Lysis of cold-storage-induced microvascular obstructions for ex vivo revitalization of marginal human kidneys.

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.

Optical Elastography for Micropressure Characterization of Zebrafish Embryonic Cardiac Development.

The proper formation of the vertebrate embryonic heart relies on various mechanical forces which determine its form and function. Measuring these forces at the microscale of the embryo is a challenge. We propose a new tool utilizing high-resolution optical elastography and stiffness measurements of surrounding tissues to non-invasively track the changes in the pressure exerted by the heart on the neighboring yolk, as well as changes in contractile patterns during early cardiac growth in-vivo, using the zebrafish embryo as a model system. Cardiac development was characterized every three hours from 24 hours post-fertilization (hpf) to 30 hpf and compared between wildtype fish and those treated with MS-222, a commonly used fish anesthetic that decreases cardiac contractility. Wildtype embryos from 24 to 30 hpf showed an average yolk indentation pressure of 0.32 mmHg to 0.41 mmHg, respectively. MS-222 treated embryos showed an average yolk indentation pressure of 0.22 mmHg to 0.29 mmHg. Yolk indentation pressure between control and treated embryos at 24 hpf and 30 hpf showed a significant difference (p < 0.05). Our method allowed for contractility and pressure evaluation at these early developmental stages, which have not been previously reported in published literature, regardless of sample or imaging modality. This research could lead to a better understanding of heart development and improved diagnostic tools for congenital heart disease.