Maya Sieber-Blum

Human epidermal neural crest stem cells (hEPI-NCSC)--characterization and directed differentiation into osteocytes and melanocytes.

Here we describe the isolation, characterisation and ex-vivo expansion of human epidermal neural crest stem cells (hEPI-NCSC) and we provide protocols for their directed differentiation into osteocytes and melanocytes. hEPI-NCSC are neural crest-derived multipotent stem cells that persist into adulthood in the bulge of hair follicles. Multipotency and self-renewal were determined by in vitro clonal analyses. hEPI-NCSC generate all major neural crest derivatives, including bone/cartilage cells, neurons, Schwann cells, myofibroblasts and melanocytes. Furthermore, hEPI-NCSC express additional neural crest stem cell markers and global stem cell genes. To variable degrees and in a donor-dependent manner, hEPI-NCSC express the six essential pluripotency genes C-MYC, KLF4, SOX2, LIN28, OCT-4/POU5F1 and NANOG. hEPI-NCSC can be expanded ex vivo into millions of stem cells that remain mulitpotent and continue to express stem cell genes. The novelty of hEPI-NCSC lies in the combination of their highly desirable traits. hEPI-NCSC are embryonic remnants in a postnatal location, the bulge of hair follicles. Therefore they are readily accessible in the hairy skin by minimal invasive procedure. hEPI-NCSC are multipotent somatic stem cells that can be isolated reproducibly and with high yield. By taking advantage of their migratory ability, hEPI-NCSC can be isolated as a highly pure population of stem cells. hEPI-NCSC can undergo robust ex vivo expansion and directed differentiation. As somatic stem cells, hEPI-NCSC are conducive to autologous transplantation, which avoids graft rejection. Together, these traits make hEPI-NCSC novel and attractive candidates for future cell-based therapies and regenerative medicine.

Epidermal Neural Crest Stem Cell (EPI-NCSC)—Mediated Recovery of Sensory Function in a Mouse Model of Spinal Cord Injury

Here we show that epidermal neural crest stem cell (EPI-NCSC) transplants in the contused spinal cord caused a 24% improvement in sensory connectivity and a substantial recovery of touch perception. Furthermore we present a novel method for the ex vivo expansion of EPI-NCSC into millions of stem cells that takes advantage of the migratory ability of neural crest stem cells and is based on a new culture medium and the use of microcarriers. Functional improvement was shown by two independent methods, spinal somatosensory evoked potentials (SpSEP) and the Semmes-Weinstein touch test. Subsets of transplanted cells differentiated into myelinating oligodendrocytes. Unilateral injections of EPI-NCSC into the lesion of midline contused mouse spinal cords elicited bilateral improvements. Intraspinal EPI-NCSC did not migrate laterally in the spinal cord or invade the spinal roots and dorsal root ganglia, thus implicating diffusible factors. EPI-NCSC expressed neurotrophic factors, angiogenic factors, and metalloproteases. The strength of EPI-NCSC thus is that they can exert a combination of pertinent functions in the contused spinal cord, including cell replacement, neuroprotection, angiogenesis and modulation of scar formation. EPI-NCSC are uniquely qualified for cell-based therapy in spinal cord injury, as neural crest cells and neural tube stem cells share a higher order stem cell and are thus ontologically closely related.

Epidermal neural crest stem cells and their use in mouse models of spinal cord injury

Epidermal neural crest stem cell (EPI-NCSC) grafts cause a significant improvement in sensory connectivity and touch perception in the contused mouse spinal cord. EPI-NCSC are derived from the embryonic neural crest but reside in a postnatal location, the bulge of hair follicles. Both mouse and human EPI-NCSC are multipotent adult stem cells capable of generating all major neural crest derivatives. EPI-NCSC of mouse and human origin express the neural crest stem cell molecular signature, genes that were initially used to create induced pluripotent stem (iPS) cells, and other neural crest and global stem cell genes. Due to their origin in the neural folds and because they share a higher order stem cell, neural crest cells, and thus EPI-NCSC, are closely related to neural tube stem cells. This close ontological relationship with the spinal cord makes EPI-NCSC attractive candidates for cell-based therapy in spinal cord injury. In two different contusion models of spinal cord injury, we have shown that EPI-NCSC integrate into the murine spinal cord tissue and that subsets differentiate into GABAergic neurons and myelinating oligodendrocytes. Intraspinal EPI-NCSC do not form tumours. In the presence of EPI-NCSC grafts, but not in control animals, there is a 24% improvement of sensory connectivity and a substantial improvement in touch perception. Unilateral transplants leading to bilateral functional improvements suggest that underlying mechanisms include diffusible molecules. EPI-NCSC indeed express genes that encode neurotrophins, other trophic factors, angiogenic factors and metalloproteases. Intraspinal EPI-NCSC thus have multiple effects in the contused spinal cord, the sum of which can explain the observed functional improvements.

Dysregulated TRK signalling is a therapeutic target in CYLD defective tumours

Individuals with germline mutations in the tumour-suppressor gene CYLD are at high risk of developing disfiguring cutaneous appendageal tumours, the defining tumour being the highly organised cylindroma. Here, we analysed CYLD mutant tumour genomes by array comparative genomic hybridisation and gene expression microarray analysis. CYLD mutant tumours were characterised by an absence of copy-number aberrations apart from LOH chromosome 16q, the genomic location of the CYLD gene. Gene expression profiling of CYLD mutant tumours showed dysregulated tropomyosin kinase (TRK) signalling, with overexpression of TRKB and TRKC in tumours when compared with perilesional skin. Immunohistochemical analysis of a tumour microarray showed strong membranous TRKB and TRKC staining in cylindromas, as well as elevated levels of ERK phosphorylation and BCL2 expression. Membranous TRKC overexpression was also observed in 70% of sporadic BCCs. RNA interference-mediated silencing of TRKB and TRKC, as well as treatment with the small-molecule TRK inhibitor lestaurtinib, reduced colony formation and proliferation in 3D primary cell cultures established from CYLD mutant tumours. These results suggest that TRK inhibition could be used as a strategy to treat tumours with loss of functional CYLD.

Human epidermal neural crest stem cells as a source of Schwann cells.

We show that highly pure populations of human Schwann cells can be derived rapidly and in a straightforward way, without the need for genetic manipulation, from human epidermal neural crest stem cells [hEPI-NCSC(s)] present in the bulge of hair follicles. These human Schwann cells promise to be a useful tool for cell-based therapies, disease modelling and drug discovery. Schwann cells are glia that support axons of peripheral nerves and are direct descendants of the embryonic neural crest. Peripheral nerves are damaged in various conditions, including through trauma or tumour-related surgery, and Schwann cells are required for their repair and regeneration. Schwann cells also promise to be useful for treating spinal cord injuries. Ex vivo expansion of hEPI-NCSC isolated from hair bulge explants, manipulating the WNT, sonic hedgehog and TGFβ signalling pathways, and exposure of the cells to pertinent growth factors led to the expression of the Schwann cell markers SOX10, KROX20 (EGR2), p75NTR (NGFR), MBP and S100B by day 4 in virtually all cells, and maturation was completed by 2 weeks of differentiation. Gene expression profiling demonstrated expression of transcripts for neurotrophic and angiogenic factors, as well as JUN, all of which are essential for nerve regeneration. Co-culture of hEPI-NCSC-derived human Schwann cells with rodent dorsal root ganglia showed interaction of the Schwann cells with axons, providing evidence of Schwann cell functionality. We conclude that hEPI-NCSCs are a biologically relevant source for generating large and highly pure populations of human Schwann cells. Summary: Human epidermal neural crest stem cells isolated from the bulge of hair follicles are used to derive Schwann cells that could be useful for regenerative therapies, disease modelling and drug discovery.

Stem cells in canine spinal cord injury--promise for regenerative therapy in a large animal model of human disease.

The use of cell transplantation for spinal cord injury is a rapidly evolving field in regenerative medicine. Numerous animal models are currently being used. However, translation to human patients is still a challenging step. Dogs are of increasing importance as a translational model for human disease since there is a greater awareness of the need to increase the quality of preclinical data. The use of dogs ultimately brings benefit to both human and veterinary medicine. In this review we analyze experimental and clinical studies using cell transplantation for canine spinal cord injury. Overall, in experimental studies, transplantation groups showed improvement over control groups. Improvements were measured at the functional, electrophysiological, histological, RNA and protein levels. Most clinical studies support beneficial effects of cell transplantation despite the fact that methodological limitations preclude definitive conclusions. However, the mechanisms of action and underlying the behavior of transplanted cells in the injured spinal cord remain unclear. Overall, we conclude here that stem cell interventions are a promising avenue for the treatment of spinal cord injury. Canines are a promising model that may help bridge the gap between translational research and human clinical trials.

Essential role of stem cell factor signaling in primary sensory neuron development.

Here we show that stem cell factor (SCF) signaling through its receptor, c-kit, is essential for the development of c-kit-expressing small- and medium-diameter primary sensory neurons. We used the W mouse, which is c-kit deficient and has a perinatal lethal phenotype due to a naturally occurring point mutation in the c-kit gene. In c-kit-null newborn mice, 52.5% of substance P immunoreactive and 31.4% of calcitonin gene-related peptide (CGRP) immunoreactive small- and medium-diameter sensory neurons were absent, whereas large-diameter sensory neurons were unaffected. Equivalent deficits occurred during embryogenesis. There was neither a developmental delay nor degeneration of differentiated neurons. We thus conclude that, in the absence of SCF signaling, neural crest-derived progenitors do not differentiate into c-kit-expressing visceral and somatic afferent neurons.

Differentiation of Human Epidermal Neural Crest Stem Cells (hEPI-NCSC) into Virtually Homogenous Populations of Dopaminergic Neurons

Here we provide a protocol for the directed differentiation of hEPI-NCSC into midbrain dopaminergic neurons, which degenerate in Parkinson’s disease. hEPI-NCSC are neural crest-derived multipotent stem cells that persist into adulthood in the bulge of hair follicles. The experimental design is distinctly different from conventional protocols for embryonic stem cells and induced pluripotent stem (iPS) cells. It includes pre-differentiation of the multipotent hEPI-NCSC into neural stem cell-like cells, followed by ventralizing, patterning, continued exposure to the TGFβ receptor inhibitor, SB431542, and at later stages of differentiation the presence of the WNT inhibitor, IWP-4. All cells expressed A9 midbrain dopaminergic neuron progenitor markers with gene expression levels comparable to those in normal human substantia nigra. The current study shows for the first time that virtually homogeneous populations of dopaminergic neurons can be derived ex vivo from somatic stem cells without the need for purification, with useful timeliness and high efficacy. This novel development is an important first step towards the establishment of fully functional dopaminergic neurons from an ontologically relevant stem cell type, hEPI-NCSC.

Transition from cylindroma to spiradenoma in CYLD‐defective tumours is associated with reduced DKK2 expression

Patients carrying heterozygous germline truncating mutations in the CYLD gene develop multiple primary hair follicle‐related tumours. A highly patterned tumour, termed cylindroma, and a highly disorganized tumour, termed spiradenoma, may both develop in the same patient. Furthermore, histological features of both tumour types have been described within the same tumour specimen. We used three‐dimensional computer‐aided reconstruction of these tumours to demonstrate contiguous growth of cylindromas into spiradenomas, thus suggesting a transition between the two tumour types. To explore factors that may influence cutaneous tumour patterning, genome‐wide transcriptomic analysis of 32 CYLD‐defective tumours was performed. Overexpression of the Wnt/β‐catenin signalling pathway was observed relative to normal perilesional tissue. Morphometric analysis was used to investigate the relationship between Wnt pathway‐related gene expression and tumour organization. This revealed an association between reduced Dickkopf 2 (DKK2—a negative regulator of the Wnt/β‐catenin signalling pathway) expression and loss of tumour patterning. Reduced DKK2 expression was associated with methylation of the DKK2 gene promoter in the majority of tumour samples assayed. RNA interference‐mediated silencing of DKK2 expression in cylindroma primary cell cultures caused an increase in colony formation, cell viability, and anchorage‐independent growth. Using these data, we propose a model where epigenetic programming may influence tumour patterning in patients with CYLD mutations. Copyright

Canine Epidermal Neural Crest Stem Cells: Characterization and Potential as Therapy Candidate for a Large Animal Model of Spinal Cord Injury

The discovery of multipotent neural crest‐derived stem cells, named epidermal neural crest stem cells (EPI‐NCSC), that persist postnatally in an easy‐to‐access location—the bulge of hair follicles—opens a spectrum of novel opportunities for patient‐specific therapies. We present a detailed characterization of canine EPI‐NCSC (cEPI‐NCSC) from multiple dog breeds and protocols for their isolation and ex vivo expansion. Furthermore, we provide novel tools for research in canines, which currently are still scarce. In analogy to human and mouse EPI‐NCSC, the neural crest origin of cEPI‐NCSC is shown by their expression of the neural crest stem cell molecular signature and other neural crest‐characteristic genes. Similar to human EPI‐NCSC, cEPI‐NCSC also expressed pluripotency genes. We demonstrated that cEPI‐NCSC can generate all major neural crest derivatives. In vitro clonal analyses established multipotency and self‐renewal ability of cEPI‐NCSC, establishing cEPI‐NCSC as multipotent somatic stem cells. A critical analysis of the literature on canine spinal cord injury (SCI) showed the need for novel treatments and suggested that cEPI‐NCSC represent viable candidates for cell‐based therapies in dog SCI, particularly for chondrodystrophic dogs. This notion is supported by the close ontological relationship between neural crest stem cells and spinal cord stem cells. Thus, cEPI‐NCSC promise to offer not only a potential treatment for canines but also an attractive and realistic large animal model for human SCI. Taken together, we provide the groundwork for the development of a novel cell‐based therapy for a condition with extremely poor prognosis and no available effective treatment.