Developing novel acellular and anti-inflammatory therapies for haemorrhagic stroke

Abstract

Stroke is a deadly and debilitating condition, with 1.2 million survivors in the UK of which one third have long term disabilities. Intracerebral haemorrhage (ICH) is responsible for 10-15% of strokes and currently there are no regenerative or protective biologic or pharmaceutical agents licenced for use, highlighting a significant unmet need. Following ICH, a neuroinflammatory response leads to high levels of inflammatory cytokines at the haemorrhage site, recruitment of leukocytes, and damage to local tissue by oxidative stress and toxicity of blood products. Stem cell therapy has shown promise in preclinical stroke models, reducing behavioural deficits and lesion volumes. It is proposed that paracrine effects of cell therapy may be responsible for therapeutic effects observed, causing the secretome or conditioned medium (CM) of mesenchymal stem cells (MSCs) to be investigated in more detail as a potential acellular therapy. Previous work in our lab has demonstrated therapeutic efficacy of MSC-CM in ischaemic stroke models, using interleukin-1a primed MSCs to produce primed conditioned medium (aCM). Here, a full in vitro characterisation of the aCM, found it to contain high levels of both pro- and anti-inflammatory cytokines, and chemokines implicated in stroke pathophysiology. In vitro assays demonstrated an anti-inflammatory and wound healing effect of aCM on microglia and endothelial cells in culture. Given these promising in vitro results and previous work in ischaemic stroke models, we hypothesised that aCM may have therapeutic efficacy in ICH. As such, we characterised a rat model of ICH and administered the aCM at 24 hours post-ICH using multiple routes of administration. aCM was found to be safe with no effects on behavioural outcomes, injury volumes, gross brain morphology, and Iba1+ cell distribution. The lack of efficacy is possibly due to timing of treatment, which may be informed by further interrogation of the model and the phases of neuroinflammation and cell recruitment to the injury site. A further study was performed using interleukin-1 receptor antagonist (IL-1Ra), comparing single and multiple doses in the first preclinical study to administer Il-1Ra in an ICH model, ultimately finding no effects for any outcome measured, though a lower than intended dose was administered. Alongside the neutral treatment effects, we discovered significant changes in brain microarchitecture using advanced magnetic resonance imaging (MRI) which have significant implications for the uses of MRI to monitor neuroinflammation and responses to ICH treatments. Future work should further explore the optimal timing of anti-inflammatory and immunomodulatory treatments and consider other methods of enhancing cell therapy efficacy.

Date of Award	1 Aug 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Alberto Saiani (Supervisor), Stuart Allan (Supervisor), Catherine Lawrence (Supervisor) & Emmanuel Pinteaux (Supervisor)