Lung thermography during the initial reperfusion period to assess pulmonary function in cellular ex vivo lung perfusion

Theranostic methodology for ex vivo donor lung rehabilitation

BACKGROUND

About 80% of donor lungs are not utilized for transplantation. Cross-circulation of ex vivo lungs with a support swine enables the rehabilitation of donor lungs that are initially deemed unsuitable for transplantation. Robust therapeutic and diagnostic modalities are needed for ex vivo lung rehabilitation; however, no standardized "theranostic" methodology has been reported.

METHODS

Ex vivo lungs (n = 23; 17 injured and 6 controls) with multi-focal contusion (n = 6, human), gastric aspiration injury (n = 8, swine), ischemia-reperfusion injury (n = 3, swine), or no injury (n = 6, swine) were used to develop a therapeutic and diagnostic (theranostic) methodology for ex vivo lung rehabilitation during cross-circulation. Airway (bronchoscopic, nebulized), intravascular, and transpleural access enabled sample collection and therapeutic delivery. Diagnostic modalities included non-invasive imaging, functional testing, and molecular assays. Therapeutic modalities included bronchoalveolar lavage, surfactant replacement, recruitment maneuvers, and cell/organoid delivery. Real-time tracking of delivered cells was performed via fluorescence and bioluminescence imaging.

FINDINGS

Diagnostic assessments revealed tissue-, cell-, and molecular-level insights at global and regional scales of ex vivo lungs during cross-circulation, which informed therapeutic management and interventions to recover donor lungs. Mesenchymal stromal cells and lung organoids were delivered bronchoscopically and transpleurally, tracked non-invasively during cross-circulation, and observed to localize within the parenchyma.

CONCLUSIONS

Application of a theranostic methodology during cross-circulation enabled real-time ex vivo lung assessment and rehabilitation across a variety of lung injuries to help increase clinical utilization of donor lungs in the future.

FUNDING

NIH (P41 EB027062, R01HL120046, U01HL134760), CFF (VUNJAK23XX0).

Low-Volume Ex Situ Lung Perfusion System for Single Lung Application in a Small Animal Model Enables Optimal Compliance With "Reduction" in 3R Principles of Animal Research

Ex situ lung perfusion (ESLP) is used for organ reconditioning, repair, and re-evaluation prior to transplantation. Since valid preclinical animal models are required for translationally relevant studies, we developed a 17 mL low-volume ESLP for double- and single-lung application that enables cost-effective optimal compliance "reduction" of the 3R principles of animal research. In single-lung mode, ten Fischer344 and Lewis rat lungs were subjected to ESLP and static cold storage using STEEN or PerfadexPlus. Key perfusion parameters, thermal lung imaging, blood gas analysis (BGA), colloid oncotic pressure (COP), lung weight gain, histological work-up, and cytokine analysis were performed. Significant differences between perfusion solutions but not between the rat strains were detected. Most relevant perfusion parameters confirmed valid ESLP with homogeneous lung perfusion, evidenced by uniform lung surface temperature. BGA showed temperature-dependent metabolic activities with differences depending on perfusion solution composition. COP is not decisive for pulmonary oedema and associated weight gain, but possibly rather observed chemokine profile and dextran sensitivity of rats. Histological examination confirmed intact lung architecture without infarcts or hemorrhages due to optimal organ procurement and single-lung application protocol using our in-house-designed ESLP system.

Technique for xenogeneic cross-circulation to support human donor lungs ex vivo

BACKGROUND

Xenogeneic cross-circulation (XC) is an experimental method for ex vivo organ support and recovery that could expand the pool of donor lungs suitable for transplantation. The objective of this study was to establish and validate a standardized, reproducible, and broadly applicable technique for performing xenogeneic XC to support and recover injured human donor lungs ex vivo.

METHODS

Human donor lungs (n = 9) declined for transplantation were procured, cannulated, and subjected to 24 hours of xenogeneic XC with anesthetized xeno-support swine (Yorkshire/Landrace) treated with standard immunosuppression (methylprednisolone, mycophenolate mofetil, tacrolimus) and complement-depleting cobra venom factor. Standard lung-protective perfusion and ventilation strategies, including periodic lung recruitment maneuvers, were used throughout xenogeneic XC. Every 6 hours, ex vivo donor lung function (gas exchange, compliance, airway pressures, pulmonary vascular dynamics, lung weight) was evaluated. At the experimental endpoint, comprehensive assessments of the lungs were performed by bronchoscopy, histology, and electron microscopy. Student's t-test and 1-way analysis of variance with Dunnett's post-hoc test was performed, and p < 0.05 was considered significant.

RESULTS

After 24 hours of xenogeneic XC, gas exchange (PaO2/FiO2) increased by 158% (endpoint: 364 ± 142 mm Hg; p = 0.06), and dynamic compliance increased by 127% (endpoint: 46 ± 20 ml/cmH₂O; p = 0.04). Airway pressures, pulmonary vascular pressures, and lung weight remained stable (p > 0.05) and within normal ranges. Over 24 hours of xenogeneic XC, gross and microscopic lung architecture were preserved: airway bronchoscopy and parenchymal histomorphology appeared normal, with intact blood-gas barrier.

CONCLUSIONS

Xenogeneic cross-circulation is a robust method for ex vivo support, evaluation, and improvement of injured human donor lungs declined for transplantation.

Emerging Imaging Modalities for Functional Assessment of Donor Lungs Ex Vivo

The severe shortage of functional donor lungs that can be offered to recipients has been a major challenge in lung transplantation. Innovative ex vivo lung perfusion (EVLP) and tissue engineering methodologies are now being developed to repair damaged donor lungs that are deemed unsuitable for transplantation. To assess the efficacy of donor lung reconditioning methods intended to rehabilitate rejected donor lungs, monitoring of lung function with improved spatiotemporal resolution is needed. Recent developments in live imaging are enabling non-destructive, direct, and longitudinal modalities for assessing local tissue and whole lung functions. In this review, we describe how emerging live imaging modalities can be coupled with lung tissue engineering approaches to promote functional recovery of ex vivo donor lungs.

Real-time Lung Weight Measurement During Cellular Ex Vivo Lung Perfusion: An Early Predictor of Transplant Suitability

BACKGROUND

Increased extravascular lung water during ex vivo lung perfusion (EVLP) is associated with ischemia reperfusion injury and poor pulmonary function. A non-invasive technique for evaluating extravascular lung water during EVLP is desired to assess the transplant suitability of lungs. We investigated real-time lung weight measurements as a reliable method for assessing pulmonary functions in cellular EVLP using a porcine lung model.

METHODS

Fifteen pigs were randomly divided into 3 groups: control (no warm ischemia) or donation after circulatory death groups with 60 or 90 min of warm ischemia (n = 5, each). Real-time lung weight gain was measured by load cells positioned at the bottom of the organ chamber.

RESULTS

Real-time lung weight gain at 2 h was significantly correlated with lung weight gain as measured on a back table ( R  = 0.979, P  < 0.01). Lung weight gain in non-suitable cases (n = 6) was significantly higher than in suitable cases (n = 9) at 40 min (51.6 ± 46.0 versus -8.8 ± 25.7 g; P  < 0.01, cutoff = +12 g, area under the curve = 0.907). Lung weight gain at 40 min was significantly correlated with PaO 2 /FiO 2 , peak inspiratory pressure, shunt ratio, wet/dry ratio, and transplant suitability at 2 h ( P  < 0.05, each). In non-suitable cases, lung weight gain at 66% and 100% of cardiac output was significantly higher than at 33% ( P  < 0.05).

CONCLUSIONS

Real-time lung weight measurement could potentially be an early predictor of pulmonary function in cellular EVLP.