Nanotransfection-based vasculogenic cell reprogramming drives functional recovery in a mouse model of ischemic stroke

Quantification of Lymphangiogenesis in the Murine Lymphedema Tail Model Using Intravital Microscopy

Background: Lymphedema is chronic limb swelling resulting from lymphatic dysfunction. It affects an estimated five million Americans. There is no cure for this disease. Assessing lymphatic growth is essential in developing novel therapeutics. Intravital microscopy (IVM) is a powerful imaging tool for investigating various biological processes in live animals. Tissue nanotransfection technology (TNT) facilitates a direct, transcutaneous nonviral vector gene delivery using a chip with nanochannel poration in a rapid (<100 ms) focused electric field. TNT was used in this study to deliver the genetic cargo in the murine tail lymphedema to assess the lymphangiogenesis. The purpose of this study is to experimentally evaluate the applicability of IVM to visualize and quantify lymphatics in the live mice model. Methods and Results: The murine tail model of lymphedema was utilized. TNT was applied to the murine tail (day 0) directly at the surgical site with genetic cargo loaded into the TNT reservoir: TNTpCMV6 group receives pCMV6 (expression vector backbone alone) (n = 6); TNTProx1 group receives pCMV6-Prox1 (n = 6). Lymphatic vessels (fluorescein isothiocyanate [FITC]-dextran stained) and lymphatic branch points (indicating lymphangiogenesis) were analyzed with the confocal/multiphoton microscope. The experimental group TNTProx1 exhibited reduced postsurgical tail lymphedema and increased lymphatic distribution compared to TNTpCMV6 group. More lymphatic branching points (>3-fold) were observed at the TNT site in TNTProx1 group. Conclusions: This study demonstrates a novel, powerful imaging tool for investigating lymphatic vessels in live murine tail model of lymphedema. IVM can be utilized for functional assessment of lymphatics and visualization of lymphangiogenesis following gene-based therapy.

Tissue Nanotransfection Silicon Chip and Related Electroporation-Based Technologies for In Vivo Tissue Reprogramming

Tissue nanotransfection (TNT), a cutting-edge technique of in vivo gene therapy, has gained substantial attention in various applications ranging from in vivo tissue reprogramming in regenerative medicine, and wound healing to cancer treatment. This technique harnesses the advancements in the semiconductor processes, facilitating the integration of conventional transdermal gene delivery methods-nanoelectroporation and microneedle technologies. TNT silicon chips have demonstrated considerable promise in reprogramming fibroblast cells of skin in vivo into vascular or neural cells in preclinical studies to assist in the recovery of injured limbs and damaged brain tissue. More recently, the application of TNT chips has been extended to the area of exosomes, which are vital for intracellular communication to track their functionality during the wound healing process. In this review, we provide an in-depth examination of the design, fabrication, and applications of TNT silicon chips, alongside a critical analysis of the electroporation-based gene transfer mechanisms. Additionally, the review discussed the existing limitations and challenges in the current technique, which may project future trajectories in the landscape of gene therapy. Through this exploration, the review aims to shed light on the prospects of TNT in the broader context of gene therapy and tissue regeneration.

Locomotor activity as an effective measure of the severity of inflammatory arthritis in a mouse model

OBJECTIVE

Mouse models are valuable in preclinical studies of inflammatory arthritis. However, current methods for measuring disease severity or responses to treatment are not optimal. In this study a smart cage system using multiple sensors to measure locomotor activity was evaluated in the K/BxN serum transfer model of inflammatory arthritis.

METHODS

Arthritis was induced in C57BL/6 mice with injections of K/BxN serum. Clinical index and ankle thickness were measured for 14 days. Locomotor activity was measured in smart cages for 23 h periods on Days 0, 7, and 13. The same measurements were taken in mice consuming diets supplemented or not with fish oil to evaluate a preventative treatment.

RESULTS

Initiation, peak and resolution phases of disease could be measured with the smart cages. Locomotor activity including speed, travel distance, number of active movements and rear movements were all significantly lower on Days 7-8 of illness (peak) compared to Days 0 and 13-14 (resolution) (one-way repeated measures analyses, p<0.05). The clinical index and ankle thickness measurements did not capture differences between dietary groups. Significantly increased activity was measured in most of the locomotor parameters in the fish oil group compared to the control mice at both Days 8 and 14 (2-way repeated measures ANOVA, p<0.05).

CONCLUSION

The measurement of locomotor activity provided a more detailed evaluation of the impact of inflammatory arthritis on animal well-being and mobility than that provided by measuring clinical index and ankle thickness, and could be a valuable tool in preclinical studies of inflammatory arthritis.

Single-cell RNA sequencing reveals the role of mitochondrial dysfunction in the cardiogenic toxicity of perfluorooctane sulfonate in human embryonic stem cells

Perfluorooctane sulfonate (PFOS), an endocrine-disrupting chemical pollutant, affects embryonic heart development; however, the mechanisms underlying its toxicity have not been fully elucidated. Here, Single-cell RNA sequencing (scRNA-seq) was used to investigate the overall effects of PFOS on myocardial differentiation from human embryonic stem cells (hESCs). Additionally, apoptosis, mitochondrial membrane potential, and ATP assays were performed. Downregulated cardiogenesis-related genes and inhibited cardiac differentiation were observed after PFOS exposure in vitro. The percentages of cardiomyocyte and cardiac progenitor cell clusters decreased significantly following exposure to PFOS, while the proportion of primitive endoderm cell was increased in PFOS group. Moreover, PFOS inhibited myocardial differentiation and blocked cellular development at the early- and middle-stage. A Gene Ontology analysis and pseudo-time trajectory illustrated that PFOS disturbed multiple processes related to cardiogenesis and oxidative phosphorylation in the mitochondria. Furthermore, PFOS decreased mitochondrial membrane potential and induced apoptosis. These results offer meaningful insights into the cardiogenic toxicity of PFOS exposure during heart formation as well as the adverse effects of PFOS on mitochondria.

Electrotransfer for nucleic acid and protein delivery

Electrotransfer of nucleic acids and proteins has become crucial in biotechnology for gene augmentation and genome editing. This review explores the applications of electrotransfer in both ex vivo and in vivo scenarios, emphasizing biomedical uses. We provide insights into completed clinical trials and successful instances of nucleic acid and protein electrotransfer into therapeutically relevant cells such as immune cells and stem and progenitor cells. In addition, we delve into emerging areas of electrotransfer where nanotechnology and deep learning techniques overcome the limitations of traditional electroporation.

ICAM-1-decorated extracellular vesicles loaded with miR-146a and Glut1 drive immunomodulation and hinder tumor progression in a murine model of breast cancer

Tumor-associated immune cells play a crucial role in cancer progression. Myeloid-derived suppressor cells (MDSCs), for example, are immature innate immune cells that infiltrate the tumor to exert immunosuppressive activity and protect cancer cells from the host's immune system and/or cancer-specific immunotherapies. While tumor-associated immune cells have emerged as a promising therapeutic target, efforts to counter immunosuppression within the tumor niche have been hampered by the lack of approaches that selectively target the immune cell compartment of the tumor, to effectively eliminate "tumor-protecting" immune cells and/or drive an "anti-tumor" phenotype. Here we report on a novel nanotechnology-based approach to target tumor-associated immune cells and promote "anti-tumor" responses in a murine model of breast cancer. Engineered extracellular vesicles (EVs) decorated with ICAM-1 ligands and loaded with miR-146a and Glut1, were biosynthesized (in vitro or in vivo) and administered to tumor-bearing mice once a week for up to 5 weeks. The impact of this treatment modality on the immune cell compartment and tumor progression was evaluated via RT-qPCR, flow cytometry, and histology. Our results indicate that weekly administration of the engineered EVs (i.e., ICAM-1-decorated and loaded with miR-146a and Glut1) hampered tumor progression compared to ICAM-1-decorated EVs with no cargo. Flow cytometry analyses of the tumors indicated a shift in the phenotype of the immune cell population toward a more pro-inflammatory state, which appeared to have facilitated the infiltration of tumor-targeting T cells, and was associated with a reduction in tumor size and decreased metastatic burden. Altogether, our results indicate that ICAM-1-decorated EVs could be a powerful platform nanotechnology for the deployment of immune cell-targeting therapies to solid tumors.

Engineered Extracellular Vesicle-Based Therapies for Valvular Heart Disease

Introduction

Valvular heart disease represents a significant burden to the healthcare system, with approximately 5 million cases diagnosed annually in the US. Among these cases, calcific aortic stenosis (CAS) stands out as the most prevalent form of valvular heart disease in the aging population.  CAS is characterized by the progressive calcification of the aortic valve leaflets, leading to valve stiffening. While aortic valve replacement is the standard of care for CAS patients, the long-term durability of prosthetic devices is poor, calling for innovative strategies to halt  or reverse disease progression. Here, we explor the potential use of novel extracellular vesicle (EV)-based nanocarriers for delivering molecular payloads to the affected valve tissue. This approach aims to reduce inflammation and potentially promote resorption of the calcified tissue.

Methods

Engineered EVs loaded with the reprogramming myeloid transcription factors, CEBPA and Spi1, known to mediate the transdifferentiation of committed endothelial cells into macrophages. We evaluated the ability of these engineered EVs to deliver DNA and transcripts encoding CEBPA and Spil into calcified aortic valve tissue obtained from patients undergoing valve replacement due to aortic stenosis. We also investigated whether these EVs could induce the transdifferentiation of endothelial cells into macrophage-like cells.

Results

Engineered EVs loaded with CEBPA + Spi1 were successfully derived from human dermal fibroblasts. Peak EV loading was found to be at 4 h after nanotransfection of donor cells.  These CEBPA + Spi1 loaded EVs effectively transfected aortic valve cells, resulting in the successful induction of transdifferentiation, both in vitro with  endothelial cells and ex vivo with valvular endothelial cells, leading to the development of anti-inflammatory macrophage-like cells.

Conclusions

Our findings highlight the potential of engineered EVs as a next generation nanocarrier to target aberrant calcifications on diseased heart valves. This development holds promise as a novel therapy for high-risk patients who may not be suitable candidates for valve replacement surgery.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00783-x.

Robust critical limb ischemia porcine model involving skeletal muscle necrosis

This work sought to develop a robust and clinically relevant swine model of critical limb ischemia (CLI) involving the onset of ischemic muscle necrosis. CLI carries about 25-40% risk of major amputation with 20% annual mortality. Currently, there is no specific treatment that targets the ischemic myopathy characteristic of CLI. Current swine models of CLI, with tolerable side-effects, fail to achieve sustained ischemia followed by a necrotic myopathic endpoint. Such limitation in experimental model hinders development of effective interventions. CLI was induced unilaterally by ligation-excision of one inch of the common femoral artery (CFA) via infra-inguinal minimal incision in female Yorkshire pigs (n = 5). X-ray arteriography was done pre- and post-CFA transection to validate successful induction of severe ischemia. Weekly assessment of the sequalae of ischemia on limb perfusion, and degree of ischemic myopathy was conducted for 1 month using X-ray arteriography, laser speckle imaging, CTA angiography, femoral artery duplex, high resolution ultrasound and histopathological analysis. The non-invasive tissue analysis of the elastography images showed specific and characteristic pattern of increased muscle stiffness indicative of the fibrotic and necrotic outcome expected with associated total muscle ischemia. The prominent onset of skeletal muscle necrosis was evident upon direct inspection of the affected tissues. Ischemic myopathic changes associated with inflammatory infiltrates and deficient blood vessels were objectively validated. A translational model of severe hindlimb ischemia causing ischemic myopathy was successfully established adopting an approach that enables long-term survival studies in compliance with regulatory requirements pertaining to animal welfare.

Engineered Extracellular Vesicles Derived from Dermal Fibroblasts Attenuate Inflammation in a Murine Model of Acute Lung Injury

Acute respiratory distress syndrome (ARDS) represents a significant burden to the healthcare system, with ≈200 000 cases diagnosed annually in the USA. ARDS patients suffer from severe refractory hypoxemia, alveolar-capillary barrier dysfunction, impaired surfactant function, and abnormal upregulation of inflammatory pathways that lead to intensive care unit admission, prolonged hospitalization, and increased disability-adjusted life years. Currently, there is no cure or FDA-approved therapy for ARDS. This work describes the implementation of engineered extracellular vesicle (eEV)-based nanocarriers for targeted nonviral delivery of anti-inflammatory payloads to the inflamed/injured lung. The results show the ability of surfactant protein A (SPA)-functionalized IL-4- and IL-10-loaded eEVs to promote intrapulmonary retention and reduce inflammation, both in vitro and in vivo. Significant attenuation is observed in tissue damage, proinflammatory cytokine secretion, macrophage activation, influx of protein-rich fluid, and neutrophil infiltration into the alveolar space as early as 6 h post-eEVs treatment. Additionally, metabolomics analyses show that eEV treatment causes significant changes in the metabolic profile of inflamed lungs, driving the secretion of key anti-inflammatory metabolites. Altogether, these results establish the potential of eEVs derived from dermal fibroblasts to reduce inflammation, tissue damage, and the prevalence/progression of injury during ARDS via nonviral delivery of anti-inflammatory genes/transcripts.

Strategies and mechanisms of neuronal reprogramming

Traumatic injury and neurodegenerative diseases of the central nervous system (CNS) are difficult to treat due to the poorly regenerative nature of neurons. Engrafting neural stem cells into the CNS is a classic approach for neuroregeneration. Despite great advances, stem cell therapy still faces the challenges of overcoming immunorejection and achieving functional integration. Neuronal reprogramming, a recent innovation, converts endogenous non-neuronal cells (e.g., glial cells) into mature neurons in the adult mammalian CNS. In this review, we summarize the progress of neuronal reprogramming research, mainly focusing on strategies and mechanisms of reprogramming. Furthermore, we highlight the advantages of neuronal reprogramming and outline related challenges. Although the significant development has been made in this field, several findings are controversial. Even so, neuronal reprogramming, especially in vivo reprogramming, is expected to become an effective treatment for CNS neurodegenerative diseases.

ETV2/ER71, the key factor leading the paths to vascular regeneration and angiogenic reprogramming

Extensive efforts have been made to achieve vascular regeneration accompanying tissue repair for treating vascular dysfunction-associated diseases. Recent advancements in stem cell biology and cell reprogramming have opened unforeseen opportunities to promote angiogenesis in vivo and generate autologous endothelial cells (ECs) for clinical use. We have, for the first time, identified a unique endothelial-specific transcription factor, ETV2/ER71, and revealed its essential role in regulating endothelial cell generation and function, along with vascular regeneration and tissue repair. Furthermore, we and other groups have demonstrated its ability to directly reprogram terminally differentiated non-ECs into functional ECs, proposing ETV2/ER71 as an effective therapeutic target for vascular diseases. In this review, we discuss the up-to-date status of studies on ETV2/ER71, spanning from its molecular mechanism to vasculo-angiogenic role and direct cell reprogramming toward ECs. Furthermore, we discuss future directions to deploy the clinical potential of ETV2/ER71 as a novel and potent target for vascular disorders such as cardiovascular disease, neurovascular impairment and cancer.

Engineered Vasculogenic Extracellular Vesicles Drive Nonviral Direct Conversions of Human Dermal Fibroblasts into Induced Endothelial Cells and Improve Wound Closure

Vasculogenic cell therapies have emerged as a powerful tool to increase vascularization and promote tissue repair/regeneration. Current approaches to cell therapies, however, rely mostly on progenitor cells, which pose significant risks (e.g., uncontrolled differentiation, tumorigenesis, and genetic/epigenetic abnormalities). Moreover, reprogramming methodologies used to generate induced endothelial cells (iECs) from induced pluripotent stem cells rely heavily on viral vectors, which pose additional translational limitations. This work describes the development of engineered human extracellular vesicles (EVs) capable of driving reprogramming-based vasculogenic therapies without the need for progenitor cells and/or viral vectors. The EVs were derived from primary human dermal fibroblasts (HDFs), and were engineered to pack transcription factor genes/transcripts of ETV2, FLI1, and FOXC2 (EFF). Our results indicate that in addition of EFF, the engineered EVs were also loaded with transcripts of angiogenic factors (e.g., VEGF-A, VEGF-KDR, FGF2). In vitro and in vivo studies indicate that such EVs effectively transfected HDFs and drove direct conversions towards iECs within 7-14 days. Finally, wound healing studies in mice indicate that engineered EVs lead to improved wound closure and vascularity. Altogether, our results show the potential of engineered human vasculogenic EVs to drive direct reprogramming processes of somatic cells towards iECs, and facilitate tissue repair/regeneration.

Identification of a physiologic vasculogenic fibroblast state to achieve tissue repair

Tissue injury to skin diminishes miR-200b in dermal fibroblasts. Fibroblasts are widely reported to directly reprogram into endothelial-like cells and we hypothesized that miR-200b inhibition may cause such changes. We transfected human dermal fibroblasts with anti-miR-200b oligonucleotide, then using single cell RNA sequencing, identified emergence of a vasculogenic subset with a distinct fibroblast transcriptome and demonstrated blood vessel forming function in vivo. Anti-miR-200b delivery to murine injury sites likewise enhanced tissue perfusion, wound closure, and vasculogenic fibroblast contribution to perfused vessels in a FLI1 dependent manner. Vasculogenic fibroblast subset emergence was blunted in delayed healing wounds of diabetic animals but, topical tissue nanotransfection of a single anti-miR-200b oligonucleotide was sufficient to restore FLI1 expression, vasculogenic fibroblast emergence, tissue perfusion, and wound healing. Augmenting a physiologic tissue injury adaptive response mechanism that produces a vasculogenic fibroblast state change opens new avenues for therapeutic tissue vascularization of ischemic wounds.

VEGF loaded nanofiber membranes inhibit chronic cerebral hypoperfusion-induced cognitive dysfunction by promoting HIF-1a/VEGF mediated angiogenesis

We investigated the potential effects and mechanisms of vascular endothelial growth factor (VEGF)-nanofiber membranes (NFMs) treatment in a rat model of chronic cerebral hypoperfusion (CCH). VEGF-NFMs treatment promoted angiogenesis in surgical temporal cortex and hippocampus, alleviating decreased CBF in these two cerebral regions. VEGF-NFMs application improved reduced NAA/Cr ratio, preventing neuronal loss. VEGF-NFMs sticking decreased the number of TUNEL-positive cells in surgical temporal cortex, ameliorated impaired synaptic plasticity, and inhibited the release of pro-inflammatory cytokines and the activation of microglia and astrocytes in surgical temporal cortex and hippocampus. Furthermore, BDNF-TrkB/PI3K/AKT, BDNF-TrkB/ERK and HIF-1a/VEGF/ERK pathways were involved in the treatment of VEGF-NFMs against CCH-induced neuronal injury. These results showed the neuroprotective effects of VEGF-NFMs sticking may initiate from neurovascular repairing followed by inhibition of neuronal apoptosis and neuronal and synaptic damage, eventually leading to the suppression of cognitive dysfunction, which provided theoretical foundation for further clinical transformation of VEGF-NFMs.

Inducible miR-1224 silences cerebrovascular Serpine1 and restores blood flow to the stroke-affected site of the brain

The α-tocotrienol (TCT) form of natural vitamin E is more potent than the better known α-tocopherol against stroke. Angiographic studies of canine stroke have revealed beneficial cerebrovascular effects of TCT. This work seeks to understand the molecular basis of such effect. In mice, TCT supplementation improved perfusion at the stroke-affected site by inducing miR-1224. miRNA profiling of a laser-capture-microdissected stroke-affected brain site identified miR-1224 as the only vascular miR induced. Lentiviral knockdown of miR-1224 significantly blunted the otherwise beneficial effects of TCT on stroke outcomes. Studies on primary brain microvascular endothelial cells revealed direct angiogenic properties of miR-1224. In mice not treated with TCT, advance stereotaxic delivery of an miR-1224 mimic to the stroke site markedly improved stroke outcomes. Mechanistic studies identified Serpine1 as a target of miR-1224. Downregulation of Serpine1 augmented the angiogenic response of the miR-1224 mimic in the brain endothelial cells. The inhibition of Serpine1, by dietary TCT and pharmacologically, increased cerebrovascular blood flow at the stroke-affected site and protected against stroke. This work assigns Serpine1, otherwise known to be of critical significance in stroke, a cerebrovascular function that worsens stroke outcomes. miR-1224-dependent inhibition of Serpine1 can be achieved by dietary TCT as well as by the small-molecule inhibitor TM5441.

Integrating Micro and Nano Technologies for Cell Engineering and Analysis: Toward the Next Generation of Cell Therapy Workflows

The emerging field of cell therapy offers the potential to treat and even cure a diverse array of diseases for which existing interventions are inadequate. Recent advances in micro and nanotechnology have added a multitude of single cell analysis methods to our research repertoire. At the same time, techniques have been developed for the precise engineering and manipulation of cells. Together, these methods have aided the understanding of disease pathophysiology, helped formulate corrective interventions at the cellular level, and expanded the spectrum of available cell therapeutic options. This review discusses how micro and nanotechnology have catalyzed the development of cell sorting, cellular engineering, and single cell analysis technologies, which have become essential workflow components in developing cell-based therapeutics. The review focuses on the technologies adopted in research studies and explores the opportunities and challenges in combining the various elements of cell engineering and single cell analysis into the next generation of integrated and automated platforms that can accelerate preclinical studies and translational research.

Emerging micro-nanotechnologies for extracellular vesicles in immuno-oncology: from target specific isolations to immunomodulation

Extracellular vesicles (EVs) have been hypothesized to incorporate a variety of crucial roles ranging from intercellular communication to tumor pathogenesis to cancer immunotherapy capabilities. Traditional EV isolation and characterization techniques cannot accurately and with specificity isolate subgroups of EVs, such as tumor-derived extracellular vesicles (TEVs) and immune-cell derived EVs, and are plagued with burdensome steps. To address these pivotal issues, multiplex microfluidic EV isolation/characterization and on-chip EV engineering may be imperative towards developing the next-generation EV-based immunotherapeutics. Henceforth, our aim is to expound the state of the art in EV isolation/characterization techniques and their limitations. Additionally, we seek to elucidate current work on total analytical system based technologies for simultaneous isolation and characterization and to summarize the immunogenic capabilities of EV subgroups, both innate and adaptive. In this review, we discuss recent state-of-art microfluidic/micro-nanotechnology based EV screening methods and EV engineering methods towards therapeutic use of EVs in immune-oncology. By venturing in this field of EV screening and immunotherapies, it is envisioned that transition into clinical settings can become less convoluted for clinicians.

An ischemia-homing bioengineered nano-scavenger for specifically alleviating multiple pathogeneses in ischemic stroke

Background

Ischemic stroke is one of the most serious global public health problems. However, the performance of current therapeutic regimens is limited due to their poor target specificity, narrow therapeutic time window, and compromised therapeutic effect. To overcome these barriers, we designed an ischemia-homing bioengineered nano-scavenger by camouflaging a catalase (CAT)-loaded self-assembled tannic acid (TA) nanoparticle with a M2-type microglia membrane (TPC@M2 NPs) for ischemic stroke treatment.

Results

The TPC@M2 NPs can on-demand release TA molecules to chelate excessive Fe²⁺, while acid-responsively liberating CAT to synergistically scavenge multiple ROS (·OH, ·O₂⁻, and H₂O₂). Besides, the M2 microglia membrane not only can be served as bioinspired therapeutic agents to repolarize M1 microglia into M2 phenotype but also endows the nano-scavenger with ischemia-homing and BBB-crossing capabilities.

Conclusions

The nano-scavenger for specific clearance of multiple pathogenic elements to alleviate inflammation and protect neurons holds great promise for combating ischemic stroke and other inflammation-related diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01602-7.

Endothelial Phospholipase Cγ2 Improves Outcomes of Diabetic Ischemic Limb Rescue Following VEGF Therapy

Therapeutic vascular endothelial growth factor (VEGF) replenishment has met with limited success for the management of critical limb-threatening ischemia. To improve outcomes of VEGF therapy, we applied single-cell RNA sequencing (scRNA-seq) technology to study the endothelial cells of the human diabetic skin. Single-cell suspensions were generated from the human skin followed by cDNA preparation using the Chromium Next GEM Single-cell 3' Kit v3.1. Using appropriate quality control measures, 36,487 cells were chosen for downstream analysis. scRNA-seq studies identified that although VEGF signaling was not significantly altered in diabetic versus nondiabetic skin, phospholipase Cγ2 (PLCγ2) was downregulated. The significance of PLCγ2 in VEGF-mediated increase in endothelial cell metabolism and function was assessed in cultured human microvascular endothelial cells. In these cells, VEGF enhanced mitochondrial function, as indicated by elevation in oxygen consumption rate and extracellular acidification rate. The VEGF-dependent increase in cell metabolism was blunted in response to PLCγ2 inhibition. Follow-up rescue studies therefore focused on understanding the significance of VEGF therapy in presence or absence of endothelial PLCγ2 in type 1 (streptozotocin-injected) and type 2 (db/db) diabetic ischemic tissue. Nonviral topical tissue nanotransfection technology (TNT) delivery of CDH5 promoter-driven PLCγ2 open reading frame promoted the rescue of hindlimb ischemia in diabetic mice. Improvement of blood flow was also associated with higher abundance of VWF+/CD31+ and VWF+/SMA+ immunohistochemical staining. TNT-based gene delivery was not associated with tissue edema, a commonly noted complication associated with proangiogenic gene therapies. Taken together, our study demonstrates that TNT-mediated delivery of endothelial PLCγ2, as part of combination gene therapy, is effective in diabetic ischemic limb rescue.

Stem Cell Homing in Intrathecal Applications and Inspirations for Improvement Paths

A transplanted stem cell homing is a directed migration from the application site to the targeted tissue. Intrathecal application of stem cells is their direct delivery to cerebrospinal fluid, which defines the homing path from the point of injection to the brain. In the case of neurodegenerative diseases, this application method has the advantage of no blood–brain barrier restriction. However, the homing efficiency still needs improvement and homing mechanisms elucidation. Analysis of current research results on homing mechanisms in the light of intrathecal administration revealed a discrepancy between in vivo and in vitro results and a gap between preclinical and clinical research. Combining the existing research with novel insights from cutting-edge biochips, nano, and other technologies and computational models may bridge this gap faster.

Modeling the gene delivery process of the needle array-based tissue nanotransfection

Hollow needle array-based tissue nanotransfection (TNT) presents an in vivo transfection approach that directly translocate exogeneous genes to target tissues by using electric pulses. In this work, the gene delivery process of TNT was simulated and experimentally validated. We adopted the asymptotic method and cell-array-based model to investigate the electroporation behaviors of cells within the skin structure. The distribution of nonuniform electric field across the skin results in various electroporation behavior for each cell. Cells underneath the hollow microchannels of the needle exhibited the highest total pore numbers compared to others due to the stronger localized electric field. The percentage of electroporated cells within the skin structure, with pore radius over 10 nm, increases from 25% to 82% as the applied voltage increases from 100 to 150 V/mm. Furthermore, the gene delivery behavior across the skin tissue was investigated through the multilayer-stack-based model. The delivery distance increased nonlinearly as the applied voltage and pulse number increased, which mainly depends on the diffusion characteristics and electric conductivity of each layer. It was also found that the skin is required to be exfoliated prior to the TNT procedure to enhance the delivery depth. This work provides the foundation for transition from the study of murine skin to translation use in large animals and human settings.

Nanotechnology-Driven Cell-Based Therapies in Regenerative Medicine

The administration of cells as therapeutic agents has emerged as a novel approach to complement the use of small molecule drugs and other biologics for the treatment of numerous conditions. Although the use of cells for structural and/or functional tissue repair and regeneration provides new avenues to address increasingly complex disease processes, it also faces numerous challenges related to efficacy, safety, and translational potential. Recent advances in nanotechnology-driven cell therapies have the potential to overcome many of these issues through precise modulation of cellular behavior. Here, we describe several approaches that illustrate the use of different nanotechnologies for the optimization of cell therapies and discuss some of the obstacles that need to be overcome to allow for the widespread implementation of nanotechnology-based cell therapies in regenerative medicine.

In Situ Deployment of Engineered Extracellular Vesicles into the Tumor Niche via Myeloid-Derived Suppressor Cells

Extracellular vesicles (EVs) have emerged as a promising carrier system for the delivery of therapeutic payloads in multiple disease models, including cancer. However, effective targeting of EVs to cancerous tissue remains a challenge. Here, it is shown that nonviral transfection of myeloid-derived suppressor cells (MDSCs) can be leveraged to drive targeted release of engineered EVs that can modulate transfer and overexpression of therapeutic anticancer genes in tumor cells and tissue. MDSCs are immature immune cells that exhibit enhanced tropism toward tumor tissue and play a role in modulating tumor progression. Current MDSC research has been mostly focused on mitigating immunosuppression in the tumor niche; however, the tumor homing abilities of these cells present untapped potential to deliver EV therapeutics directly to cancerous tissue. In vivo and ex vivo studies with murine models of breast cancer show that nonviral transfection of MDSCs does not hinder their ability to home to cancerous tissue. Moreover, transfected MDSCs can release engineered EVs and mediate antitumoral responses via paracrine signaling, including decreased invasion/metastatic activity and increased apoptosis/necrosis. Altogether, these findings indicate that MDSCs can be a powerful tool for the deployment of EV-based therapeutics to tumor tissue.

Designer Extracellular Vesicles Modulate Pro-Neuronal Cell Responses and Improve Intracranial Retention

Gene/oligonucleotide therapies have emerged as a promising strategy for the treatment of different neurological conditions. However, current methodologies for the delivery of neurogenic/neurotrophic cargo to brain and nerve tissue are fraught with caveats, including reliance on viral vectors, potential toxicity, and immune/inflammatory responses. Moreover, delivery to the central nervous system is further compounded by the low permeability of the blood brain barrier. Extracellular vesicles (EVs) have emerged as promising delivery vehicles for neurogenic/neurotrophic therapies, overcoming many of the limitations mentioned above. However, the manufacturing processes used for therapeutic EVs remain poorly understood. Here, we conducted a detailed study of the manufacturing process of neurogenic EVs by characterizing the nature of cargo and surface decoration, as well as the transfer dynamics across donor cells, EVs, and recipient cells. Neurogenic EVs loaded with Ascl1, Brn2, and Myt1l (ABM) are found to show enhanced neuron-specific tropism, modulate electrophysiological activity in neuronal cultures, and drive pro-neurogenic conversions/reprogramming. Moreover, murine studies demonstrate that surface decoration with glutamate receptors appears to mediate enhanced EV delivery to the brain. Altogether, the results indicate that ABM-loaded designer EVs can be a promising platform nanotechnology to drive pro-neuronal responses, and that surface functionalization with glutamate receptors can facilitate the deployment of EVs to the brain.

Transient Middle Cerebral Artery Occlusion with an Intraluminal Suture Enables Reproducible Induction of Ischemic Stroke in Mice

Ischemic stroke is a leading cause of mortality and chronic disability worldwide, underscoring the need for reliable and accurate animal models to study this disease's pathology, molecular mechanisms of injury, and treatment approaches. As most clinical strokes occur in regions supplied by the middle cerebral artery (MCA), several experimental models have been developed to simulate an MCA occlusion (MCAO), including transcranial MCAO, micro- or macro-sphere embolism, thromboembolisation, photothrombosis, Endothelin-1 injection, and - the most common method for ischemic stroke induction in murine models - intraluminal MCAO. In the intraluminal MCAO model, the external carotid artery (ECA) is permanently ligated, after which a partially-coated monofilament is inserted and advanced proximally to the common carotid artery (CCA) bifurcation, before being introduced into the internal carotid artery (ICA). The coated tip of the monofilament is then advanced to the origin of the MCA and secured for the duration of occlusion. With respect to other MCAO models, this model offers enhanced reproducibility regarding infarct volume and cognitive/functional deficits, and does not require a craniotomy. Here, we provide a detailed protocol for the surgical induction of unilateral transient ischemic stroke in mice, using the intraluminal MCAO model. Graphic abstract: Overview of the intraluminal monofilament method for transient middle cerebral artery occlusion (MCAO) in mouse.