Designer organs: The future of personalized transplantation.

Organ transplantation is the definitive treatment for end-stage solid organ diseases, yet biological and logistical barriers reduce the rate of successful organ transplants. As such, there is a need for gene therapy and gene modulation strategies in the organ transplantation setting to prevent rejection, expand the donor pool of available organs, and attenuate ischemia-reperfusion damage. As we are entering an era of "precision medicine," the organ transplant field is becoming equipped with the tools necessary to personalize and optimize organs designed specifically to withstand injurious pathways that occur during transplantation, such that the concept of "designer organs" will be a reality in the near future. In this review, we highlight the recent progress using gene knockout and knock-in strategies used mainly in the context of xenotransplantation. We also discuss advancements in CRISPR-Cas9 gene editing and RNA interference in relation to organ transplantation. Lastly, we discuss the exciting future implications of customized gene therapy in the transplantation setting, and its ability to potentially create a future where organs intended for transplant are personalized to maximize both graft and patient survival.

Dendritic amphiphilic siRNA: Selective albumin binding, in vivo efficacy, and low toxicity.

Although an increasing number of small interfering RNA (siRNA) therapies are reaching the market, the challenge of efficient extra-hepatic delivery continues to limit their full therapeutic potential. Drug delivery vehicles and hydrophobic conjugates are being used to overcome the delivery bottleneck. Previously, we reported a novel dendritic conjugate that can be appended efficiently to oligonucleotides, allowing them to bind albumin with nanomolar affinity. Here, we explore the ability of this novel albumin-binding conjugate to improve the delivery of siRNA in vivo. We demonstrate that the conjugate binds albumin exclusively in circulation and extravasates to various organs, enabling effective gene silencing. Notably, we show that the conjugate achieves a balance between hydrophobicity and safety, as it significantly reduces the side effects associated with siRNA interactions with blood components, which are commonly observed in some hydrophobically conjugated siRNAs. In addition, it reduces siRNA monocyte uptake, which may lead to cytokine/inflammatory responses. This work showcases the potential of using this dendritic conjugate as a selective albumin binding handle for the effective and safe delivery of nucleic acid therapeutics. We envision that these properties may pave the way for new opportunities to overcome delivery hurdles of oligonucleotides in future applications.

Review of Current Machine Perfusion Therapeutics for Organ Preservation.

Because of the high demand of organs, the usage of marginal grafts has increased. These marginal organs have a higher risk of developing ischemia-reperfusion injury, which can lead to posttransplant complications. Ex situ machine perfusion (MP), compared with the traditional static cold storage, may better protect these organs from ischemia-reperfusion injury. In addition, MP can also act as a platform for dynamic administration of pharmacological agents or gene therapy to further improve transplant outcomes. Numerous therapeutic agents have been studied under both hypothermic (1-8°C) and normothermic settings. Here, we review all the therapeutics used during MP in different organ systems (lung, liver, kidney, heart). The major categories of therapeutic agents include vasodilators, mesenchymal stem cells, antiinflammatory agents, antiinfection agents, siRNA, and defatting agents. Numerous animal and clinical studies have examined MP therapeutic agents, some of which have even led to the successful reconditioning of discarded grafts. More clinical studies, especially randomized controlled trials, will need to be conducted in the future to solidify these promising results and to define the role of MP therapeutic agents in solid organ transplantation.

Therapeutics administered during ex vivo liver machine perfusion: An overview.

Although the use of extended criteria donors has increased the pool of available livers for transplant, it has also introduced the need to develop improved methods of protection against ischemia-reperfusion injury (IRI), as these "marginal" organs are particularly vulnerable to IRI during the process of procurement, preservation, surgery, and post-transplantation. In this review, we explore the current basic science research investigating therapeutics administered during ex vivo liver machine perfusion aimed at mitigating the effects of IRI in the liver transplantation process. These various categories of therapeutics are utilized during the perfusion process and include invoking the RNA interference pathway, utilizing defatting cocktails, and administering classes of agents such as vasodilators, anti-inflammatory drugs, human liver stem cell-derived extracellular vesicles, and δ-opioid agonists in order to reduce the damage of IRI. Ex vivo machine perfusion is an attractive alternative to static cold storage due to its ability to continuously perfuse the organ, effectively deliver substrates and oxygen required for cellular metabolism, therapeutically administer pharmacological or cytoprotective agents, and continuously monitor organ viability during perfusion. The use of administered therapeutics during machine liver perfusion has demonstrated promising results in basic science studies. While novel therapeutic approaches to combat IRI are being developed through basic science research, their use in clinical medicine and treatment in patients for liver transplantation has yet to be explored.

The role of normothermic machine perfusion in liver transplantation.

To expand the donor pool of suitable organs for transplantation, there is an increased interest in utilizing extended criteria donor grafts (ECD). Ex-situ machine perfusion has shown to be a promising new modality in the organ preservation field to reduce injury and recover ECD liver grafts. Machine perfusion (MP) is considered a significant improvement in the field of transplantation over the past 20 years. Normothermic machine perfusion has entered the clinical arena in the last decade and has shown promising results to improve the quality of marginal organs and to increase the pool of liver grafts. It allows assessment of viability and function of grafts prior to transplantation. In addition, it has the potential to serve as a platform for pharmacologic organ treatment and graft optimization. Machine perfusion moved from the experimental phase to a more mature phase after safety was confirmed by initial clinical trials. Now, it is time to confirm its superiority and cost-effectiveness before a broader clinical use. In this paper we review the history, current status including outcomes of all clinical trials, limitations, and future trends of normothermic machine preservation.