Faculty Bibliography

Cell-based therapy has demonstrated safety and efficacy in experimental animal models of stroke, as well as safety in stroke patients. However, various questions remain regarding the therapeutic window, dosage, route of administration, and the most appropriate cell type and source, as well as mechanisms of action and immune-modulation to optimize treatment based on stem cell therapy. Various delivery routes have been used in experimental stroke models, including intracerebral, intraventricular, subarachnoid, intra-arterial, intraperitoneal, intravenous, and intranasal routes. From a clinical point of view, it is necessary to demonstrate which is the most feasible, safest, and most effective for use with stroke patients. Therefore, further experimental studies concerning the safety, efficacy, and mechanisms of action involved in these therapeutic effects are required to determine their optimal clinical use.

Ultrasound-targeted microbubble destruction (UTMD) has been shown to be a promising tool to deliver proteins to select body areas. This study aimed to analyze whether UTMD was able to deliver brain-derived neurotrophic factor (BDNF) to the brain, enhancing functional recovery and white matter repair, in an animal model of subcortical stroke induced by endothelin (ET)-1. UTMD was used to deliver BDNF to the brain 24 h after stroke. This technique was shown to be safe, given there were no cases of hemorrhagic transformation or blood brain barrier (BBB) leakage. UTMD treatment was associated with increased brain BDNF levels at 4 h after administration. Targeted ultrasound delivery of BDNF improved functional recovery associated with fiber tract connectivity restoration, increasing oligodendrocyte markers and remyelination compared to BDNF alone administration in an experimental animal model of white matter injury.

INTRODUCTION/BACKGROUND:Despite its high incidence, nerve fiber (axon and myelin) damage after cerebral infarct has not yet been extensively investigated. The aim of this study was to investigate white matter repair after adipose-derived mesenchymal stem cell (ADMSC) administration in an experimental model of subcortical stroke. Furthermore, we aimed to analyze the ADMSC secretome and whether this could be implicated in this repair function. METHODS:An animal model of subcortical ischemic stroke with white matter affectation was induced in rats by injection of endothelin-1. At 24 hours, 2 × 10(6) ADMSC were administered intravenously to the treatment group. Functional evaluation, lesion size, fiber tract integrity, cell death, proliferation, white matter repair markers (Olig-2, NF, and MBP) and NogoA were all studied after sacrifice (7 days and 28 days). ADMSC migration and implantation in the brain as well as proteomics analysis and functions of the secretome were also analyzed. RESULTS:Neither ADMSC migration nor implantation to the brain was observed after ADMSC administration. In contrast, ADMSC implantation was detected in peripheral organs. The treatment group showed a smaller functional deficit, smaller lesion area, less cell death, more oligodendrocyte proliferation, more white matter connectivity and higher amounts of myelin formation. The treated animals also showed higher levels of white matter-associated markers in the injured area than the control group. Proteomics analysis of the ADMSC secretome identified 2,416 proteins, not all of them previously described to be involved in brain plasticity. CONCLUSIONS:White matter integrity in subcortical stroke is in part restored by ADMSC treatment; this is mediated by repair molecular factors implicated in axonal sprouting, remyelination and oligodendrogenesis. These findings are associated with improved functional recovery after stroke.

INTRODUCTION/BACKGROUND:Based on the positive results observed in experimental animal models, adipose tissue-derived mesenchymal stem cells (AD-MSCs) constitute a promising therapy for stroke treatment. However, several aspects need to be clarified to identify the optimal conditions for successful clinical translation. AREAS COVERED/METHODS:This review focuses on AD-MSC treatment for ischemic and hemorrhagic stroke in experimental animal models. In addition, we will explore the optimization of treatment conditions including AD-MSC production, administration routes and therapeutic windows for their appropriate use in patients. Finally we will provide an update on clinical trials on this therapy. EXPERT OPINION/CONCLUSIONS:Compared with other cell types, AD-MSCs have been less investigated in stroke studies. Currently, experimental animal models have shown safety and efficacy with this treatment after stroke. Due to several advantages of AD-MSCs, such as their abundance and accessibility, they can be considered a promising strategy for use in patients. However, many questions are still to be resolved regarding their mechanisms of action, immune system modulation and the effects of AD-MSCs on all components of the brain that may be affected after ischemic and hemorrhagic strokes.

Angiotensin type 1 receptor blockers (ARBs) have induced improved functional recovery and reduced infarct volume in experimental animal models of stroke. Clinical data have indicated a positive correlation between prestroke treatment with ARBs and reduced stroke severity and better outcomes; however, the mechanisms of these beneficial effects are not yet well understood. This study compares the protective and possible reparative effects of continuous oral treatment with olmesartan (OLM) with OLM pretreatment and withdrawal after permanent middle cerebral artery occlusion (pMCAO) in rats. Fifty-two Sprague-Dawley rats were randomly assigned to five groups: MCAO(-/OLM) (OLM 10 mg/kg/day for 14 days after infarct), MCAO(OLM/OLM) (OLM 10 mg/kg/day for 7 days before and 14 days after infarct), MCAO(OLM/-) (OLM 10 mg/kg/day for 7 days before infarct), sham, and control. We analyzed functional recovery; lesion size; cell death; expression of the pro-oxidant enzyme NADPH oxidase 4 (NOX-4); isolectin-B4; and repair markers such as glial fibrillary acidic protein, vascular endothelial growth factor (VEGF), and brain-derived neurotrophic factor (BDNF). All of the OLM-treated groups showed significantly better functional scores and reduced infarct sizes and cell death compared with the control group 14 days after pMCAO. Levels of NOX-4, VEGF, and BDNF were significantly lower in the brains of the MCAO(OLM/OLM) and sham groups compared with the other groups. OLM treatment improved functional recovery and reduced lesion size and cell death after cerebral ischemia. Only the continuous administration of OLM before and after stroke reduced oxidative stress levels, with better tissue preservation, without triggering brain repair marker activation.

BACKGROUND:Rat adipose tissue-derived-mesenchymal stem cells (rAD-MSCs) have proven to be safe in experimental animal models of stroke. However, in order to use human AD-MSCs (hAD-MSCs) as a treatment for stroke patients, a proof of concept is needed. We analyzed whether the xenogeneic hAD-MSCs were as safe and effective as allogeneic rAD-MSCs in permanent Middle Cerebral Artery Occlusion (pMCAO) in rats. METHODS:Sprague-Dawley rats were randomly divided into three groups, which were intravenously injected with xenogeneic hAD-MSCs (2 × 10(6)), allogeneic rAD-MSCs (2 × 10(6)) or saline (control) at 30 min after pMCAO. Behavior, cell implantation, lesion size and cell death were evaluated. Brain markers such as GFAP (glial fibrillary acid protein), VEGF (vascular endothelial growth factor) and SYP (synaptophysin) and tumor formation were analyzed. RESULTS:Compared to controls, recovery was significantly better at 24 h and continued to be so at 14 d after IV administration of either hAD-MSCs or rAD-MSCs. No reduction in lesion size or migration/implantation of cells in the damaged brain were observed in the treatment groups. Nevertheless, cell death was significantly reduced with respect to the control group in both treatment groups. VEGF and SYP levels were significantly higher, while those of GFAP were lower in the treated groups. At three months, there was no tumor formation. CONCLUSIONS:hAD-MSCs and rAD-MSCs were safe and without side effects or tumor formation. Both treatment groups showed equal efficacy in terms of functional recovery and decreased ischemic brain damage (cell death and glial scarring) and resulted in higher angiogenesis and synaptogenesis marker levels.

BACKGROUND AND PURPOSE/OBJECTIVE:Translational research is beginning to reveal the importance of trophic factors as a therapy for cellular brain repair. The purpose of this study was to analyze whether brain-derived neurotrophic factor (BDNF) administration could mediate oligodendrogenesis and remyelination after white matter injury in subcortical stroke. METHODS:Ischemia was induced in rats by injection of endothelin-1. At 24 hours, 0.4 μg/kg of BDNF or saline was intravenously administered to the treatment and control groups, respectively. Functional evaluation, MRI, and fiber tract integrity on tractography images were analyzed. Proliferation (KI-67) and white matter repair markers (A2B5, 2',3'-cyclic-nucleotide 3'-phosphodiesterase [CNPase], adenomatous polyposis coli [APC], platelet-derived growth factor receptor alpha [PDGFR-α], oligodendrocyte marker O4 [O4], oligodendrocyte transcription factor [Olig-2], and myelin basic protein [MBP]) were analyzed at 7 and 28 days. RESULTS:The BDNF-treated animals showed less functional deficit at 28 days after treatment than the controls (P<0.05). Although T2-MRI did not show differences in lesion size at 7 and 28 days between groups, diffusion tensor imaging tractography analysis revealed significantly better tract connectivity at 28 days in the BDNF group than in the controls (P<0.05). Increased proliferation of oligodendrocyte progenitors was observed in treated animals at 7 days (P<0.05). Finally, the levels of white matter repair markers (A2B5, CNPase, and O4 at 7 days; Olig-2 and MBP at 28 days) were higher in the BDNF group than in the controls (P<0.05). CONCLUSIONS:BDNF administration exerted better functional outcome, oligodendrogenesis, remyelination, and fiber connectivity than controls in rats subjected to subcortical damage in ischemic stroke.

BACKGROUND:After acute ischemia, the tissue that is at risk of infarction can be detected by perfusion-weighted imaging/diffusion-weighted imaging (PWI/DWI) mismatch but the time that is needed to process PWI limits its use. As DWI is highly sensitive to acute ischemic tissue damage, we hypothesized that different ADC patterns represent areas with a different potential for recovery. METHODS:In a model of permanent middle cerebral artery occlusion (pMCAO), Sprague-Dawley rats were randomly distributed to sham surgery and pMCAO. We further separated the pMCAO group according to intralesional ADC pattern (homogeneous or heterogeneous). At 24 h after ischemia induction, we analyzed lesion size, functional outcome, cell death expression, and brain protection markers including ROS enzyme NOX-4. MRI included DWI (ADC maps), DTI (tractography), and PWI (CBF, CBV and MTT). RESULTS:The lesion size was similar in pMCAO rats. Animals with a heterogeneous pattern in ADC maps showed better functional outcome in Rotarod test (p = 0.032), less expression of cell death (p = 0.014) and NOX-4 (p = 0.0063), higher intralesional CBF (p = 0.0026) and larger PWI/DWI mismatch (p = 0.007). CONCLUSIONS:In a rodent model for ischemic stroke, intralesional heterogeneity in ADC maps was related to better functional outcome in lesions of similar size and interval after pMCAO. DWI ADC maps may assist in the early identification of ischemic tissue with an increased potential for recovery as higher expression of acute protection markers, lower expression of cell death, increased PWI/DWI mismatch, and higher intralesional CBF were present in animals with a heterogeneous ADC pattern.

INTRODUCTION/BACKGROUND:Stroke is a major worldwide cause of death and disability. Currently, intravenous thrombolysis and reperfusion therapies, but not the so-called neuroprotectant drugs, have been shown to be effective for acute ischemic stroke. Thus, new strategies to promote brain plasticity are necessary. Stem cell administration is an attractive future therapeutic approach. AREAS COVERED/METHODS:Brain protection and repair mechanisms are activated after stroke. This article is focused on the capacity of stem cell-based therapy to enhance this postinfarct brain plasticity and recovery. Future therapeutic considerations and prospects for stroke are discussed. EXPERT OPINION/CONCLUSIONS:Although cell therapy is promising in stroke treatment, mechanisms of action need to be characterized in detail. Further, the different mechanisms of axonal plasticity and remodeling involucrated in brain repair, not only in the gray but also in white matter, must be investigated through noninvasive techniques, and a multidisciplinary approach is fundamental in this.

More recently, growing interests have brought cell therapy to the forefront of promising new approaches towards efficacious treatment for stroke. Of all cell-types, adipose tissue-derived mesenchymal stem cells (AD-MSC) are considered good candidates for stroke treatment because of their abundance and easy harvesting without invasive surgery from healthy donors. A wide number of experimental studies have demonstrated the potential of AD-MSC administration for improving functional deficits and have led to the first clinical trials in stroke patients. Trophic factor release and paracrine interactions, transdifferentiation potential, and immunomodulatory effects have all been cited as the main functional mechanisms involved in AD-MSC therapy. These properties make AD-MSC therapy of special interest in fomenting the enhancement of natural brain repair mechanisms such as neurogenesis, gliagenesis, oligodendrogenesis, axonal sprouting, nerve repair, and angiogenesis. This review will focus on studies showing promising results of AD-MSC in stroke treatment.