RESUMEN
For decades, transplantation has been a life-saving treatment for those fortunate enough to gain access. Nevertheless, many patients die waiting for an organ and countless more never make it onto the waitlist because of a shortage of donor organs. Concurrently, thousands of donated organs are declined for transplant each year because of concerns about poor outcomes post-transplant. The decline of any donated organ-even if medically justified-is tragic for both the donor family and potential recipients. In this Personal Viewpoint, we discuss the need for a new mindset in how we honor the gift of organ donation. We believe that the use of transplant-declined human organs in translational research has the potential to hasten breakthrough discoveries in a multitude of scientific and medical areas. More importantly, such breakthroughs will allow us to properly value every donated organ. We further discuss the many practical challenges that such research presents and offer some possible solutions based on experiences in our own research laboratories. Finally, we share our perspective on what we believe are the necessary next steps to ensure a future where every donated organ realizes its full potential to impact the lives of current and future patients.
Asunto(s)
Trasplante de Órganos , Obtención de Tejidos y Órganos , Humanos , Donantes de Tejidos , Listas de EsperaRESUMEN
After cessation of blood flow or similar ischaemic exposures, deleterious molecular cascades commence in mammalian cells, eventually leading to their death1,2. Yet with targeted interventions, these processes can be mitigated or reversed, even minutes or hours post mortem, as also reported in the isolated porcine brain using BrainEx technology3. To date, translating single-organ interventions to intact, whole-body applications remains hampered by circulatory and multisystem physiological challenges. Here we describe OrganEx, an adaptation of the BrainEx extracorporeal pulsatile-perfusion system and cytoprotective perfusate for porcine whole-body settings. After 1 h of warm ischaemia, OrganEx application preserved tissue integrity, decreased cell death and restored selected molecular and cellular processes across multiple vital organs. Commensurately, single-nucleus transcriptomic analysis revealed organ- and cell-type-specific gene expression patterns that are reflective of specific molecular and cellular repair processes. Our analysis comprises a comprehensive resource of cell-type-specific changes during defined ischaemic intervals and perfusion interventions spanning multiple organs, and it reveals an underappreciated potential for cellular recovery after prolonged whole-body warm ischaemia in a large mammal.
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Supervivencia Celular , Citoprotección , Perfusión , Porcinos , Isquemia Tibia , Animales , Muerte Celular , Perfilación de la Expresión Génica , Isquemia/metabolismo , Isquemia/patología , Isquemia/prevención & control , Especificidad de Órganos , Perfusión/métodos , Porcinos/anatomía & histologíaRESUMEN
The current obesity epidemic has caused a significant decline in the health of our donor population. Organs from obese deceased donors are more prone to ischemia reperfusion injury resulting from organ preservation. As a consequence, these donors are more likely to be discarded under the assumption that nothing can be done to make them viable for transplant. Our current methods of organ preservation-which remain relatively unchanged over the last ~40 years-were originally adopted in the context of a much healthier donor population. But methods that are suitable for healthier deceased donors are likely not optimal for organs from obese donors. Naturally occurring models of acute obesity and fasting in hibernating mammals demonstrate that obesity and resilience to cold preservation-like conditions are not mutually exclusive. Moreover, recent advances in our understanding of the metabolic dysfunction that underlies obesity suggest that it may be possible to improve the resilience of organs from obese deceased donors. In this mini-review, we explore how we might adapt our current practice of organ preservation to better suit the current reality of our deceased donor population.
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Pandemias , Daño por Reperfusión , Animales , Humanos , Mamíferos , Obesidad/epidemiología , Preservación de Órganos/métodos , Pandemias/prevención & control , Daño por Reperfusión/metabolismo , Donantes de TejidosRESUMEN
Despite the profound shortage of organs available for transplant in the U.S., over 5,000 donated organs were declined for use in 2020. Many of these organs were declined due to donor comorbidities or preservation injuries that predispose grafts to rejection and loss. The risks of these poor outcomes can potentially be reduced by pre-transplant application of normothermic machine perfusion (NMP). To date, the clinical use of NMP has focused on extending preservation and improving organ assessment, but the opportunity for ex situ therapeutic delivery may be the most transformative aspect of this technology. In this Personal Viewpoint, we argue that the endothelial cells (ECs) that line the graft vasculature are an accessible, under-exploited, and attractive target for transplant therapeutics delivered during NMP. We further contend that molecularly targeted nanoparticles (NPs) represent a promising therapeutic vehicle particularly well-suited to NMP. However, to achieve this potential, we need to answer the following three key questions: (1) What EC sub-populations exist within an organ? (2) How can these cells be accessed? (3) And most important, how can preferential retention of NPs by the cells of interest be maximized? Here we argue for creating an EC-targeting atlas as a body of knowledge that answers these questions.
Asunto(s)
Células Endoteliales , Preservación de Órganos , Aloinjertos , Humanos , Preservación de Órganos/métodos , Perfusión/métodos , Donantes de TejidosRESUMEN
In preclinical research, histological analysis of tissue samples is often limited to qualitative or semiquantitative scoring assessments. The reliability of this analysis can be impaired by the subjectivity of these approaches, even when read by experienced pathologists. Furthermore, the laborious nature of manual image assessments often leads to the analysis being restricted to a relatively small number of images that may not accurately represent the whole sample. Thus, there is a clear need for automated image analysis tools that can provide robust and rapid quantification of histologic samples from paraffin-embedded or cryopreserved tissues. To address this need, we have developed a color image analysis algorithm (DigiPath) to quantify distinct color features in histologic sections. We demonstrate the utility of this tool across multiple types of tissue samples and pathologic features, and compare results from our program to other quantitative approaches such as color thresholding and hand tracing. We believe this tool will enable more thorough and reliable characterization of histological samples to facilitate better rigor and reproducibility in tissue-based analyses.
RESUMEN
Patients undergoing organ transplantation transition from one life-altering issue (organ dysfunction) to a lifelong commitment-immunosuppression. Regimens of immunosuppressive agents (ISAs) come with significant side effects and comorbidities. Recently, the use of nanoparticles (NPs) as a solution to the problems associated with the long-term and systemic use of ISAs in transplantation has emerged. This minireview describes the role of NPs in organ transplantation and discusses obstacles to clinical implementation and pathways to clinical translation.
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Inmunosupresores , Trasplante de Órganos , Rechazo de Injerto/tratamiento farmacológico , Rechazo de Injerto/prevención & control , Humanos , Tolerancia Inmunológica , Terapia de Inmunosupresión , Inmunosupresores/uso terapéuticoRESUMEN
Immune surveillance cells such as T cells and phagocytes utilize integral plasma membrane receptors to recognize surface signatures on triggered and activated cells such as those in apoptosis. One such family of plasma membrane sensors, the transmembrane immunoglobulin and mucin domain (Tim) proteins, specifically recognize phosphatidylserine (PS) but elicit distinct immunological responses. The molecular basis for the recognition of lipid signals on target cell surfaces is not well understood. Previous results suggest that basic side chains present at the membrane interface on the Tim proteins might facilitate association with additional anionic lipids including but not necessarily limited to PS. We, therefore, performed a comparative quantitative analysis of the binding of the murine Tim1, Tim3, and Tim4, to synthetic anionic phospholipid membranes under physiologically relevant conditions. X-ray reflectivity and vesicle binding studies were used to compare the water-soluble domain of Tim3 with results previously obtained for Tim1 and Tim4. Although a calcium link was essential for all three proteins, the three homologs differed in how they balance the hydrophobic and electrostatic interactions driving membrane association. The proteins also varied in their sensing of phospholipid chain unsaturation and showed different degrees of cooperativity in their dependence on bilayer PS concentration. Surprisingly, trace amounts of anionic phosphatidic acid greatly strengthened the bilayer association of Tim3 and Tim4, but not Tim1. A novel mathematical model provided values for the binding parameters and illuminated the complex interplay among ligands. In conclusion, our results provide a quantitative description of the contrasting selectivity used by three Tim proteins in the recognition of phospholipids presented on target cell surfaces. This paradigm is generally applicable to the analysis of the binding of peripheral proteins to target membranes through the heterotropic cooperative interactions of multiple ligands.
Asunto(s)
Proteínas de la Membrana , Mucinas , Animales , Receptor Celular 1 del Virus de la Hepatitis A , Membranas , Ratones , FosfatidilserinasRESUMEN
Thousands of kidneys from higher-risk donors are discarded annually because of the increased likelihood of complications posttransplant. Given the severe organ shortage, there is a critical need to improve utilization of these organs. To this end, normothermic machine perfusion (NMP) has emerged as a platform for ex vivo assessment and potential repair of marginal organs. In a recent study of 8 transplant-declined human kidneys on NMP, we discovered microvascular obstructions that impaired microvascular blood flow. However, the nature and physiologic impact of these lesions were unknown. Here, in a study of 39 human kidneys, we have identified that prolonged cold storage of human kidneys induces accumulation of fibrinogen within tubular epithelium. Restoration of normoxic conditions-either ex vivo during NMP or in vivo following transplant-triggered intravascular release of fibrinogen correlating with red blood cell aggregation and microvascular plugging. Combined delivery of plasminogen and tissue plasminogen activator during NMP lysed the plugs leading to a significant reduction in markers of renal injury, improvement in indicators of renal function, and improved delivery of vascular-targeted nanoparticles. Our study suggests a new mechanism of cold storage injury in marginal organs and provides a simple treatment with immediate translational potential.
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Trasplante de Riñón , Preservación de Órganos , Humanos , Riñón , Trasplante de Riñón/efectos adversos , Perfusión , Activador de Tejido PlasminógenoRESUMEN
Endothelial cells play a central role in the process of inflammation. Their biologic relevance, as well as their accessibility to IV injected therapeutics, make them a strong candidate for treatment with molecularly-targeted nanomedicines. Typically, the properties of targeted nanomedicines are first optimized in vitro in cell culture and then in vivo in rodent models. While cultured cells are readily available for study, results obtained from isolated cells can lack relevance to more complex in vivo environments. On the other hand, the quantitative assays needed to determine the impact of nanoparticle design on targeting efficacy are difficult to perform in animal models. Moreover, results from animal models often translate poorly to human systems. To address the need for an improved testing platform, we developed an isolated vessel perfusion system to enable dynamic and quantitative study of vascular-targeted nanomedicines in readily obtainable human vessels isolated from umbilical cords or placenta. We show that this platform technology enables the evaluation of parameters that are critical to targeting efficacy (including flow rate, selection of targeting molecule, and temperature). Furthermore, biologic replicates can be easily produced by evaluating multiple vessel segments from the same human donor in independent, modular chambers. The chambers can also be adapted to house vessels of a variety of sizes, allowing for the subsequent study of vessel segments in vivo following transplantation into immunodeficient mice. We believe this perfusion system can help to address long-standing issues in endothelial targeted nanomedicines and thereby enable more effective clinical translation.
RESUMEN
Endosomal escape is a key step for intracellular drug delivery of nucleic acids, but reliable and sensitive methods for its quantitation remain an unmet need. In order to rationally optimize the mRNA transfection efficiency of a library of polymeric materials, we designed a deactivated Renilla luciferase-derived molecular probe whose activity can be restored only in the cytosol. This probe can be coencapsulated with mRNA in the same delivery vehicle, thereby accurately measuring its endosomal escape efficiency. We examined a library of poly(amine-co-ester) (PACE) polymers with different end groups using this probe and observed a strong correlation between endosomal escape and transfection efficiency (R2 = 0.9334). In addition, we found that mRNA encapsulation efficiency and endosomal escape, but not uptake, were determinant factors for transfection efficiency. The polymers with high endosomal escape/transfection efficiency in vitro also showed good transfection efficiency in vivo, and mRNA expression was primarily observed in spleens after intravenous delivery. Together, our study suggests that the luciferase probe can be used as an effective tool to quantitate endosomal escape, which is essential for rational optimization of intracellular drug delivery systems.
Asunto(s)
Técnicas de Transferencia de Gen , Luciferasas de Renilla/genética , Sondas Moleculares/genética , ARN Mensajero/genética , Citosol/química , Citosol/efectos de los fármacos , Regulación de la Expresión Génica/genética , Humanos , Luciferasas de Renilla/química , Sondas Moleculares/química , Nanopartículas/química , Transfección/métodosRESUMEN
Accurate analysis of blood concentration and circulation half-life is an important consideration for any intravenously administered agent in preclinical development or for therapeutic application. However, the currently available tools to measure these parameters are laborious, expensive, and inefficient for handling multiple samples from complex multivariable experiments. Here we describe a robust high-throughput quantitative microscopy-based method to measure the blood concentration and circulation half-life of any fluorescently labeled agent using only a small (2 µL) amount of blood volume, enabling additional end-point measurements to be assessed in the same subject. To validate this method, we demonstrate its use to measure the circulation half-life in mice of two types of fluorescently labeled polymeric nanoparticles of different sizes and surface chemistries and of a much smaller fluorescently labeled monoclonal antibody. Furthermore, we demonstrate the improved accuracy of this method compared to previously described methods.
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Monitoreo de Drogas/métodos , Ensayos Analíticos de Alto Rendimiento/métodos , Microscopía/métodos , Preparaciones Farmacéuticas/administración & dosificación , Preparaciones Farmacéuticas/química , Animales , Femenino , Semivida , Humanos , Inyecciones Intravenosas , Masculino , Ratones , Ratones Endogámicos BALB C , Nanopartículas/químicaRESUMEN
Formation of a perfusable microvascular network (µVN) is critical for tissue engineering of solid organs. Stromal cells can support endothelial cell (EC) self-assembly into a µVN, but distinct stromal cell populations may play different roles in this process. Here we describe the differential effects that two widely used stromal cell populations, fibroblasts (FBs) and pericytes (PCs), have on µVN formation. We examined the effects of adding defined stromal cell populations on the self-assembly of ECs derived from human endothelial colony forming cells (ECFCs) into perfusable µVNs in fibrin gels cast within a microfluidic chamber. ECs alone failed to fully assemble a perfusable µVN. Human lung FBs stimulated the formation of EC-lined µVNs within microfluidic devices. RNA-seq analysis suggested that FBs produce high levels of hepatocyte growth factor (HGF). Addition of recombinant HGF improved while the c-MET inhibitor, Capmatinib (INCB28060), reduced µVN formation within devices. Human placental PCs could not substitute for FBs, but in the presence of FBs, PCs closely associated with ECs, formed a common basement membrane, extended microfilaments intercellularly, and reduced microvessel diameters. Different stromal cell types provide different functions in microvessel assembly by ECs. FBs support µVN formation by providing paracrine growth factors whereas PCs directly interact with ECs to modify microvascular morphology.
RESUMEN
Tissue engineering may address organ shortages currently limiting clinical transplantation. Off-the-shelf engineered vascularized organs will likely use allogeneic endothelial cells (ECs) to construct microvessels required for graft perfusion. Vasculogenic ECs can be differentiated from committed progenitors (human endothelial colony-forming cells or HECFCs) without risk of mutation or teratoma formation associated with reprogrammed stem cells. Like other ECs, these cells can express both class I and class II major histocompatibility complex (MHC) molecules, bind donor-specific antibody (DSA), activate alloreactive T effector memory cells, and initiate rejection in the absence of donor leukocytes. CRISPR/Cas9-mediated dual ablation of ß2-microglobulin and class II transactivator (CIITA) in HECFC-derived ECs eliminates both class I and II MHC expression while retaining EC functions and vasculogenic potential. Importantly, dually ablated ECs no longer bind human DSA or activate allogeneic CD4+ effector memory T cells and are resistant to killing by CD8+ alloreactive cytotoxic T lymphocytes in vitro and in vivo. Despite absent class I MHC molecules, these ECs do not activate or elicit cytotoxic activity from allogeneic natural killer cells. These data suggest that HECFC-derived ECs lacking MHC molecule expression can be utilized for engineering vascularized grafts that evade allorejection.
Asunto(s)
Aloinjertos/inmunología , Células Endoteliales/inmunología , Rechazo de Injerto/prevención & control , Proteínas Nucleares/genética , Ingeniería de Tejidos/métodos , Transactivadores/genética , Microglobulina beta-2/genética , Aloinjertos/irrigación sanguínea , Aloinjertos/provisión & distribución , Animales , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/inmunología , Sistemas CRISPR-Cas/genética , Diferenciación Celular , Células Cultivadas , Modelos Animales de Enfermedad , Células Endoteliales/metabolismo , Células Progenitoras Endoteliales , Femenino , Sangre Fetal/citología , Técnicas de Inactivación de Genes , Rechazo de Injerto/sangre , Rechazo de Injerto/inmunología , Voluntarios Sanos , Humanos , Isoanticuerpos/inmunología , Células Asesinas Naturales/inmunología , Activación de Linfocitos/genética , Ratones , Microvasos/citología , Microvasos/inmunología , Microvasos/trasplante , Proteínas Nucleares/inmunología , Trasplante de Órganos/efectos adversos , Trasplante de Órganos/métodos , Cultivo Primario de Células , Transactivadores/inmunología , Microglobulina beta-2/inmunologíaRESUMEN
Some synthetic polymers can block cell death when applied following an injury that would otherwise kill the cell. This cellular rescue occurs through interactions of the polymers with cell membranes. However, general principles for designing synthetic polymers to ensure strong, but nondisruptive, cell membrane targeting are not fully elucidated. Here, we tailored biomimetic phosphorylcholine-containing block copolymers to interact with cell membranes and determined their efficacy in blocking neuronal death following oxygen-glucose deprivation. By adjusting the hydrophilicity and membrane affinity of poly(2-methacryloyloxyethyl phosphorylcholine) (polyMPC)-based triblock copolymers, the surface active regime in which the copolymers function effectively as membrane-targeting cellular rescue agents was determined. We identified nonintrusive interactions between the polymer and the cell membrane that alter the collective dynamics of the membrane by inducing rigidification without disrupting lipid packing or membrane thickness. In general, our results open new avenues for biological applications of polyMPC-based polymers and provide an approach to designing membrane-targeting agents to block cell death after injury.
Asunto(s)
Materiales Biocompatibles/farmacología , Metacrilatos/química , Fosforilcolina/análogos & derivados , Polímeros/química , Materiales Biocompatibles/química , Biomimética/métodos , Muerte Celular/efectos de los fármacos , Membrana Celular/efectos de los fármacos , Humanos , Interacciones Hidrofóbicas e Hidrofílicas/efectos de los fármacos , Metacrilatos/farmacología , Fosforilcolina/química , Fosforilcolina/farmacología , Polímeros/farmacologíaRESUMEN
Degradable poly(amine-co-ester) (PACE) terpolymers hold tremendous promise for siRNA delivery because these materials can be formulated into delivery vehicles with highly efficient siRNA encapsulation, providing effective knockdown with low toxicity. Here, we demonstrate that PACE nanoparticles (NPs) provide substantial protein knockdown in human embryonic kidney cells (HEK293) and hard-to-transfect primary human umbilical vein endothelial cells (HUVECs). After intravenous administration, NPs of solid PACE (sPACE)-synthesized with high monomer content of a hydrophobic lactone-accumulated in the liver and, to a lesser extent, in other tissues. Within the liver, a substantial fraction of sPACE NPs were phagocytosed by liver macrophages, while a smaller fraction of NPs accumulated in hepatic stellate cells and liver sinusoidal endothelial cells, suggesting that sPACE NPs could deliver siRNA to diverse cell populations within the liver. To test this hypothesis, we loaded sPACE NPs with siRNA designed to knockdown Nogo-B, a protein that has been implicated in the progression of alcoholic liver disease and liver fibrosis. These sPACE:siRNA NPs produced up to 60% Nogo-B protein suppression in the liver after systemic administration. We demonstrate that sPACE NPs can effectively deliver siRNA therapeutics to the liver to mediate protein knockdown in vivo.
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Hígado/metabolismo , Nanopartículas , Proteínas Nogo/genética , Poliaminas/química , Animales , Células Endoteliales/metabolismo , Técnicas de Silenciamiento del Gen , Células HEK293 , Células Estrelladas Hepáticas/metabolismo , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , ARN Interferente Pequeño/administración & dosificaciónRESUMEN
Complement promotes vascular inflammation in transplant organ rejection and connective tissue diseases. Here we identify ZFYVE21 as a complement-induced Rab5 effector that induces non-canonical NF-κB in endothelial cells (EC). In response to membrane attack complexes (MAC), ZFYVE21 is post-translationally stabilized on MAC+Rab5+ endosomes in a Rab5- and PI(3)P-dependent manner. ZFYVE21 promotes SMURF2-mediated polyubiquitinylation and proteasome-dependent degradation of endosome-associated PTEN to induce vesicular enrichment of PI(3,4,5)P3 and sequential recruitment of activated Akt and NF-κB-inducing kinase (NIK). Pharmacologic alteration of cellular phosphoinositide content with miltefosine reduces ZFYVE21 induction, EC activation, and allograft vasculopathy in a humanized mouse model. ZFYVE21 induction distinctly occurs in response to MAC and is detected in human renal and synovial tissues. Our data identifies ZFYVE21 as a Rab5 effector, defines a Rab5-ZFYVE21-SMURF2-pAkt axis by which it mediates EC activation, and demonstrates a role for this pathway in complement-mediated conditions.
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Proteínas Portadoras/metabolismo , Endosomas/metabolismo , Rechazo de Injerto/patología , FN-kappa B/metabolismo , Vasculitis/patología , Aloinjertos/patología , Animales , Línea Celular , Complejo de Ataque a Membrana del Sistema Complemento/metabolismo , Vasos Coronarios/patología , Vasos Coronarios/trasplante , Modelos Animales de Enfermedad , Femenino , Células Endoteliales de la Vena Umbilical Humana , Humanos , Péptidos y Proteínas de Señalización Intracelular , Proteínas de la Membrana , Ratones , Ratones SCID , Fosfatos de Fosfatidilinositol/metabolismo , Ubiquitina-Proteína Ligasas/metabolismo , Proteínas de Unión al GTP rab5/metabolismoRESUMEN
There is a diverse class of peripheral membrane-binding proteins that specifically bind phosphatidylserine (PS), a lipid that signals apoptosis or cell fusion depending on the membrane context of its presentation. PS-receptors are specialized for particular PS-presenting pathways, indicating that they might be sensitive to the membrane context. In this review, we describe a combination of thermodynamic, structural, and computational techniques that can be used to investigate the mechanisms underlying this sensitivity. As an example, we focus on three PS-receptors of the T-cell Immunoglobulin and Mucin containing (TIM) protein family, which we have previously shown to differ in their sensitivity to PS surface density.
Asunto(s)
Fosfatidilserinas/metabolismo , Animales , Apoptosis/fisiología , Receptor Celular 1 del Virus de la Hepatitis A/metabolismo , Receptor 2 Celular del Virus de la Hepatitis A/metabolismo , Humanos , Lípidos/química , Glicoproteínas de Membrana/metabolismo , Proteínas de la Membrana/metabolismo , Membranas/metabolismo , Receptores de Superficie Celular/metabolismo , Receptores Virales/metabolismoRESUMEN
Gene delivery is known to be a complicated multi-step biological process. It has been observed that subtle differences in the structure and properties of polymeric materials used for gene delivery can lead to dramatic differences in transfection efficiency. Therefore, screening of properties is pivotal to optimizing the polymer. So far, most polymeric materials are built in a "bottom-up" manner, i.e. synthesized from monomers that allow modification of polymer composition or structural factors. With this method, we previously synthesized and screened a library of biodegradable poly(amine-co-ester) (PACE) terpolymers for optimized DNA delivery. However, it can be tedious and time consuming to synthesize a polymer library for screening, particularly when small changes of a factor need to be tested, when multiple factors are involved, and when the effects of different factors are synergistic. In the present work, we evaluate the potential of PACE to deliver mRNA. After observing that mRNA transfection efficiency was highly dependent on both end group composition and molecular weight (MW) of PACE in a synergistic manner, we developed a "top-down" process we called actuation, to simultaneously vary these two factors. Some of the actuated PACE (aPACE) materials presented superior mRNA delivery properties compared to regular PACE, with up to a 106-fold-increase in mRNA transfection efficiency in vitro. Moreover, when aPACE was used to deliver mRNA coding for erythropoietin (EPO) in vivo, it produced high levels of EPO in the blood for up to 48â¯h without inducing systemic toxicity. This polymer constitutes a new delivery vehicle for mRNA-based treatments that provides safe yet potent protein production.
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Poliaminas/química , Poliésteres/química , ARN Mensajero/administración & dosificación , Animales , Línea Celular , Supervivencia Celular , Eritropoyetina/genética , Femenino , Técnicas de Transferencia de Gen , Humanos , Hidrólisis , Interacciones Hidrofóbicas e Hidrofílicas , Ratones Endogámicos BALB C , Peso Molecular , Nanopartículas/química , Polimerizacion , Bibliotecas de Moléculas Pequeñas , TransfecciónRESUMEN
Successful molecular targeting of nanoparticle drug carriers can enhance therapeutic specificity and reduce systemic toxicity. Typically, ligands specific for cognate receptors expressed on the intended target cell type are conjugated to the nanoparticle surface. This approach, often called active targeting, seems to imply that the conjugated ligand imbues the nanoparticle with homing capacity. However, ligand-receptor interactions are mediated by short-range forces and cannot produce magnetic-like attraction over larger distances. Successful targeting actually involves two key characteristics: contact of the nanoparticle with the intended target cell and subsequent ligand-mediated retention at the site. Here we propose a conceptual framework, based on recent literature combined with basic principles of molecular interactions, to guide rational design of nanoparticle targeting strategies.
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Sistemas de Liberación de Medicamentos/métodos , Nanopartículas/química , Animales , Portadores de Fármacos/química , Humanos , LigandosRESUMEN
Normothermic machine perfusion (NMP) is a technique that utilizes extracorporeal membrane oxygenation to recondition and repair kidneys at near body temperature prior to transplantation. The application of this new technology has been fueled by a significant increase in the use of the kidneys that were donated after cardiac death, which are more susceptible to ischemic injury. Preliminary results indicate that NMP itself may be able to repair marginal organs prior to transplantation. In addition, NMP serves as a platform for delivery of therapeutics. The isolated setting of NMP obviates problems of targeting a particular therapy to an intended organ and has the potential to reduce the harmful effects of systemic drug delivery. There are a number of emerging therapies that have shown promise in this platform. Nutrients, therapeutic gases, mesenchymal stromal cells, gene therapies, and nanoparticles, a newly explored modality, have been successfully delivered during NMP. These technologies may be effective at blocking multiple mechanisms of ischemia- reperfusion injury (IRI) and improving renal transplant outcomes. This review addresses the mechanisms of renal IRI, examines the potential for NMP as a platform for pretransplant allograft modulation, and discusses the introduction of various therapies in this setting.