/- mice), and neutrophils (anti-Ly6G antibody) in combination with CXCR4 blockade in SL4 CRCs. Depletion of Ly6Clow monocytes or neutrophils improved anti-VEGFR2-induced SL4 tumor growth delay similar to the CXCR4 blockade. In CT26 CRCs, highly resistant to anti-VEGFR2 therapy, CXCR4 blockade enhanced anti-VEGFR2-induced tumor growth delay but specific depletion of Ly6G+ neutrophils did not. The discovery of CXCR4-dependent recruitment of Ly6Clow monocytes in tumors unveiled a heretofore unknown mechanism of resistance to anti-VEGF therapies. Our findings also provide a rapidly translatable strategy to enhance the outcome of anti-VEGF cancer therapies.

Phenotyping reproductive stage chilling and frost tolerance in wheat using targeted metabolome and lipidome profiling.

INTRODUCTION: Frost events lead to A$360 million of yield losses annually to the Australian wheat industry, making improvement of chilling and frost tolerance an important trait for breeding. OBJECTIVES: This study aimed to use metabolomics and lipidomics to explore genetic variation in acclimation potential to chilling and to identify metabolite markers for chilling tolerance in wheat. METHODS: We established a controlled environment screening assay that is able to reproduce field rankings of wheat germplasm for chilling and frost tolerance. This assay, together with targeted metabolomics and lipidomics approaches, were used to compare metabolite and lipid levels in flag leaves of two wheat varieties with contrasting chilling tolerance. RESULTS: The sensitive variety Wyalkatchem showed a strong reduction in amino acids after the first cold night, followed by accumulation of osmolytes such as fructose, glucose, putrescine and shikimate over a 4-day period. Accumulation of osmolytes is indicative of acclimation to water stress in Wyalkatchem. This response was not observed for tolerant variety Young. The two varieties also displayed significant differences in lipid accumulation. Variation in two lipid clusters, resulted in a higher unsaturated to saturated lipid ratio in Young after 4 days cold treatment and the lipids PC(34:0), PC(34:1), PC(35:1), PC(38:3), and PI(36:4) were the main contributors to the unsaturated to saturated ratio change. This indicates that Young may have superior ability to maintain membrane fluidity following cold exposure, thereby avoiding membrane damage and water stress observed for Wyalkatchem. CONCLUSION: Our study suggests that metabolomics and lipidomics markers could be used as an alternative phenotyping method to discriminate wheat varieties with differences in cold acclimation.

A chemotaxis model of feather primordia pattern formation during avian development.

The orderly formation of the avian feather array is a classic example of periodic pattern formation during embryonic development. Various mathematical models have been developed to describe this process, including Turing/activator-inhibitor type reaction-diffusion systems and chemotaxis/mechanical-based models based on cell movement and tissue interactions. In this paper we formulate a mathematical model founded on experimental findings, a set of interactions between the key cellular (dermal and epidermal cell populations) and molecular (fibroblast growth factor, FGF, and bone morphogenetic protein, BMP) players and a medially progressing priming wave that acts as the trigger to initiate patterning. Linear stability analysis is used to show that FGF-mediated chemotaxis of dermal cells is the crucial driver of pattern formation, while perturbations in the form of ubiquitous high BMP expression suppress patterning, consistent with experiments. Numerical simulations demonstrate the capacity of the model to pattern the skin in a spatial-temporal manner analogous to avian feather development. Further, experimental perturbations in the form of bead-displacement experiments are recapitulated and predictions are proposed in the form of blocking mesenchymal cell proliferation.

Structural features determining flower-promoting activity of Arabidopsis FLOWERING LOCUS T.

In Arabidopsis thaliana, the genes FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1) have antagonistic roles in regulating the onset of flowering: FT activates and TFL1 represses flowering. Both encode small, closely related transcription cofactors of ∼175 amino acids. Previous studies identified a potential ligand binding residue as well as a divergent external loop as critical for the differences in activity of FT and TFL1, but the mechanisms for the differential action of FT and TFL1 remain unclear. Here, we took an unbiased approach to probe the importance of residues throughout FT protein, testing the effects of hundreds of mutations in vivo. FT is surprisingly robust to a wide range of mutations, even in highly conserved residues. However, specific mutations in at least four different residues are sufficient to convert FT into a complete TFL1 mimic, even when expressed from TFL1 regulatory sequences. Modeling the effects of these mutations on the surface charge of FT protein suggests that the affected residues regulate the docking of an unknown ligand. These residues do not seem to alter the interaction with FD or 14-3-3 proteins, known FT interactors. Potential candidates for differential mediators of FT and TFL1 activities belong to the TCP (for TEOSINTE BRANCHED1, CYCLOIDEA, PCF) family of transcription factors.

A phase I study of PRO131921, a novel anti-CD20 monoclonal antibody in patients with relapsed/refractory CD20+ indolent NHL: correlation between clinical responses and AUC pharmacokinetics.

PRO131921 is a third-generation, humanized anti-CD20 monoclonal antibody with increased antibody-dependent cytotoxicity and complement-dependent cytotoxicity compared to rituximab. In this phase I study, PRO131921 was administered as a single agent to patients with CD20+, relapsed or refractory, indolent non-Hodgkin lymphoma (NHL) who had been treated with a prior rituximab-containing regimen. The primary aim of this study was safety and tolerability of PRO131921. The secondary aim of the study, and focus of this report, was to determine the pharmacokinetics (PK) profile of PRO131921 and establish a correlation between drug exposure and clinical efficacy. Patients were treated with PRO131921 by intravenous infusion weekly for 4 weeks and the dose was escalated based on safety in a 3+3 design. Twenty-four patients were treated with PRO131921 at doses from 25mg/m(2) to 800 mg/m(2). Analysis of PK data demonstrated a correlation between higher normalized drug exposure (normalized AUC) and tumor shrinkage (p = .0035). Also, normalized AUC levels were higher among responders and subjects displaying tumor shrinkage versus subjects progressing or showing no regression (p = 0.030). In conclusion, PRO131921 demonstrated clinical activity in rituximab-relapsed and refractory indolent NHL patients. The observation that higher normalized AUC may be associated with improved clinical responses has potential implications in future trials of monoclonal antibody-based therapies, and emphasizes the importance of early PK studies to optimize antibody efficacy.

A low-input high resolution sequential chromatin immunoprecipitation method captures genome-wide dynamics of bivalent chromatin.

BACKGROUND: Bivalent chromatin is an exemplar of epigenetic plasticity. This co-occurrence of active-associated H3K4me3 and inactive-associated H3K27me3 histone modifications on opposite tails of the same nucleosome occurs predominantly at promoters that are poised for future transcriptional upregulation or terminal silencing. We know little of the dynamics, resolution, and regulation of this chromatin state outside of embryonic stem cells where it was first described. This is partly due to the technical challenges distinguishing bone-fide bivalent chromatin, where both marks are on the same nucleosome, from allelic or sample heterogeneity where there is a mix of H3K4me3-only and H3K27me3-only mononucleosomes. RESULTS: Here, we present a robust and sensitive method to accurately map bivalent chromatin genome-wide, along with controls, from as little as 2 million cells. We optimized and refined the sequential ChIP protocol which uses two sequential overnight immunoprecipitation reactions to robustly purify nucleosomes that are truly bivalent and contain both H3K4me3 and H3K27me3 modifications. Our method generates high quality genome-wide maps with strong peak enrichment and low background, which can be analyzed using standard bioinformatic packages. Using this method, we detect 8,789 bivalent regions in mouse embryonic stem cells corresponding to 3,918 predominantly CpG rich and developmentally regulated gene promoters. Furthermore, profiling Dppa2/4 knockout mouse embryonic stem cells, which lose both H3K4me3 and H3K27me3 at approximately 10% of bivalent promoters, demonstrated the ability of our method to capture bivalent chromatin dynamics. CONCLUSIONS: Our optimized sequential reChIP method enables high-resolution genome-wide assessment of bivalent chromatin together with all required controls in as little as 2 million cells. We share a detailed protocol and guidelines that will enable bivalent chromatin landscapes to be generated in a range of cellular contexts, greatly enhancing our understanding of bivalent chromatin and epigenetic plasticity beyond embryonic stem cells.

Delivery of mRNA Encoding Interleukin-12 and a Stimulator of Interferon Genes Agonist Potentiates Antitumor Efficacy through Reversing T Cell Exhaustion.

T cell exhaustion has emerged as a major hurdle that impedes the clinical translation of stimulator of interferon genes (STING) agonists. It is crucial to explore innovative strategies to rejuvenate exhausted T cells and potentiate the antitumor efficacy. Here, we propose an approach utilizing MSA-2 as a STING agonist, along with nanoparticle-mediated delivery of mRNA encoding interleukin-12 (IL-12) to restore the function of T cells. We developed a lipid nanoparticle (DMT7-IL12 LNP) that encapsulated IL12 mRNA. Our findings convincingly demonstrated that the combination of MSA-2 and DMT7-IL12 LNP can effectively reverse the exhausted T cell phenotype, as evidenced by the enhanced secretion of cytokines, such as tumor necrosis factor alpha, interferon gamma, and Granzyme B, coupled with reduced levels of inhibitory molecules such as T cell immunoglobulin and mucin domain-3 and programmed cell death protein-1 on CD8+ T cells. Furthermore, this approach led to improved survival and tumor regression without causing any systemic toxicity in melanoma and lung metastasis models. These findings suggest that mRNA encoding IL-12 in conjunction with STING agonists has the potential to confer superior clinical outcomes, representing a promising advancement in cancer immunotherapy.

Derivation and long-term maintenance of porcine skeletal muscle progenitor cells.

Culture of muscle cells from livestock species has typically involved laborious enzyme-based approaches that yield heterogeneous populations with limited proliferative and myogenic differentiation capacity, thus limiting their use in physiologically-meaningful studies. This study reports the use of a simple explant culture technique to derive progenitor cell populations from porcine muscle that could be maintained and differentiated long-term in culture. Fragments of semitendinosus muscle from 4 to 8 week-old piglets (n = 4) were seeded on matrigel coated culture dishes to stimulate migration of muscle-derived progenitor cells (MDPCs). Cell outgrowths appeared within a few days and were serially passaged and characterised using RT-qPCR, immunostaining and flow cytometry. MDPCs had an initial mean doubling time of 1.4 days which increased to 2.5 days by passage 14. MDPC populations displayed steady levels of the lineage-specific markers, PAX7 and MYOD, up until at least passage 2 (positive immunostaining in about 40% cells for each gene), after which the expression of myogenic markers decreased gradually. Remarkably, MDPCs were able to readily generate myotubes in culture up until passage 8. Moreover, a decrease in myogenic capacity during serial passaging was concomitant with a gradual increase in the expression of the pre-adipocyte markers, CD105 and PDGFRA, and an increase in the ability of MDPCs to differentiate into adipocytes. In conclusion, explant culture provided a simple and efficient method to harvest enriched myogenic progenitors from pig skeletal muscle which could be maintained long-term and differentiated in vitro, thus providing a suitable system for studies on porcine muscle biology and applications in the expanding field of cultured meat.

Targeted mRNA Nanoparticles Ameliorate Blood-Brain Barrier Disruption Postischemic Stroke by Modulating Microglia Polarization.

The ischemic stroke is a major global health concern, with high mortality and disability rates. Unfortunately, there is a dearth of effective clinical interventions for managing poststroke neuroinflammation and blood-brain barrier (BBB) disruption that are crucial for the brain injury evolving and neurological deficits. By leveraging the pathological progression of an ischemic stroke, we developed an M2 microglia-targeting lipid nanoparticle (termed MLNP) approach that can selectively deliver mRNA encoding phenotype-switching interleukin-10 (mIL-10) to the ischemic brain, creating a beneficial feedback loop that drives microglial polarization toward the protective M2 phenotypes and augments the homing of mIL-10-loaded MLNPs (mIL-10@MLNPs) to ischemic regions. In a transient middle cerebral artery occlusion (MCAO) mouse model of an ischemic stroke, our findings demonstrate that intravenously injected mIL-10@MLNPs induce IL-10 production and enhance the M2 polarization of microglia. The resulting positive loop reinforces the resolution of neuroinflammation, restores the impaired BBB, and prevents neuronal apoptosis after stroke. Using a permanent distal MCAO mouse model of an ischemic stroke, the neuroprotective effects of mIL-10@MLNPs have been further validated by the attenuation of the sensorimotor and cognitive neurological deficits. Furthermore, the developed mRNA-based targeted therapy has great potential to extend the therapeutic time window at least up to 72 h poststroke. This study depicts a simple and versatile LNP platform for selective delivery of mRNA therapeutics to cerebral lesions, showcasing a promising approach for addressing an ischemic stroke and associated brain conditions.

Uncovering microstructural architecture from histology.

Microstructural tissue organization underlies the complex connectivity of the brain and controls properties of connective, muscle, and epithelial tissue. However, discerning microstructural architecture with high resolution for large fields of view remains prohibitive. We address this challenge with computational scattered light imaging (ComSLI), which exploits the anisotropic light scattering of aligned structures. Using a rotating lightsource and a high-resolution camera, ComSLI determines fiber architecture with micrometer resolution from histological sections across preparation and staining protocols. We show complex fiber architecture in brain and non-brain sections, including histological paraffin-embedded sections with various stains, and demonstrate its applicability on animal and human tissue, including disease cases with altered microstructure. ComSLI opens new avenues for investigating fiber architecture in new and archived sections across organisms, tissues, and diseases.

Roles of macrophages in tumor development: a spatiotemporal perspective.

Macrophages are critical regulators of tissue homeostasis but are also abundant in the tumor microenvironment (TME). In both primary tumors and metastases, such tumor-associated macrophages (TAMs) seem to support tumor development. While we know that TAMs are the dominant immune cells in the TME, their vast heterogeneity and associated functions are only just being unraveled. In this review, we outline the various known TAM populations found thus far and delineate their specialized roles associated with the main stages of cancer progression. We discuss how macrophages may prime the premetastatic niche to enable the growth of a metastasis and then how subsequent metastasis-associated macrophages can support secondary tumor growth. Finally, we speculate on the challenges that remain to be overcome in TAM research.