Eisuke Kako

Human Dental Pulp-Derived Stem Cells Protect Against Hypoxic-Ischemic Brain Injury in Neonatal Mice

Background and Purpose— Perinatal hypoxia-ischemia (HI) has high rates of neurological deficits and mortality. So far, no effective treatment for HI brain injury has been developed. In this study, we investigated the therapeutic effects of stem cells from human exfoliated deciduous teeth (SHED) for the treatment of neonatal HI brain injury. Methods— Unilateral HI was induced in postnatal day 5 (P5) mice. Twenty-four hours later, SHED, human skin fibroblasts, or serum-free conditioned medium derived from these cells was injected into the injured brain. The effects of cell transplantation or conditioned medium injection on the animals’ neurological and pathophysiological recovery were evaluated. Results— Transplanted SHED, but not fibroblasts, significantly reduced the HI-induced brain-tissue loss and improved neurological function. SHED also improved the survival of the HI mice. The engrafted SHED rarely differentiated into neural lineages; however, their transplantation inhibited the expression of proinflammatory cytokines, increased the expression of anti-inflammatory ones, and significantly reduced apoptosis. Notably, the intracerebral administration of SHED-conditioned medium also significantly improved the neurological outcome, inhibited apoptosis, and reduced tissue loss. Conclusions— SHED transplantation into the HI-injured brain resulted in remarkable neurological and pathophysiological recovery. Our findings indicate that paracrine factors derived from SHED support a neuroprotective microenvironment in the HI brain. SHED graft and SHED-conditioned medium may provide a novel neuroprotective therapy for HI.

Subventricular Zone-Derived Oligodendrogenesis in Injured Neonatal White Matter in Mice Enhanced by a Nonerythropoietic Erythropoietin Derivative†‡§

Perinatal hypoxia‐ischemia (HI) frequently causes white‐matter injury, leading to severe neurological deficits and mortality, and only limited therapeutic options exist. The white matter of animal models and human patients with HI‐induced brain injury contains increased numbers of oligodendrocyte progenitor cells (OPCs). However, the origin and fates of these OPCs and their potential to repair injured white matter remain unclear. Here, using cell‐type‐ and region‐specific genetic labeling methods in a mouse HI model, we characterized the Olig2‐expressing OPCs. We found that after HI, Olig2+ cells increased in the posterior part of the subventricular zone (pSVZ) and migrated into the injured white matter. However, their oligodendrocytic differentiation efficiency was severely compromised compared with the OPCs in normal tissue, indicating the need for an intervention to promote their differentiation. Erythropoietin (EPO) treatment is a promising candidate, but it has detrimental effects that preclude its clinical use for brain injury. We found that long‐term postinjury treatment with a nonerythropoietic derivative of EPO, asialo‐erythropoietin, promoted the maturation of pSVZ‐derived OPCs and the recovery of neurological function, without affecting hematopoiesis. These results demonstrate the limitation and potential of endogenous OPCs in the pSVZ as a therapeutic target for treating neonatal white‐matter injury. STEM Cells2012;30:2234–2247

Enhancement of ventricular-subventricular zone-derived neurogenesis and oligodendrogenesis by erythropoietin and its derivatives.

In the postnatal mammalian brain, stem cells in the ventricular-subventricular zone (V-SVZ) continuously generate neuronal and glial cells throughout life. Genetic labeling of cells of specific lineages have demonstrated that the V-SVZ is an important source of the neuroblasts and/or oligodendrocyte progenitor cells (OPCs) that migrate toward injured brain areas in response to several types of insult, including ischemia and demyelinating diseases. However, this spontaneous regeneration is insufficient for complete structural and functional restoration of the injured brain, so interventions to enhance these processes are sought for clinical applications. Erythropoietin (EPO), a clinically applied erythropoietic factor, is reported to have cytoprotective effects in various kinds of insult in the central nervous system. Moreover, recent studies suggest that EPO promotes the V-SVZ-derived neurogenesis and oligodendrogenesis. EPO increases the proliferation of progenitors in the V-SVZ and/or the migration and differentiation of their progenies in and around injured areas, depending on the dosage, timing, and duration of treatment, as well as the type of animal model used. On the other hand, EPO has undesirable side effects, including thrombotic complications. We recently demonstrated that a 2-week treatment with the EPO derivative asialo-EPO promotes the differentiation of V-SVZ-derived OPCs into myelin-forming mature oligodendrocytes in the injured white matter of neonatal mice without causing erythropoiesis. Here we present an overview of the multifaceted effects of EPO and its derivatives in the V-SVZ and discuss the possible applications of these molecules in regenerative medicine.

Prospects and Limitations of Using Endogenous Neural Stem Cells for Brain Regeneration

Neural stem cells (NSCs) are capable of producing a variety of neural cell types, and are indispensable for the development of the mammalian brain. NSCs can be induced in vitro from pluripotent stem cells, including embryonic stem cells and induced-pluripotent stem cells. Although the transplantation of these exogenous NSCs is a potential strategy for improving presently untreatable neurological conditions, there are several obstacles to its implementation, including tumorigenic, immunological, and ethical problems. Recent studies have revealed that NSCs also reside in the adult brain. The endogenous NSCs are activated in response to disease or trauma, and produce new neurons and glia, suggesting they have the potential to regenerate damaged brain tissue while avoiding the above-mentioned problems. Here we present an overview of the possibility and limitations of using endogenous NSCs in regenerative medicine.

Age-related requisite concentration of sevoflurane for adequate sedation with combined epidural-general anesthesia

Background The requisite anesthetic concentration of sevoflurane required to obtain adequate sedation when sufficient analgesics are supplied has not been determined. The purpose of this study was to determine the requisite age-associated concentration of sevoflurane to obtain an adequate level of anesthesia during combined epidural-general anesthesia by bispectral index (BIS) monitoring. Methods Twenty-seven elective abdominal surgery patients (American Society of Anesthesiologists physical status I-II) were enrolled. The patients were divided into two groups of more or less than 60 years of age. We investigated the concentration of sevoflurane required to obtain an adequate sedation level during combined epidural-general anesthesia, maintaining the BIS value between 40 and 60. Results The requisite sevoflurane concentration required to keep the BIS value at 40-60 was not stable during surgery. In the younger group, the maximum concentration of sevoflurane needed during surgery was 1.95 ± 0.14 (95% confidence interval: 1.87-2.10) vol%, while it was 1.54 ± 0.44 (95% confidence interval: 1.27-1.80) vol% in the older group (P < 0.01). Conclusions The requisite concentration of sevoflurane required with combined epidural-general anesthesia was 2.5 vol% for the younger group and 2.0 vol% for the older group as determined by BIS monitoring. We believe that these percentages are sufficient to avoid awareness during surgery with adequate analgesia.

Promotion of neuronal migration towards the injured mouse cerebral cortex using sustained release of chemoattractant from gelatin hydrogel microspheres

After traumatic damage of the central nervous system (CNS), meningeal fibroblasts receive transforming growth factor(TGF) signal, invade in the lesion site, actively proliferate, and secrete extracellular matrix proteins (Komuta et al., Cell Mol. Neurobiol. 30: 101–111, 2010). Those cells and proteins consistently form a fibrotic scar which is considered as a major obstacle for axonal regeneration after injury. We have previously examined the development of fibrotic scar formation in postnatal mice with a surgical transection of the nigrostriatal dopaminergic pathway. The fibrotic scar was not formed and axonal regeneration occurred in the brain injured at postnatal day 7 (P7), while the fibrotic scar was formed and axons did not regenerate in the brains injured after P14 (Kawano et al., J. Neurosci. Res. 80: 191–202, 2005). Recently, we have demonstrated that cultured meningeal fibroblasts form fibrotic scar-like clusters by an addition of TGF1 (KimuraKuroda et al., Mol. Cell. Neurosci. 43: 177–187, 2010). Using this in vitro model, we examined the relationship between the postnatal development of fibrotic scar formation and the cell responses for TGF1. Meningeal fibroblasts from P0 and P14 rats were isolated, cultured and added with TGF1 (1–10 ng/ml). Meningeal fibroblasts taken from P14 rats responded to TGF1 to actively proliferate, form clusters and express the markers of fibrotic scar fibronectin and type IV collagen. In contrast, meningeal fibroblasts taken from P0 rats less proliferated and did not form clusters. Furthermore, most of fibrotic scar markers were not up-regulated in those cells. The present results agree well with our previous in vivo finding, and further suggest that failure of neonatal meningeal fibroblasts to respond to TGF1 inhibits the fibrotic scar formation and allow the axonal regeneration after brain injury.