Can combined cellular and 11beta hydroxysteroid dehydrogenase type 1 gene therapy attenuate inflammation in Acute Respiratory Distress Syndrome?

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Mahida, Rahul Yashwantsinh ORCID: https://orcid.org/0000-0003-1100-8684 (2020). Can combined cellular and 11beta hydroxysteroid dehydrogenase type 1 gene therapy attenuate inflammation in Acute Respiratory Distress Syndrome? University of Birmingham. Ph.D.

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Abstract

Acute Respiratory Distress Syndrome (ARDS) is an inflammatory disorder of the lungs, for which there is no effective pharmacotherapy. 11β hydroxysteroid dehydrogenase type 1 (HSD-1) acts as a reductase to convert cortisone into cortisol, and is normally expressed by alveolar macrophages (AMs). A previous study has shown evidence of impaired alveolar HSD-1 reductase activity and relative alveolar cortisol deficiency in ARDS patients. Mesenchymal stem cells (MSCs) administration has been effective at attenuating inflammation in pre-clinical models of lung injury.

This thesis reports a series of investigations into the role of AM dysfunction in ARDS pathogenesis, and whether use of transgenic MSCs (tMSCs) expressing HSD-1 offers a potential therapy for ARDS by enhancing AM efferocytosis. It also investigates the impact of expansion on the ability of MSCs to attenuate lung injury.

Expansion of MSCs for 1 month had no effect on the ability of MSCs to promote alveolar epithelial wound healing, however the ability of MSCs to stimulate IL-10 release from macrophages was impaired. Lentiviral transfection was used to create HSD-1 tMSCs, which expressed functional HSD-1.

Development of sepsis-related ARDS is associated with decreased AM HSD-1 reductase activity and efferocytosis, which contributes to the increased alveolar neutrophil apoptosis, alveolar inflammation and mortality observed. Dysregulated AM function contributes to ARDS pathogenesis, therefore upregulation of AM efferocytosis may offer a therapeutic strategy for ARDS patients.

ARDS broncho-alveolar lavage fluid (BALF) treatment of healthy AMs in vitro can decrease rac1 gene expression and impair efferocytosis, thereby replicating the AM functional defect observed in ARDS patients. Following ARDS BALF treatment, AMs increase expression of pro-efferocytosis receptors CD206 and MerTK, as an unsuccessful compensatory mechanism to restore normal efferocytosis.

HSD-1 tMSC co-culture was unsuccessful at restoring AM efferocytosis both ex vivo and in an in vitro model of ARDS, indicating that HSD-1 independent mechanisms contribute to impaired AM efferocytosis in ARDS. HSD-1 tMSC therapy reduced cellular inflammation in a model of murine peritonitis, but also caused bacterial overgrowth due to immunosuppression, indicating that HSD-1 tMSC therapy is unlikely to have utility in patients with sepsis-related ARDS. However, further studies using multiple low doses of HSD-1 tMSCs in HSD-1 knockout mice in conjunction with antibiotic therapy are required to fully assess the therapeutic potential of HSD-1 tMSCs. Rho-associated protein kinase (ROCK) inhibitor treatment partially restored AM efferocytosis in an in vitro model of ARDS, indicating that targeting of the ROCK pathway may offer therapeutic potential in ARDS patients.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):