Oxygen is the key molecule for aerobic metabolism, but no animal cells can produce it, creating an extreme dependency on external supply. In contrast, microalgae are photosynthetic microorganisms, therefore, they are able to produce oxygen as plant cells do. As hypoxia is one of the main issues in organ transplantation, especially during preservation, the main goal of this work was to develop the first generation of perfusable photosynthetic solutions, exploring its feasibility for ex vivo organ preservation. Here, the microalgae Chlamydomonas reinhardtii was incorporated in a standard preservation solution, and key aspects such as alterations in cell size, oxygen production and survival were studied. Osmolarity and rheological features of the photosynthetic solution were comparable to human blood. In terms of functionality, the photosynthetic solution proved to be not harmful and to provide sufficient oxygen to support the metabolic requirement of zebrafish larvae and rat kidney slices. Thereafter, isolated porcine kidneys were perfused, and microalgae reached all renal vasculature, without inducing damage. After perfusion and flushing, no signs of tissue damage were detected, and recovered microalgae survived the process. Altogether, this work proposes the use of photosynthetic microorganisms as vascular oxygen factories to generate and deliver oxygen in isolated organs, representing a novel and promising strategy for organ preservation.

The lack of organs available for transplantation is a global problem. The high mortality rates on the waiting list and the high number of discarded livers are reasons to develop new tools in the preservation and transplantation process.New tools should also be available for low-income countries. This article reports the development of customized normothermic machine perfusion (NMP). An ex vivo dual perfusion machine was designed, composed of a common reservoir organ box (CRO), a centrifugal pump (portal system, low pressure), and a roller pump (arterial system, high pressure). Porcine livers (n = 5) were perfused with an oxygenated normothermic (37℃) strategy for 3 hours. Hemodynamic variables, metabolic parameters, and bile production during preservation were analyzed. Arterial and portal flow remain stable during perfusion. Total bilirubin production was 11.25 mL (4-14.5) at 180 minutes. The median pH value reached 7.32 (7.25-7.4) at 180 minutes. Lactate values decreased progressively to normalization at 120 minutes. This perfusion setup was stable and able to maintain the metabolic activity of a liver graft in a porcine animal model. Design and initial results from this customized NMP are promising for a future clinical application in low-income countries.

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