Peripheral blood monocytes as a therapeutic target for marrow stromal cells in stroke patients

Interesting, 20 years of animal research showing positive results, but with NO STROKE LEADERSHIP we never ever seem to have gotten to human testing. WHAT FUCKING INCOMPETENCY IN ALL OF STROKE!

The latest here:

 

Peripheral blood monocytes as a therapeutic target for marrow stromal cells in stroke patients

Nikunj Satani^1*, Kaushik Parsha¹, Courtney Davis¹, Adrian Gee², Scott D. Olson³, Jaroslaw Aronowski¹ and Sean I. Savitz¹

• ¹Department of Neurology, McGovern Medical School, Institute for Stroke and Cerebrovascular Diseases, The University of Texas Health Science Center at Houston, Houston, TX, United States
• ²Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, United States
• ³Department of Pediatric Surgery, McGovern Medical School at UTHealth, The University of Texas Health Science Center at Houston, Houston, TX, United States

Background: Systemic administration of marrow stromal cells (MSCs) leads to the release of a broad range of factors mediating recovery in rodent stroke models. The release of these factors could depend on the various cell types within the peripheral blood as they contact systemically administered MSCs. In this study, we assessed the immunomodulatory interactions of MSCs with peripheral blood derived monocytes (Mϕ) collected from acute stroke patients.

Methods: Peripheral blood from stroke patients was collected at 5–7 days (N = 5) after symptom onset and from age-matched healthy controls (N = 5) using mononuclear cell preparation (CPT) tubes. After processing, plasma and other cellular fractions were removed, and Mϕ were isolated from the mononuclear fraction using CD14 microbeads. Mϕ were then either cultured alone or co-cultured with MSCs in a trans-well cell-culture system. Secretomes were analyzed after 24 h of co-cultures using a MAGPIX reader.

Results: Our results show that there is a higher release of IFN-γ and IL-10 from monocytes isolated from peripheral blood at day 5–7 after stroke compared with monocytes from healthy controls. In trans-well co-cultures of MSCs and monocytes isolated from stroke patients, we found statistically significant increased levels of IL-4 and MCP-1, and decreased levels of IL-6, IL-1β, and TNF-α. Addition of MSCs to monocytes increased the secretions of Fractalkine, IL-6, and MCP-1, while the secretions of TNF-α decreased, as compared to the secretions from monocytes alone. When MSCs were added to monocytes from stroke patients, they decreased the levels of IL-1β, and increased the levels of IL-10 significantly more as compared to when they were added to monocytes from control patients.

Conclusion: The systemic circulation of stroke patients may differentially interact with MSCs to release soluble factors integral to their paracrine mechanisms of benefit. Our study finds that the effect of MSCs on Mϕ is different on those derived from stroke patients blood as compared to healthy controls. These findings suggest immunomodulation of peripheral immune cells as a therapeutic target for MSCs in patients with acute stroke.

Discussion

More than 20 years of research indicates that intravenously delivered MSCs confers benefit in animal stroke models but MSCs do not enter into the brain but remain in peripheral tissues (4, 36–38). MSCs release multiple bioactive factors, such as cytokines and MVs, which may contribute to the underlying beneficial effects in stroke and other disease models (39–42). Acute stroke induces an initial state of systemic inflammation characterized by an increase in the levels of circulating pro-inflammatory immune cells. The cellular components of peripheral blood are therefore potential targets of how MSCs modulate the immune response to injury. For example, the interaction MSCs with monocytes in the peripheral circulation may play an important role in the downstream effects of MSCs. A previous study has already shown that monocytes are major players in prognosis and risk of infection after stroke (43). The study also showed that the total number of monocytes in circulation increase around day 2 after stroke onset, but reach highest number around day 7 after stroke onset. Hence, we decided to study the interaction of MSCs with peripheral monocytes derived from stroke patients at day 5–7 after stroke onset.

 

Introduction

Mesenchymal stromal cells (MSCs) have shown promising results in preclinical studies for their therapeutic effects after ischemic stroke (1). Multiple clinical trials are examining the safety and potential efficacy of MSCs in stroke patients (2, 3). A comprehensive meta-analysis and systematic review on all the preclinical studies over the past 20 years shows that intravenous delivery of MSCs leads to functional recovery after stroke (4). There has been accumulating evidence which suggests that MSCs predominantly exert their beneficial influence via paracrine and immunomodulatory mechanisms (5). MSCs release cytokines and growth factors capable of modulating the behavior of a broad number of target cells (immunocytes, microglia, neurons etc) (6–9), resulting in immunomodulation, decreased apoptosis, increased angiogenesis, synaptogenesis, and endogenous neural stem cell activation (10–12). Immune cells such as T and B lymphocytes, monocytes (Mφ), dendritic cells have been shown to be targets for MSC derived factors (13, 14). Membrane vesicles/microparticles (MVs) are released from MSCs and are considered to play a role in intercellular communication (15–17). Cargo carried by MVs is instrumental in modulating target cell responses (18, 19).

MSCs express TLR (Toll-like Receptors) family of receptors, which may confer upon them, an ability to respond to the local microenvironment, which influences the MSC response (20–22). Recent in vitro studies report that pre-conditioning MSCs with inflammatory factors increases the release of mechanistically relevant bioactive factors and enhances their efficacy (23–25). Upon systemic administration, peripheral blood is the first environment encountered by MSCs where they invariably interact with the various immune cell components of peripheral blood, including monocytes. In the immediate timing after the ischemic stroke event, there is an induction of a peripheral inflammatory response evidenced by an increase in peripheral pro-inflammatory cells and cytokines (26, 27). Blood-derived monocytes (Mφ) have been shown to play a pivotal role in inflammation, both at the onset of stroke, as well as to aggravate the stroke lesions (28, 29). In addition, circulating monocytes have the potential of differentiating into many different types of cells including macrophages, given the right conditions (30). It has been shown that ischemic stroke differentially regulates monocyte subsets, which directly affect ischemic stroke pathology and could affect stroke outcomes (28).

The aim of this study, therefore, was to investigate the effects of exposing MSCs to peripheral blood derived monocytes from stroke patients, as measured by the release of cytokines. Since the interaction between MSCs and circulating monocytes in stroke patients may be an important aspect of MSC induced immune modulation (31), we studied the effects of co-culturing monocytes, isolated from healthy controls and stroke patients, and MSCs, on the cytokine release profiles from MSCs. We also observed the percentage change between secretome release from co-cultures of MSCs and monocytes vs. that from monocytes alone.

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