Therapeutic potential of amniotic fluid-derived cells for treating the injured nervous system.

There is a need for improved therapy for acquired brain injury, which has proven resistant to treatment by numerous drugs in clinical trials and continues to represent one of the leading causes of disability worldwide. Research into cell-based therapies for the treatment of brain injury is growing rapidly, but the ideal cell source has yet to be determined. Subpopulations of cells found in amniotic fluid, which is readily obtained during routine amniocentesis, can be easily expanded in culture, have multipotent differentiation capacity, are non-tumourigenic, and avoid the ethical complications associated with embryonic stem cells, making them a promising cell source for therapeutic purposes. Beneficial effects of amniotic fluid cell transplantation have been reported in various models of nervous system injury. However, evidence that amniotic fluid cells can differentiate into mature, functional neurons in vivo and incorporate into the existing circuitry to replace lost or damaged neurons is lacking. The mechanisms by which amniotic fluid cells improve outcomes after experimental nervous system injury remain unclear. However, studies reporting the expression and release of neurotrophic, angiogenic, and immunomodulatory factors by amniotic fluid cells suggest they may provide neuroprotection and (or) stimulate endogenous repair and remodelling processes in the injured nervous system. In this paper, we address recent research related to the neuronal differentiation of amniotic fluid-derived cells, the therapeutic efficacy of these cells in animal models of nervous system injury, and the possible mechanisms mediating the positive outcomes achieved by amniotic fluid cell transplantation.

Neuropilin 1 directly interacts with Fer kinase to mediate semaphorin 3A-induced death of cortical neurons.

Neuropilins (NRPs) are receptors for the major chemorepulsive axonal guidance cue semaphorins (Sema). The interaction of Sema3A/NRP1 during development leads to the collapse of growth cones. Here we show that Sema3A also induces death of cultured cortical neurons through NRP1. A specific NRP1 inhibitory peptide ameliorated Sema3A-evoked cortical axonal retraction and neuronal death. Moreover, Sema3A was also involved in cerebral ischemia-induced neuronal death. Expression levels of Sema3A and NRP1, but not NRP2, were significantly increased early during brain reperfusion following transient focal cerebral ischemia. NRP1 inhibitory peptide delivered to the ischemic brain was potently neuroprotective and prevented the loss of motor functions in mice. The integrity of the injected NRP1 inhibitory peptide into the brain remained unchanged, and the intact peptide permeated the ischemic hemisphere of the brain as determined using MALDI-MS-based imaging. Mechanistically, NRP1-mediated axonal collapse and neuronal death is through direct and selective interaction with the cytoplasmic tyrosine kinase Fer. Fer RNA interference effectively attenuated Sema3A-induced neurite retraction and neuronal death in cortical neurons. More importantly, down-regulation of Fer expression using Fer-specific RNA interference attenuated cerebral ischemia-induced brain damage. Together, these studies revealed a previously unknown function of NRP1 in signaling Sema3A-evoked neuronal death through Fer in cortical neurons.

Detection of acute brain injury by Raman spectral signature.

Brain injury can lead to irreversible tissue loss and functional deficit along with significant health care costs. Raman spectroscopy can be used as a non-invasive technique to provide detailed information on the molecular composition of diseased and damaged tissues. This technique was used to examine acute mouse brain injury, focusing on the motor cortex, a region directly involved in controlling execution of movement. The spectral profile obtained from the injured brain tissue revealed a markedly different signature, particularly in the amide I and amide III vibrational region when compared to that of healthy brain tissue. Most noticeably, there was a significant reduction of the amide I vibration at the acute injury site and the appearance of two distinct features at 1586 and 1618 cm(-1). Complementary immunohistochemical analysis of the injured brain tissue showed an abundant expression of Caspase 3 (a cysteine protease marker used for apoptosis), suggesting that the injury-induced specific Raman shifts may be correlated with cell death. Taken together, this study demonstrates that Raman spectroscopy can play an important role in detecting the changes that occur in the injured brain and provide a possible technology for monitoring the recovery process.

Proteomic analysis of synaptosomal protein expression reveals that cerebral ischemia alters lysosomal Psap processing.

Cerebral ischemia (CI) induces dramatic changes in synaptic structure and function that precedes delayed post-ischemic neuronal death. Here, a proteomic analysis was used to identify the effects of focal CI on synaptosomal protein levels. Contralateral and ipsilateral synaptosomes, prepared from adult mice subjected to 60 min middle cerebral artery occlusion, were isolated following 3, 6 and 20 h of reperfusion. Synaptosomal protein samples (n=3) were labeled using the cleavable ICAT system prior to analysis with nanoLC-MS/MS. Each sample was analyzed by LC-MS to identify differential expressions using InDEPT software and differentially expressed peptides were identified by targeted LC-MS/MS. A total of 62 differentially expressed proteins were identified and Gene Ontology classification (cellular component) indicated that the majority of the proteins were located in the mitochondria and other components consistent with synaptic localization. The observed alterations in synaptic protein levels poorly correlated with gene expression, indicating the involvement of post-transcriptional regulatory mechanisms in determining post-ischemic synaptic protein content. Additionally, immunohistochemistry analysis of prosaposin (Psap) and saposin C (SapC) indicates that CI disrupts Psap processing and glycosphingolipid metabolism. These results demonstrate that the synapse is adversely affected by CI and may play a role in mediating post-ischemic neuronal viability.

Cerebral ischemia causes dysregulation of synaptic adhesion in mouse synaptosomes.

Synaptic pathology is observed during hypoxic events in the central nervous system in the form of altered dendrite structure and conductance changes. These alterations are rapidly reversible, on the return of normoxia, but are thought to initiate subsequent neuronal cell death. To characterize the effects of hypoxia on regulators of synaptic stability, we examined the temporal expression of cell adhesion molecules (CAMs) in synaptosomes after transient middle cerebral artery occlusion (MCAO) in mice. We focused on events preceding the onset of ischemic neuronal cell death (<48 h). Synaptosome preparations were enriched in synaptically localized proteins and were free of endoplasmic reticulum and nuclear contamination. Electron microscopy showed that the synaptosome preparation was enriched in spheres (approximately 650 nm in diameter) containing secretory vesicles and postsynaptic densities. Forebrain mRNA levels of synaptically located CAMs was unaffected at 3 h after MCAO. This is contrasted by the observation of consistent downregulation of synaptic CAMs at 20 h after MCAO. Examination of synaptosomal CAM protein content indicated that certain adhesion molecules were decreased as early as 3 h after MCAO. For comparison, synaptosomal Agrn protein levels were unaffected by cerebral ischemia. Furthermore, a marked increase in the levels of p-Ctnnb1 in ischemic synaptosomes was observed. p-Ctnnb1 was detected in hippocampal fiber tracts and in cornu ammonis 1 neuronal nuclei. These results indicate that ischemia induces a dysregulation of a subset of synaptic proteins that are important regulators of synaptic plasticity before the onset of ischemic neuronal cell death.

Inhibition of adenine nucleotide translocator pore function and protection against apoptosis in vivo by an HIV protease inhibitor.

Inhibitors of HIV protease have been shown to have antiapoptotic effects in vitro, yet whether these effects are seen in vivo remains controversial. In this study, we have evaluated the impact of the HIV protease inhibitor (PI) nelfinavir, boosted with ritonavir, in models of nonviral disease associated with excessive apoptosis. In mice with Fas-induced fatal hepatitis, Staphylococcal enterotoxin B-induced shock, and middle cerebral artery occlusion-induced stroke, we demonstrate that PIs significantly reduce apoptosis and improve histology, function, and/or behavioral recovery in each of these models. Further, we demonstrate that both in vitro and in vivo, PIs block apoptosis through the preservation of mitochondrial integrity and that in vitro PIs act to prevent pore function of the adenine nucleotide translocator (ANT) subunit of the mitochondrial permeability transition pore complex.

Absence of the transcription factor E2F1 attenuates brain injury and improves behavior after focal ischemia in mice.

Because of observations that cultured neurons from mice deficient in the transcription factor E2F1 exhibit resistance after treatment with a wide variety of cell-death inducers, the authors investigated whether resistance extended to a cerebral ischemic insult. No differences in cerebral blood flow or physiologic parameters were observed in the mutant E2F1 littermates after the focal ligation. After 2 hours of left middle cerebral artery occlusion and 1 day of reperfusion, a 33% smaller infarct (P < 0.05) was observed by 2,3,5-triphenyltetrazolium staining in the brains of E2F1-null mice compared with their E2F1+/+ and +/- littermates. A milder ischemic insult produced by 20 minutes of middle cerebral artery occlusion and 7 days of reperfusion produced a greater difference in the E2F1-null animals with a 71% smaller infarct (P < 0.001) compared to littermate controls. A decrease in neuronal damage after mild ischemia in E2F1-null mice was observed by immunohistochemical monitoring of the loss in neuronal-specific microtubule-associated protein 2 cytoskeletal protein and the appearance of nuclear DNA fragmentation by terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling. This decreased brain damage was evidenced by improved behavior in motor function of E2F1 -/- mice compared with their E2F1 +/+ littermates by 7 days of reperfusion. In an effort to address the underlying molecular mechanism of the resistance of E2F1-null mice, the expression of several downstream proapoptotic target genes (p73, Apaf1, Arf) of the E2F1 transcription factor was measured by quantitative polymerase chain reaction. Although an attenuated increase in Hsp68 mRNA was found in E2F1 -/- mice, no changes in the proapoptotic transcripts were found after ischemia, and a mechanistic inference was not possible. The authors conclude that the transcription factor E2F1 does modulate neuronal viability in brain after cerebral ischemia and corroborates the findings with cultured neurons.

Derivatised alpha-tocopherol as a CoQ10 carrier in a novel water-soluble formulation.

We have derivatised alpha-tocopherol (vitamin E) to a water-soluble polyoxyethanyl-alpha - tocopheryl sebacate (PTS) and discovered that it formed a non-covalent complex with CoQ10 at a molar ratio of 2:1 (PTS-CoQ10). This complex was water-soluble and remained stable for extended periods of time. After oral delivery of the formulation into rats PTS was hydrolysed to vitamin E and elevated levels of both vitamin E and CoQ10 in blood plasma were detected within 1 h. Thus, this aqueous formulation contains a combination of two potent antioxidants. The formulation's efficacy was tested against ischemic brain damage caused by a transient (8 min) bilateral occlusion of the common carotid arteries in rats. The animals received PTS-CoQ10 by two intraperitoneal injections given immediately after ischemia and 3 h later and the brain damage was assessed up to 12 days post-ischemia. A significant neuroprotection was observed in the CA1 hippocampal region, for example at 12 days approximately 50% of CA1 neurons were still alive in the treated animals versus less than 5% in the non-treated group. Our data is consistent with previously published observations indicating the therapeutic potential of antioxidants for treatments of ischemia/reperfusion injuries and the formulation described here is particularly appropriate for the application in acute conditions, such as stroke or cardiac arrest.

Nanomicellar formulation of coenzyme Q10 (Ubisol-Q10) effectively blocks ongoing neurodegeneration in the mouse 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model: potential use as an adjuvant treatment in Parkinson's disease.

Although the support for the use of antioxidants, such as coenzyme Q(10) (CoQ(10)), to treat Parkinson's disease (PD) comes from the extensive scientific evidence, the results of conducted thus far clinical trials are inconclusive. It is assumed that the efficacy of CoQ(10) is hindered by insolubility, poor bioavailability, and lack of brain penetration. We have developed a nanomicellar formulation of CoQ(10) (Ubisol-Q(10)) with improved properties, including the brain penetration, and tested its effectiveness in mouse MPTP (1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine) model with the objectives to assess its potential use as an adjuvant therapy for PD. We used a subchronic MPTP model (5-daily MPTP injections), characterized by 50% loss of dopamine neurons over a period of 28 days. Ubisol-Q(10) was delivered in drinking water. Prophylactic application of Ubisol-Q(10), started 2 weeks before the MPTP exposure, significantly offset the neurotoxicity (approximately 50% neurons died in MPTP group vs. 17% in MPTP+ Ubisol-Q(10) group by day 28). Therapeutic application of Ubisol-Q(10), given after the last MPTP injection, was equally effective. At the time of intervention on day 5 nearly 25% of dopamine neurons were already lost, but the treatment saved the remaining 25% of cells, which otherwise would have died by day 28. This was confirmed by cell counts, analyses of striatal dopamine levels, and improved animals' motor skill on a beam walk test. Similar levels of neuroprotection were obtained with 3 different Ubisol-Q(10) concentrations tested, that is, 30 mg, 6 mg, or 3 mg CoQ(10)/kg body weight/day, showing clearly that high doses of CoQ(10) were not required to deliver these effects. Furthermore, the Ubisol-Q(10) treatments brought about a robust astrocytic activation in the brain parenchyma, indicating that astroglia played an active role in this neuroprotection. Thus, we have shown for the first time that Ubisol-Q(10) was capable of halting the neurodegeneration already in progress; however, to maintain it a continuous supplementation of Ubisol-Q(10) was required. The pathologic processes initiated by MPTP resumed if supplementation was withdrawn. We suggest that in addition to brain delivery of powerful antioxidants, Ubisol-Q(10) might have also supported subcellular oxidoreductase systems allowing them to maintain a favorable cellular redox status, especially in astroglia, facilitating their role in neuroprotection. Based on this data further clinical testing of this formulation in PD patients might be justifiable.

Neuroprotective effects of GDNF-expressing human amniotic fluid cells.

Brain injury continues to be one of the leading causes of disability worldwide. Despite decades of research, there is currently no pharmacologically effective treatment for preventing neuronal loss and repairing the brain. As a result, novel therapeutic approaches, such as cell-based therapies, are being actively pursued to repair tissue damage and restore neurological function after injury. In this study, we examined the neuroprotective potential of amniotic fluid (AF) single cell clones, engineered to secrete glial cell derived neurotrophic factor (AF-GDNF), both in vitro and in a surgically induced model of brain injury. Our results show that pre-treatment with GDNF significantly increases cell survival in cultures of AF cells or cortical neurons exposed to hydrogen peroxide. Since improving the efficacy of cell transplantation depends on enhanced graft cell survival, we investigated whether AF-GDNF cells seeded on polyglycolic acid (PGA) scaffolds could enhance graft survival following implantation into the lesion cavity. Encouragingly, the AF-GDNF cells survived longer than control AF cells in serum-free conditions and continued to secrete GDNF both in vitro and following implantation into the injured motor cortex. AF-GDNF implantation in the acute period following injury was sufficient to activate the MAPK/ERK signaling pathway in host neural cells in the peri-lesion area, potentially boosting endogenous neuroprotective pathways. These results were complemented with promising trends in beam walk tasks in AF-GDNF/PGA animals during the 7 day timeframe. Further investigation is required to determine whether significant behavioural improvement can be achieved at a longer timeframe.

Development of BMP7-producing human cells, using a third generation lentiviral gene delivery system.

Bone morphogenetic protein 7 (BMP7), a member of the transforming growth factor ß (TGF-ß) superfamily, plays important roles in the development of various tissues and organs in mouse and human. In particular, BMP7 is critical for the formation of the nervous system and it is considered to have therapeutic potential in brain injury and stroke. One approach to make BMP7 more suitable for therapeutic purposes is the development of efficient vectors that allow the consistent, reliable and cost-effective production of the BMP7 protein. In this study, we developed an efficient BMP7 delivery system, using a third generation lentiviral vector to produce functional BMP7 protein. The lentiviral transduction of several human cell types, including human embryonic kidney 293 (HEK293) cells, amniotic fluid cells, NTera2 neurons (NT2-N) and primary neuronal cultures resulted in BMP7 expression. The production of BMP7 protein was achieved for at least 4 weeks post-transduction, as determined by enzyme-linked immunosorbent assay (ELISA). SMAD phosphorylation and neuronal differentiation assays verified the bioactivity and functionality of the lentiviral-based BMP7 protein, respectively. In addition, the intracerebroventricular injection of the lentivirus resulted in exogenous BMP7 expression in both neurons and astrocytes in the mouse brain. Taken together, this gene delivery system provides a reliable source of functional BMP7 protein for future in vitro and in vivo studies.

Human amniotic fluid cells form functional gap junctions with cortical cells.

The usage of stem cells is a promising strategy for the repair of damaged tissue in the injured brain. Recently, amniotic fluid (AF) cells have received a lot of attention as an alternative source of stem cells for cell-based therapies. However, the success of this approach relies significantly on proper interactions between graft and host tissue. In particular, the reestablishment of functional brain networks requires formation of gap junctions, as a key step to provide sufficient intercellular communication. In this study, we show that AF cells express high levels of CX43 (GJA1) and are able to establish functional gap junctions with cortical cultures. Furthermore, we report an induction of Cx43 expression in astrocytes following injury to the mouse motor cortex and demonstrate for the first time CX43 expression at the interface between implanted AF cells and host brain cells. These findings suggest that CX43-mediated intercellular communication between AF cells and cortical astrocytes may contribute to the reconstruction of damaged tissue by mediating modulatory, homeostatic, and protective factors in the injured brain and hence warrants further investigation.

Neuroregenerative strategies in the brain: emerging significance of bone morphogenetic protein 7 (BMP7).

Every year thousands of people suffer from brain injuries and stroke, and develop motor, sensory, and cognitive problems as a result of neuronal loss in the brain. Unfortunately, the damaged brain has a limited ability to enact repair and current modes of treatment are not sufficient to offset the damage. An extensive list of growth factors, neurotrophic factors, cytokines, and drugs has been explored as potential therapies. However, only a limited number of them may actually have the potential to effectively offset the brain injury or stroke-related problems. One of the treatments considered for future brain repair is bone morphogenetic protein 7 (BMP7), a factor currently used in patients to treat non-neurological diseases. The clinical application of BMP7 is based on its neuroprotective role in stroke animal models. This paper reviews the current approaches considered for brain repair and discusses the novel convergent strategies by which BMP7 potentially can induce neuroregeneration.

Calpain cleavage of collapsin response mediator proteins in ischemic mouse brain.

Collapsin response mediator proteins (CRMPs) are important brain-specific proteins with distinct functions in modulating growth cone collapse and axonal guidance during brain development. Our previous studies have shown that calpain cleaves CRMP3 in the adult mouse brain during cerebral ischemia [S.T. Hou et al. (2006) J. Neurosci., 26, 2241-2249]. Here, the expression of all CRMP family members (1-5) was examined in mouse brains that were subjected to middle cerebral artery occlusion. Among the five CRMPs, the expressions of CRMP1, CRMP3 and CRMP5 were the most abundant in the cerebral cortex and all CRMPs were targeted for cleavage by ischemia-activated calpain. Sub-cellular fractionation analysis showed that cleavage of CRMPs by calpain occurred not only in the cytoplasm but also in the synaptosomes isolated from ischemic brains. Moreover, synaptosomal CRMPs appeared to be at least one-fold more sensitive to cleavage compared with those isolated from the cytosolic fraction in an in-vitro experiment, suggesting that synaptosomal CRMPs are critical targets during cerebral ischemia-induced neuronal injury. Finally, the expression of all CRMPs was colocalized with TUNEL-positive neurons in the ischemic mouse brain, which further supports the notion that CRMPs may play an important role in neuronal death following cerebral ischemia. Collectively, these studies demonstrated that CRMPs are targets of calpains during cerebral ischemia and they also highlighted an important potential role that CRMPs may play in modulating ischemic neuronal death.

Role of Sox2 in the development of the mouse neocortex.

The mammalian neocortex is established from neural stem and progenitor cells that utilize specific transcriptional and environmental factors to create functional neurons and astrocytes. Here, we examined the mechanism of Sox2 action during neocortical neurogenesis and gliogenesis. We established a robust Sox2 expression in neural stem and progenitor cells within the ventricular zone, which persisted until the cells exited the cell cycle. Overexpression of constitutively active Sox2 in neural progenitors resulted in upregulation of Notch1, recombination signal-sequence binding protein-J (RBP-J) and hairy enhancer of split 5 (Hes5) transcripts and the Sox2 high mobility group (HMG) domain seemed sufficient to confer these effects. While Sox2 overexpression permitted the differentiation of progenitors into astroglia, it inhibited neurogenesis, unless the Notch pathway was blocked. Moreover, neuronal precursors engaged a serine protease(s) to eliminate the overexpressed Sox2 protein and relieve the repression of neurogenesis. Glial precursors and differentiated astrocytes, on the other hand, maintained Sox2 expression until they reached a quiescent state. Sox2 expression was re-activated by signals that triggered astrocytic proliferation (i.e., injury, mitogenic and gliogenic factors). Taken together, Sox2 appears to act upstream of the Notch signaling pathway to maintain the cell proliferative potential and to ensure the generation of sufficient cell numbers and phenotypes in the developing neocortex.