Viability of Mesenchymal Stem Cells in an Ex Vivo Circulation System

Influence of administration of mesenchymal stromal cell on pediatric oxygenator performance and inflammatory response

Objective

Mesenchymal stromal cells have important immunomodulatory and neuroprotective properties. The aim of this study was to evaluate the feasibility of mesenchymal stromal cell administration into a cardiopulmonary bypass (CPB) circuit, including a pediatric oxygenator, and to assess the immunomodulatory response of the circulating blood prime.

Methods

A bypass circuit with a pediatric oxygenator, including integral filter was primed with bank whole blood. Normal saline (control) or 120 × 10⁶ mesenchymal stromal cells were injected into the venous reservoir after 80 minutes of perfusion. To assess oxygenator function, immune reaction, and cytokine/chemokine levels, the ex vivo circulation was maintained for 300 minutes after administration.

Results

There were no differences in flow rate, trans-oxygenator pressure gradient, blood oxygen, and carbon dioxide levels between control and cell delivery groups. No adhesion of mesenchymal stromal cells was observed on the filter mesh by scanning electron microscopy. Lymphocyte surface marker assay found no difference in the number of B cells, T cells, or natural killer cells between the 2 groups, indicating no immunogenicity of allogeneic mesenchymal stromal cells under ex vivo CPB conditions. CPB significantly changed the level of interleukin (IL) 4, IL-6, IL-8, IP-10, macrophage colony stimulating factor, macrophage inflammatory protein-1β, monocyte chemoattractant protein-1, and IL-1α over time. IL-6 level was significantly increased after cell administration.

Conclusions

The administration of mesenchymal stromal cells does not interfere with oxygenator function. Allogeneic mesenchymal stromal cells show no immunogenicity, and increase plasma IL-6 level during ex vivo circulation. Further investigation is necessary to determine the effect of mesenchymal stromal cell delivery through CPB during pediatric cardiac surgery.

Venovenous ECMO treatment, outcomes, and complications in adults according to large case series: A systematic review

Background:

Venovenous extracorporeal membrane oxygenation (VV ECMO) has gained popularity for the treatment of refractory respiratory failure during and after the 2009 influenza pandemic, and still represents a precious therapeutic resource for severe novel coronavirus 2019 infection. However, most of the published studies are small case series, and only two randomized trials exist in literature.

Aim:

Aim of this systematic review is to describe trends in VV ECMO treatment outcomes according to large studies only.

Methods:

We searched and included studies with more than 100 VV ECMO cases dated up to August 1st, 2019.

Results:

Thirty-three studies published in the period 2011–2019 met inclusion criteria, for a total of 12,860 patients (age 46.3 ± 17.4 years). ARDS was mainly by pneumonia, in 3126 (37%) cases; further 401(7%) patients had H1N1 Influenza A infection. Cannulation-related complications occurred in 502 (7%) cases. Weighted mean (95% confidence interval) of VV ECMO duration was 8.9 (8.7–9.1) days, and ICU stay was 23.6 (22.4–24.8) days. Mortality at the longest follow up available was 40%. Data collection in 70% of the studies had a duration of >5 years.

Conclusion:

This study reveals the characteristics of large case VV ECMO studies.

Combined Mesenchymal Stromal Cell Therapy and Extracorporeal Membrane Oxygenation in Acute Respiratory Distress Syndrome. A Randomized Controlled Trial in Sheep

Rationale: Mesenchymal stromal cell (MSC) therapy is a promising intervention for acute respiratory distress syndrome (ARDS), although trials to date have not investigated its use alongside extracorporeal membrane oxygenation (ECMO). Recent preclinical studies have suggested that combining these interventions may attenuate the efficacy of ECMO.Objectives: To determine the safety and efficacy of MSC therapy in a model of ARDS and ECMO.Methods: ARDS was induced in 14 sheep, after which they were established on venovenous ECMO. Subsequently, they received either endobronchial induced pluripotent stem cell-derived human MSCs (hMSCs) (n = 7) or cell-free carrier vehicle (vehicle control; n = 7). During ECMO, a low Vt ventilation strategy was employed in addition to protocolized hemodynamic support. Animals were monitored and supported for 24 hours. Lung tissue, bronchoalveolar fluid, and plasma were analyzed, in addition to continuous respiratory and hemodynamic monitoring.Measurements and Main Results: The administration of hMSCs did not improve oxygenation (Pa_O2/Fi_O2 mean difference = -146 mm Hg; P = 0.076) or pulmonary function. However, histological evidence of lung injury (lung injury score mean difference = -0.07; P = 0.04) and BAL IL-8 were reduced. In addition, hMSC-treated animals had a significantly lower cumulative requirement for vasopressor. Despite endobronchial administration, animals treated with hMSCs had a significant elevation in transmembrane oxygenator pressure gradients. This was accompanied by more pulmonary artery thromboses and adherent hMSCs found on explanted oxygenator fibers.Conclusions: Endobronchial hMSC therapy in an ovine model of ARDS and ECMO can impair membrane oxygenator function and does not improve oxygenation. These data do not recommend the safe use of hMSCs during venovenous ECMO.

Increased mobilization of mesenchymal stem cells in patients with acute respiratory distress syndrome undergoing extracorporeal membrane oxygenation

Background

The acute respiratory distress syndrome (ARDS) is characterized by pulmonary epithelial and endothelial barrier dysfunction and injury. In severe forms of ARDS, extracorporeal membrane oxygenation (ECMO) is often the last option for life support. Endothelial progenitor (EPC) and mesenchymal stem cells (MSC) can regenerate damaged endothelium and thereby improve pulmonary endothelial dysfunction. However, we still lack sufficient knowledge about how ECMO might affect EPC- and MSC-mediated regenerative pathways in ARDS. Therefore, we investigated if ECMO impacts EPC and MSC numbers in ARDS patients.

Methods

Peripheral blood mononuclear cells from ARDS patients undergoing ECMO (n = 16) and without ECMO support (n = 12) and from healthy volunteers (n = 16) were isolated. The number and presence of circulating EPC and MSC was detected by flow cytometry. Serum concentrations of vascular endothelial growth factor (VEGF) and angiopoietin 2 (Ang2) were determined.

Results

In the ECMO group, MSC subpopulations were higher by 71% compared to the non-ECMO group. Numbers of circulating EPC were not significantly altered. During ECMO, VEGF and Ang2 serum levels remained unchanged compared to the non-ECMO group (p = 0.16), but Ang2 serum levels in non-survivors of ARDS were significantly increased by 100% (p = 0.02) compared to survivors.

Conclusions

ECMO support in ARDS is specifically associated with an increased number of circulating MSC, most likely due to enhanced mobilization, but not with a higher numbers of EPC or serum concentrations of VEGF and Ang2.