BackgroundIt has long been thought that mammalian cardiomyocytes are terminally-differentiated and unable to proliferate. However, myocytes in more primitive animals such as zebrafish are able to dedifferentiate and proliferate to regenerate amputated cardiac muscle.Methodology/Principal FindingsHere we test the hypothesis that mature mammalian cardiomyocytes retain substantial cellular plasticity, including the ability to dedifferentiate, proliferate, and acquire progenitor cell phenotypes. Two complementary methods were used: 1) cardiomyocyte purification from rat hearts, and 2) genetic fate mapping in cardiac explants from bi-transgenic mice. Cardiomyocytes isolated from rodent hearts were purified by multiple centrifugation and Percoll gradient separation steps, and the purity verified by immunostaining and RT-PCR. Within days in culture, purified cardiomyocytes lost their characteristic electrophysiological properties and striations, flattened and began to divide, as confirmed by proliferation markers and BrdU incorporation. Many dedifferentiated cardiomyocytes went on to express the stem cell antigen c-kit, and the early cardiac transcription factors GATA4 and Nkx2.5. Underlying these changes, inhibitory cell cycle molecules were suppressed in myocyte-derived cells (MDCs), while microRNAs known to orchestrate proliferation and pluripotency increased dramatically. Some, but not all, MDCs self-organized into spheres and re-differentiated into myocytes and endothelial cells in vitro. Cell fate tracking of cardiomyocytes from 4-OH-Tamoxifen-treated double-transgenic MerCreMer/ZEG mouse hearts revealed that green fluorescent protein (GFP) continues to be expressed in dedifferentiated cardiomyocytes, two-thirds of which were also c-kit+.Conclusions/SignificanceContradicting the prevailing view that they are terminally-differentiated, postnatal mammalian cardiomyocytes are instead capable of substantial plasticity. Dedifferentiation of myocytes facilitates proliferation and confers a degree of stemness, including the expression of c-kit and the capacity for multipotency.

Effective treatment of brain neurological disorders such as Alzheimer's disease, multiple sclerosis, or tumors should be possible with drug delivery through blood–brain barrier (BBB) or blood–brain tumor barrier (BTB) and targeting specific types of brain cells with drug release into the cell cytoplasm. A polymeric nanobioconjugate drug based on biodegradable, nontoxic, and nonimmunogenic polymalic acid as a universal delivery nanoplatform was used for design and synthesis of nanomedicine drug for i.v. treatment of brain tumors. The polymeric drug passes through the BTB and tumor cell membrane using tandem monoclonal antibodies targeting the BTB and tumor cells. The next step for polymeric drug action was inhibition of tumor angiogenesis by specifically blocking the synthesis of a tumor neovascular trimer protein, laminin-411, by attached antisense oligonucleotides (AONs). The AONs were released into the target cell cytoplasm via pH-activated trileucine, an endosomal escape moiety. Drug delivery to the brain tumor and the release mechanism were both studied for this nanobiopolymer. Introduction of a trileucine endosome escape unit resulted in significantly increased AON delivery to tumor cells, inhibition of laminin-411 synthesis in vitro and in vivo, specific accumulation in brain tumors, and suppression of intracranial glioma growth compared with pH-independent leucine ester. The availability of a systemically active polymeric drug delivery system that passes through the BTB, targets tumor cells, and inhibits glioma growth gives hope for a successful strategy of glioma treatment. This delivery system with drug release into the brain-specific cell type could be useful for treatment of various brain pathologies.

Adult hippocampal neurogenesis is involved in memory and learning, and disrupted neurogenesis is implicated in cognitive impairment and mood disorders, including anxiety and depression. Some long-term peripheral illnesses and metabolic disorders, as well as normal aging, create a state of chronic peripheral inflammation. These conditions are associated with behavioral disturbances linked to disrupted adult hippocampal neurogenesis, such as cognitive impairment, deficits in learning and memory, and depression and anxiety. Pro-inflammatory cytokines released in the periphery are involved in peripheral immune system-to-brain communication by activating resident microglia in the brain. Activated microglia reduce neurogenesis by suppressing neuronal stem cell proliferation, increasing apoptosis of neuronal progenitor cells, and decreasing survival of newly developing neurons and their integration into existing neuronal circuits. In this review, we summarize evolving evidence that the state of chronic peripheral inflammation reduces adult hippocampal neurogenesis, which, in turn, produces the behavioral disturbances observed in chronic inflammatory disorders. As there are no data available on neurogenesis in humans with chronic peripheral inflammatory disease, we focus on animal models and, in parallel, consider the evidence of cognitive disturbance and mood disorders in human patients.

Summary The mesoderm- and epithelial-mesenchymal transition-associated transcription factor FOXC1 is specifically overexpressed in basal-like breast cancer (BLBC), but its biochemical function is not understood. Here we demonstrate that FOXC1 controls cancer stem cell (CSC) properties enriched in BLBC cells via activation of Smoothened (SMO)-independent Hedgehog (Hh) signaling. This non-canonical activation of Hh is specifically mediated by Gli2. We further show that the N-terminal domain of FOXC1 (aa 1–68) binds directly to an internal region (aa 898–1168) of Gli2, enhancing the DNA-binding and transcription-activating capacity of Gli2. FOXC1 expression correlates with that of Gli2 and its targets in human breast cancers. Moreover, FOXC1 overexpression reduces sensitivity to anti-Hedgehog (Hh) inhibitors in BLBC cells and xenograft tumors. Together, these findings reveal FOXC1-mediated non-canonical Hh signaling that determines the BLBC stem-like phenotype and anti-Hh sensitivity, supporting inhibition of FOXC1 pathways as potential approaches for improving BLBC treatment.

A new prototype of nanoconjugate, Polycefin, was synthesized for targeted delivery of antisense oligonucleotides and monoclonal antibodies to brain tumors. The macromolecular carrier contains: 1. biodegradable, nonimmunogenic, nontoxic β-poly(L-malic acid) of microbial origin; 2. Morpholino antisense oligonucleotides targeting laminin α4 and β1 chains of laminin-8, which is specifically overexpressed in glial brain tumors; 3. monoclonal anti-transferrin receptor antibody for specific tissue targeting; 4. oligonucleotide releasing disulfide units; 5. L-valine containing, pHsensitive membrane disrupting unit(s), 6. protective poly(ethylene glycol); 7. a fluorescent dye (optional). Highly purified modules were conjugated directly with N-hydroxysuccinimidyl esteractivated β-poly-(L-malic acid) at pendant carboxyl groups or at thiol containing spacers via thioether and disulfide bonds. Products were chemically validated by physical, chemical, and functional tests. In vitro experiments using two human glioma cell lines U87MG and T98G demonstrated that Polycefin was delivered into the tumor cells by a receptor-mediated endocytosis mechanism and was able to inhibit the synthesis of laminin-8 α4 and β1 chains at the same time.Inhibition of laminin-8 expression was in agreement with the designed endosomal membrane disruption and drug releasing activity. In vivo imaging showed the accumulation of intravenously injected Polycefin in brain tumor tissue via the antibody-targeted transferrin receptor-mediated endosomal pathway in addition to a less efficient mechanism known for high molecular mass biopolymers as enhanced permeability and retention effect. Polycefin was nontoxic to normal and tumor astrocytes in a wide range of concentrations, accumulated in brain tumor, and could be used for specific targeting of several biomarkers simultaneously.