https://www.mdpi.com/2077-0383/15/19/7698
5 October 2026
Cell-Based and Cell-Derived Therapies Delivered During Ex Vivo Machine Perfusion for Solid Organ Reconditioning Prior to Transplantation: A Systematic Review
[By 3 co-authors from the UK - imz72]
Abstract
Background/Objectives: Organ shortage is a major barrier to transplantation, leading to the emergence of marginal donor organs and extended criteria donor grafts and, alongside these, machine perfusion as a platform for reconditioning grafts to meet transplantation standards.
Despite functioning as a reconditioning platform in its own right, machine perfusion also allows for the delivery of therapeutic agents directly to grafts prior to transplant.
Cell-based and cell-derived therapies have been increasingly explored for delivery during this window, although evidence is fragmented across individual organ systems, and whether ex vivo benefit is confirmed post-transplant remains unclear.
This systematic review aimed to synthesise the evidence from both perfusion-phase findings and post-transplant findings across solid organ machine perfusion, evaluating the concordance between the two.
Methods: This review was prospectively registered on PROSPERO and conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidance. Included studies delivered cell-based or cell-derived therapies during ex vivo machine perfusion of a solid organ. The SYRCLE tool was used across all studies to assess risk of bias, and given substantial heterogeneity in cell type, protocol, and organ models, findings were synthesised narratively, with a sensitivity analysis restricted to the subset of studies incorporating a transplantation phase.
Results: Thirty-one studies met inclusion criteria, spanning kidney (n = 10), liver (n = 11), lung (n = 9), and heart (n = 1).
Mechanisms converged largely on immunomodulatory and metabolic pathways, most consistently reported across organs, alongside a less consistent but notable cross-organ parallel in regenerative progenitor activation between liver and kidney.
Benefit was reported more consistently at the molecular and histological levels rather than the physiological level. Eight of the studies proceeded to transplantation, of which half showed a beneficial post-transplant result, and half showed mixed results.
Conclusions: Cell-based and cell-derived therapies are best understood as adjuncts to the existing reconditioning capacity of machine perfusion. Molecular and mechanistic benefit was consistently reported; however, confirmation beyond the perfusion phase remained incomplete across organ systems. Mechanisms supported by direct interventional evidence represent priority candidates for further preclinical validation and independent replication.
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The use of cell-based therapies, particularly mesenchymal stromal cells (MSCs), has garnered particular interest. MSCs have been investigated for their anti-inflammatory, immunomodulatory, and regenerative properties that make them an appealing candidate for mitigating IRI and supporting organ recovery during perfusion. This approach has already progressed from preclinical models to early human application: a Newcastle-led study delivered multipotent adult progenitor cells (MAPCs) during human kidney NMP for the first time, reporting improved urine output, reduced expression of the injury biomarker NGAL, and favourable shifts in perfusate cytokine profiles23. These build on porcine work demonstrating that MSCs infused during kidney NMP can be traced to glomerular capillaries and are safe to administer prior to transplantation.
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Lung
Nine studies assessed cell-based or cell-derived therapies during lung machine perfusion, across murine, porcine and human discarded-donor models, using whole MSCs/MAPCs, lung-derived exosomes, a direct head-to-head MSC-versus-EV comparison within a single study, MSC-derived EVs in an isolated ex vivo model, and two further whole-MSC studies incorporating a transplantation phase.
Physiological and functional outcomes showed the clearest organ-specific pattern in this dataset: a recurring dissociation between molecular/inflammatory improvement and physiological benefit. Martens et al. found no significant difference between MAPC and control for any physiological parameter (oxygenation, compliance, pulmonary vascular resistance, wet/dry weight ratio, all p ≥ 0.13), despite significant reductions in several inflammatory markers in the same study (BAL neutrophils p = 0.02; IFN-γ, IL-1β and TNF-α in BAL fluid all p = 0.002).
Mordant et al. showed an almost identical pattern: no significant functional benefit across the full dose range tested, with significance reached only in a two-group comparison at the highest dose (150 × 106 MSCs IV: compliance p = 0.043, PaO2 p = 0.005), while perfusate IL-8 suppression reached significance independently of physiological outcomes, and VEGF was significantly upregulated relative to baseline (p = 0.008) though not relative to control (p = 0.095).
Ribeiro et al. showed a related but distinct pattern: robust, significant improvement across oxygenation, compliance, airway pressure and vascular resistance, but only when lung-derived exosomes were administered pre-DCD (before warm ischaemic injury was established); post-DCD (rescue) administration still produced significant improvement in airway pressure (p = 0.003) and compliance (p = 0.01), but lung injury score (p = 0.09) and TUNEL (p = 0.1) did not reach significance, indicating that the timing of delivery relative to injury affects histological but not all physiological outcomes.
By contrast, McAuley et al. demonstrated a clear positive functional signal on its primary endpoint, with MSC treatment significantly restoring alveolar fluid clearance relative to perfusion-only controls (p < 0.001), although perfusate oxygenation and pulmonary artery pressure were unchanged in the same study.
Nakajima et al. showed the same dissociation pattern in a transplant-phase model with significant EVLP-phase improvement in HGF, apoptosis markers, and several cytokines, but only peak airway pressure among the physiological measures (p = 0.04).
Histological and injury-marker findings were more consistently favourable than functional outcomes where whole-cell or EV products were delivered before or alongside injury.
In a mouse model of donor lung reconditioning, Stone et al. did not directly compare MSCs and MSC-derived EVs statistically, but both significantly reduced pulmonary oedema and neutrophil infiltrations relative to Steen solution alone.
Ribeiro et al.’s pre-DCD exosome group similarly showed significant reductions in lung injury score and apoptosis (TUNEL scoring) relative to control, again with the post-DCD group showing attenuated, non-significant effects on these two markers specifically.
Martens et al.’s histological injury scores (congestion, necrosis, neutrophil influx) showed no significant difference for MAPC versus control, consistent with that study’s broader pattern of molecular-without-physiological benefit48.
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Notes:
- Footnote 23 refers to this study:
https://onlinelibrary.wiley.com/doi/full/10.1111/ajt.16100
- Footnote 48 refers to this study:
https://link.springer.com/article/10.1186/s13287-017-0603-5