Transplantation of Human Cortically-Specified Neuroepithelial Progenitor Cells Leads to Improved Functional Outcomes in a Mouse Model of Stroke

Primitive and Definitive Neural Precursor Cells Are Present in Human Cerebral Organoids

Activation of neural stem cells (NSCs) correlates with improved functional outcomes in mouse models of injury. In the murine brain, NSCs have been extensively characterized and comprise (1) primitive NSCs (pNSCs) and (2) definitive NSCs (dNSCs). pNSCs are the earliest cells in the NSC lineage giving rise to dNSCs in the embryonic and adult mouse brain. pNSCs are quiescent under baseline conditions and can be activated upon injury. Herein, we asked whether human pNSCs and dNSCs can be isolated during the maturation of human cerebral organoids (COs) and activated by drugs known to regulate mouse NSC behavior. We demonstrate that self-renewing, multipotent pNSC and dNSC populations are present in human COs and express genes previously characterized in mouse NSCs. The drug NWL283, an inhibitor of apoptosis, reduced cell death in COs but did not improve NSC survival. Metformin, a drug used to treat type II diabetes that is known to promote NSC activation in mice, was found to expand human NSC pools. Together, these findings are the first to identify and characterize human pNSCs, advancing our understanding of the human NSC lineage and highlighting drugs that enhance their activity.

An update on stem cell therapy for stroke patients: Where are we now?

With a foundation built upon initial work from the 1980s demonstrating graft viability in cerebral ischemia, stem cell transplantation has shown immense promise in promoting survival, enhancing neuroprotection and inducing neuroregeneration, while mitigating both histological and behavioral deficits that frequently accompany ischemic stroke. These findings have led to a number of clinical trials that have thoroughly supported a strong safety profile for stem cell therapy in patients but have generated variable efficacy. As preclinical evidence continues to expand through the investigation of new cell lines and optimization of stem cell delivery, it remains critical for translational models to adhere to the protocols established through basic scientific research. With the recent shift in approach towards utilization of stem cells as a conjunctive therapy alongside standard thrombolytic treatments, key issues including timing, route of administration, and stem cell type must each be appropriately translated from the laboratory in order to resolve the question of stem cell efficacy for cerebral ischemia that ultimately will enhance therapeutics for stroke patients towards improving quality of life.

Inhibition of Apoptosis in a Model of Ischemic Stroke Leads to Enhanced Cell Survival, Endogenous Neural Precursor Cell Activation and Improved Functional Outcomes

Stroke results in neuronal cell death, which causes long-term disabilities in adults. Treatment options are limited and rely on a narrow window of opportunity. Apoptosis inhibitors demonstrate efficacy in improving neuronal cell survival in animal models of stroke. However, many inhibitors non-specifically target apoptosis pathways and high doses are needed for treatment. We explored the use of a novel caspase-3/7 inhibitor, New World Laboratories (NWL) 283, with a lower IC50 than current caspase-3/7 inhibitors. We performed in vitro and in vivo assays to determine the efficacy of NWL283 in modulating cell death in a preclinical model of stroke. In vitro and in vivo assays show that NWL283 enhances cell survival of neural precursor cells. Delivery of NWL283 following stroke enhances endogenous NPC migration and leads to increased neurogenesis in the stroke-injured cortex. Furthermore, acute NWL283 administration is neuroprotective at the stroke injury site, decreasing neuronal cell death and reducing microglia activation. Coincident with NWL283 delivery for 8 days, stroke-injured mice exhibited improved functional outcomes that persisted following cessation of the drug. Therefore, we propose that NWL283 is a promising therapeutic warranting further investigation to enhance stroke recovery.

Cryogel-based neurostimulation electrodes to activate endogenous neural precursor cells

The delivery of electrical pulses to the brain via penetrating electrodes, known as brain stimulation, has been recognized as an effective clinical approach for treating neurological disorders. Resident brain neural precursor cells (NPCs) are electrosensitive cells that respond to electrical stimulation by expanding in number, migrating and differentiating which are important characteristics that support neural repair. Here, we report the design of a conductive cryogel brain stimulation electrode specifically developed for NPC activation. The cryogel electrode has a modulus switching mechanism permitting facile penetration and reducing the mechanical mismatch between brain tissue and the penetrating electrode. The cryogel demonstrated good in vivo biocompatibility and reduced the interfacial impedance to deliver the stimulating electric field with lower voltage under charge-balanced current controlled stimulation. An ex vivo assay reveals that electrical stimulation using the cryogel electrodes results in significant expansion in the size of NPC pool. Hence, the cryogel electrodes have the potential to be used for NPC activation to support endogenous neural repair. STATEMENT OF SIGNIFICANCE: The objective of this study is to develop a cryogel-based stimulation electrode as an alternative to traditional electrode materials to be used in regenerative medicine applications for enhancing neural regeneration in brain. The electrode offers benefits such as adaptive modulus for implantation, high charge storage and injection capacities, and modulus matching with brain tissue, allowing for stable delivery of electric field for long-term neuromodulation. The electrochemical properties of cryogel electrodes were characterized in living tissue with an ex vivo set-up, providing a deeper understanding of stimulation capacity in brain environments. The cryogel electrode is biocompatible and enables low voltage, current-controlled stimulation for effective activation of endogenous neural precursor cells, revealing their potential utility in neural stem cell-mediated brain repair.

The Role of Concomitant Nrf2 Targeting and Stem Cell Therapy in Cerebrovascular Disease

Despite the reality that a death from cerebrovascular accident occurs every 3.5 min in the United States, there are few therapeutic options which are typically limited to a narrow window of opportunity in time for damage mitigation and recovery. Novel therapies have targeted pathological processes secondary to the initial insult, such as oxidative damage and peripheral inflammation. One of the greatest challenges to therapy is the frequently permanent damage within the CNS, attributed to a lack of sufficient neurogenesis. Thus, recent use of cell-based therapies for stroke have shown promising results. Unfortunately, stroke-induced inflammatory and oxidative damage limit the therapeutic potential of these stem cells. Nuclear factor erythroid 2-related factor 2 (Nrf2) has been implicated in endogenous antioxidant and anti-inflammatory activity, thus presenting an attractive target for novel therapeutics to enhance stem cell therapy and promote neurogenesis. This review assesses the current literature on the concomitant use of stem cell therapy and Nrf2 targeting via pharmaceutical and natural agents, highlighting the need to elucidate both upstream and downstream pathways in optimizing Nrf2 treatments in the setting of cerebrovascular disease.

Neuroinflammation, Stem Cells, and Stroke

Stroke remains a significant unmet clinical need with few treatment options that have a very narrow therapeutic window, thereby causing massive mortality and morbidity in the United States and around the world. Accordingly, finding safe and effective novel treatments with a wider therapeutic window stands as an urgent need in stroke. The progressive inflammation that occurs centrally and peripherally after stroke serves as a unique therapeutic target to retard and even halt the secondary cell death. Stem cell therapy represents a potent approach that can diminish inflammation in both the stroke brain and periphery (eg, spleen), advancing a paradigm shift from a traditionally brain-focused therapy to treating stroke as a neurological disorder with a significant peripheral pathology. The purpose of this review article is to highlight the inflammation-mediated secondary cell death that plagues both brain and spleen in stroke and to evaluate the therapeutic potential of stem cell therapy in dampening these inflammatory responses.