FAST-IT: Find A Simple Test - In TIA (transient ischaemic attack): a prospective cohort study to develop a multivariable prediction model for diagnosis of TIA through proteomic discovery and candidate lipid mass spectrometry, neuroimaging and machine learning-study protocol

INTRODUCTION

Transient ischaemic attack (TIA) may be a warning sign of stroke and difficult to differentiate from minor stroke and TIA-mimics. Urgent evaluation and diagnosis is important as treating TIA early can prevent subsequent strokes. Recent improvements in mass spectrometer technology allow quantification of hundreds of plasma proteins and lipids, yielding large datasets that would benefit from different approaches including machine learning. Using plasma protein, lipid and radiological biomarkers, our study will develop predictive algorithms to distinguish TIA from minor stroke (positive control) and TIA-mimics (negative control). Analysis including machine learning employs more sophisticated modelling, allowing non-linear interactions, adapting to datasets and enabling development of multiple specialised test-panels for identification and differentiation.

METHODS AND ANALYSIS

Patients attending the Emergency Department, Stroke Ward or TIA Clinic at the Royal Adelaide Hospital with TIA, minor stroke or TIA-like symptoms will be recruited consecutively by staff-alert for this prospective cohort study. Advanced neuroimaging will be performed for each participant, with images assessed independently by up to three expert neurologists. Venous blood samples will be collected within 48 hours of symptom onset. Plasma proteomic and lipid analysis will use advanced mass spectrometry (MS) techniques. Principal component analysis and hierarchical cluster analysis will be performed using MS software. Output files will be analysed for relative biomarker quantitative differences between the three groups. Differences will be assessed by linear regression, one-way analysis of variance, Kruskal-Wallis H-test, χ² test or Fisher's exact test. Machine learning methods will also be applied including deep learning using neural networks.

ETHICS AND DISSEMINATION

Patients will provide written informed consent to participate in this grant-funded study. The Central Adelaide Local Health Network Human Research Ethics Committee approved this study (HREC/18/CALHN/384; R20180618). Findings will be disseminated through peer-reviewed publication and conferences; data will be managed according to our Data Management Plan (DMP2020-00062).

Delayed Treatment with Human Dental Pulp Stem Cells Accelerates Functional Recovery and Modifies Responses of Peri-Infarct Astrocytes Following Photothrombotic Stroke in Rats

Dental pulp contains multipotent mesenchymal stem cells that improve outcomes when administered early after temporary middle cerebral artery occlusion in rats. To further assess the therapeutic potential of these cells, we tested whether functional recovery following stroke induced by photothrombosis could be modified by a delayed treatment that was initiated after the infarct attained maximal volume. Photothrombosis induces permanent focal ischemia resulting in tissue changes that better reflect key aspects of the many human strokes in which early restoration of blood flow does not occur. Human dental pulp stem cells (approximately 400 × 10³ viable cells) or vehicle were injected into the infarct and adjacent brain tissue of Sprague-Dawley rats at 3 days after the induction of unilateral photothrombotic stroke in the sensorimotor cortex. Forepaw function was tested up to 28 days after stroke. Cellular changes in peri-infarct tissue at 28 days were assessed using immunohistochemistry. Rats treated with the stem cells showed faster recovery compared with vehicle-treated animals in a test of forelimb placing in response to vibrissae stimulation and in first attempt success in a skilled forelimb reaching test. Total success in the skilled reaching test and forepaw use during exploration in a Perspex cylinder were not significantly different between the 2 groups. At 28 days after stroke, rats treated with the stem cells showed decreased immunolabeling for glial fibrillary acidic protein in tissue up to 1 mm from the infarct, suggesting decreased reactive astrogliosis. Synaptophysin, a marker of synapses, and collagen IV, a marker of capillaries, were not significantly altered at this time by the stem-cell treatment. These results indicate that dental pulp stem cells can accelerate recovery without modifying initial infarct formation. Decreases in reactive astrogliosis in peri-infarct tissue could have contributed to the change by promoting adaptive responses in neighboring neurons.

Using Dental Pulp Stem Cells for Stroke Therapy

Stroke is a leading cause of permanent disability world-wide, but aside from rehabilitation, there is currently no clinically-proven pharmaceutical or biological agent to improve neurological disability. Cell-based therapies using stem cells, such as dental pulp stem cells, are a promising alternative for treatment of neurological diseases, including stroke. The ischaemic environment in stroke affects multiple cell populations, thus stem cells, which act through cellular and molecular mechanisms, are promising candidates. The most common stem cell population studied in the neurological setting has been mesenchymal stem cells due to their accessibility. However, it is believed that neural stem cells, the resident stem cell of the adult brain, would be most appropriate for brain repair. Using reprogramming strategies, alternative sources of neural stem and progenitor cells have been explored. We postulate that a cell of closer origin to the neural lineage would be a promising candidate for reprogramming and modification towards a neural stem or progenitor cell. One such candidate population is dental pulp stem cells, which reside in the root canal of teeth. This review will focus on the neural potential of dental pulp stem cells and their investigations in the stroke setting to date, and include an overview on the use of different sources of neural stem cells in preclinical studies and clinical trials of stroke.

Characterization of p75 neurotrophin receptor expression in human dental pulp stem cells

Human adult dental pulp stem cells (DPSC) are a heterogeneous stem cell population, which are able to differentiate down neural, chondrocyte, osteocyte and adipocyte lineages. We studied the expression pattern of p75 neurotrophin receptors (p75NTR), a marker of neural stem cells, within human DPSC populations from eight donors. p75NTR are expressed at low levels (<10%) in DPSC. Importantly, p75(+) DPSC represent higher expression levels of SOX1 (neural precursor cell marker), SOX2 (cell pluripotency marker) and nestin (neural stem cell marker) in comparison to p75(-) DPSC. Our results suggest that p75(+) hDPSC may denote a subpopulation with greater neurogenic potential.

Adult human dental pulp stem cells promote blood-brain barrier permeability through vascular endothelial growth factor-a expression

Stem cell therapy is a promising new treatment option for stroke. Intravascular administration of stem cells is a valid approach as stem cells have been shown to transmigrate the blood-brain barrier. The mechanism that causes this effect has not yet been elucidated. We hypothesized that stem cells would mediate localized discontinuities in the blood-brain barrier, which would allow passage into the brain parenchyma. Here, we demonstrate that adult human dental pulp stem cells express a soluble factor that increases permeability across an in vitro model of the blood-brain barrier. This effect was shown to be the result of vascular endothelial growth factor-a. The effect could be amplified by exposing dental pulp stem cell to stromal-derived factor 1, which stimulates vascular endothelial growth factor-a expression. These findings support the use of dental pulp stem cell in therapy for stroke.

TOOTH (The Open study Of dental pulp stem cell Therapy in Humans): Study protocol for evaluating safety and feasibility of autologous human adult dental pulp stem cell therapy in patients with chronic disability after stroke

RATIONALE

Stroke represents a significant global disease burden. As of 2015, there is no chemical or biological therapy proven to actively enhance neurological recovery during the chronic phase post-stroke. Globally, cell-based therapy in stroke is at the stage of clinical translation and may improve neurological function through various mechanisms such as neural replacement, neuroprotection, angiogenesis, immuno-modulation, and neuroplasticity. Preclinical evidence in a rodent model of middle cerebral artery ischemic stroke as reported in four independent studies indicates improvement in neurobehavioral function with adult human dental pulp stem cell therapy. Human adult dental pulp stem cells present an exciting potential therapeutic option for improving post-stroke disability.

AIMS

TOOTH (The Open study Of dental pulp stem cell Therapy in Humans) will investigate the use of autologous stem cell therapy for stroke survivors with chronic disability, with the following objectives: (a) determine the maximum tolerable dose of autologous dental pulp stem cell therapy; (b) define that dental pulp stem cell therapy at the maximum tolerable dose is safe and feasible in chronic stroke; and (c) estimate the parameters of efficacy required to design a future Phase 2/3 clinical trial.

METHODS AND DESIGN

TOOTH is a Phase 1, open-label, single-blinded clinical trial with a pragmatic design that comprises three stages: Stage 1 will involve the selection of 27 participants with middle cerebral artery ischemic stroke and the commencement of autologous dental pulp stem cell isolation, growth, and testing in sequential cohorts (n = 3). Stage 2 will involve the transplantation of dental pulp stem cell in each cohort of participants with an ascending dose and subsequent observation for a 6-month period for any dental pulp stem cell-related adverse events. Stage 3 will investigate the neurosurgical intervention of the maximum tolerable dose of autologous dental pulp stem cell followed by 9 weeks of intensive task-specific rehabilitation. Advanced magnetic resonance and positron emission tomography neuro-imaging, and clinical assessment will be employed to probe any change afforded by stem cell therapy in combination with rehabilitation.

SAMPLE SIZE ESTIMATES

Nine participants will step-wise progress in Stage 2 to a dose of up to 10 million dental pulp stem cell, employing a cumulative 3 + 3 statistical design with low starting stem cell dose and subsequent dose escalation, assuming that an acceptable probability of dose-limiting complications is between 1 in 6 (17%) and 1 in 3 (33%) of patients. In Stage 3, another 18 participants will receive an intracranial injection with the maximum tolerable dose of dental pulp stem cell.

OUTCOMES

The primary outcomes to be measured are safety and feasibility of intracranial administration of autologous human adult DPSC in patients with chronic stroke and determination of the maximum tolerable dose in human subjects. Secondary outcomes include estimation of the measures of effectiveness required to design a future Phase 2/3 clinical trial.

Transcranial Magnetic Stimulation of Human Adult Stem Cells in the Mammalian Brain

Introduction: The burden of stroke on the community is growing, and therefore, so is the need for a therapy to overcome the disability following stroke. Cellular-based therapies are being actively investigated at a pre-clinical and clinical level. Studies have reported the beneficial effects of exogenous stem cell implantation, however, these benefits are also associated with limited survival of implanted stem cells. This exploratory study investigated the use of transcranial magnetic stimulation (TMS) as a complementary therapy to increase stem cell survival following implantation of human dental pulp stem cells (DPSC) in the rodent cortex.

Methods: Sprague-Dawley rats were anesthetized and injected with 6 × 10⁵ DPSC or control media via an intracranial injection, and then received real TMS (TMS_{0.2 Hz}) or sham TMS (TMS_sham) every 2nd day beginning on day 3 post DPSC injection for 2 weeks. Brain sections were analyzed for the survival, migration and differentiation characteristics of the implanted cells.

Results: In animals treated with DPSC and TMS_{0.2 Hz} there were significantly less implanted DPSC and those that survived remained in the original cerebral hemisphere compared to animals that received TMS_sham. The surviving implanted DPSC in TMS_{0.2 Hz} were also found to express the apoptotic marker Caspase-3.

Conclusions: We suggest that TMS at this intensity may cause an increase in glutamate levels, which promotes an unfavorable environment for stem cell implantation, proliferation and differentiation. It should be noted that only one paradigm of TMS was tested as this was conducted as a exploratory study, and further TMS paradigms should be investigated in the future.

Human adult dental pulp stem cells enhance poststroke functional recovery through non-neural replacement mechanisms

Human adult dental pulp stem cells (DPSCs), derived from third molar teeth, are multipotent and have the capacity to differentiate into neurons under inductive conditions both in vitro and following transplantation into the avian embryo. In this study, we demonstrate that the intracerebral transplantation of human DPSCs 24 hours following focal cerebral ischemia in a rodent model resulted in significant improvement in forelimb sensorimotor function at 4 weeks post-treatment. At this time, 2.3 ± 0.7% of engrafted cells had survived in the poststroke brain and demonstrated targeted migration toward the stroke lesion. In the peri-infarct striatum, transplanted DPSCs differentiated into astrocytes in preference to neurons. Our data suggest that the dominant mechanism of action underlying DPSC treatment that resulted in enhanced functional recovery is unlikely to be due to neural replacement. Functional improvement is more likely to be mediated through DPSC-dependent paracrine effects. This study provides preclinical evidence for the future use of human DPSCs in cell therapy to improve outcome in stroke patients.

Single-dose lentiviral gene transfer for lifetime airway gene expression

BACKGROUND

Cystic fibrosis (CF) is caused by a defect in cystic fibrosis transmembrane conductance regulator (CFTR) activity, often resulting in an incurable airway disease. Gene therapy into the conducting airway epithelium is a potential cure for CF; however, most gene vectors do not result in long-lived expression, and require re-dosing. Perversely, intrinsic host immune responses can then block renewed gene transfer.

METHODS

To investigate whether persistent gene expression could be achieved after a single dosing event, thus avoiding the issue of blocking host responses, we used a gene transfer protocol that combined an airway pretreatment using lysophosphatidylcholine with a human immunodeficiency virus type-1 (vesicular stomatitis virus G pseudotype) derived lentiviral vector to test whether an integrating vector could produce gene expression able to last for a substantial part of the lifetime of the laboratory mouse.

RESULTS

We found that a single dose of LV-LacZ produced immediate as well as lifetime mouse airway expression, confirming our hypothesis that use of an integrating vector extends transgene expression. Importantly, LV-CFTR dosing achieved at least 12 months of CFTR expression, representing partial functional correction of the CFTR defect in CF-null mice.

CONCLUSIONS

These findings validate the potential of this methodology for developing a gene transfer treatment for CF airway disease.

Gene delivery to airway epithelial cells in vivo: a direct comparison of apical and basolateral transduction strategies using pseudotyped lentivirus vectors

Lentivirus vectors are being investigated as gene delivery vehicles for cystic fibrosis airway gene therapy. Vesicular stomatitis virus G glycoprotein (VSV-G)-pseudotyped vectors transduce airway epithelia via receptors that are located predominantly on the basolateral surface of the airway epithelium. Effective transduction with VSV-G-pseudotyped vectors requires the use of a pre-treatment that disrupts epithelial tight junctions, allowing access to these basolateral receptors. In contrast, it has been reported that apically targeted lentiviral vectors allow efficient gene transfer in the absence of any pre-treatment. In a direct comparison of transduction by a VSV-G-pseudotyped vector, in combination with a pre-treatment with lysophosphatidylcholine (LPC), and the same vector pseudotyped with the apically targeted baculovirus GP64 envelope (without any pre-treatment), the GP64 vector was found to be significantly less efficient. However, when a pre-treatment with LPC was used the level of transduction with the GP64-pseudotyped lentiviral vector was not significantly different to that resulting from the VSV-G-pseudotyped vector. The cell types transduced with each vector were essentially the same, with the majority of cells transduced being respiratory (ciliated cells). However, unlike the VSV-G-pseudotyped vector, which results in persisting gene expression, transduction with the GP64-pseudotyped vector resulted in gene expression that declined to undetectable levels over six months, whether or not an LPC pre-treatment was used.