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Human brain cells generated by in vitro cell programming provide exciting prospects for disease modeling, drug discovery and cell therapy. These applications frequently require efficient and clinically compliant tools for genetic modification of the cells. Recombinant adeno-associated viruses (AAVs) fulfill these prerequisites for a number of reasons, including the availability of a myriad of AAV capsid variants with distinct cell type specificity (also called tropism). Here, we harnessed a customizable parallel screening approach to assess a panel of natural or synthetic AAV capsid variants for their efficacy in lineage-related human neural cell types. We identified common lead candidates suited for the transduction of directly converted, early-stage induced neural stem cells (iNSCs), induced pluripotent stem cell (iPSC)-derived later-stage, radial glia-like neural progenitors, as well as differentiated astrocytic and mixed neuroglial cultures. We then selected a subset of these candidates for functional validation in iNSCs and iPSC-derived astrocytes, using shRNA-induced downregulation of the citrate transporter SLC25A1 and overexpression of the transcription factor NGN2 for proofs-of-concept. Our study provides a comparative overview of the susceptibility of different human cell programming-derived brain cell types to AAV transduction and a critical discussion of the assets and limitations of this specific AAV capsid screening approach.

Infectious diseases like malaria, tuberculosis or HIV are among the leading causes of death worldwide according to WHO estimations. Nevertheless, the fight against infectious diseases is aggravated through growing development of resistance towards current drugs and due to their severe adverse effects. The introduction of the lipophilic organometallic moiety ferrocene, a compound with a sandwich-like structure, in an existing bioactive molecule is a promising tool for the development of new more efficient drugs with innovative mechanisms of action. Thus, this review summarizes recent developments in the field of ferrocene conjugation to bioactive molecules like natural products, synthetically derived drugs, peptides as well as heterobimetallic complexes. Hereby, we will provide the reader with a summary of the most potent ferrocene derivatives reported for a plethora of infectious diseases by tabulating and critically assessing the corresponding IC50 values and the minimal inhibitory concentrations (MIC). Owing to the diverse field of infectious diseases the reported ferrocene derivatives were classified according to their targets into four main groups: antiparasitic (with antimalarial agents as biggest group), antibacterial, antifungal and antiviral agents.

High levels of reactive oxygen species (ROS) in tumors have been shown to exert anti-tumor activity, leading to the concept of ROS induction as therapeutic strategy. The organometallic compound ferrocene (Fc) generates ROS through a reversible one-electron oxidation. Incorporation of Fc into a tumor-targeting, bioactive molecule can enhance its therapeutic activity and enable tumor specific delivery. Therefore, we conjugated Fc to five synthetic, Arg-Gly-Asp (RGD)-based integrin binding ligands to enable targeting of the cell adhesion and signaling receptor integrin subtypes αvβ3, α5β1, or αvβ6, which are overexpressed in various, distinct tumors. We designed and synthesized a library of integrin-ligand-ferrocene (ILF) derivatives and showed that ILF conjugates maintained the high integrin affinity and selectivity of their parent ligands. A thorough biological characterization allowed us to identify the two most promising ligands, an αvβ3 (L2b) and an αvβ6 (L3b) targeting ILF, which displayed selective integrin-dependent cell uptake and pronounced ferrocene-mediated anti-tumor effects in vitro, along with increased ROS production and DNA damage. Hence, ILFs are promising candidates for the selective, tumor-targeted delivery of ferrocene to maximize its anti-cancer efficacy and minimize systemic toxicity, thereby improving the therapeutic window of ferrocene compared to currently used non-selective anti-cancer drugs.

Functional selectivity is the ligand-specific activation of certain signal transduction pathways at a receptor and has been described for G protein-coupled receptors. However, it has not yet been described for ligands interacting with integrins without αI domain. Here, we show by molecular dynamics simulations that four side chain-modified derivatives of tauroursodeoxycholic acid (TUDC), an agonist of α5β1 integrin, differentially shift the conformational equilibrium of α5β1 integrin towards the active state, in line with the extent of β1 integrin activation from immunostaining. Unlike TUDC, 24-nor-ursodeoxycholic acid (norUDCA)-induced β1 integrin activation triggered only transient activation of extracellular signal-regulated kinases and p38 mitogen-activated protein kinase and, consequently, only transient insertion of the bile acid transporter Bsep into the canalicular membrane, and did not involve activation of epidermal growth factor receptor. These results provide evidence that TUDC and norUDCA exert a functional selectivity at α5β1 integrin and may provide a rationale for differential therapeutic use of UDCA and norUDCA.

Background: Neoatherosclerosis represents an accelerated manifestation of atherosclerosis in nascent neointima after stenting, associated with adverse events. We investigated whether improved reendothelialization using RGD-coated stents results in diminished vascular permeability and reduced foam cell formation compared to standard DES in atherosclerotic rabbits. Methods and Results: Neointimal foam cell formation was induced in rabbits (n = 7). Enhanced endothelial integrity in RGD-coated stents resulted in decreased vascular permeability relative to DES, which was further confirmed by SEM and TEM. Cell culture experiments examined the effect of everolimus on endothelial integrity. Increasing concentrations of everolimus resulted in a dose-dependent decrease of endothelial cell junctions and foam cell transformation of monocytes, confirming the relevance of endothelial integrity in preventing permeability of LDL. Conclusion: Incomplete endothelial integrity was confirmed as a key factor of neointimal foam cell formation following stent implantation. Pro-healing stent coatings may facilitate reendothelialization and reduce the risk of neoatherosclerosis.

Functional selectivity is the ligand-specific activation of certain signal transduction pathways at a receptor and has been described for G protein-coupled receptors. However, it has not yet been described for ligands interacting with integrins without αI domain. Here, we show by molecular dynamics simulations that four side chain-modified derivatives of tauroursodeoxycholic acid (TUDC), an agonist of α5β1 integrin, differentially shift the conformational equilibrium of α5β1 integrin towards the active state, in line with the extent of β1 integrin activation from immunostaining. Unlike TUDC, 24-nor-ursodeoxycholic acid (norUDCA)-induced β1 integrin activation triggered only transient activation of extracellular signal-regulated kinases and p38 mitogen-activated protein kinase and, consequently, only transient insertion of the bile acid transporter Bsep into the canalicular membrane, and did not involve activation of epidermal growth factor receptor. These results provide evidence that TUDC and norUDCA exert a functional selectivity at α5β1 integrin and may provide a rationale for differential therapeutic use of UDCA and norUDCA.