Circadian clocks are cell autonomous, transcriptionally based, molecular mechanisms that confer the selective advantage of anticipation, enabling cells/organs to respond to environmental factors in a temporally appropriate manner. Critical to circadian clock function are 2 transcription factors, CLOCK and BMAL1. The purpose of the present study was to reveal novel physiologic functions of BMAL1 in the heart, as well as to determine the pathologic consequences of chronic disruption of this circadian clock component. To address this goal, we generated cardiomyocyte-specific Bmal1 knockout (CBK) mice. Following validation of the CBK model, combined microarray and in silico analyses were performed, identifying 19 putative direct BMAL1 target genes, which included a number of metabolic (e.g., β-hydroxybutyrate dehydrogenase 1 [Bdh1]) and signaling (e.g., the p85α regulatory subunit of phosphatidylinositol 3-kinase [Pik3r1]) genes. Results from subsequent validation studies were consistent with regulation of Bdh1 and Pik3r1 by BMAL1, with predicted impairments in ketone body metabolism and signaling observed in CBK hearts. Furthermore, CBK hearts exhibited depressed glucose utilization, as well as a differential response to a physiologic metabolic stress (i.e., fasting). Consistent with BMAL1 influencing critical functions in the heart, echocardiographic, gravimetric, histologic, and molecular analyses revealed age-onset development of dilated cardiomyopathy in CBK mice, which was associated with a severe reduction in life span. Collectively, our studies reveal that BMAL1 influences metabolism, signaling, and contractile function of the heart.

A bio-inspired hydrogel for 3D bioprinting of soft free-standing neural tissues is presented. The novel filler-free bioinks were designed by combining natural polymers for extracellular matrix biomimicry with synthetic polymers to endow desirable rheological properties for 3D bioprinting. Crosslinking of thiolated Pluronic F-127 with dopamine-conjugated (DC) gelatin and DC hyaluronic acid through a thiol–catechol reaction resulted in thermally gelling bioinks with Herschel–Bulkley fluid rheological behavior. Microextrusion 3D bioprinting was used to fabricate free-standing cell-laden tissue constructs. The bioinks exhibited flattened parabolic velocity profiles with tunable low shear regions. Two pathways were investigated for curing the bioink: chelation and photocuring. The storage modulus of the cured bioinks ranged from 6.7 to 11.7 kPa. The iron (III) chelation chemistry produced crosslinked neural tissues of relatively lower storage modulus than the photocuring approach. In vitro cell viability studies using the 3D bioprinted neural tissues showed that the cured bioink was biocompatible based on minimal cytotoxic response observed over seven days in culture relative to control studies using alginate hydrogels. Rodent Schwann cell-, rodent neuronal cell-, and human glioma cell-laden tissue constructs were printed and cultured over seven days and exhibited comparable viability relative to alginate bioink controls. The ability to fabricate soft, free-standing 3D neural tissues with low modulus has implications in the biofabrication of microphysiological neural systems for disease modeling as well as neural tissues and innervated tissues for regenerative medicine.

Grade IV astrocytomas, or glioblastomas (GBMs), are the most common malignant primary brain tumor in adults. The median GBM patient survival of 12–15 months has remained stagnant, in spite of treatment strategies, making GBMs a tremendous challenge clinically. This is at least in part due to the complex interaction of GBM cells with the brain microenvironment and their tendency to aggressively infiltrate normal brain tissue. GBMs frequently invade supratentorial brain regions that are richly innervated by neurotransmitter projections, most notably acetylcholine (ACh). Here, we asked whether ACh signaling influences the biology of GBMs. We examined the expression and function of known ACh receptors (AChRs) in large GBM datasets, as well as, human GBM cell lines and patient-derived xenograft lines. Using RNA-Seq data from the “The Cancer Genome Atlas” (TCGA), we confirmed the expression of AChRs and demonstrated the functionality of these receptors in GBM cells with time-lapse calcium imaging. AChR activation did not alter cell proliferation or migration, however, it significantly increased cell invasion through complex extracellular matrices. This was due to the enhanced activity of matrix metalloproteinase-9 (MMP-9) from GBM cells, which we found to be dependent on an intracellular calcium-dependent mechanism. Consistent with these findings, AChRs were significantly upregulated in regions of GBM infiltration in situ (Ivy Glioblastoma Atlas Project) and elevated expression of muscarinic AChR M₃ correlated with reduced patient survival (TCGA). Data from the Repository for Molecular Brain Neoplasia Data (REMBRANDT) dataset also showed the co-expression of choline transporters, choline acetyltransferase, and vesicular acetylcholine transporters, suggesting that GBMs express all the proteins required for ACh synthesis and release. These findings identify ACh as a modulator of GBM behavior and posit that GBMs may utilize ACh as an autocrine signaling molecule.

Stem cells present in the adult brain are regulated by neuronal activity; malignant gliomas, which most likely originate from this population of cells, could also be regulated in this manner. A recent study by Venkatesh et al. published in Cell has identified Neuroligin-3 (NLGN3) as a mitogen promoting high-grade glioma growth.