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

Priming and Combined Strategies for the Application of Mesenchymal Stem Cells in Ischemic Stroke: A Promising Approach

Ischemic stroke (IS) is a leading cause of death and disability worldwide. Tissue plasminogen activator (tPA) administration and mechanical thrombectomy are the main treatments but have a narrow time window. Mesenchymal stem cells (MSCs), which are easily scalable in vitro and lack ethical concerns, possess the potential to differentiate into various types of cells and secrete a great number of growth factors for neuroprotection and regeneration. Moreover, MSCs have low immunogenicity and tumorigenic properties, showing safety and preliminary efficacy both in preclinical studies and clinical trials of IS. However, it is unlikely that MSC treatment alone will be sufficient to maximize recovery due to the low survival rate of transplanted cells and various mechanisms of ischemic brain damage in the different stages of IS. Preconditioning was used to facilitate the homing, survival, and secretion ability of the grafted MSCs in the ischemic region, while combination therapies are alternatives that can maximize the treatment effects, focusing on multiple therapeutic targets to promote stroke recovery. In this case, the combination therapy can yield a synergistic effect. In this review, we summarize the type of MSCs, preconditioning methods, and combined strategies as well as their therapeutic mechanism in the treatment of IS to accelerate the transformation from basic research to clinical application.

Dental pulp stem cell transplantation facilitates neuronal neuroprotection following cerebral ischemic stroke

OBJECTIVES

This study aimed to identify and evaluate the intracranial transplantation of dental pulp stem cells (DPSCs) as a possible ischemic stroke therapy that mitigates neuronal death/apoptosis.

MATERIALS AND METHODS

DPSCs were isolated from the impacted third molars of healthy volunteers and then intracranially injected at 24 h post-ischemic stroke to Sprague Dawley rats that had been subjected to 2 h of middle cerebral artery occlusion. Neurological functional deficits were assessed using the modified neurological severity score (mNSS), and cerebral edema was quantified using brain water content. Neuronal death/apoptosis was indicated by TdT-mediated dUTP Nick-End Labeling (TUNEL) staining, NeuN immunofluorescence and immunohistochemistry, and Western blot analysis of the protein expression of anti-apoptotic indicator of Bcl-2 and apoptotic indicators of Bax and caspase 3.

RESULTS

DPSC transplantation could ameliorate neurological dysfunction and brain edema, reduce infarct volume, decrease the percentage of TUNEL-positive nuclei, increase the number and percentage of NeuN-positive cells in ischemic penumbra, increase the ratio of Bcl-2 and Bax and down-regulate the production of caspase 3 in the cortical infarct zone.

CONCLUSIONS

DPSC therapy via intracranial injection exerted remarkably neuroprotection mainly by inhibiting neuronal death/apoptosis.

Dental-Pulp Stem Cells as a Therapeutic Strategy for Ischemic Stroke

Regenerative medicine aims to restore human functions by regenerating organs and tissues using stem cells or living tissues for the treatment of organ and tissue defects or dysfunction. Clinical trials investigating the treatment of cerebral infarction using mesenchymal stem cells, a type of somatic stem cell therapy, are underway. The development and production of regenerative medicines using somatic stem cells is expected to contribute to the treatment of cerebral infarction, a central nervous system disease for which there is no effective treatment. Numerous experimental studies have shown that cellular therapy, including the use of human dental pulp stem cells, is an attractive strategy for patients with ischemic brain injury. This review describes the basic research, therapeutic mechanism, clinical trials, and future prospects for dental pulp stem cell therapy, which is being investigated in Japan in first-in-human clinical trials for the treatment of patients with acute cerebral ischemia.

Human pluripotent stem cell-derived ectomesenchymal stromal cells promote more robust functional recovery than umbilical cord-derived mesenchymal stromal cells after hypoxic-ischaemic brain damage

Aims: Hypoxic-ischaemic encephalopathy (HIE) is one of the most serious complications in neonates and infants. Mesenchymal stromal cell (MSC)-based therapy is emerging as a promising treatment avenue for HIE. However, despite its enormous potential, the clinical application of MSCs is limited by cell heterogeneity, low isolation efficiency and unpredictable effectiveness. In this study, we examined the therapeutic effects and underlying mechanisms of human pluripotent stem cell-derived ectomesenchymal stromal cells (hPSC-EMSCs) in a rat model of HIE.

Methods: hPSC-EMSCs were induced from either human embryonic stem cells or induced pluripotent stem cells. Stem cells or the conditioned medium (CM) derived from stem cells were delivered intracranially or intranasally to neonatal rats with HIE. Human umbilical cord-derived MSCs (hUC-MSCs) were used as the therapeutic comparison control and phosphate-buffered saline (PBS) was used as a negative control. Lesion size, apoptosis, neurogenesis, astrogliosis and microgliosis were evaluated. The rotarod test and Morris water maze were used to determine brain functional recovery. The PC-12 cell line, rat primary cortical neurons and neural progenitor cells were used to evaluate neurite outgrowth and the neuroprotective and neurogenesis effects of hPSC-EMSCs/hUC-MSCs. RNA-seq and enzyme-linked immunosorbent assays were used to determine the secretory factors that were differentially expressed between hPSC-EMSCs and hUC-MSCs. The activation and suppression of extracellular signal-regulated kinase (ERK) and cAMP response element-binding protein (CREB) were characterised using western blotting and immunofluorescent staining.

Results: hPSC-EMSCs showed a higher neuroprotective potential than hUC-MSCs, as demonstrated by a more significant reduction in lesion size and apoptosis in the rat brain following hypoxia-ischaemia (HI). Compared with PBS treatment, hPSC-EMSCs promoted endogenous neurogenesis and alleviated astrogliosis and microgliosis. hPSC-EMSCs were more effective than hUC-MSCs. hPSC-EMSCs achieved a greater recovery of brain function than hUC-MSCs and PBS in rats with HIE. CM derived from hPSC-EMSCs had neuroprotective and neurorestorative effects in vitro through anti-apoptotic and neurite outgrowth- and neurogenesis-promoting effects. Direct comparisons between hPSC-EMSCs and hUC-MSCs revealed the significant enrichment of a group of secretory factors in hPSC-EMSCs, including nerve growth factor (NGF), platelet-derived growth factor-AA and transforming growth factor-β₂, which are involved in neurogenesis, synaptic transmission and neurotransmitter transport, respectively. Mechanistically, the CM derived from hPSC-EMSCs was found to potentiate NGF-induced neurite outgrowth and the neuronal differentiation of NPCs via the ERK/CREB pathway. Suppression of ERK or CREB abolished CM-potentiated neuritogenesis and neuronal differentiation. Finally, intranasal delivery of the CM derived from hPSC-EMSCs significantly reduced brain lesion size, promoted endogenous neurogenesis, mitigated inflammatory responses and improved functional recovery in rats with HIE.

Conclusion: hPSC-EMSCs promote functional recovery after HI through multifaceted neuromodulatory activities via paracrine/trophic mechanisms. We propose the use of hPSC-EMSCs for the treatment of HIE, as they offer an excellent unlimited cellular source of MSCs.

Differential effects of the cell cycle inhibitor, olomoucine, on functional recovery and on responses of peri-infarct microglia and astrocytes following photothrombotic stroke in rats

Background

Following stroke, changes in neuronal connectivity in tissue surrounding the infarct play an important role in both spontaneous recovery of neurological function and in treatment-induced improvements in function. Microglia and astrocytes influence this process through direct interactions with the neurons and as major determinants of the local tissue environment. Subpopulations of peri-infarct glia proliferate early after stroke providing a possible target to modify recovery. Treatment with cell cycle inhibitors can reduce infarct volume and improve functional recovery. However, it is not known whether these inhibitors can influence neurological function or alter the responses of peri-infarct glia without reducing infarction. The present study aimed to address these issues by testing the effects of the cell cycle inhibitor, olomoucine, on recovery and peri-infarct changes following photothrombotic stroke.

Methods

Stroke was induced by photothrombosis in the forelimb sensorimotor cortex in Sprague-Dawley rats. Olomoucine was administered at 1 h and 24 h after stroke induction. Forelimb function was monitored up to 29 days. The effects of olomoucine on glial cell responses in peri-infarct tissue were evaluated using immunohistochemistry and Western blotting.

Results

Olomoucine treatment did not significantly affect maximal infarct volume. Recovery of the affected forelimb on a placing test was impaired in olomoucine-treated rats, whereas recovery in a skilled reaching test was substantially improved. Olomoucine treatment produced small changes in aspects of Iba1 immunolabelling and in the number of CD68-positive cells in cerebral cortex but did not selectively modify responses in peri-infarct tissue. The content of the astrocytic protein, vimentin, was reduced by 30% in the region of the lesion in olomoucine-treated rats.

Conclusions

Olomoucine treatment modified functional recovery in the absence of significant changes in infarct volume. The effects on recovery were markedly test dependent, adding to evidence that skilled tasks requiring specific training and general measures of motor function can be differentially modified by some interventions. The altered recovery was not associated with specific changes in key responses of peri-infarct microglia, even though these cells were considered a likely target for early olomoucine treatment. Changes detected in peri-infarct reactive astrogliosis could contribute to the altered patterns of functional recovery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02208-w.