ERRγ agonist under mechanical stretching manifests hypertrophic cardiomyopathy phenotypes of engineered cardiac tissue through maturation

Engineered cardiac tissue (ECT) using human induced pluripotent stem cell-derived cardiomyocytes is a promising tool for modeling heart disease. However, tissue immaturity makes robust disease modeling difficult. Here, we established a method for modeling hypertrophic cardiomyopathy (HCM) malignant (MYH7 R719Q) and nonmalignant (MYBPC3 G115∗) pathogenic sarcomere gene mutations by accelerating ECT maturation using an ERRγ agonist, T112, and mechanical stretching. ECTs treated with T112 under 10% elongation stimulation exhibited more organized and mature characteristics. Whereas matured ECTs with the MYH7 R719Q mutation showed broad HCM phenotypes, including hypertrophy, hypercontraction, diastolic dysfunction, myofibril misalignment, fibrotic change, and glycolytic activation, matured MYBPC3 G115∗ ECTs displayed limited phenotypes, which were primarily observed only under our new maturation protocol (i.e., hypertrophy). Altogether, ERRγ activation combined with mechanical stimulation enhanced ECT maturation, leading to a more accurate manifestation of HCM phenotypes, including non-cardiomyocyte activation, consistent with clinical observations.

Site-specific R-loops induce CGG repeat contraction and fragile X gene reactivation

Here, we describe an approach to correct the genetic defect in fragile X syndrome (FXS) via recruitment of endogenous repair mechanisms. A leading cause of autism spectrum disorders, FXS results from epigenetic silencing of FMR1 due to a congenital trinucleotide (CGG) repeat expansion. By investigating conditions favorable to FMR1 reactivation, we find MEK and BRAF inhibitors that induce a strong repeat contraction and full FMR1 reactivation in cellular models. We trace the mechanism to DNA demethylation and site-specific R-loops, which are necessary and sufficient for repeat contraction. A positive feedback cycle comprising demethylation, de novo FMR1 transcription, and R-loop formation results in the recruitment of endogenous DNA repair mechanisms that then drive excision of the long CGG repeat. Repeat contraction is specific to FMR1 and restores the production of FMRP protein. Our study therefore identifies a potential method of treating FXS in the future.

Mesenchymal Stem Cell Behavior on Soft Hydrogels with Aligned Surface Topographies

Human mesenchymal stem cells (HMSCs) are important for cell-based therapies. However, the success of HMSC therapy requires large-scale in vitro expansion of these multipotent cells. The traditional expansion of HMSCs on tissue-culture-treated stiff polystyrene induces significant changes in their shape, multipotency, and secretome, leading to early senescence and subdued paracrine activity. To enhance their therapeutic potential, here, we have developed two-dimensional soft hydrogels with imprinted microscale aligned grooves for use as HMSC culture substrates. We showed that, depending on the dimensions of the topographical features, these substrates led to lower cellular spreading and cytoskeletal tension, maintaining multipotency and osteogenic and adipogenic differentiate potential, while lowering cellular senescence. We also observed a greater capacity of HMSCs to produce anti-inflammatory cytokines after short-term priming on these hydrogel substrates. Overall, these soft hydrogels with unique surface topography have shown great promise as in vitro culture substrates to maximize the therapeutic potential of HMSCs.

Anatomical transcriptome of G protein-coupled receptors leads to the identification of a novel therapeutic candidate GPR52 for psychiatric disorders

Many drugs of abuse and most neuropharmacological agents regulate G protein-coupled receptors (GPCRs) in the central nervous system (CNS)_ENREF_1. The striatum, in which dopamine D1 and D2 receptors are enriched, is strongly innervated by the ventral tegmental area (VTA), which is the origin of dopaminergic cell bodies of the mesocorticolimbic dopamine system_ENREF_3 and plays a central role in the development of psychiatric disorders_ENREF_4. Here we report the comprehensive and anatomical transcript profiling of 322 non-odorant GPCRs in mouse tissue by quantitative real-time PCR (qPCR), leading to the identification of neurotherapeutic receptors exclusively expressed in the CNS, especially in the striatum. Among them, GPR6, GPR52, and GPR88, known as orphan GPCRs, were shown to co-localize either with a D2 receptor alone or with both D1 and D2 receptors in neurons of the basal ganglia. Intriguingly, we found that GPR52 was well conserved among vertebrates, is Gs-coupled and responsive to the antipsychotic drug, reserpine. We used three types of transgenic (Tg) mice employing a Cre-lox system under the control of the GPR52 promoter, namely, GPR52-LacZ Tg, human GPR52 (hGPR52) Tg, and hGPR52-GFP Tg mice. Detailed histological investigation suggests that GPR52 may modulate dopaminergic and glutamatergic transmission in neuronal circuits responsible for cognitive function and emotion. In support of our prediction, GPR52 knockout and transgenic mice exhibited psychosis-related and antipsychotic-like behaviors, respectively. Therefore, we propose that GPR52 has the potential of being a therapeutic psychiatric receptor. This approach may help identify potential therapeutic targets for CNS diseases.