Transcriptome signature of miRNA-26b KO mouse model suggests novel targets

MicroRNA-26b protects against MASH development in mice and can be efficiently targeted with lipid nanoparticles

The prevalence of metabolic dysfunction-associated steatohepatitis (MASH) is increasing, urging more research into the underlying mechanisms. MicroRNA-26b (Mir26b) might play a role in several MASH-related pathways. Therefore, we aimed to determine the role of Mir26b in MASH and its therapeutic potential using Mir26b mimic-loaded lipid nanoparticles (LNPs). Apoe-/-Mir26b-/-, Apoe-/-Lyz2creMir26bfl/fl mice, and respective controls were fed a Western-type diet to induce MASH. Plasma and liver samples were characterized regarding lipid metabolism, hepatic inflammation, and fibrosis. Additionally, Mir26b mimic-loaded LNPs were injected in Apoe-/-Mir26b-/- mice to rescue the phenotype and key results were validated in human precision-cut liver slices. Finally, kinase profiling was used to elucidate underlying mechanisms. Apoe-/-Mir26b-/- mice showed increased hepatic lipid levels, coinciding with increased expression of scavenger receptor a and platelet glycoprotein 4. Similar effects were found in mice lacking myeloid-specific Mir26b. Additionally, hepatic TNF and IL-6 levels and amount of infiltrated macrophages were increased in Apoe-/-Mir26b-/- mice. Moreover, Tgfb expression was increased by the Mir26b deficiency, leading to more hepatic fibrosis. A murine treatment model with Mir26b mimic-loaded LNPs reduced hepatic lipids, rescuing the observed phenotype. Kinase profiling identified increased inflammatory signaling upon Mir26b deficiency, which was rescued by LNP treatment. Finally, Mir26b mimic-loaded LNPs also reduced inflammation in human precision-cut liver slices. Overall, our study demonstrates that the detrimental effects of Mir26b deficiency in MASH can be rescued by LNP treatment. This novel discovery leads to more insight into MASH development, opening doors to potential new treatment options using LNP technology.

miR-26 Deficiency Causes Alterations in Lens Transcriptome and Results in Adult-Onset Cataract

Purpose

Despite strong evidence demonstrating that normal lens development requires regulation governed by microRNAs (miRNAs), the functional role of specific miRNAs in mammalian lens development remains largely unexplored.

Methods

A comprehensive analysis of miRNA transcripts in the newborn mouse lens, exploring both differential expression between lens epithelial cells and lens fiber cells and overall miRNA abundance, was conducted by miRNA sequencing. Mouse lenses lacking each of three abundantly expressed lens miRNAs (miR-184, miR-26, and miR-1) were analyzed to explore the role of these miRNAs in lens development.

Results

Mice lacking all three copies of miR-26 (miR-26TKO) developed postnatal cataracts as early as 4 to 6 weeks of age. RNA sequencing analysis of neonatal lenses from miR-26TKO mice exhibited abnormal reduced expression of a cohort of genes found to be lens enriched and linked to cataract (e.g., Foxe3, Hsf4, Mip, Tdrd7, and numerous crystallin genes) and abnormal elevated expression of genes related to neural development (Lhx3, Neurod4, Shisa7, Elavl3), inflammation (Ccr1, Tnfrsf12a, Csf2ra), the complement pathway, and epithelial to mesenchymal transition (Tnfrsf1a, Ccl7, Stat3, Cntfr).

Conclusions

miR-1, miR-184, and miR-26 are each dispensable for normal embryonic lens development. However, loss of miR-26 causes lens transcriptome changes and drives cataract formation.

Exploring craniofacial and dental development with microRNAs

microRNAs (miRs) are small RNA molecules that regulate many cellular and developmental processes. They control gene expression pathways during specific developmental time points and are required for tissue homeostasis and stem cell maintenance. miRs as therapeutic reagents in tissue regeneration and repair hold great promise and new technologies are currently being designed to facilitate their expression or inhibition. Due to the large amount of miR research in cells and cancer many cellular processes and gene networks have been delineated however, their in vivo response can be different in complex tissues and organs. Specifically, this report will discuss animal developmental models to understand the role of miRs as well as xenograft, disease, and injury models. We will discuss the role of miRs in clinical studies including their diagnostic function, as well as their potential ability to correct craniofacial diseases.

MicroRNA-26b Attenuates Platelet Adhesion and Aggregation in Mice

Platelets are key regulators of haemostasis, making platelet dysfunction a major driver of thrombosis. Numerous processes that determine platelet function are influenced by microRNAs (miRs). MiR-26b is one of the highest-expressed miRs in healthy platelets, and its expression in platelets is changed in a diseased state. However, the exact effect of this miR on platelet function has not been studied yet. In this study, we made use of a whole-body knockout of miR-26b in ApoE-deficient mice in order to determine its impact on platelet function, thrombus formation and platelet signalling both ex vivo and in vivo. We show that a whole-body deficiency of miR-26b exacerbated platelet adhesion and aggregation ex vivo. Additionally, in vivo, platelets adhered faster, and larger thrombi were formed in mice lacking miR-26b. Moreover, isolated platelets from miR-26b-deficient mice showed a hyperactivated Src and EGFR signalling. Taken together, we show here for the first time that miR-26b attenuates platelet adhesion and aggregation, possibly through Src and EGFR signalling.