Nanoparticle targeting to the endothelium during normothermic machine perfusion of human kidneys

Abstract

Ex vivo normothermic machine perfusion (NMP) is a new clinical strategy to assess and resuscitate organs likely to be declined for transplantation, thereby increasing the number of viable organs available. Short periods of NMP provide a window of opportunity to deliver therapeutics directly to the organ and, in particular, to the vascular endothelial cells (ECs) that constitute the first point of contact with the recipient’s immune system. ECs are the primary targets of both ischemia-reperfusion injury and damage from preformed antidonor antibodies, and reduction of perioperative EC injury could have long-term benefits by reducing the intensity of the host’s alloimmune response. Using NMP to administer therapeutics directly to the graft avoids many of the limitations associated with systemic drug delivery. We have previously shown that polymeric nanoparticles (NPs) can serve as depots for long-term drug release, but ensuring robust NP accumulation within a target cell type (graft ECs in this case) remains a fundamental challenge of nanomedicine. We show that surface conjugation of an anti-CD31 antibody enhances targeting of NPs to graft ECs of human kidneys undergoing NMP. Using a two-color quantitative microscopy approach, we demonstrate that targeting can enhance EC accumulation by about 5-to 10-fold or higher in discrete regions of the renal vasculature. In addition, our studies reveal that NPs can also non-specifically accumulate within obstructed regions of the vasculature that are poorly perfused. These quantitative preclinical human studies demonstrate the therapeutic potential for targeted nanomedicines delivered during ex vivo NMP.

The future of marginal kidney repair in the context of normothermic machine perfusion

“…Leading centers in the UK, Canada, The Netherlands, and the United States have all begun to move NMP technology forward8, 24, 25, 26 (Table 1). Normothermic perfusion technologies have begun to make their way into the clinic in an attempt to recondition marginal organs and reverse aspects of IRI.…”

“…In contrast to other theorized treatments, nanoparticles have long‐lasting effects and well‐established slow‐release profiles that extend beyond the period of normothermic perfusion. Recently and for the first time, endothelial targeted nanoparticles have been delivered in an NMP setting 8. With all of the benefits of this system, NMP is emerging as a device to deliver therapies within an opportunistic window in an attempt to reduce the injurious effects of ischemic injury.…”

“…Moreover, studies have shown that targeting will typically lead to internalization of NPs, which then provides an intracellular depot effect for effective drug delivery 41. Preliminary work with targeted, dye‐loaded poly(lactic acid)‐poly(ethylene) glycol (PLA‐PEG) nanoparticles has provided evidence that enhanced retention in specific vascular beds in kidneys is possible during NMP 8. Performing studies of this nature in discard human kidneys opens new possibilities in the development of therapeutics.…”

“…Testing the effects of these drugs during NMP helps us to mitigate any challenges that arise from cell culture or rodent models. Results from Tietjen et al highlighted that while there was an 80‐fold benefit of targeting observed in cell culture, this result translated to an average 2‐ to 4‐fold benefit in target specificity when applied to an NMP setting 8. This phenomenon has been observed in a plethora of studies investigating the efficacy of NPs as therapeutic agents and necessitates more therapeutically relevant models.…”

“…In a range of experimental studies, nanoparticles have been used to target the endothelium and tubular epithelial cells 7. More recently, nanoparticle targeting to vascular endothelium has been successfully demonstrated in human kidneys during NMP 8. In this review, we discuss the role of a variety of therapies, ending with nanoparticles, in an isolated, pretransplant setting to prevent complications of IRI.…”