Targeted Delivery of siRNA Lipoplexes to Cancer Cells Using Macrophage Transient Horizontal Gene Transfer

Macrophage based drug delivery: Key challenges and strategies

As a natural immune cell and antigen presenting cell, macrophages have been studied and engineered to treat human diseases. Macrophages are well-suited for use as drug carriers because of their biological characteristics, such as excellent biocompatibility, long circulation, intrinsic inflammatory homing and phagocytosis. Meanwhile, macrophages' uniquely high plasticity and easy re-education polarization facilitates their use as part of efficacious therapeutics for the treatment of inflammatory diseases or tumors. Although recent studies have demonstrated promising advances in macrophage-based drug delivery, several challenges currently hinder further improvement of therapeutic effect and clinical application. This article focuses on the main challenges of utilizing macrophage-based drug delivery, from the selection of macrophage sources, drug loading, and maintenance of macrophage phenotypes, to drug migration and release at target sites. In addition, corresponding strategies and insights related to these challenges are described. Finally, we also provide perspective on shortcomings on the road to clinical translation and production.

Nano-Engineering Strategies for Tumor-Specific Therapy

Nanodelivery systems (NDSs) provide promising prospects for decreasing drug doses, reducing side effects, and improving therapeutic effects. However, the bioapplications of NDSs are still compromised by their fast clearance, indiscriminate biodistribution, and limited tumor accumulation. Hence, engineering modification of NDSs aiming at promoting tumor-specific therapy and avoiding systemic toxicity is usually needed. An NDS integrating various functionalities, including flexible camouflage, specific biorecognition, and sensitive stimuli-responsiveness, into one sequence would be "smart" and highly effective. Herein, we systematically summarize the related principles, methods, and progress. At the end of the review, we predict the obstacles to precise nanoengineering and prospects for the future application of NDSs.

Recent Advances in Engineering Carriers for siRNA Delivery

RNA interference (RNAi) technology has been a promising treatment strategy for combating intractable diseases. However, the applications of RNAi in clinical are hampered by extracellular and intracellular barriers. To overcome these barriers, various siRNA delivery systems have been developed in the past two decades. The first approved RNAi therapeutic, Patisiran (ONPATTRO) using lipids as the carrier, for the treatment of amyloidosis is one of the most important milestones. This has greatly encouraged researchers to work on creating new functional siRNA carriers. In this review, the recent advances in siRNA carriers consisting of lipids, polymers, and polymer-modified inorganic particles for cancer therapy are summarized. Representative examples are presented to show the structural design of the carriers in order to overcome the delivery hurdles associated with RNAi therapies. Finally, the existing challenges and future perspective for developing RNAi as a clinical modality will be discussed and proposed. It is believed that the addressed contributions in this review will promote the development of siRNA delivery systems for future clinical applications.

Efficient gene delivery by multifunctional star poly (β-amino ester)s into difficult-to-transfect macrophages for M1 polarization

Gene delivery to macrophages holds great promise for cancer immunotherapy. However, traditional gene delivery methods exhibit low transfection efficiency in macrophages. The star-shaped topological structure of polymers is known to encapsulate genes inside their cores, thereby facilitating sustained release of the genetic material. Herein, combining the structural advantages of star polymers and the transfection advantages of poly (β-amino ester)s (PAEs), we developed a novel linear oligomer grafting-onto strategy to synthesize a library of multi-terminal star structured PAEs (SPAEs), and evaluated their gene delivery efficiency in various tissue cells. The transfection with human hepatocellular carcinoma cells (HepG2, HCC-LM3 cells and MHCC-97H cells), rat normal liver cells (BRL-3 A cells), human ovarian cancer cells (A2780 cells), African green monkey kidney cells (Vero cells), human cervical cancer cells (HeLa cells), human chondrosarcoma cells (SW1353 cells), and difficult-to-transfect human epidermal keratinocytes (HaCaT cells) and normal human fibroblast cells (NHF cells) showed that SPAEs exhibited superior transfection profile. The GFP transfection efficiency of top-performing SPAEs in HeLa cells (96.1%) was 2.1-fold, and 3.2-fold higher compared to jetPEI and Lipo3000, respectively, indicating that the star-shaped topological structure can significantly enhance the transfection efficiency of PAEs. More importantly, the top-performing SPAEs could efficiently deliver Nod2 DNA to difficult-to-transfect RAW264.7 macrophages, with a high transfection efficiency of 33.9%, which could promote macrophage M1 polarization and enhanced CD8+ T cell response in co-incubation experiments. This work advances gene therapy by targeting difficult-to-transfect macrophages and remodeling the tumor immune microenvironment.

Biomimetic Systems Involving Macrophages and Their Potential for Targeted Drug Delivery

The concept of targeted drug delivery can be described in terms of the drug systems' ability to mimic the biological objects' property to localize to target cells or tissues. For example, drug delivery systems based on red blood cells or mimicking some of their useful features, such as long circulation in stealth mode, have been known for decades. On the contrary, therapeutic strategies based on macrophages have gained very limited attention until recently. Here, we review two biomimetic strategies associated with macrophages that can be used to develop new therapeutic modalities: first, the mimicry of certain types of macrophages (i.e., the use of macrophages, including tumor-associated or macrophage-derived particles as a carrier for the targeted delivery of therapeutic agents); second, the mimicry of ligands, naturally absorbed by macrophages (i.e., the use of therapeutic agents specifically targeted at macrophages). We discuss the potential applications of biomimetic systems involving macrophages for new advancements in the treatment of infections, inflammatory diseases, and cancer.

Non-Coding RNAs: Foes or Friends for Targeting Tumor Microenvironment

Non-coding RNAs (ncRNAs) are a group of molecules critical for cell development and growth regulation. They are key regulators of important cellular pathways in the tumor microenvironment. To analyze ncRNAs in the tumor microenvironment, the use of RNA sequencing technology has revolutionized the field. The advancement of this technique has broadened our understanding of the molecular biology of cancer, presenting abundant possibilities for the exploration of novel biomarkers for cancer treatment. In this review, we will summarize recent achievements in understanding the complex role of ncRNA in the tumor microenvironment, we will report the latest studies on the tumor microenvironment using RNA sequencing, and we will discuss the potential use of ncRNAs as therapeutics for the treatment of cancer.

Design and fabrication of intracellular therapeutic cargo delivery systems based on nanomaterials: current status and future perspectives

Intracellular cargo delivery, the introduction of small molecules, proteins, and nucleic acids into a specific targeted site in a biological system, is an important strategy for deciphering cell function, directing cell fate, and reprogramming cell behavior. With the advancement of nanotechnology, many researchers use nanoparticles (NPs) to break through biological barriers to achieving efficient targeted delivery in biological systems, bringing a new way to realize efficient targeted drug delivery in biological systems. With a similar size to many biomolecules, NPs possess excellent physical and chemical properties and a certain targeting ability after functional modification on the surface of NPs. Currently, intracellular cargo delivery based on NPs has emerged as an important strategy for genome editing regimens and cell therapy. Although researchers can successfully deliver NPs into biological systems, many of them are delivered very inefficiently and are not specifically targeted. Hence, the development of efficient, target-capable, and safe nanoscale drug delivery systems to deliver therapeutic substances to cells or organs is a major challenge today. In this review, on the basis of describing the research overview and classification of NPs, we focused on the current research status of intracellular cargo delivery based on NPs in biological systems, and discuss the current problems and challenges in the delivery process of NPs in biological systems.

Bioinspired nanogels as cell-free DNA trapping and scavenging organelles for rheumatoid arthritis treatment

Excessive cell-free DNA (cfDNA) in the serum and synovium is considered a causative factor of rheumatoid arthritis (RA). Thus, cfDNA scavenging by using cationic polymers has been an effective therapeutic avenue, while these stratagems still suffer from systemic toxicity and unstable capture of cfDNA. Here, inspired by the biological charge-trapping effects and active degradation function of enzyme-containing organelles in vivo, we proposed a cationic peptide dendrimer nanogel with deoxyribonuclease I (DNase I) conjugation for the treatment of RA. Benefitting from their naturally derived peptide components, the resultant nanogels were highly biocompatible. More attractively, by tailoring them with a larger size and higher surface charge density, these cationic nanogels could achieve the fastest targeting capability, highest accumulation amounts, longer persistence time, and superior DNA scavenging capacity in inflamed joints. Based on these features, we have demonstrated that the organelle mimicking cationic nanogels could significantly down-regulate toll-like receptor (TLR)-9 signaling pathways and attenuate RA symptoms in collagen-induced arthritis mice. These results make the bioinspired DNase I conjugated cationic nanogels an ideal candidate for treating RA and other immune dysregulation diseases.

Macrophages as Promising Carriers for Nanoparticle Delivery in Anticancer Therapy

Macrophages play a critical role in the immune response due to their ability to recognize and remove pathogens, as well as present antigens, which are involved in inflammation, but they are also one of the most abundant immune cell populations present in the tumor microenvironment. In recent years, macrophages have become promising cellular carriers for drug and nanoparticle delivery to the tumor microenvironment, mainly due to their natural properties such as biocompatibility, degradability, lack of immunogenicity, long half-life in circulation, crossing biological barriers, and the possibility of migration and accumulation at a site of inflammation such as a tumor. For the effectiveness of this therapeutic strategy, known as "Trojan horse", it is important that the nanoparticles engulfed by macrophages do not affect their proper functioning. In our review, we discussed how the size, shape, chemical and mechanical properties of nanoparticles influence their internalization by macrophages. In addition, we described the promising research utilizing macrophages, their cell membranes and macrophage-derived exosomes as drug carriers in anticancer therapy. As a prospect of the wider use of this therapeutic strategy, we postulate its future application in boron delivery to the tumor environment in boron neutron capture therapy.

Biomaterial-Assisted Macrophage Cell Therapy for Regenerative Medicine

Although most tissue types are capable of some form of self-repair and regeneration, injuries that are larger than a critical threshold or those occurring in the setting of certain diseases can lead to impaired healing and ultimately loss of structure and function. The immune system plays an important role in tissue repair and must be considered in the design of therapies in regenerative medicine. In particular, macrophage cell therapy has emerged as a promising strategy that leverages the reparative roles of these cells. Macrophages are critical for successful tissue repair and accomplish diverse functions throughout all phases of the process by dramatically shifting in phenotypes in response to microenvironmental cues. Depending on their response to various stimuli, they may release growth factors, support angiogenesis, and facilitate extracellular matrix remodeling. However, this ability to rapidly shift phenotype is also problematic for macrophage cell therapy strategies, because adoptively transferred macrophages fail to maintain therapeutic phenotypes following their administration to sites of injury or inflammation. Biomaterials are a potential way to control macrophage phenotype in situ while also enhancing their retention at sites of injury. Cell delivery systems incorporated with appropriately designed immunomodulatory signals have potential to achieve tissue regeneration in intractable injuries where traditional therapies have failed. Here we explorecurrent challenges in macrophage cell therapy, especially retention and phenotype control, how biomaterials may overcome them, and opportunities for next generation strategies. Biomaterials will be an essential tool to advance macrophage cell therapy for widespread clinical applications.

Lack of Rab27a attenuates foam cell formation and macrophage inflammation in uremic apolipoprotein E knockout mice

As the most common cardiovascular disease, atherosclerosis (AS), is a leading cause of high mortality in patients with chronic renal failure. Rab27a has been reported to regulate the progression of cardiovascular and renal diseases. Nevertheless, little studies investigated the role and mechanism of Rab27a in uremic-accelerated AS (UAAS). An animal model of UAAS was established in apolipoprotein E knockout (apoE^-/-) mice using 5/6 nephrectomy (NX). We conducted in vitro and in vivo functional experiments to explore the role of Rab27a in UAAS, including the presence of oxidized low-density lipoprotein (ox-LDL). Rab27a expression was upregulated in the plaque tissues of NX apoE^-/- mice. The knockout of Rab27a (Rab27a^-/-) reduced AS-induced artery injury, as manifested by the reductions of plaque area, collagen deposition, inflammation and lipid droplet. Besides, cholesterol efflux was increased, while the expression of lipid metabolism-related proteins and the secretions of pro-inflammatory factors were decreased in ox-LDL-induced NX Rab27a^-/- apoE^-/- mice group. Further, Rab27a deletion inhibited the activation of nuclear factor κB (NF-κB) pathway. In conclusion, our study indicated that Rab27a deficiency attenuated foam cell formation and macrophage inflammation, depending on the NF-κB pathway activation, to inhibit AS progression in uremic apoE^-/- mice. This finding may provide a new targeting strategy for UAAS therapy.

Kanser Tedavisi İçin MikroRNA’ların Çok İşlevli Nano-taşıyıcılar İle Dağıtımı

Hücre proliferasyonu ve apoptozis gibi kanserden sorumlu biyolojik süreçlerde etkili olan miRNA’lar, farklı kanser türleri ve evrelerinin teşhis ve tedavisinde yeni biyobelirteçler olarak işlev görür. Bunun yanı sıra bazı miRNA’ların onkogen ve tümör baskılayıcı özelliği nanoteknoloji ile entegre edilmesiyle kanser oluşumunu engeller. Son yıllarda miRNA’ların kanser tedavisinde kullanılmasını sağlayan diğer bir yaklaşım ise nano-taşıyıcılardır. İlaçlar, peptitler veya genler gibi aktif bileşikleri taşımak için geliştirilen bu nano-taşıyıcıların kanser tedavisinde kullanımları umut vadetmektedir. Bu derleme, miRNA dağıtımında kullanılan nano-taşıyıcı türleri hakkında kısa bir bilgi sunmaktadır. Ayrıca nanoteknolojideki gelişmelerle birlikte miRNA’ların kanser teşhis ve tedavisinde kullanımın yanısıra gen susturma mekanizması olan RNA interferansından kısaca bahsedilmektedir.

Ionizable lipid nanoparticles deliver mRNA to pancreatic β cells via macrophage-mediated gene transfer

Systemic messenger RNA (mRNA) delivery to organs outside the liver, spleen, and lungs remains challenging. To overcome this issue, we hypothesized that altering nanoparticle chemistry and administration routes may enable mRNA-induced protein expression outside of the reticuloendothelial system. Here, we describe a strategy for delivering mRNA potently and specifically to the pancreas using lipid nanoparticles. Our results show that delivering lipid nanoparticles containing cationic helper lipids by intraperitoneal administration produces robust and specific protein expression in the pancreas. Most resultant protein expression occurred within insulin-producing β cells. Last, we found that pancreatic mRNA delivery was dependent on horizontal gene transfer by peritoneal macrophage exosome secretion, an underappreciated mechanism that influences the delivery of mRNA lipid nanoparticles. We anticipate that this strategy will enable gene therapies for intractable pancreatic diseases such as diabetes and cancer.

Macrophage cell membrane-based nanoparticles: a new promising biomimetic platform for targeted delivery and treatment

Synthetic nanoparticles with surface bioconjugation are promising platforms for targeted therapy, but their simple biological functionalization is still a challenging task against the complex intercellular environment. Once synthetic nanoparticles enter the body, they are phagocytosed by immune cells by the immune system. Recently, the cell membrane camouflage strategy has emerged as a novel therapeutic tactic to overcome these issues by utilizing the fundamental properties of natural cells. Macrophage, a type of immune system cells, plays critical roles in various diseases, including cancer, atherosclerosis, rheumatoid arthritis, infection and inflammation, due to the recognition and engulfment function of removing substances and pathogens. Macrophage membranes inherit the surface protein profiles and biointerfacing properties of source cells. Therefore, the macrophage membrane cloaking can protect synthetic nanoparticles from phagocytosis by the immune cells. Meanwhile, the macrophage membrane can make use of the natural correspondence to accurately recognize antigens and target inflamed tissue or tumor sites. In this review, we have summarized the advances in the fabrication, characterization and homing capacity of macrophage membrane cloaking nanoparticles in various diseases, including cancers, immune diseases, cardiovascular diseases, central nervous system diseases, and microbial infections. Although macrophage membrane-camouflaged nanoparticles are currently in the fetal stage of development, there is huge potential and challenge to explore the conversion mode in the clinic.

Recent Advancements in the Design of Nanodelivery Systems of siRNA for Cancer Therapy

RNA interference (RNAi) has increased the possibility of restoring RNA drug targets for cancer treatment. Small interfering RNA (siRNA) is a promising therapeutic RNAi tool that targets the defective gene by inhibiting its mRNA expression and stopping its translation. However, siRNAs have flaws like poor intracellular trafficking, RNase degradation, rapid kidney filtration, off-targeting, and toxicity, which limit their therapeutic efficiency. Nanocarriers (NCs) have been designed to overcome such flaws and increase antitumor activity. Combining siRNA and anticancer drugs can give synergistic effects in cancer cells, making them a significant gene-modification tool in cancer therapy. Our discussion of NCs-mediated siRNA delivery in this review includes their mechanism, limitations, and advantages in comparison with naked siRNA delivery. We will also discuss organic NCs (polymers and lipids) and inorganic NCs (quantum dots, carbon nanotubes, and gold) that have been reported for extensive delivery of therapeutic siRNA to tumor sites. Finally, we will conclude by discussing the studies based on organic and inorganic NCs-mediated siRNA drug delivery systems conducted in the years 2020 and 2021.

Macrophage In Vitro and In Vivo Tracking via Anchored Microcapsules

A new promising trend in personalized medicine is the use of autologous cells (macrophages or stem cells) for cell-based therapy and also as a "Trojan horse" for targeted delivery of a drug carrier. The natural ability of macrophages for chemotaxis allows them to deliver cargo to the damaged area, significantly reducing side effects on healthy organ tissues. Therefore, it is important to develop tools to track their behavior in the organism. While labeled containers can serve as anchored tags for imaging macrophages in vivo, they can affect the properties and functions of macrophages. This work demonstrates that 3 μm sized capsules based on biocompatible polyelectrolytes and fluorescently labeled with both Cy7 and RITC dyes do not affect cell functionalization in vitro, such as viability, proliferation, and movement of transformed monocyte/macrophage-like cells (RAW 264.7) and primary bone marrow derived macrophages (BMDM) at maximal loading of five capsules per cell. In addition, capsules allowed fluorescent detection of ex vivo loaded cells 24 h after the tail vein injection in vivo and visualization of microcapsule-laden macrophages ex vivo using confocal microscopy. We have delivered about 62.5% of injected BMDM containing 12.5 million capsules with 3.75 μg of high-molecular-weight cargo (0.3 pg/capsule) to the liver. Our results demonstrate that 3 μm polyelectrolyte fluorescently labeled microcapsules can be used for safe macrophage loading, allowing cell tracking and drug delivery, which will facilitate development of macrophage-based cell therapy protocols.

Application of lipid-based nanoparticles in cancer immunotherapy

Immunotherapy is revolutionizing the clinical management of patients with different cancer types by sensitizing autologous or allogenic immune cells to the tumor microenvironment which eventually leads to tumor cell lysis without rapidly killing normal cells. Although immunotherapy has been widely demonstrated to be superior to chemotherapies, only a few populations of patients with specific cancer types respond to such treatment due to the failure of systemic immune activation. In addition, severe immune-related adverse events are rapidly observed when patients with very few responses are given higher doses of such therapies. Recent advances of lipid-based nanoparticles (NPs) development have made it possible to deliver not only small molecules but also mRNAs to achieve systemic anticancer immunity through cytotoxic immune cell activation, checkpoint blockade, and chimeric antigen receptor cell therapies, etc. This review summarized recent development and applications of LNPs in anticancer immunotherapy. The diversity of lipid-based NPs would encapsulate payloads with different structures and molecular weights to achieve optimal antitumor immunity through multiple mechanisms of action. The discussion about the components of lipid-based NPs and their immunologic payloads in this review hopefully shed more light on the future direction of anticancer immunotherapy.

Silver nanoclusters show advantages in macrophage tracing in vivo and modulation of anti-tumor immuno-microenvironment

Macrophage-based nanomedicine represents an emerging powerful strategy for cancer therapy. Unfortunately, some obstacles and challenges limit the translational applications of macrophage-mediated nanodrug delivery system. For instance, tracking and effective cell delivery for targeted tumor sites remain to be overcome, and controlling the states of macrophages is still rather difficult due to their plastic nature in response to external stimuli. To address these critical issues, here, we reported a novel type of silver nanoclusters (AgNCs) with excellent fluorescent intensity, especially long-lasting cell labeling stability after endocytosis by macrophages, indicating promising applications in tracking macrophage-based nanomedicine delivery. Our mechanistic investigations uncovered that these merits originate from the escape of AgNCs from lysosomal degradation within macrophages. In addition, the AgNCs would prime the M1-like polarization of macrophages (at least in part) through the toll-like receptor 4 signaling pathway. The engineered macrophages laden with AgNCs could be employed for lung metastasis breast cancer treatment, showing the effective targeting propensity to metastatic tumors, remarkable regulation of tumor immune microenvironment and inhibition of tumor growth. Collectively, AgNC-trained macrophages appear to be a promising strategy for tumor immune-microenvironment regulation, which might be generalized to a wider spectrum of cancer therapeutics.

Harnessing anti-tumor and tumor-tropism functions of macrophages via nanotechnology for tumor immunotherapy

Reprogramming the immunosuppressive tumor microenvironment by modulating macrophages holds great promise in tumor immunotherapy. As a class of professional phagocytes and antigen-presenting cells in the innate immune system, macrophages can not only directly engulf and clear tumor cells, but also play roles in presenting tumor-specific antigen to initiate adaptive immunity. However, the tumor-associated macrophages (TAMs) usually display tumor-supportive M2 phenotype rather than anti-tumor M1 phenotype. They can support tumor cells to escape immunological surveillance, aggravate tumor progression, and impede tumor-specific T cell immunity. Although many TAMs-modulating agents have shown great success in therapy of multiple tumors, they face enormous challenges including poor tumor accumulation and off-target side effects. An alternative solution is the use of advanced nanostructures, which not only can deliver TAMs-modulating agents to augment therapeutic efficacy, but also can directly serve as modulators of TAMs. Another important strategy is the exploitation of macrophages and macrophage-derived components as tumor-targeting delivery vehicles. Herein, we summarize the recent advances in targeting and engineering macrophages for tumor immunotherapy, including (1) direct and indirect effects of macrophages on the augmentation of immunotherapy and (2) strategies for engineering macrophage-based drug carriers. The existing perspectives and challenges of macrophage-based tumor immunotherapies are also highlighted.

Magnetically Actuated Cell-Robot System: Precise Control, Manipulation, and Multimode Conversion

Border-nearing microrobots with self-propelling and navigating capabilities have promising applications in micromanipulation and bioengineering, because they can stimulate the surrounding fluid flow for object transportation. However, ensuring the biosafety of microrobots is a concurrent challenge in bioengineering applications. Here, macrophage template-based microrobots (cell robots) that can be controlled individually or in chain-like swarms are proposed, which can transport various objects. The cell robots are constructed using the phagocytic ability of macrophages to load nanomagnetic particles while maintaining their viability. The robots exhibit high position control accuracy and generate a flow field that can be used to transport microspheres and sperm when exposed to an external magnetic field near a wall. The cell robots can also form chain-like swarms to transport a large object (more than 100 times the volume). This new insight into the manipulation of macrophage-based cell robots provides a new concept by converting other biological cells into microrobots for micromanipulation in biomedical applications.

Dual Affinity to RBCs and Target Cells (DART) Enhances Both Organ- and Cell Type-Targeting of Intravascular Nanocarriers

A long-standing goal of nanomedicine is to improve a drug's benefit by loading it into a nanocarrier that homes solely to a specific target cell and organ. Unfortunately, nanocarriers usually end up with only a small percentage of the injected dose (% ID) in the target organ, due largely to clearance by the liver and spleen. Further, cell-type-specific targeting is rarely achieved without reducing target organ accumulation. To solve these problems, we introduce DART (dual affinity to RBCs and target cells), in which nanocarriers are conjugated to two affinity ligands, one binding red blood cells and one binding a target cell (here, pulmonary endothelial cells). DART nanocarriers first bind red blood cells and then transfer to the target organ's endothelial cells as the bound red blood cells squeeze through capillaries. We show that within minutes after intravascular injection in mice nearly 70% ID of DART nanocarriers accumulate in the target organ (lungs), more than doubling the % ID ceiling achieved by a multitude of prior technologies, finally achieving a majority % ID in a target organ. Humanized DART nanocarriers in ex vivo perfused human lungs recapitulate this phenomenon. Furthermore, DART enhances the selectivity of delivery to target endothelial cells over local phagocytes within the target organ by 6-fold. DART's marked improvement in both organ- and cell-type targeting may thus be helpful in localizing drugs for a multitude of medical applications.

Targeting Proliferating Tumor-Infiltrating Macrophages Facilitates Spatial Redistribution of CD8+ T Cells in Pancreatic Cancer

Tumor-associated macrophages (TAMs) play crucial roles in cancer progression, but the contributions and regulation of different macrophage subpopulations remain unclear. Here, we report a high level of TAM infiltration in human and mouse pancreatic ductal adenocarcinoma (PDAC) models and that the targeting of proliferating F4/80+ macrophages facilitated cytotoxic CD8+ T-cell-dependent antitumor immune responses. A well-defined KPC-derived PDAC cell line and the murine Panc02 PDAC cell line were used. Treatment of PDAC-bearing mice with clodronate liposomes, an agent that chemically depletes macrophages, did not impact macrophage subpopulations in the local tumor microenvironment (TME). However, further investigation using both BrdU and Ki67 to evaluate proliferating cells showed that clodronate liposomes treatment reduced proliferating macrophages in the KPC and Panc02 models. We further evaluated the distance between CD8+ T cells and PanCK+ tumor cells, and clodronate liposomes treatment significantly increased the number of CD8+ T cells in close proximity (<30 µm) to PanCK+ PDAC cells, with increased numbers of tumor-infiltrating IFN-γ+CD8+ T cells. This study suggests that targeting proliferating tumor-infiltrating macrophages may increase CD8+ cytotoxic lymphocyte (CTL) infiltration and facilitate the spatial redistribution of CD8+ T cells in tumors, contributing to the antitumor effect.

Extracellular Vesicles Mediate the Intercellular Exchange of Nanoparticles

To exert their therapeutic effects, nanoparticles (NPs) often need to travel into the tissues composed of multilayered cells. Accumulative evidence has revealed the crucial role of transcellular transport route (entry into one cell, exocytosis, and re-entry into another) in this process. While NP endocytosis and subcellular transport are intensively characterized, the exocytosis and re-entry steps are poorly understood, which becomes a barrier for NP delivery into complex tissues. Here, the authors term the exocytosis and re-entry steps together as intercellular exchange. A collagen-based three-dimension assay is developed to specifically quantify the intercellular exchange of NPs, and distinguish the contributions of several potential mechanisms. The authors show that NPs can be exocytosed freely or enclosed inside extracellular vesicles (EVs) for re-entry, while direct cell-cell contact is hardly involved. EVs account for a significant fraction of NP intercellular exchange, and its importance in NP transport is demonstrated in vitro and in vivo. While freely released NPs engage with the same receptors for re-entry, EV-enclosed ones bypass this dependence. These studies provide an easy and precise system to investigate the intercellular exchange stage of NP delivery, and shed the first light in the importance of EVs in NP transport between cells and into complex tissues.

Nanotechnology-enhanced immunotherapy for metastatic cancer

A vast majority of cancer deaths occur as a result of metastasis. Unfortunately, effective treatments for metastases are currently lacking due to the difficulty of selectively targeting these small, delocalized tumors distributed across a variety of organs. However, nanotechnology holds tremendous promise for improving immunotherapeutic outcomes in patients with metastatic cancer. In contrast to conventional cancer immunotherapies, rationally designed nanomaterials can trigger specific tumoricidal effects, thereby improving immune cell access to major sites of metastasis such as bone, lungs, and lymph nodes, optimizing antigen presentation, and inducing a persistent immune response. This paper reviews the cutting-edge trends in nano-immunoengineering for metastatic cancers with an emphasis on different nano-immunotherapeutic strategies. Specifically, it discusses directly reversing the immunological status of the primary tumor, harnessing the potential of peripheral immune cells, preventing the formation of a pre-metastatic niche, and inhibiting the tumor recurrence through postoperative immunotherapy. Finally, we describe the challenges facing the integration of nanoscale immunomodulators and provide a forward-looking perspective on the innovative nanotechnology-based tools that may ultimately prove effective at eradicating metastatic diseases.

The Challenges and Opportunities in the Development of MicroRNA Therapeutics: A Multidisciplinary Viewpoint

microRNAs (miRs) are emerging as attractive therapeutic targets because of their small size, specific targetability, and critical role in disease pathogenesis. However, <20 miR targeting molecules have entered clinical trials, and none progressed to phase III. The difficulties in miR target identification, the moderate efficacy of miR inhibitors, cell type-specific delivery, and adverse outcomes have impeded the development of miR therapeutics. These hurdles are rooted in the functional complexity of miR's role in disease and sequence complementarity-dependent/-independent effects in nontarget tissues. The advances in understanding miR's role in disease, the development of efficient miR inhibitors, and innovative delivery approaches have helped resolve some of these hurdles. In this review, we provide a multidisciplinary viewpoint on the challenges and opportunities in the development of miR therapeutics.

Lipids and Lipid Derivatives for RNA Delivery

RNA-based therapeutics have shown great promise in treating a broad spectrum of diseases through various mechanisms including knockdown of pathological genes, expression of therapeutic proteins, and programmed gene editing. Due to the inherent instability and negative-charges of RNA molecules, RNA-based therapeutics can make the most use of delivery systems to overcome biological barriers and to release the RNA payload into the cytosol. Among different types of delivery systems, lipid-based RNA delivery systems, particularly lipid nanoparticles (LNPs), have been extensively studied due to their unique properties, such as simple chemical synthesis of lipid components, scalable manufacturing processes of LNPs, and wide packaging capability. LNPs represent the most widely used delivery systems for RNA-based therapeutics, as evidenced by the clinical approvals of three LNP-RNA formulations, patisiran, BNT162b2, and mRNA-1273. This review covers recent advances of lipids, lipid derivatives, and lipid-derived macromolecules used in RNA delivery over the past several decades. We focus mainly on their chemical structures, synthetic routes, characterization, formulation methods, and structure-activity relationships. We also briefly describe the current status of representative preclinical studies and clinical trials and highlight future opportunities and challenges.

Functionalized Nanoparticles Targeting Tumor-Associated Macrophages as Cancer Therapy

The tumor microenvironment (TME) plays a central role in regulating antitumor immune responses. As an important part of the TME, alternatively activated type 2 (M2) macrophages drive the development of primary and secondary tumors by promoting tumor cell proliferation, tumor angiogenesis, extracellular matrix remodeling and overall immunosuppression. Immunotherapy approaches targeting tumor-associated macrophages (TAMs) in order to reduce the immunosuppressive state in the TME have received great attention. Although these methods hold great potential for the treatment of several cancers, they also face some limitations, such as the fast degradation rate of drugs and drug-induced cytotoxicity of organs and tissues. Nanomedicine formulations that prevent TAM signaling and recruitment to the TME or deplete M2 TAMs to reduce tumor growth and metastasis represent encouraging novel strategies in cancer therapy. They allow the specific delivery of antitumor drugs to the tumor area, thereby reducing side effects associated with systemic application. In this review, we give an overview of TAM biology and the current state of nanomedicines that target M2 macrophages in the course of cancer immunotherapy, with a specific focus on nanoparticles (NPs). We summarize how different types of NPs target M2 TAMs, and how the physicochemical properties of NPs (size, shape, charge and targeting ligands) influence NP uptake by TAMs in vitro and in vivo in the TME. Furthermore, we provide a comparative analysis of passive and active NP-based TAM-targeting strategies and discuss their therapeutic potential.

Immunoengineering the next generation of arthritis therapies

Immunoengineering continues to revolutionize healthcare, generating new approaches for treating previously intractable diseases, particularly in regard to cancer immunotherapy. In joint diseases, such as osteoarthritis (OA) and rheumatoid arthritis (RA), biomaterials and anti-cytokine treatments have previously been at that forefront of therapeutic innovation. However, while many of the existing anti-cytokine treatments are successful for a subset of patients, these treatments can also pose severe risks, adverse events and off-target effects due to continuous delivery at high dosages or a lack of disease-specific targets. The inadequacy of these current treatments has motivated the development of new immunoengineering strategies that offer safer and more efficacious alternative therapies through the precise and controlled targeting of specific upstream immune responses, including direct and mechanistically-driven immunoengineering approaches. Advances in the understanding of the immunomodulatory pathways involved in musculoskeletal disease, in combination with the growing emphasis on personalized medicine, stress the need for carefully considering the delivery strategies and therapeutic targets when designing therapeutics to better treat RA and OA. Here, we focus on recent advances in biomaterial and cell-based immunomodulation, in combination with genetic engineering, for therapeutic applications in joint diseases. The application of immunoengineering principles to the study of joint disease will not only help to elucidate the mechanisms of disease pathogenesis but will also generate novel disease-specific therapeutics by harnessing cellular and biomaterial responses. STATEMENT OF SIGNIFICANCE: It is now apparent that joint diseases such as osteoarthritis and rheumatoid arthritis involve the immune system at both local (i.e., within the joint) and systemic levels. In this regard, targeting the immune system using both biomaterial-based or cellular approaches may generate new joint-specific treatment strategies that are well-controlled, safe, and efficacious. In this review, we focus on recent advances in immunoengineering that leverage biomaterials and/or genetically engineered cells for therapeutic applications in joint diseases. The application of such approaches, especially synergistic strategies that target multiple immunoregulatory pathways, has the potential to revolutionize our understanding, treatment, and prevention of joint diseases.

Hydrogel nanoparticle degradation influences the activation and survival of primary macrophages

The effect of nanoparticle (NP) internalization on cell fate has emerged as an important consideration for nanomedicine design, as macrophages and other phagocytes are the primary clearance mechanisms of administered NP formulations. Pro-survival signaling is thought to be concurrent with phagocytosis and recent work has shown increased macrophage survival following lysosomal processing of internalized NPs. These observations have opened the door to explorations of NP physiochemical properties aimed at tuning the NP-driven macrophage survival at the lysosomal synapse. Here, we report that NP-induced macrophage survival and activation is strongly dependent on NP degradation rate using a series of thiol-containing poly(ethylene glycol) diacrylate-based NPs of equivalent size and zeta potential. Rapidly degrading, high thiol-containing NPs allowed for dramatic enhancement of cell longevity that was concurrent with macrophage stimulation after 2 weeks in ex vivo culture. While equivalent NP internalization resulted in suppressed caspase activity across the NP series, macrophage activation was correlated with increasing thiol content, leading to increased lysosomal activity and a robust pro-survival phenotype. Our results provide insight on tuning NP physiochemical properties as design handles for maximizing ex vivo macrophage longevity, which has implications for improving macrophage-based immune assays, biomanufacturing, and cell therapies.

Non-viral nanoparticles for RNA interference: Principles of design and practical guidelines

Ribonucleic acid interference (RNAi) is an innovative treatment strategy for a myriad of indications. Non-viral synthetic nanoparticles (NPs) have drawn extensive attention as vectors for RNAi due to their potential advantages, including improved safety, high delivery efficiency and economic feasibility. However, the complex natural process of RNAi and the susceptible nature of oligonucleotides render the NPs subject to particular design principles and requirements for practical fabrication. Here, we summarize the requirements and obstacles for fabricating non-viral nano-vectors for efficient RNAi. To address the delivery challenges, we discuss practical guidelines for materials selection and NP synthesis in order to maximize RNA encapsulation efficiency and protection against degradation, and to facilitate the cytosolic release of oligonucleotides. The current status of clinical translation of RNAi-based therapies and further perspectives for reducing the potential side effects are also reviewed.

Recent Advances in Macrophage-Mediated Drug Delivery Systems

Macrophages have been extensively used in the development of drug delivery systems, as they can prolong the circulation and release of drugs, extend their half-life, increase their stability and targeting ability, and reduce immunogenicity. Moreover, they have good biocompatibility and degradability and offer abundant surface receptors for targeted delivery of a wide variety of drugs. Macrophage-mediated drug delivery systems can be prepared by loading drugs or drug-loaded nanoparticles into macrophages, macrophage membranes or macrophage-derived vesicles. Although such systems can be used to treat inflammation, cancer, HIV infection and other diseases, they require further research and optimization since they have been assembled from diverse sources and therefore can have quite different physical and chemical properties. Moreover, potential cell-drug interactions can limit their application, and the biological activity of membrane proteins might be lost during membrane extraction and storage. In this review, we summarize the recent advances in this field and discuss the preparation of macrophage-mediated drug delivery systems, their advantages over other delivery systems, their potential applications and future lines of research.

Mannosylated Cationic Copolymers for Gene Delivery to Macrophages

Macrophages are desirable targets for gene therapy of cancer and other diseases. Cationic diblock copolymers of polyethylene glycol (PEG) and poly-L-lysine (PLL) or poly{N-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} (pAsp(DET)) are synthesized and used to form polyplexes with a plasmid DNA (pDNA) that are decorated with mannose moieties, serving as the targeting ligands for the C type lectin receptors displayed at the surface of macrophages. The PEG-b-PLL copolymers are known for its cytotoxicity, so PEG-b-PLL-based polyplexes are cross-linked using reducible reagent dithiobis(succinimidyl propionate) (DSP). The cross-linked polyplexes display low toxicity to both mouse embryonic fibroblasts NIH/3T3 cell line and mouse bone marrow-derived macrophages (BMMΦ). In macrophages mannose-decorated polyplexes demonstrate an ≈8 times higher transfection efficiency. The cross-linking of the polyplexes decrease the toxicity, but the transfection enhancement is moderate. The PEG-b-pAsp(DET) copolymers display low toxicity with respect to the IC-21 murine macrophage cell line and are used for the production of non-cross-linked pDNA-contained polyplexes. The obtained mannose modified polyplexes exhibit ca. 500-times greater transfection activity in IC-21 macrophages compared to the mannose-free polyplexes. This result greatly exceeds the targeting gene transfer effects previously described using mannose receptor targeted non-viral gene delivery systems. These results suggest that Man-PEG-b-pAsp(DET)/pDNA polyplex is a potential vector for immune cells-based gene therapy.

Polycation fluorination improves intraperitoneal siRNA delivery in metastatic pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a growing medical problem associated with extensive metastasis and high mortality. Intraperitoneal (IP) administration of therapeutics promises to help the treatment of cancers originated from organs in the peritoneal cavity. In this study, we evaluated how physicochemical properties of self-assembled polycation/siRNA nanoparticles affect their IP delivery efficacy in an orthotopic PDAC model. We have examined the effect of covalent polycation modification with lipophobic and hydrophobic tetrafluoro-p-toluic acid (TFTA), hydrophobic cholesterol, and hydrophilic poly(ethylene glycol) respectively. The surface charge of the three different nanoparticles was also modulated by coating the surface with serum albumin. We found that positively charged fluorine-containing particles with lipophobic properties based on a mixture of positively charged polymeric AMD3100 CXCR4 antagonist (PAMD) and PAMD modified with TFTA (mPAMD-TFTA)/siRNA displayed the best cell uptake and transfection efficacy in vitro. Biodistribution evaluation of the nanoparticles in a syngeneic orthotopic PDAC model revealed that the fluorine-containing formulation also achieved the highest PDAC tumor accumulation after IP administration. With a combination of CXCR4 inhibition by PAMD and PLK1 downregulation by siRNA, the treatment with mPAMD-TFTA/siPLK1 showed significant inhibition of both primary and metastatic PDAC tumors. Overall, our study provides insights into and guides the design of the nanoparticles for improved IP delivery of siRNA in PDAC.

HIF1α epigenetically repressed macrophages via CRISPR/Cas9-EZH2 system for enhanced cancer immunotherapy

Immune suppressive microenvironment in tumor emerges as the main obstacle for cancer immunotherapy. In this study, we identified that HIF1α was activated in the tumor associated macrophages and acted as an important factor for the immune suppressive microenvironment. Epigenetically silencing of Hif1α via histone H3 methylation in the promoter region was achieved by CRISPR/dCas9-EZH2 system, in which histone H3 methylase EZH2 was recruited to the promoter region specifically. The Hif1α silenced macrophage, namely HERM (Hif1α Epigenetically Repressed Macrophage) manifested as inheritable tumor suppressing phenotype. In the subcutaneous B16-F10 melanoma syngeneic model, intratumoral injection of HERMs reprogrammed the immune suppressive microenvironment to the active one, reducing tumor burden and prolonging overall survival. Additionally, HERMs therapy remarkably inhibited tumor angiogenesis. Together, our study has not only identified a promising cellular and molecular target for reverting immune suppressive microenvironment, but also provided a potent strategy for reprogramming tumor microenvironment via epigenetically reprogrammed macrophages.

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Macrophage are trained to promote cancer progression under hypoxic tumor microenvironment.

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HIF1α epigenetically repressed macrophage (HERM) is characterized as anti-tumoral function and suppress tumor progression.

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HERMs unleash immune suppression and promote cancer immunity.

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HERMs inhibit tumor angiogenesis and reduce tumor burden.

Lipid/polymer-based nanocomplexes in nucleic acid delivery as cancer vaccines

Cancer vaccines consist of nucleic acid derivatives such as plasmid DNA, small interfering RNA and mRNA, and can be customized according to the patient's needs. Nanomedicines have proven to be exceptionally good as miniaturized drug carriers, and thus they offer great advantages for delivering cancer vaccines. This review provides an overview of the literature on cancer vaccines, from their inception to current developments in the field.

Designing and Immunomodulating Multiresponsive Nanomaterial for Cancer Theranostics

Cancer has been widely investigated yet limited in its manifestation. Cancer treatment holds innovative and futuristic strategies considering high disease heterogeneity. Chemotherapy, radiotherapy and surgery are the most explored pillars; however optimal therapeutic window and patient compliance recruit constraints. Recently evolved immunotherapy demonstrates a vital role of the host immune system to prevent metastasis recurrence, still undesirable clinical response and autoimmune adverse effects remain unresolved. Overcoming these challenges, tunable biomaterials could effectively control the co-delivery of anticancer drugs and immunomodulators. Current status demands a potentially new approach for minimally invasive, synergistic, and combinatorial nano-biomaterial assisted targeted immune-based treatment including therapeutics, diagnosis and imaging. This review discusses the latest findings of engineering biomaterial with immunomodulating properties and implementing novel developments in designing versatile nanosystems for cancer theranostics. We explore the functionalization of nanoparticle for delivering antitumor therapeutic and diagnostic agents promoting immune response. Through understanding the efficacy of delivery system, we have enlightened the applicability of nanomaterials as immunomodulatory nanomedicine further advancing to preclinical and clinical trials. Future and present ongoing improvements in engineering biomaterial could result in generating better insight to deal with cancer through easily accessible immunological interventions.

Improved ionic-liquid-functionalized macroporous supports able to purify nucleic acids in one step

Nucleic acids are relevant biopolymers in therapy and diagnosis, for which their purity and biological activity are of crucial relevance. However, these features are difficult to achieve by cost-effective methods. Herein, we report the functionalization of a macroporous chromatographic support functionalized with an ionic liquid (IL) with remarkable performance to purify nucleic acids. An initial screening with distinct IL chemical structures supported in silica was carried out, allowing to identify the IL 1-methyl-3-propylimidazolium chloride as the most promising ligand. A chromatographic macroporous matrix able to be used in preparative liquid chromatography was then functionalized and binding/elution studies were performed. The IL 1-methyl-3-propylimidazolium chloride acts as a multimodal ligand with a remarkable dynamic binding capacity. This macroporous support allows the (one-step) purification of nucleic acids, namely small RNAs, ribosomal RNA, and genomic DNA, from a bacterial lysate, and can be regenerated and reused without compromising its separation performance.

Application of advances in endocytosis and membrane trafficking to drug delivery

Multidisciplinary research efforts in the field of drug delivery have led to the development of a variety of drug delivery systems (DDS) designed for site-specific delivery of diagnostic and therapeutic agents. Since efficient uptake of drug carriers into target cells is central to effective drug delivery, a comprehensive understanding of the biological pathways for cellular internalization of DDS can facilitate the development of DDS capable of precise tissue targeting and enhanced therapeutic outcomes. Diverse methods have been applied to study the internalization mechanisms responsible for endocytotic uptake of extracellular materials, which are also the principal pathways exploited by many DDS. Chemical inhibitors remain the most commonly used method to explore endocytotic internalization mechanisms, although genetic methods are increasingly accessible and may constitute more specific approaches. This review highlights the molecular basis of internalization pathways most relevant to internalization of DDS, and the principal methods used to study each route. This review also showcases examples of DDS that are internalized by each route, and reviews the general effects of biophysical properties of DDS on the internalization efficiency. Finally, options for intracellular trafficking and targeting of internalized DDS are briefly reviewed, representing an additional opportunity for multi-level targeting to achieve further specificity and therapeutic efficacy.

Genetically modified macrophages accomplish targeted gene delivery to the inflamed brain in transgenic Parkin Q311X(A) mice: importance of administration routes

Cell-based drug delivery systems have generated an increasing interest in recent years. We previously demonstrated that systemically administered macrophages deliver therapeutics to CNS, including glial cell line-derived neurotrophic factor (GDNF), and produce potent effects in Parkinson’s disease (PD) mouse models. Herein, we report fundamental changes in biodistribution and brain bioavailability of macrophage-based formulations upon different routes of administration: intravenous, intraperitoneal, or intrathecal injections. The brain accumulation of adoptively transferred macrophages was evaluated by various imaging methods in transgenic Parkin Q311(X)A mice and compared with those in healthy wild type littermates. Neuroinflammation manifested in PD mice warranted targeting macrophages to the brain for each route of administration. The maximum amount of cell-carriers in the brain, up to 8.1% ID/g, was recorded followed a single intrathecal injection. GDNF-transfected macrophages administered through intrathecal route provided significant increases of GDNF levels in different brain sub-regions, including midbrain, cerebellum, frontal cortex, and pons. No significant offsite toxicity of the cell-based formulations in mouse brain and peripheral organs was observed. Overall, intrathecal injection appeared to be the optimal administration route for genetically modified macrophages, which accomplished targeted gene delivery, and significant expression of reporter and therapeutic genes in the brain.

Following the Fate of Dye-Containing Liposomes In Vitro

The rather limited success of translation from basic research to clinical application has been highlighted as a major issue in the nanomedicine field. To identify the factors influencing the applicability of nanosystems as drug carriers and potential nanomedicine, we focused on following their fate through fluorescence-based assays, namely flow cytometry and imaging. These methods are often used to follow the nanocarrier internalization and targeting; however, the validity of the obtained results strictly depends on how much the nanosystem’s fate can be inferred from the fate of fluorescent dyes. To evaluate the parameters that affect the physicochemical and biological stability of the labeled nanosystems, we studied the versatility of two lipid dyes, TopFluor^®-PC and Cy5-DSPE, in conventional liposomes utilizing well-defined in vitro assays. Our results suggest that the dye can affect the major characteristics of the system, such as vesicle size and zeta-potential. However, a nanocarrier can also affect the dye properties. Medium, temperature, time, fluorophore localization and its concentration, as well as their interplay, affect the outcome of tracing experiments. Therefore, an in-depth characterization of the labeled nanosystem should be fundamental to understand the conditions that validate the results within the screening process in optimization of nanocarrier.

Stromal Modulation and Treatment of Metastatic Pancreatic Cancer with Local Intraperitoneal Triple miRNA/siRNA Nanotherapy

Nanomedicines achieve tumor-targeted delivery mainly through enhanced permeability and retention (EPR) effect following intravenous (IV) administration. Unfortunately, the EPR effect is severely compromised in pancreatic cancer due to hypovascularity and dense desmoplastic stroma. Intraperitoneal (IP) administration may be an effective EPR-independent local delivery approach to target peritoneal tumors. Besides improved delivery, effective combination delivery strategies are needed to improve pancreatic cancer therapy by targeting both cancer cells and cellular interactions within the tumor stroma. Here, we described simple cholesterol-modified polymeric CXCR4 antagonist (PCX) nanoparticles (to block cancer-stroma interactions) for codelivery of anti-miR-210 (to inactivate stroma-producing pancreatic stellate cells (PSCs)) and siKRAS^G12D (to kill pancreatic cancer cells). IP administration delivered the nanoparticles to an orthotopic syngeneic pancreatic tumors as a result of preferential localization to the tumors and metastases with disrupted mesothelium and effective tumor penetration. The local IP delivery resulted in nearly 15-fold higher tumor accumulation than delivery by IV injection. Through antagonism of CXCR4 and downregulation of miR-210/KRAS^G12D, the triple-action nanoparticles favorably modulated desmoplastic tumor microenvironment via inactivating PSCs and promoting the infiltration of cytotoxic T cells. The combined therapy displayed improved therapeutic effect when compared with individual therapies as documented by the delayed tumor growth, depletion of stroma, reduction of immunosuppression, inhibition of metastasis, and prolonged survival. Overall, we present data that a local IP delivery of a miRNA/siRNA combination holds the potential to improve pancreatic cancer therapy.

Advances in living cell-based anticancer therapeutics

This review summarizes recent advances in the applications of living cells as drug carriers or active drugs for anticancer drug delivery and cancer therapy.

GDNF-expressing macrophages restore motor functions at a severe late-stage, and produce long-term neuroprotective effects at an early-stage of Parkinson's disease in transgenic Parkin Q311X(A) mice

There is an unmet medical need in the area of Parkinson's disease (PD) to develop novel therapeutic approaches that can stop and reverse the underlying mechanisms responsible for the neuronal death. We previously demonstrated that systemically administered autologous macrophages transfected ex vivo to produce glial cell line-derived neurotrophic factor (GDNF) readily migrate to the mouse brain with acute toxin-induced neuroinflammation and ameliorate neurodegeneration in PD mouse models. We hypothesized that the high level of cytokines due to inflammatory process attracted GDNF-expressing macrophages and ensured targeted drug delivery to the PD brain. Herein, we validated a therapeutic potential of GDNF-transfected macrophages in a transgenic Parkin Q311X(A) mice with slow progression and mild brain inflammation. Systemic administration of GDNF-macrophages at a severe late stage of the disease leaded to a near complete restoration of motor functions in Parkin Q311X(A) mice and improved brain tissue integrity with healthy neuronal morphology. Furthermore, intravenous injections of GDNF-macrophages at an early stage of disease resulted in potent sustained therapeutic effects in PD mice for more than a year after the treatment. Importantly, multiple lines of evidence for therapeutic efficacy were observed including: diminished neuroinflammation and α-synuclein aggregation, increased survival of dopaminergic neurons, and improved locomotor functions. In summary, GDNF-transfected macrophages represent a promising therapeutic strategy for PD at both late- and early-stages of the disease.