CNS progenitor cells promote a permissive environment for neurite outgrowth via a matrix metalloproteinase-2-dependent mechanism

CHRM3 is a novel prognostic factor of poor prognosis and promotes glioblastoma progression via activation of oncogenic invasive growth factors

Glioblastoma (GBM) is the most aggressive cancer of the brain and has a high mortality rate due to the lack of effective treatment strategy. Clarification of molecular mechanisms of GBM's characteristic invasive growth is urgently needed to improve the poor prognosis. Single-nuclear sequencing of primary and recurrent GBM samples revealed that levels of M3 muscarinic acetylcholine receptor (CHRM3) were significantly higher in the recurrent samples than in the primary samples. Moreover, immunohistochemical staining of an array of GBM samples showed that high levels of CHRM3 correlated with poor prognosis, consistent with The Cancer Genome Atlas database. Knockdown of CHRM3 inhibited GBM cell growth and invasion. An assay of orthotopic GBM animal model in vivo indicated that inhibition of CHRM3 significantly suppressed GBM progression with prolonged survival time. Transcriptome analysis revealed that CHRM3 knockdown significantly reduced an array of classic factors involved in cancer invasive growth, including MMP1/MMP3/MMP10/MMP12 and CXCL1/CXCL5/CXCL8. Taken together, CHRM3 is a novel and vital factor of GBM progression via regulation of multiple oncogenic genes and may serve as a new biomarker for prognosis and therapy of GBM patients.

Automating iPSC generation to enable autologous photoreceptor cell replacement therapy

BACKGROUND

Inherited retinal degeneration is a leading cause of incurable vision loss in the developed world. While autologous iPSC mediated photoreceptor cell replacement is theoretically possible, the lack of commercially available technologies designed to enable high throughput parallel production of patient specific therapeutics has hindered clinical translation.

METHODS

In this study, we describe the use of the Cell X precision robotic cell culture platform to enable parallel production of clinical grade patient specific iPSCs. The Cell X is housed within an ISO Class 5 cGMP compliant closed aseptic isolator (Biospherix XVivo X2), where all procedures from fibroblast culture to iPSC generation, clonal expansion and retinal differentiation were performed.

RESULTS

Patient iPSCs generated using the Cell X platform were determined to be pluripotent via score card analysis and genetically stable via karyotyping. As determined via immunostaining and confocal microscopy, iPSCs generated using the Cell X platform gave rise to retinal organoids that were indistinguishable from organoids derived from manually generated iPSCs. In addition, at 120 days post-differentiation, single-cell RNA sequencing analysis revealed that cells generated using the Cell X platform were comparable to those generated under manual conditions in a separate laboratory.

CONCLUSION

We have successfully developed a robotic iPSC generation platform and standard operating procedures for production of high-quality photoreceptor precursor cells that are compatible with current good manufacturing practices. This system will enable clinical grade production of iPSCs for autologous retinal cell replacement.

Matrix Metalloproteinases and Glaucoma

Matrix metalloproteinases (MMPs) are enzymes that decompose extracellular matrix (ECM) proteins. MMPs are thought to play important roles in cellular processes, such as cell proliferation, differentiation, angiogenesis, migration, apoptosis, and host defense. MMPs are distributed in almost all intraocular tissues and are involved in physiological and pathological mechanisms of the eye. MMPs are also associated with glaucoma, a progressive neurodegenerative disease of the eyes. MMP activity affects intraocular pressure control and apoptosis of retinal ganglion cells, which are the pathological mechanisms of glaucoma. It also affects the risk of glaucoma development based on genetic pleomorphism. In addition, MMPs may affect the treatment outcomes of glaucoma, including the success rate of surgical treatment and side effects on the ocular surface due to glaucoma medications. This review discusses the various relationships between MMP and glaucoma.

MMP2 Modulates Inflammatory Response during Axonal Regeneration in the Murine Visual System

Neuroinflammation has been put forward as a mechanism triggering axonal regrowth in the mammalian central nervous system (CNS), yet little is known about the underlying cellular and molecular players connecting these two processes. In this study, we provide evidence that MMP2 is an essential factor linking inflammation to axonal regeneration by using an in vivo mouse model of inflammation-induced axonal regeneration in the optic nerve. We show that infiltrating myeloid cells abundantly express MMP2 and that MMP2 deficiency results in reduced long-distance axonal regeneration. However, this phenotype can be rescued by restoring MMP2 expression in myeloid cells via a heterologous bone marrow transplantation. Furthermore, while MMP2 deficiency does not affect the number of infiltrating myeloid cells, it does determine the coordinated expression of pro- and anti-inflammatory molecules. Altogether, in addition to its role in axonal regeneration via resolution of the glial scar, here, we reveal a new mechanism via which MMP2 facilitates axonal regeneration, namely orchestrating the expression of pro- and anti-inflammatory molecules by infiltrating innate immune cells.

Changes in Gene and Protein Expression of Metalloproteinase-2 and -9 and Their Inhibitors TIMP2 and TIMP3 in Different Parts of Fluoride-Exposed Rat Brain

Fluoride (F) exposure decreases brain receptor activity and neurotransmitter production. A recent study has shown that chronic fluoride exposure during childhood can affect cognitive function and decrease intelligence quotient, but the mechanism of this phenomenon is still incomplete. Extracellular matrix (ECM) and its enzymes are one of the key players of neuroplasticity which is essential for cognitive function development. Changes in the structure and the functioning of synapses are caused, among others, by ECM enzymes. These enzymes, especially matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs), are involved in both physiological processes, such as learning or memory, and pathological processes like glia scare formation, brain tissue regeneration, brain-blood barrier damage and inflammation. Therefore, in this study, we examined the changes in gene and protein expression of MMP2, MMP9, TIMP2 and TIMP3 in the prefrontal cortex, hippocampus, striatum and cerebellum of rats (Wistar) exposed to relatively low F doses (50 mg/L in drinking water) during the pre- and neonatal period. We found that exposure to F during pre- and postnatal period causes a change in the mRNA and protein level of MMP2, MMP9, TIMP2 and TIMP3 in the prefrontal cortex, striatum, hippocampus and cerebellum. These changes may be associated with many disorders that are observed during F intoxication. MMPs/TIMPs imbalance may contribute to cognitive impairments. Moreover, our results suggest that a chronic inflammatory process and blood-brain barrier (BBB) damage occur in rats’ brains exposed to F.

Intravitreal stem cell paracrine properties as a potential neuroprotective therapy for retinal photoreceptor neurodegenerative diseases

Retinal degenerations are the leading causes of irreversible visual loss worldwide. Many pathologies included under this umbrella involve progressive degeneration and ultimate loss of the photoreceptor cells, with age-related macular degeneration and inherited and ischemic retinal diseases the most relevant. These diseases greatly impact patients’ daily lives, with accompanying marked social and economic consequences. However, the currently available treatments only delay the onset or slow progression of visual impairment, and there are no cures for these photoreceptor diseases. Therefore, new therapeutic strategies are being investigated, such as gene therapy, optogenetics, cell replacement, or cell-based neuroprotection. Specifically, stem cells can secrete neurotrophic, immunomodulatory, and anti-angiogenic factors that potentially protect and preserve retinal cells from neurodegeneration. Further, neuroprotection can be used in different types of retinal degenerative diseases and at different disease stages, unlike other potential therapies. This review summarizes stem cell-based paracrine neuroprotective strategies for photoreceptor degeneration, which are under study in clinical trials, and the latest preclinical studies. Effective retinal neuroprotection could be the next frontier in photoreceptor diseases, and the development of novel neuroprotective strategies will address the unmet therapeutic needs.

CRISPR-Cas9 genome engineering: Treating inherited retinal degeneration

Gene correction is a valuable strategy for treating inherited retinal degenerative diseases, a major cause of irreversible blindness worldwide. Single gene defects cause the majority of these retinal dystrophies. Gene augmentation holds great promise if delivered early in the course of the disease, however, many patients carry mutations in genes too large to be packaged into adeno-associated viral vectors and some, when overexpressed via heterologous promoters, induce retinal toxicity. In addition to the aforementioned challenges, some patients have sustained significant photoreceptor cell loss at the time of diagnosis, rendering gene replacement therapy insufficient to treat the disease. These patients will require cell replacement to restore useful vision. Fortunately, the advent of induced pluripotent stem cell and CRISPR-Cas9 gene editing technologies affords researchers and clinicians a powerful means by which to develop strategies to treat patients with inherited retinal dystrophies. In this review we will discuss the current developments in CRISPR-Cas9 gene editing in vivo in animal models and in vitro in patient-derived cells to study and treat inherited retinal degenerative diseases.

Current Advances in Pharmacotherapy and Technology for Diabetic Retinopathy: A Systematic Review

Diabetic retinopathy (DR) is classically defined by its vascular lesions and damage in the neurons of the retina. The cellular and clinical elements of DR have many features of chronic inflammation. Understanding the individual cell-specific inflammatory changes in the retina may lead to novel therapeutic approaches to prevent vision loss. The systematic use of available pharmacotherapy has been reported as a useful adjunct tool to laser photocoagulation, a gold standard therapy for DR. Direct injections or intravitreal anti-inflammatory and antiangiogenesis agents are widely used pharmacotherapy to effectively treat DR and diabetic macular edema (DME). However, their effectiveness is short term, and the delivery system is often associated with adverse effects, such as cataract and increased intraocular pressure. Further, systemic agents (particularly hypoglycemic, hypolipidemic, and antihypertensive agents) and plants-based drugs have also provided promising treatment in the progression of DR. Recently, advancements in pluripotent stem cells technology enable restoration of retinal functionalities after transplantation of these cells into animals with retinal degeneration. This review paper summarizes the developments in the current and potential pharmacotherapy and therapeutic technology of DR. Literature search was done on online databases, PubMed, Google Scholar, clinitrials.gov, and browsing through individual ophthalmology journals and leading pharmaceutical company websites.

Fingolimod Enhances Oligodendrocyte Differentiation of Transplanted Human Induced Pluripotent Stem Cell-Derived Neural Progenitors

Multiple sclerosis (MS) is an autoimmune disease which affects myelin in the central nervous system (CNS) and leads to serious disability. Currently available treatments for MS mainly suppress the immune system. Regenerative medicine-based approaches attempt to increase myelin repair by targeting endogenous progenitors or transplanting stem cells or their derivatives. Fingolimod exerts anti-inflammatory effects and directly affects neural cells. In this study we assessed the effect of fingolimod on transplanted human induced pluripotent stem cell derived neural progenitors (hiPSC-NPs). hiPSC-NPs were labeled by green fluorescence protein (GFP) and transplanted into the corpus callosum of mice which were chronically demyelinated after cuprizone (CPZ) feedings for 10 weeks. The animals received fingolimod from 1 day prior to NPs transplantation via gavage as well as daily intraperitoneal cyclosporine A from 2 days before cell transplantation until the time of sampling. At either 7 or 21 days after NPs transplantation, the animals were sacrificed and their brains were histologically evaluated for the number of transplanted cells and their fate. In the animals treated with fingolimod, we observed higher numbers of NPs within the injection site compared to the animals who did not receive fingolimod showing that hiPSC- NPs were more efficiently differentiated to the oligodendrocyte lineage. These data have suggested that repetitive treatment with fingolimod, beside its anti-inflammatory effect, may enhance the survival and differentiation of transplanted NPs to oligodendrocyte lineage cells to participate in myelin repair.

Differential regulation of NSC phenotype and genotype by chronically activated microglia within cocultures

Under disease or injury conditions in the central nervous system (CNS), activated microglia release cytokines and chemokines to modulate the microenvironment and influence tissue remodeling. To exploit the full potential of neural stem cell (NSC) transplantation approaches, a permissive microenvironment needs to be created for their survival, homing and differentiation. To investigate the role of chronically activated microglia in the fate of NSCs, spontaneously immortalized murine microglial cells (SIM-A9) were cocultured with embryonic murine cortical NSCs on 2D substrates or within 3D gels. Standalone NSC cultures served as controls. Cytokines and chemokines released by NSCs and SIM-A9 cells in standalone and cocultures were quantified. Coculturing with SIM-A9 cells suppressed NSC viability, neurite outgrowth, neural differentiation and TUJ1 gene expression, and promoted glia formation in both 2D and 3D cultures, over a 10-day period. The seven most-abundantly released analytes by microglia (MCP-1, MIP2, G-CSF, MIP-1α, MIP-1β, TNF-α, IL-6) were tested for their individual effects on NSCs, to investigate if the outcomes in cocultures were due to the synergistic effects of analytes or the influence of any individual analyte. All the seven analytes significantly suppressed cell survival compared to controls, but exposure to MIP-1β, IL-6, or MCP-1 enhanced neurite outgrowth and neural lineage commitment. Results attest to (i) the strong role of activated microglia in regulating NSC fate, (ii) the utility of selective analytes released by activated microglia in promoting neurogenesis and neuritogenesis, and (iii) the need to protect transplanted NSCs from the host inflammatory microenvironment to ensure their survival and functionality in treating neurological disorders.

cGMP production of patient-specific iPSCs and photoreceptor precursor cells to treat retinal degenerative blindness

Immunologically-matched, induced pluripotent stem cell (iPSC)-derived photoreceptor precursor cells have the potential to restore vision to patients with retinal degenerative diseases like retinitis pigmentosa. The purpose of this study was to develop clinically-compatible methods for manufacturing photoreceptor precursor cells from adult skin in a non-profit cGMP environment. Biopsies were obtained from 35 adult patients with inherited retinal degeneration and fibroblast lines were established under ISO class 5 cGMP conditions. Patient-specific iPSCs were then generated, clonally expanded and validated. Post-mitotic photoreceptor precursor cells were generated using a stepwise cGMP-compliant 3D differentiation protocol. The recapitulation of the enhanced S-cone phenotype in retinal organoids generated from a patient with NR2E3 mutations demonstrated the fidelity of these protocols. Transplantation into immune compromised animals revealed no evidence of abnormal proliferation or tumor formation. These studies will enable clinical trials to test the safety and efficiency of patient-specific photoreceptor cell replacement in humans.

Matrix Metalloproteinases During Axonal Regeneration, a Multifactorial Role from Start to Finish

By proteolytic cleavage, matrix metalloproteinases (MMPs) not only remodel the extracellular matrix (ECM) but they also modify the structure and activity of other proteinases, growth factors, signaling molecules, cell surface receptors, etc. Their vast substrate repertoire adds a complex extra dimension of biological control and turns MMPs into important regulatory nodes in the protease web. In the central nervous system (CNS), the detrimental impact of elevated MMP activities has been well-described for traumatic injuries and many neurodegenerative diseases. Nonetheless, there is ample proof corroborating MMPs as fine regulators of CNS physiology, and well-balanced MMP activity is instrumental to development, plasticity, and repair. In this manuscript, we review the emerging evidence for MMPs as beneficial modulators of axonal regeneration in the mammalian CNS. By exploring the multifactorial causes underlying the inability of mature axons to regenerate, and describing how MMPs can help to overcome these hurdles, we emphasize the benign actions of these Janus-faced proteases.

Retinal functional alterations in mice lacking intermediate filament proteins glial fibrillary acidic protein and vimentin

Vimentin (Vim) and glial fibrillary acidic protein (GFAP) are important components of the intermediate filament (IF) (or nanofilament) system of astroglial cells. We conducted full-field electroretinogram (ERG) recordings and found that whereas photoreceptor responses (a-wave) were normal in uninjured GFAP(-/-)Vim(-/-) mice, b-wave amplitudes were increased. Moreover, we found that Kir (inward rectifier K(+)) channel protein expression was reduced in the retinas of GFAP(-/-)Vim(-/-) mice and that Kir-mediated current amplitudes were lower in Müller glial cells isolated from these mice. Studies have shown that the IF system, in addition, is involved in the retinal response to injury and that attenuated Müller cell reactivity and reduced photoreceptor cell loss are observed in IF-deficient mice after experimental retinal detachment. We investigated whether the lack of IF proteins would affect cell survival in a retinal ischemia-reperfusion model. We found that although cell loss was induced in both genotypes, the number of surviving cells in the inner retina was lower in IF-deficient mice. Our findings thus show that the inability to produce GFAP and Vim affects normal retinal physiology and that the effect of IF deficiency on retinal cell survival differs, depending on the underlying pathologic condition.

Effect of discarded keratin-based biocomposite hydrogels on the wound healing process in vivo

Biocompatible keratin-based hydrogels prepared by electron beam irradiation (EBI) were examined in wound healing. As the EBI dose increased to 60 kGy, the tensile strength of the hydrogels increased, while the percentage of elongation of the hydrogels decreased. After 7 days, the dehydrated wool-based hydrogels show the highest mechanical properties (the % elongation of 1341 and the tensile strength of 6030 g/cm(2) at an EBI dose of 30 kGy). Excision wound models were used to evaluate the effects of human hair-based hydrogels and wool-based hydrogels on various phases of healing. On post-wounding days 7 and 14, wounds treated with either human hair-based or wool-based hydrogels were greatly reduced in size compared to wounds that received other treatments, although the hydrocolloid wound dressing-treated wound also showed a pronounced reduction in size compared to an open wound as measured by a histological assay. On the 14th postoperative day, the cellular appearances were similar in the hydrocolloid wound dressing and wool-based hydrogel-treated wounds, and collagen fibers were substituted with fibroblasts and mixed with fibroblasts in the dermis. Furthermore, the wound treated with a human hair-based hydrogel showed almost complete epithelial regeneration, with the maturation of immature connective tissue and hair follicles and formation of a sebaceous gland.

Patient-Specific iPSC-Derived RPE for Modeling of Retinal Diseases

Inherited retinal diseases, such as age-related macular degeneration and retinitis pigmentosa, are the leading cause of blindness in the developed world. Currently, treatments for these conditions are limited. Recently, considerable attention has been given to the possibility of using patient-specific induced pluripotent stem cells (iPSCs) as a treatment for these conditions. iPSCs reprogrammed from adult somatic cells offer the possibility of generating patient-specific cell lines in vitro. In this review, we will discuss the current literature pertaining to iPSC modeling of retinal disease, gene therapy of iPSC-derived retinal pigmented epithelium (RPE) cells, and retinal transplantation. We will focus on the use of iPSCs created from patients with inherited eye diseases for testing the efficacy of gene or drug-based therapies, elucidating previously unknown mechanisms and pathways of disease, and as a source of autologous cells for cell replacement.

Neuroprotective effects of intravitreally transplanted adipose tissue and bone marrow-derived mesenchymal stem cells in an experimental ocular hypertension model

BACKGROUND AIMS

The purpose of this study was to investigate the neuroprotective effects of bone marrow bone marrow-derived and adipose tissue-derived mesenchymal stromal cells (MSCs) that were intravitreally transplanted in an experimental ocular hypertension (OHT) model.

METHODS

An OHT rat model was generated by means of intracameral injection of hyaluronic acid into the anterior chamber. MSCs labeled with green fluorescence protein were transplanted intravitreally 1 week after OHT induction. At the end of the second and fourth weeks, retinal ganglion cells were visualized with the use of a flat-mount retina method and were evaluated by means of immunofluorescence staining against green fluorescence protein, vimentin, CD105, and cytokines (interleukin [IL]-1Ra, prostaglandin E2 receptor, IL-6, transforming growth factor-β1, interferon-γ and tumor necrosis factor-α).

RESULTS

The retinal ganglion cell numbers per area were significantly improved in stem cell-treated OHT groups compared with that in the non-treated OHT group (P < 0.05). The results of immunohistochemical analyses indicated that a limited number of stem cells had integrated into the ganglion cell layer and the inner nuclear layer. The number of cells expressing proinflammatory cytokines (interferon-γ and tumor necrosis factor-α) decreased in the MSC-transferred group compared with that in the OHT group after 4 weeks (P < 0.01). On the other hand, IL-1Ra and prostaglandin E2 receptor expressions were increased in the rat bone marrow-derived MSC group but were more significant in the rat adipose tissue-derived MSC group (P < 0.01).

CONCLUSIONS

After intravitreal transplantation, MSCs showed a neuroprotective effect in the rat OHT model. Therefore, MSCs promise an alternative therapy approach for functional recovery in the treatment of glaucoma.

Development of a murine ocular posterior segment explant culture for the study of intravitreous vector delivery

The objective of this study was to develop a murine retinal/choroidal/scleral explant culture system to facilitate the intravitreous delivery of vectors. Posterior segment explants from adult mice of 2 different age groups (4 wk and 15 wk) were cultured in serum-free medium for variable time periods. Tissue viability was assessed by gross morphology, cell survival quantification, activated caspase-3 expression, and immunohistochemistry. To model ocular gene therapy, explants were exposed to varying transducing units of a lentiviral vector expressing the gene for green fluorescent protein for 48 h. Explant retinal cells remained viable for approximately 1 wk, although the ganglion cell layer developed apoptosis between 4 and 7 d. Following vector infusion into the posterior segment cups, viral transduction was noted in multiple retinal layers in both age groups. An age of donor mouse influence was noted and older mice did not transduce as well as younger mice. This explant offers an easily managed posterior segment ocular culture with minimum disturbance of the tissue, and may be useful for investigating methods of enhancing retinal gene therapy under controlled conditions.

Stem cells as tools for studying the genetics of inherited retinal degenerations

The ability to provide early clinical intervention for inherited disorders is heavily dependent on knowledge of a patient's disease-causing mutations and the resultant pathophysiologic mechanism(s). Without knowing a patient's disease-causing gene, and how gene mutations alter the health and functionality of affected cells, it would be difficult to develop and deliver patient-specific molecular or small molecule therapies. Many believe that the field of stem cell biology holds the keys to the future development of disease-, patient-, and cell-specific therapies. In the case of the eye, which is susceptible to an extremely common late-onset degenerative disease known as age-related macular degeneration, stem cell-based therapies could increase the quality of life for millions of patients worldwide. Furthermore, autologous, patient-specific induced pluripotent stem cells could be a viable source to treat rare Mendelian retinal degenerative diseases such as retinitis pigmentosa, Stargardt disease, and Best disease, to name a few.

βB2-Crystallin Promotes Axonal Regeneration in the Injured Optic Nerve in Adult Rats

The purpose of the study was to further scrutinize the potential of βB2-crystallin in supporting regeneration of injured retinal ganglion cell axons both in vitro and in vivo. Retinal explants obtained from animals after treatment either with lens injury (LI) alone or with combined LI 5 days or 3 days before or simultaneously with an optic nerve crush (ONC) were cultured for 96 h under regenerative conditions, and the regenerating axons were quantified and compared with untreated controls. These measurements were then repeated with LI replaced by intravitreal injections of γ-crystallin and β-crystallin at 5 days before ONC. Finally, βB2-crystallin-overexpressing transfected neural progenitor cells (βB2-crystallin-NPCs) in the eye were studied after crushing the optic nerve in vivo. Regeneration was monitored with the aid of immunoblotting of the retina and optic nerve both distal and proximal to the lesion site, and this was compared with controls that received injections of phosphate buffer only. LI performed 5 days or 3 days before ONC significantly promoted axonal outgrowth in vitro (p < 0.001), while LI performed alone before explantation did not. Intravitreal injections of β-crystallin and γ-crystallin mimicked the effects of LI and significantly increased axonal regeneration in culture at the same time intervals (p < 0.001). Western blot analysis revealed that crystallins were present in the proximal optic nerve stump at the lesion site in ONC, but were neither expressed in the undamaged distal optic nerve nor in uninjured tissue. βB2-crystallin-NPCs supported the regeneration of cut optic nerve axons within the distal optic nerve stump in vivo. The reported data suggest that βB2-crystallin-producing "cell factories" could be used to provide novel therapeutic drugs for central nervous system injuries.

Inhibition of MMP-2 but not MMP-9 influences inner ear spiral ganglion neurons in vitro

Matrix metalloproteinases (MMPs) play an important role in modeling of the extracellular matrix. There is increasing evidence that these proteases are important in neurite elongation and axonal guidance during development in the central nervous system and retina. Moreover, they are also expressed after acute injury and can be the key mediators of pathogenesis. However, the role of MMPs in the inner ear is largely unknown. Our group recently demonstrated that general inhibition of MMPs resulted in auditory hair cell loss in vitro. In the present study, we investigated the role of MMPs in inner ear spiral ganglion neuron (SGN) survival, neuritogenesis and neurite extension by blocking MMPs known to be involved in axonal guidance, neurite elongation, and apoptosis in other neuronal systems. Spiral ganglion (SG) explants from 5-day-old Wistar rats were treated with different concentrations of the general MMP inhibitor GM6001, a specific MMP-2 inhibitor, and a specific MMP-9 inhibitor, in vitro. The general inhibitor of MMPs and the specific inhibition of MMP-2 significantly reduced both the number of neurites that extended from SG explants, as well as the length of individual neurites. However, neither the general inhibitor of MMPs nor the specific inhibition of MMP-2 influenced SGN survival. Inhibition of MMP-9 had no influence on SGNs. The data suggest that MMPs, and more specifically MMP-2, influence the growth of developing afferent neurites in the mammalian inner ear in vivo.

Mobilizing endogenous stem cells for retinal repair

Irreversible vision loss is most often caused by the loss of function and subsequent death of retinal neurons, such as photoreceptor cells-the cells that initiate vision by capturing and transducing signals of light. One reason why retinal degenerative diseases are devastating is that, once retinal neurons are lost, they don't grow back. Stem cell-based cell replacement strategy for retinal degenerative diseases are leading the way in clinical trials of transplantation therapy, and the exciting findings in both human and animal models point to the possibility of restoring vision through a cell replacement regenerative approach. A less invasive method of retinal regeneration by mobilizing endogenous stem cells is, thus, highly desirable and promising for restoring vision. Although many obstacles remain to be overcome, the field of endogenous retinal repair is progressing at a rapid pace, with encouraging results in recent years.

Stem cells for investigation and treatment of inherited retinal disease

Vision is the most important human sense. It facilitates every major activity of daily living ranging from basic communication, mobility and independence to an appreciation of art and nature. Heritable diseases of the retina, such as age-related macular degeneration and retinitis pigmentosa, are the leading cause of blindness in the developed world, collectively affecting as many as one-third of all people over the age of 75, to some degree. For decades, scientists have dreamed of preventing vision loss or of restoring the vision of patients affected with retinal degeneration through some type of drug, gene or cell-based transplantation approach. In this review, we will discuss the current literature pertaining to retinal transplantation. We will focus on the use of induced pluripotent stem cells for interrogation of disease pathophysiology, analysis of drug and gene therapeutics and as a source of autologous cells for cell replacement.

Stem cell therapy for glaucoma: possibilities and practicalities

Glaucoma is a progressive, neurodegenerative, optic neuropathy in which currently available therapies cannot always prevent, and do not reverse, vision loss. Stem cell transplantation may provide a promising new avenue for treating many presently incurable degenerative conditions, including glaucoma. This article will explore the various ways in which transplantation of stem or progenitor cells may be applied for the treatment of glaucoma. We will critically discuss the translational prospects of two cell transplantation-based treatment modalities: neuroprotection and retinal ganglion cell replacement. In addition, we will identify specific questions that need to be addressed and obstacles to overcome on the path to clinical translation, and offer insight into potential strategies for approaching this goal.

Scaffolds and stem cells: delivery of cell transplants for retinal degenerations

Retinal degenerations and optic neuropathies often lead to death of photoreceptors or retinal ganglion cells, respectively. Stem cell therapies are showing promise for these diseases in preclinical models and are beginning to transition into human trials, but cell delivery and integration remain major challenges. Focusing on photoreceptor- and progenitor-directed approaches, in this article, the authors review how advances in tissue engineering and cell scaffold design are enhancing cell therapies for retinal degeneration.

Advances in repairing the degenerate retina by rod photoreceptor transplantation

Despite very different aetiologies, age-related macular degeneration (AMD) and most inherited retinal disorders culminate in the same final common pathway, loss of the light-sensitive photoreceptors. There are few clinical treatments and none can reverse the loss of vision. Photoreceptor replacement by transplantation is proposed as a broad treatment strategy applicable to all degenerations. The past decade has seen a number of landmark achievements in this field, which together provide strong justification for continuing investigation into photoreceptor replacement strategies. These include proof of principle for restoring vision by rod-photoreceptor transplantation in mice with congenital stationary night blindness and advances in stem cell biology, which have led to the generation of complete optic structures in vitro from embryonic stem cells. The latter represents enormous potential for generating suitable and renewable donor cells with which to achieve the former. However, there are still challenges presented by the degenerating recipient retinal environment that must be addressed as we move to translating these technologies towards clinical application.

Regenerative therapies for central nervous system diseases: a biomaterials approach

The central nervous system (CNS) has a limited capacity to spontaneously regenerate following traumatic injury or disease, requiring innovative strategies to promote tissue and functional repair. Tissue regeneration strategies, such as cell and/or drug delivery, have demonstrated promising results in experimental animal models, but have been difficult to translate clinically. The efficacy of cell therapy, which involves stem cell transplantation into the CNS to replace damaged tissue, has been limited due to low cell survival and integration upon transplantation, while delivery of therapeutic molecules to the CNS using conventional methods, such as oral and intravenous administration, have been limited by diffusion across the blood-brain/spinal cord-barrier. The use of biomaterials to promote graft survival and integration as well as localized and sustained delivery of biologics to CNS injury sites is actively being pursued. This review will highlight recent advances using biomaterials as cell- and drug-delivery vehicles for CNS repair.

Role of Matrix Metalloproteinases in Migration and Neurotrophic Properties of Nasal Olfactory Stem and Ensheathing Cells

Adult olfactory ectomesenchymal stem cells (OE-MSCs) and olfactory ensheathing cells (OECs), both from the nasal olfactory lamina propria, display robust regenerative properties when transplanted into the nervous system, but the mechanisms supporting such therapeutic effects remain unknown. Matrix metalloproteinases (MMPs) are an important family of proteinases contributing to cell motility and axonal outgrowth across the extracellular matrix (ECM) in physiological and pathological conditions. In this study, we have characterized for the first time in nasal human OE-MSCs the expression profile of some MMPs currently associated with cell migration and invasiveness. We demonstrate different patterns of expression for MMP-1, MMP-2, MMP-9, and MT1-MMP upon cell migration when compared with nonmigrating cells. Our results establish a correspondence between the localization of these proteinases in the migration front with the ability of cells to migrate. Using various modulators of MMP activity, we also show that at least MMP-2, MMP-9, and MT1-MMP contribute to OE-MSC migration in an in vitro 3D test. Furthermore, we demonstrate under the same conditions of culture used for in vivo transplantation that OE-MSCs and OECs secrete neurotrophic factors that promote neurite outgrowth of cortical and dorsal root ganglia (DRG) neurons, as well as axo-dendritic differentiation of cortical neurons. These effects were abolished by the depletion of MMP-2 and MMP-9 from the culture conditioned media. Altogether, our results provide the first evidence that MMPs may contribute to the therapeutic features of OE-MSCs and OECs through the control of their motility and/or their neurotrophic properties. Our data provide new insight into the mechanisms of neuroregeneration and will contribute to optimization of cell therapy strategies.

Role of HIF-1α-activated Epac1 on HSC-mediated neuroplasticity in stroke model

Exchange protein activated by cAMP-1 (Epac1) plays an important role in cell proliferation, cell survival and neuronal signaling, and activation of Epac1 in endothelial progenitor cells increases their homing to ischemic muscles and promotes neovascularization in a model of hind limb ischemia. Moreover, upregulation of Epac1 occurs during organ development and in diseases such as myocardial hypertrophy, diabetes, and Alzheimer's disease. We report here that hypoxia upregulated Epac1 through HIF-1α induction in the CD34-immunosorted human umbilical cord blood hematopoietic stem cells (hUCB(34)). Importantly, implantation of hUCB(34) subjected to hypoxia-preconditioning (HP-hUCB(34)) improved stroke outcome, more than did implantation of untreated hUCB(34), in rodents subjected to cerebral ischemia, and this required Epac1-to-matrix metalloprotease (MMP) signaling. This improved therapeutic efficacy correlated with better engraftment and differentiation of these cells in the ischemic host brain. In addition, more than did implantation of untreated HP-hUCB(34), implantation of HP-hUCB(34) improved cerebral blood flow into the ischemic brain via induction of angiogenesis, facilitated proliferation/recruitment of endogenous neural progenitor cells in the ischemic brain, and promoted neurite outgrowth following cerebral ischemia. Consistent with our proposed role of Epac1-to-MMP signaling in hypoxia-preconditioning, the above mentioned effects of implanting HP-hUCB(34) could be abolished by pharmacological inhibition and genetic disruption/deletion of Epac1 or MMPs. We have discovered a HIF-1α-to-Epac1-to-MMP signaling pathway that is required for the improved therapeutic efficacy resulting from hypoxia preconditioning of hUCB(34) in vitro prior to their implantation into the host brain in vivo.

Secretome of peripheral blood mononuclear cells enhances wound healing

Non-healing skin ulcers are often resistant to most common therapies. Treatment with growth factors has been demonstrated to improve closure of chronic wounds. Here we investigate whether lyophilized culture supernatant of freshly isolated peripheral blood mononuclear cells (PBMC) is able to enhance wound healing. PBMC from healthy human individuals were prepared and cultured for 24 hours. Supernatants were collected, dialyzed and lyophilized (SEC^PBMC). Six mm punch biopsy wounds were set on the backs of C57BL/6J-mice and SEC^PBMC containing emulsion or controls were applied daily for three days. Morphology and neo-angiogenesis were analyzed by H&E-staining and CD31 immuno-staining, respectively. In vitro effects on diverse skin cells were investigated by migration assays, cell cycle analysis, and tube formation assay. Signaling pathways were analyzed by Western blot analysis. Application of SEC^PBMC on 6 mm punch biopsy wounds significantly enhanced wound closure. H&E staining of the wounds after 6 days revealed that wound healing was more advanced after application of SEC^PBMC containing emulsion. Furthermore, there was a massive increase in CD31 positive cells, indicating enhanced neo-angiogenesis. In primary human fibroblasts (FB) and keratinocytes (KC) migration but not proliferation was induced. In endothelial cells (EC) SEC^PBMC induced proliferation and tube-formation in a matrigel-assay. In addition, SEC^PBMC treatment of skin cells led to the induction of multiple signaling pathways involved in cell migration, proliferation and survival. In summary, we could show that emulsions containing the secretome of PBMC derived from healthy individuals accelerates wound healing in a mouse model and induce wound healing associated mechanisms in human primary skin cells. The formulation and use of such emulsions might therefore represent a possible novel option for the treatment of non-healing skin ulcers.

The extracellular matrix glycoprotein tenascin-R regulates neurogenesis during development and in the adult dentate gyrus of mice

Abnormal generation of inhibitory γ-aminobutyric acid synthesizing (GABAergic) neurons is characteristic of neuropsychological disorders. We provide evidence that the extracellular matrix molecule tenascin-R (TNR) – being predominantly expressed, among neurons, by subpopulation of interneurons - plays a role in the generation of GABAergic and granule neurons in the murine dentate gyrus by regulating fate determination of neural stem/progenitor cells (NSCs). During development, absence of TNR in constitutively TNR-deficient (TNR−/−) mice results in increased numbers of dentate gyrus GABAergic neurons, being associated with decreased expression of its receptor β1 integrin, increased activation of p38 MAPK, and increased expression of the GABAergic specification gene ASCL1. Postnatally, increased GABAergic input to adult hippocampal NSCs in TNR−/− mice is associated not only with increased numbers of GABAergic and, particularly, parvalbumin-immunoreactive neurons, as seen during development, but also with increased numbers of granule neurons, thus contributing to the increased differentiation of NSCs into granule cells. These findings indicate the importance of TNR in the regulation of hippocampal neurogenesis and suggest that TNR acts through distinct direct and indirect mechanisms during development and in the adult.

Repair of the degenerate retina by photoreceptor transplantation

Despite different aetiologies, age-related macular degeneration and most inherited retinal disorders culminate in the same final common pathway, the loss of photoreceptors. There are few treatments and none reverse the loss of vision. Photoreceptor replacement by transplantation is proposed as a broad treatment strategy applicable to all degenerations. Recently, we demonstrated restoration of vision following rod-photoreceptor transplantation into a mouse model of stationary night-blindness, raising the critical question of whether photoreceptor replacement is equally effective in different types and stages of degeneration. We present a comprehensive assessment of rod-photoreceptor transplantation across six murine models of inherited photoreceptor degeneration. Transplantation is feasible in all models examined but disease type has a major impact on outcome, as assessed both by the morphology and number of integrated rod-photoreceptors. Integration can increase (Prph2(+/Δ307)), decrease (Crb1(rd8/rd8), Gnat1(-/-), Rho(-/-)), or remain constant (PDE6β(rd1/rd1), Prph2(rd2/rd2)) with disease progression, depending upon the gene defect, with no correlation with severity. Robust integration is possible even in late-stage disease. Glial scarring and outer limiting membrane integrity, features that change with degeneration, significantly affect transplanted photoreceptor integration. Combined breakdown of these barriers markedly increases integration in a model with an intact outer limiting membrane, strong gliotic response, and otherwise poor transplantation outcome (Rho(-/-)), leading to an eightfold increase in integration and restoration of visual function. Thus, it is possible to achieve robust integration across a broad range of inherited retinopathies. Moreover, transplantation outcome can be improved by administering appropriate, tailored manipulations of the recipient environment.

The matrix metalloproteinase inhibitor marimastat promotes neural progenitor cell differentiation into neurons by gelatinase-independent TIMP-2-dependent mechanisms

Metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs), produced in the brain by cells of non-neural and neural origin, including neural progenitors (NPs), are emerging as regulators of nervous system development and adult brain functions. In the present study, we explored whether MMP-2, MMP-9, and TIMP-2, abundantly produced in the brain, modulate NP developmental properties. We found that treatment of NPs, isolated from the murine fetal cerebral cortex or adult subventricular zone, with the clinically tested broad-spectrum MMP inhibitor Marimastat profoundly affected the NP differentiation fate. Marimastat treatment allowed for an enrichment of our cultures in neuronal cells, inducing NPs to generate higher percentage of neurons and a lower percentage of astrocytes, possibly affecting NP commitment. Consistently with its proneurogenic effect, Marimastat early downregulated the expression of Notch target genes, such as Hes1 and Hes5. MMP-2 and MMP-9 profiling on proliferating and differentiating NPs revealed that MMP-9 was not expressed under these conditions, whereas MMP-2 increased in the medium as pro-MMP-2 (72 kDa) during differentiation; its active form (62 kDa) was not detectable by gel zymography. MMP-2 silencing or administration of recombinant active MMP-2 demonstrated that MMP-2 does not affect NP neuronal differentiation, nor it is involved in the Marimastat proneurogenic effect. We also found that TIMP-2 is expressed in NPs and increases during late differentiation, mainly as a consequence of astrocyte generation. Endogenous TIMP-2 did not modulate NP neurogenic potential; however, the proneurogenic action of Marimastat was mediated by TIMP-2, as demonstrated by silencing experiments. In conclusion, our data exclude a major involvement of MMP-2 and MMP-9 in the regulation of basal NP differentiation, but highlight the ability of TIMP-2 to act as key effector of the proneurogenic response to an inducing stimulus such as Marimastat.

Axonal growth towards Xenopus skin in vitro is mediated by matrix metalloproteinase activity

We have previously demonstrated that the growth of peripheral nervous system axons is strongly attracted towards limb buds and skin explants in vitro. Here, we show that directed axonal growth towards skin explants of Xenopus laevis in matrigel is associated with expression of matrix metalloproteinase (MMP)-18 and also other MMPs, and that this long-range neurotropic activity is inhibited by the broad-spectrum MMP inhibitors BB-94 and GM6001. We also show that forced expression of MMP-18 in COS-7 cell aggregates enhances axonal growth from Xenopus dorsal root ganglia explants. Nidogen is the target of MMPs released by cultured skin in matrigel, whereas other components remain intact. Our results suggest a novel link between MMP activity and extracellular matrix breakdown in the control of axonal growth.

Nuclear reprogramming and induced pluripotent stem cells: a review for surgeons

Induced pluripotent stem cells (iPSCs) are generated from somatic cells by the exogenous expression of defined transcription factors. iPSCs share the defining features of embryonic stem cells (ESCs) in that they are able to self-renew indefinitely and maintain the potential to develop into all cell types of the body. These cells have key advantages over ESCs in that they are autologous to the donor cells and can be generated from individuals at any age. iPSCs also circumvent ethical and political issues surrounding the destruction of embryos that is necessary in the isolation of ESCs. This review briefly describes the advent of iPSC technology and the concepts of nuclear reprogramming, and discusses the potential application of this powerful biological tool in both surgical research and regenerative medicine.

Matrix metalloproteinases in neuropathic pain and migraine: friends, enemies, and therapeutic targets

Matrix metalloproteinases (MMPs) constitute a family of zinc-dependent endopeptidases that mediate extracellular matrix turnover and associated processes, such as cell survival, growth, and differentiation. This paper discusses important functions of MMP in the normal and injured nervous system, focusing on the role played by these proteases in neurological pain syndromes, most prominently in neuropathic pain and migraine headaches. In the past decade, metalloproteinases emerged as key modulators of neuropathic pain, with MMP-9 acting as an initiator of the neuropathic cascade. Increased MMP activity was detected in migraine patients, independent of aura, in tight association with metabolic derangements. The therapeutic implications of MMP inhibition are considered in the context of neurogenic pain regulation.

Time associated decline in neurotrophic properties of neural stem cell grafts render them dependent on brain region-specific environmental support

Fetal neural stem/precursor cells (NPCs) possess powerful neurotrophic properties by which they can facilitate self repair processes in the adult central nervous system. The therapeutic value of NPC therapy in neurodegenerative diseases is critically dependent on their long term survival and enduring functional properties. An important aspect of NPC neurotrophic properties is their ability to support their own survival independent of any exogenous growth factor. Here, we examined whether NPCs survive and maintain their properties for extended periods of time, or become dependent on environmental support. Two months following transplantation to naïve brains, large grafts were detected in the ventricles and hippocampus, but only little survival was evident in the striatum. To point at possible regional characteristics which underlie the differential survival of NPC grafts we performed several manipulations of the brain environment. Acute neurotoxic injury with 6-hydroxydopamine induced a 3-fold increase in striatal graft survival, associated with induction of nestin, CD31, β1-integrin, GFAP and cycling cells. Disruption of the extracellular matrix structure of this reactive niche by continuous blockage of host striatum β1-integrin caused 73% reduction in graft survival. In the hippocampus, NPC graft survival did not correspond to β1-integrin and CD31 expression. This suggests that hippocampal environmental support to graft survival rely on different mechanisms than in the reactive striatum. In correlation with in vivo findings, long term cultured neural precursors exhibited an increase in apoptotic cells and dramatic decline in neurotrophic effects, as indicated by two in vitro functional assays. We conclude that long-term changes in transplanted NPC properties render them dependent on region specific environmental support. The major extracellular matrix protein β1-integrin is essential for providing tissue support for graft survival in the striatum. The neurotrophic properties of transplanted neural stem cells are limited in time, representing a shortcoming which should be taken into consideration when developing clinical transplantation protocols for chronic neurological disorders.

Neuronal and glial differentiation during lizard (Gallotia galloti) visual system ontogeny

We studied the histogenesis of the lizard visual system (E30 to adulthood) by using a selection of immunohistochemical markers that had proved relevant for other vertebrates. By E30, the Pax6(+) pseudostratified retinal epithelium shows few newborn retinal ganglion cells (RGCs) in the centrodorsal region expressing neuron- and synaptic-specific markers such as betaIII-tubulin (Tuj1), synaptic vesicle protein-2 (SV2), and vesicular glutamate transporter-1 (VGLUT1). Concurrently, pioneer RGC axons run among the Pax2(+) astroglia in the optic nerve and reach the superficial optic tectum. Between E30 and E35, the optic chiasm and optic tract remain acellular, but the latter contains radial processes with subpial endfeet expressing vimentin (Vim). From E35, neuron- and synaptic-specific stainings spread in the retina and optic tectum, whereas retinal Pax6, and Tuj1/SV2 in RGC axons decrease. Müller glia and abundant optic nerve glia express a variety of glia-specific markers until adulthood. Subpopulations of optic nerve glia are also VGLUT1(+) and cluster differentiation-44 (CD44)-positive but cytokeratin-negative, unlike the case in other regeneration-competent species. Specifically, coexpression of CD44/Vim and glutamine synthetase (GS)/VGLUT1 reflects glial specialization, insofar as most CD44(+) glia are GS(-). In the adult optic tract and tectum, radial glia and free astroglia coexist. The latter show different immunocharacterization (Pax2(-)/CD44(-) /Vim(-)) compared with that in the optic nerve. We conclude that upregulation of Tuj1 and SV2 is required for axonal outgrowth and search for appropriate targets, whereas Pax2(+) optic nerve astroglia and Vim(+) radial glia may aid in early axonal guidance. Spontaneous axonal regrowth seems to succeed despite the heterogeneous mammalian-like glial environment in the lizard optic nerve.

Mechanisms of action of mesenchymal stem cells in cutaneous wound repair and regeneration

Mesenchymal stem cells (MSCs) are multipotent cells with the capacity for self-renewal and differentiation and have a broad tissue distribution. These characteristics make them candidate cells for wound healing and regeneration in a variety of disorders. Endogenous MSCs or exogenously delivered MSCs can traffic and migrate to injured tissue and participate in the healing of this tissue. The concentrated conditioned medium from MSCs can modulate wound repair without MSCs being present in the wound. The therapeutic effects of MSCs might be attributable to their ability to differentiate and transdifferentiate into tissue-specific cells, to fuse with the resident cells, to secrete a wide array of paracrine factors in order to stimulate the survival and functional recovery of the resident cells, or to regulate the local microenviroment or niche and immune response. These mechanisms are probably independent but not mutually exclusive. In many circumstances, a combination of these protective mechanisms might work together to affect cutaneous wound healing. This review gives a brief overview and discusses the mechanisms by which MSCs promote skin repair and regeneration, although the specific mechanisms in each type of cutaneous wound are still unclear and controversial. A comprehensive understanding of the mechanisms should allow us to find advanced and better treatment strategies for various skin diseases, even those that are currently incurable.

Lectican proteoglycans, their cleaving metalloproteinases, and plasticity in the central nervous system extracellular microenvironment

The extracellular matrix (ECM) in the central nervous system actively orchestrates and modulates changes in neural structure and function in response to experience, after injury, during disease, and with changes in neuronal activity. A component of the multi-protein, ECM aggregate in brain, the chondroitin sulfate (CS)-bearing proteoglycans (PGs) known as lecticans, inhibit neurite outgrowth, alter dendritic spine shape, elicit closure of critical period plasticity, and block target reinnervation and functional recovery after injury as the major component of a glial scar. While removal of the CS chains from lecticans with chondroitinase ABC improves plasticity, proteolytic cleavage of the lectican core protein may change the conformation of the matrix aggregate and also modulate neural plasticity. This review centers on the roles of the lecticans and the endogenous metalloproteinase families that proteolytically cleave lectican core proteins, the matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs), in neural plasticity. These extracellular metalloproteinases modulate structural neural plasticity-including changes in neurite outgrowth and dendritic spine remodeling-and synaptic plasticity. Some of these actions have been demonstrated to occur via cleavage of the PG core protein. Other actions of the proteases include cleavage of non-matrix substrate proteins, whereas still other actions may occur directly at the cell surface without proteolytic cleavage. The data convincingly demonstrate that metalloproteinases modulate physiological and pathophysiological neural plasticity.

The interaction between cell adhesion molecule L1, matrix metalloproteinase 14, and adenine nucleotide translocator at the plasma membrane regulates L1-mediated neurite outgrowth of murine cerebellar neurons

We have identified the adenine nucleotide translocator (ANT) isoforms ANT1 and ANT2 that are present in the plasma membrane of mouse cerebellar neurons as novel binding partners of the cell adhesion molecule L1. The direct interaction between ANT and L1 is mediated by sites within the fibronectin type III domains of L1 and the first and third extracellular loops of the ANT proteins. We also show that L1 interacts with the ANT binding partner matrix metalloprotease 14 (MMP14) and that the ANT proteins bind directly to the L1 interaction partner glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Moreover, we provide evidence that the functional interplay between L1, ANT proteins, MMP14, and GAPDH at the plasma membrane mediates L1-induced neurite outgrowth of cerebellar neurons. Disruption of this interplay by ANT inhibitors, ANT-derived synthetic peptides, and/or function-blocking MMP14 and ANT antibodies leads to alterations in L1-dependent neurite outgrowth. Stimulation of L1-mediated signaling in cerebellar neurons triggers transient ATP secretion via ANT proteins and leads to transient src family-dependent tyrosine phosphorylation of L1, ANT1, ANT2, and MMP14. Thus, our results indicate that plasma membrane-localized ANT1 and ANT2 regulate L1-mediated neurite outgrowth in conjunction with MMP14.

New perspectives of tissue remodelling with neural stem and progenitor cell-based therapies

Compelling evidence exists that neural stem cell-based therapies protect the central nervous system (CNS) from chronic inflammatory degeneration, such as that occurring in experimental autoimmune encephalomyelitis and stroke. It was first assumed that stem cells directly replace lost cells but it is now becoming clearer that they might be able to protect the nervous system through mechanisms other than cell replacement. In immune-mediated experimental demyelination and stroke, transplanted neural stem/precursor cells (NPCs) are able to mediate efficient bystander myelin repair and axonal rescue. This is dependent on multiple capacities that transplanted NPCs exhibit within specific microenvironments after transplantation. However, a comprehensive understanding of the mechanisms by which NPCs exert their therapeutic impact is lacking. Here we will review some of the most recent evidence--and discuss some of the likely mechanisms--that support the remarkable capacity of NPCs to cross-talk with endogenous cells and to remodel the injured nervous system when applied as novel therapeutic regimes. We foresee that the exploitation of the innate mechanisms regulating these modalities of cell-to-cell communication has realistic chances of revolutionizing most of the actual understanding of stem cell biology and its application to regenerative medicine and CNS repair.

Transplantation of Schwann cells differentiated from adipose-derived stem cells modifies reactive gliosis after contusion brain injury in rats

This study investigated whether transplantation of Schwann cells differentiated from adipose-derived stem cells (ADSC-SCs) of rats could promote functional improvement after contusion brain injury, with a focus on the effect on reactive gliosis. ADSCs were isolated and expanded from groin adipose tissue of Sprague-Dawley rats and then differentiated into Schwann cells. ADSCSCs were transplanted into the contused rat brain. Immunofluorescence and Western blotting were used to analyse reactive gliosis, and locomotor function of the rats was assessed. Hemiparalysed rats transplanted with ADSC-SCs showed significant locomotor function recovery compared with rats transplanted with undifferentiated ADSCs or control rats injected with medium alone. Transplanted ADSC-SCs significantly reduced glial scar formation and neurocan protein levels compared with transplanted undifferentiated ADSCs. In conclusion, transplantation of ADSC-SCs can effectively promote locomotor functional recovery and reduce reactive gliosis after contusion brain injury in rats.