Cell-Derived Vesicles for Single-Molecule Imaging of Membrane Proteins

Most recent advances and applications of extracellular vesicles in tackling neurological challenges

Over the past few decades, there has been a notable increase in the global burden of central nervous system (CNS) diseases. Despite advances in technology and therapeutic options, neurological and neurodegenerative disorders persist as significant challenges in treatment and cure. Recently, there has been a remarkable surge of interest in extracellular vesicles (EVs) as pivotal mediators of intercellular communication. As carriers of molecular cargo, EVs demonstrate the ability to traverse the blood-brain barrier, enabling bidirectional communication. As a result, they have garnered attention as potential biomarkers and therapeutic agents, whether in their natural form or after being engineered for use in the CNS. This review article aims to provide a comprehensive introduction to EVs, encompassing various aspects such as their diverse isolation methods, characterization, handling, storage, and different routes for EV administration. Additionally, it underscores the recent advances in their potential applications in neurodegenerative disorder therapeutics. By exploring their unique capabilities, this study sheds light on the promising future of EVs in clinical research. It considers the inherent challenges and limitations of these emerging applications while incorporating the most recent updates in the field.

Cell Death Persists in Rapid Extrusion of Lysis-Resistant Coated Cardiac Myoblasts

As the demand for organ transplants continues to grow faster than the supply of available donor organs, a new source of functional organs is needed. High resolution high throughput 3D bioprinting is one approach towards generating functional organs for transplantation. For high throughput printing, the need for increased print resolutions (by decreasing printing nozzle diameter) has a consequence: it increases the forces that cause cell damage during the printing process. Here, a novel cell encapsulation method provides mechanical protection from complete lysis of individual living cells during extrusion-based bioprinting. Cells coated in polymers possessing the mechanical properties finely-tuned to maintain size and shape following extrusion, and these encapsulated cells are protected from mechanical lysis. However, the shear forces imposed on the cells during extrusion still cause sufficient damage to compromise the cell membrane integrity and adversely impact normal cellular function. Cellular damage occurred during the extrusion process independent of the rapid depressurization.

The Effects of Chloride Flux on Drosophila Heart Rate

Approaches are sought after to regulate ionotropic and chronotropic properties of the mammalian heart. Electrodes are commonly used for rapidly exciting cardiac tissue and resetting abnormal pacing. With the advent of optogenetics and the use of tissue-specific expression of light-activated channels, cardiac cells cannot only be excited but also inhibited with ion-selective conductance. As a proof of concept for the ability to slow down cardiac pacing, anion-conducting channelrhodopsins (GtACR1/2) and the anion pump halorhodopsin (eNpHR) were expressed in hearts of larval Drosophila and activated by light. Unlike body wall muscles in most animals, the equilibrium potential for Cl⁻ is more positive as compared to the resting membrane potential in larval Drosophila. As a consequence, upon activating the two forms of GtACR1 and 2 with low light intensity the heart rate increased, likely due to depolarization and opening of voltage-gated Ca²⁺ channels. However, with very intense light activation the heart rate ceases, which may be due to Cl^– shunting to the reversal potential for chloride. Activating eNpHR hyperpolarizes body wall and cardiac muscle in larval Drosophila and rapidly decreases heart rate. The decrease in heart rate is related to light intensity. Intense light activation of eNpHR stops the heart from beating, whereas lower intensities slowed the rate. Even with upregulation of the heart rate with serotonin, the pacing of the heart was slowed with light. Thus, regulation of the heart rate in Drosophila can be accomplished by activating anion-conducting channelrhodopsins using light. These approaches are demonstrated in a genetically amenable insect model.

Cell-Derived Vesicles for in Vitro and in Vivo Targeted Therapeutic Delivery

Efficient delivery of therapeutics across the cell membrane to the interior of the cell remains a challenge both in vitro and in vivo. Here, we demonstrate that vesicles derived from cellular membranes can be efficiently loaded with cargo that can then be delivered to the interior of the cell. These vesicles demonstrated cell-targeting specificity as well as the ability to deliver a wide range of different cargos. We utilized this approach to deliver both lipophilic and hydrophilic cargos including therapeutics and DNA in vitro. We further demonstrated in vivo targeting and delivery using fluorescently labeled vesicles to target tumor xenografts in an animal. Cell-derived vesicles can be generated in high yields and are easily loaded with a variety of cargos. The ability of these vesicles to specifically target the same cell type from which they originated provides an efficient means of delivering cargo, such as therapeutics, both in vitro and in vivo.

Brain Region Specific Single-Molecule Fluorescence Imaging

We developed an approach utilizing nanoscale vesicles extracted from brain regions combined with single molecule imaging to monitor how an animal's physiological condition regulates the dynamics of protein distributions in different brain regions. This method was used to determine the effect of nicotine on the distribution of receptor stoichiometry in different mouse brain regions. Nicotine-induced upregulation of α4β2 nicotinic acetylcholine receptors (nAChRs) is associated with changes in their expression, trafficking, and stoichiometry. The structural assembly of nAChRs has been quantified in cell culture based systems using single molecule techniques. However, these methods are not capable of quantifying biomolecule assembly that takes place in a live animal. Both nicotine-induced upregulation and changes in nAChR stoichiometry differ across brain regions. Our single molecule approach revealed that nicotine acts differentially across brain regions to alter assembly in response to exposure and withdrawal.

Bioengineered stem cell membrane functionalized nanocarriers for therapeutic targeting of severe hindlimb ischemia

Bioengineering strategies to enhance the natural targeting function of nanocarriers would expand their therapeutic applications. Here, we designed bioengineered stem cell membrane-functionalized nanocarriers (BSMNCs) harboring C-X-C chemokine receptor type 4 (CXCR4) to achieve robust targeting and also to increase their retention time in ischemic tissue. Stem cell membrane coated nanocarrier (SMNCs) or poly (lactic-co-glycolic acid) (PLGA) nanocarriers (PNCs) and BSMNCs were prepared by functionalizing PNCs with human adipose-derived stem cells (hASCs) membranes and hASCs engineered to overexpress CXCR4-receptor, respectively. The functionalization of PNCs with stem cell membranes derived from hASCs significantly enhance the nanocarrier penetration across endothelial cell barrier compare to PNCs. In addition, stem cell membrane functionalization on PNCs also significantly decreased the nanoparticles uptake in J774 (murine) and THP (human) macrophages respectively from 84% to 76%-29% and 24%. Interestingly, BSMNCs showed much higher level of accumulation in ischemic tissue than SMNCs. Systemic retro-orbital injection of BSMNCs loaded with VEGF into mice with hindlimb ischemia resulted substantially enhancement of blood reperfusion, muscle repair, and limb salvage compared to animals treated with SMNCs loaded with similar concentration of VEGF. The reported strategy could be used to create biocompatible and custom-tailored biomimetic nanoparticles with various hybrid functionalities, which may overcome the limitations of current nanoparticle-based therapeutic and imaging platforms.