Isolation of human multipotent neural progenitors from adult filum terminale

Advances in Neural Stem Cell Therapy for Spinal Cord Injury: Safety, Efficacy, and Future Perspectives

Spinal cord injury (SCI) is a devastating central nervous system injury that leads to severe disabilities in motor and sensory functions, causing significant deterioration in patients' quality of life. Owing to the complexity of SCI pathophysiology, there has been no effective treatment for reversing neural tissue damage and recovering neurological functions. Several novel therapies targeting different stages of pathophysiological mechanisms of SCI have been developed. Among these, treatments using stem cells have great potential for the regeneration of damaged neural tissues. In this review, we have summarized recent preclinical and clinical studies focusing on neural stem cells (NSCs). NSCs are multipotent cells with specific differentiation capabilities for neural lineage. Several preclinical studies have demonstrated the regenerative effects of transplanted NSCs in SCI animal models through both paracrine effects and direct neuronal differentiation, restoring synaptic connectivity and neural networks. Based on the positive results of several preclinical studies, phase I and II clinical trials using NSCs have been performed. Despite several hurdles and issues that need to be addressed in the clinical use of NSCs in patients with SCI, gradual progress in the technical development and therapeutic efficacy of NSCs treatments has enhanced the prospects for cell-based treatments in SCI.

Filum Terminale: A Comprehensive Review with Anatomical, Pathological, and Surgical Considerations

The conus medullaris is the distal tapering end of the spinal cord, and the filum terminale (FT) is regarded as a bundle of non-functional fibrous tissue; therefore, some scholars call it the spinal ligament, while others describe the human FT as "remnants of the spinal cord." It was later found that in the human spinal cord, the FT is composed of an intradural segment and an epidural segment, and the end of the FT is connected to the coccyx periosteum. Because some nerve tissue is also found in the FT, as research progresses, FT may have the potential for transplantation. A lack of exhaustive overviews on the FT in the present literature prompted us to conduct this review. Considering that a current comprehensive review seemed to be the need of the hour, herein, we attempted to summarize previous research and theories on the FT, elucidate its anatomy, and understand its pathological involvement in various diseases.

A Guide to Extract Spinal Cord for Translational Stem Cell Biology Research: Comparative Analysis of Adult Human, Porcine, and Rodent Spinal Cord Stem Cells

Improving the clinical translation of animal-based neural stem/progenitor cell (NSPC) therapies to humans requires an understanding of intrinsic human and animal cell characteristics. We report a novel in vitro method to assess spinal cord NSPCs from a small (rodent) and large (porcine) animal model in comparison to human NSPCs. To extract live adult human, porcine, and rodent spinal cord tissue, we illustrate a strategy using an anterior or posterior approach that was simulated in a porcine model. The initial expansion of primary NSPCs is carried out using the neurosphere assay followed by a pharmacological treatment phase during which NSPCs derived from humans, porcines, and rodents are assessed in parallel using the same defined parameters. Using this model, NSPCs from all species demonstrated multi-lineage differentiation and self-renewal. Importantly, these methods provide conditions to enable the direct comparison of species-dependent cell behavior in response to specific exogenous signals.

Endogenous spinal cord stem cells in multiple sclerosis and its animal model

The adult mammalian spinal cord (SC) harbors neural stem cells (NSCs). The SC-NSCs are mostly quiescent during physiological conditions but are quickly activated in traumatic injury models. The SC-NSCs generate mostly glia, but are able to differentiate into neurons when affected by favourable conditions. An example is the inflammatory milieu in the SC of rat EAE, where the SC-NSCs migrate into demyelinated lesions and give rise to both glia and neurons. In MS, cells with progenitor phenotypes accumulate in inflammatory lesions both in brain and SC, but the extent to which these cells contribute to repair remains to be revealed.

Optimized Clump Culture Methods for Adult Human Multipotent Neural Cells

Adult human multipotent neural cell (ahMNC) is a candidate for regeneration therapy for neurodegenerative diseases. Here, we developed a primary clump culture method for ahMNCs to increase the efficiency of isolation and in vitro expansion. The same amount of human temporal lobe (1 g) was partially digested and then filtered through strainers with various pore sizes, resulting in four types of clumps: Clump I > 100 µm, 70 µm < Clump II < 100 µm, 40 µm < Clump III < 70 µm, and Clump IV < 40 µm. At 3 and 6 days after culture, Clump II showed significantly higher number of colonies than the other Clumps. Moreover, ahMNCs derived from Clump II (ahMNCs-Clump II) showed stable proliferation, and shortened the time to first passage from 19 to 15 days, and the time to 1 × 10⁹ cells from 42 to 34 days compared with the previous single-cell method. ahMNCs-Clump II had neural differentiation and pro-angiogenic potentials, which are the characteristics of ahMNCs. In conclusion, the novel clump culture method for ahMNCs has significantly higher efficiency than previous techniques. Considering the small amount of available human brain tissue, the clump culture method would promote further clinical applications of ahMNCs.

Rapid Serum-Free Isolation of Oligodendrocyte Progenitor Cells from Adult Rat Spinal Cord

Oligodendrocyte progenitor cells (OPCs) play a pivotal role in both health and disease within the central nervous system, with oligodendrocytes, arising from resident OPCs, being the main myelinating cell type. Disruption in OPC numbers can lead to various deleterious health defects. Numerous studies have described techniques for isolating OPCs to obtain a better understanding of this cell type and to open doors for potential treatments of injury and disease. However, the techniques used in the majority of these studies involve several steps and are time consuming, with current culture protocols using serum and embryonic or postnatal cortical tissue as a source of isolation. We present a primary culture method for the direct isolation of functional adult rat OPCs, identified by neuron-glial antigen 2 (NG2) and platelet derived growth factor receptor alpha (PDGFrα) expression, which can be obtained from the adult spinal cord. Our method uses a simple serum-free cocktail of 3 growth factors - FGF₂, PDGF_AA, and IGF-I, to expand adult rat OPCs in vitro to 96% purity. Cultured cells can be expanded for at least 10 passages with very little manipulation and without losing their phenotypic progenitor cell properties, as shown by immunocytochemistry and RT-PCR. Cultured adult rat OPCs also maintain their ability to differentiate into GalC positive cells when incubated with factors known to stimulate their differentiation. This new isolation method provides a new source of easily accessible adult stem cells and a powerful tool for their expansion in vitro for studies aimed at central nervous system repair.

Brain tissue banking for stem cells for our future

In our lab we study neurogenesis and the development of brain tumors. We work towards treatment strategies for glioblastoma and towards using autologous neural stem cells for tissue regeneration strategies for brain damage and neurodegenerative disorders. It has been our policy to try to establish living cell cultures from all human biopsy material that we obtain. We hypothesized that small pieces of brain tissue could be cryopreserved and that live neural stem cells could be recovered at a later time. DMSO has been shown to possess a remarkable ability to diffuse through cell membranes and pass into cell interiors. Its chemical properties prevent the formation of damaging ice crystals thus allowing cell storage at or below −180 C. We report here a protocol for successful freezing of small pieces of tissue derived from human brain and human brain tumours. Virtually all specimens could be successfully revived. Assays of phenotype and behaviour show that the cell cultures derived were equivalent to those cultures previously derived from fresh tissue.

Characterization of the Filum terminale as a neural progenitor cell niche in both rats and humans

Neural stem cells (NSCs) reside in a unique microenvironment within the central nervous system (CNS) called the NSC niche. Although they are relatively rare, niches have been previously characterized in both the brain and spinal cord of adult animals. Recently, another potential NSC niche has been identified in the filum terminale (FT), which is a thin band of tissue at the caudal end of the spinal cord. While previous studies have demonstrated that NSCs can be isolated from the FT, the in vivo architecture of this tissue and its relation to other NSC niches in the CNS has not yet been established. In this article we report a histological analysis of the FT NSC niche in postnatal rats and humans. Immunohistochemical characterization reveals that the FT is mitotically active and its cells express similar markers to those in other CNS niches. In addition, the organization of the FT most closely resembles that of the adult spinal cord niche. J. Comp. Neurol. 525:661–675, 2017. © 2016 Wiley Periodicals, Inc.

Effects of Neuroinflammation on Neural Stem Cells

Neural stem/progenitor cells (NSCs/NPCs) are present in different locations in the central nervous system. In the subgranular zone (SGZ) there is a constant generation of new neurons under normal conditions. New neurons are also formed from the subventricular zone (SVZ) NSCs, and they migrate anteriorly as neuroblast to the olfactory bulb in rodents, whereas in humans migration is directed toward striatum. Most CNS injuries elicit proliferation and migration of the NSCs toward the injury site, indicating the activation of a regenerative response. However, regeneration from NSC is incomplete, and this could be due to detrimental cues encountered during inflammation. Different CNS diseases and trauma cause activation of the innate and adaptive immune responses that influence the NSCs. Furthermore, NSCs in the brain react differently to inflammatory cues than their counterparts in the spinal cord. In this review, we have summarized the effects of inflammation on NSCs in relation to their origin and briefly described the NSC activity during different neurological diseases or experimental models.

Adult human neural stem cell therapeutics: Current developmental status and prospect

Over the past two decades, regenerative therapies using stem cell technologies have been developed for various neurological diseases. Although stem cell therapy is an attractive option to reverse neural tissue damage and to recover neurological deficits, it is still under development so as not to show significant treatment effects in clinical settings. In this review, we discuss the scientific and clinical basics of adult neural stem cells (aNSCs), and their current developmental status as cell therapeutics for neurological disease. Compared with other types of stem cells, aNSCs have clinical advantages, such as limited proliferation, inborn differentiation potential into functional neural cells, and no ethical issues. In spite of the merits of aNSCs, difficulties in the isolation from the normal brain, and in the in vitro expansion, have blocked preclinical and clinical study using aNSCs. However, several groups have recently developed novel techniques to isolate and expand aNSCs from normal adult brains, and showed successful applications of aNSCs to neurological diseases. With new technologies for aNSCs and their clinical strengths, previous hurdles in stem cell therapies for neurological diseases could be overcome, to realize clinically efficacious regenerative stem cell therapeutics.

Expansion of multipotent stem cells from the adult human brain

The discovery of stem cells in the adult human brain has revealed new possible scenarios for treatment of the sick or injured brain. Both clinical use of and preclinical research on human adult neural stem cells have, however, been seriously hampered by the fact that it has been impossible to passage these cells more than a very few times and with little expansion of cell numbers. Having explored a number of alternative culturing conditions we here present an efficient method for the establishment and propagation of human brain stem cells from whatever brain tissue samples we have tried. We describe virtually unlimited expansion of an authentic stem cell phenotype. Pluripotency proteins Sox2 and Oct4 are expressed without artificial induction. For the first time multipotency of adult human brain-derived stem cells is demonstrated beyond tissue boundaries. We characterize these cells in detail in vitro including microarray and proteomic approaches. Whilst clarification of these cells' behavior is ongoing, results so far portend well for the future repair of tissues by transplantation of an adult patient's own-derived stem cells.

The postnatal human filum terminale is a source of autologous multipotent neurospheres capable of generating motor neurons

BACKGROUND

Neural progenitor cells (NPCs) are undifferentiated and mitotic and can be induced to differentiate into neurons and glia, the building blocks of the nervous system. NPCs have great therapeutic potential for nervous system trauma and degenerative disorders. They have been identified in the mammalian central nervous system, but current sources are difficult to access surgically and come from regions that are critical for normal brain function.

OBJECTIVE

To identify and characterize in detail a novel source of human NPCs in the filum terminale (FT), a vestigial structure at the caudal end of the spinal cord, which is easily accessed and plays no functional role in the postnatal nervous system.

METHODS

Cells were isolated and cultured in vitro from the FT of terminated fetuses and from children and adolescents who had undergone surgical resections for tethered spinal cords. Cell culture techniques, immunohistochemistry, and immunocytochemistry were applied to examine FT cells.

RESULTS

: FT cells gave rise to neurospheres that proliferated over extended periods of time in culture. These neurospheres were positive for neural stem/progenitor cell markers by immunocytochemical staining. The neurospheres were able to be induced to differentiate in vitro into neurons and glial cells, which were confirmed by the use of antibodies against the cell type-specific markers. Moreover, they have been induced to form motor neurons capable of innervating striated muscle in vitro.

CONCLUSION

Multipotent NPC cells from the FT are both accessible and expendable. They may allow autologous cell-based transplantation therapy that circumvents immunological rejection.

The isolation, differentiation, and survival in vivo of multipotent cells from the postnatal rat filum terminale

Neural stem cells (NSCs) are undifferentiated cells in the central nervous system (CNS) that are capable of self-renewal and can be induced to differentiate into neurons and glia. Current sources of mammalian NSCs are confined to regions of the CNS that are critical to normal function and surgically difficult to access, which limits their therapeutic potential in human disease. We have found that the filum terminale (FT), a previously unexplored, expendable, and easily accessible tissue at the caudal end of the spinal cord, is a source of multipotent cells in postnatal rats and humans. In this study, we used a rat model to isolate and characterize the potential of these cells. Neurospheres derived from the rat FT are amenable to in vitro expansion in the presence of a combination of growth factors. These proliferating, FT-derived cells formed neurospheres that could be induced to differentiate into neural progenitor cells, neurons, astrocytes, and oligodendrocytes by exposure to serum and/or adhesive substrates. Through directed differentiation using sonic hedgehog and retinoic acid in combination with various neurotrophic factors, FT-derived neurospheres generated motor neurons that were capable of forming neuromuscular junctions in vitro. In addition, FT-derived progenitors that were injected into chick embryos survived and could differentiate into both neurons and glia in vivo.

Distribution and characterization of progenitor cells within the human filum terminale

Background

Filum terminale (FT) is a structure that is intimately associated with conus medullaris, the most caudal part of the spinal cord. It is well documented that certain regions of the adult human central nervous system contains undifferentiated, progenitor cells or multipotent precursors. The primary objective of this study was to describe the distribution and progenitor features of this cell population in humans, and to confirm their ability to differentiate within the neuroectodermal lineage.

Methodology/Principal Findings

We demonstrate that neural stem/progenitor cells are present in FT obtained from patients treated for tethered cord. When human or rat FT-derived cells were cultured in defined medium, they proliferated and formed neurospheres in 13 out of 21 individuals. Cells expressing Sox2 and Musashi-1 were found to outline the central canal, and also to be distributed in islets throughout the whole FT. Following plating, the cells developed antigen profiles characteristic of astrocytes (GFAP) and neurons (β-III-tubulin). Addition of PDGF-BB directed the cells towards a neuronal fate. Moreover, the cells obtained from young donors shows higher capacity for proliferation and are easier to expand than cells derived from older donors.

Conclusion/Significance

The identification of bona fide neural progenitor cells in FT suggests a possible role for progenitor cells in this extension of conus medullaris and may provide an additional source of such cells for possible therapeutic purposes.

Filum terminale, human, progenitor cells, neuron, astrocytes, spinal cord.

Markers of pluripotency and differentiation in human neural precursor cells derived from embryonic stem cells and CNS tissue

Cell transplantation therapies for central nervous system (CNS) deficits such as spinal cord injury (SCI) have been shown to be effective in several animal models. One cell type that has been transplanted is neural precursor cells (NPCs), for which there are several possible sources. We have studied NPCs derived from human embryonic stem cells (hESCs) and human fetal CNS tissue (hfNPCs), cultured as neurospheres, and the expression of pluripotency and neural genes during neural induction and in vitro differentiation. mRNA for the pluripotency markers Nanog, Oct-4, Gdf3, and DNMT3b were downregulated during neural differentiation of hESCs. mRNA for these markers was found in nonpluripotent hfNPC at higher levels compared to hESC-NPCs. However, Oct-4 protein was found in hESC-NPCs after 8 weeks of culture, but not in hfNPCs. Similarly, SSEA-4 and CD326 were only found in hESC-NPCs. NPCs from both sources differentiated as expected to cells with typical features of neurons and astrocytes. The expressions of neuronal markers in hESC-NPCs were affected by the composition of cell culture medium, while this did not affect hfNPCs. Transplantation of hESC-NPC or hfNPC neurospheres into immunodeficient mouse testis or subcutaneous tissue did not result in tumor formation. In contrast, typical teratomas appeared in all animals after transplantation of hESC-NPCs to injured or noninjured spinal cords of immunodeficient rats. Our data show that transplantation to the subcutaneous tissue or the testes of immunodeficient mice is not a reliable method for evaluation of the tumor risk of remaining pluripotent cells in grafts.

Brain tumor stem cells maintain overall phenotype and tumorigenicity after in vitro culturing in serum-free conditions

Traditional in vitro culturing of tumor cells has been shown to induce changes so that cultures no longer represent the tumor of origin. Serum-free culturing conditions are used in a variety of cancers to propagate stem-like cells in vitro. Limited reports, however, exist on the effects of such propagation. We have compared cells from brain tumor biopsies cultivated under serum-free conditions at passages 2 and 10 to describe the effects of in vitro culturing. We were able to establish cell lines from 7 of 10 biopsies from patients with glioblastoma. The cell lines adapted to conditions and had 2.2 times increased population doubling rate at later passages. Karyotyping and comparative genomic hybridization analysis revealed that all examined cell lines had cytogenetic aberrations commonly found in glioblastomas, and there were only minor differences between tumor and early and late passages in the same culture. Whole-transcriptome analysis shows that tumors had interindividual differences. Changes in the overall expression patterns through passaging were modest, with a significant change in only 14 genes; the variation among cultures was, however, reduced through passages. The ability to differentiate differed among tumors but was maintained throughout passaging. The cells initiated tumors upon transplantation to immunodeficient mice with differing phenotypes, but a given cell culture maintained tumor phenotype after serial cultivation. The cultures established maintained individual characteristics specific to culture identity. Thus, each cell culture reflects an image of the tumor--or a personalized model--from which it was derived and remains representative after moderate expansion.