Human mesenchymal stem cells isolated from olfactory biopsies but not bone enhance CNS myelination in vitro

Olfactory Ecto-Mesenchymal Stem Cells in Modeling and Treating Alzheimer's Disease

Alzheimer's disease (AD) is a condition in the brain that is marked by a gradual and ongoing reduction in memory, thought, and the ability to perform simple tasks. AD has a poor prognosis but no cure yet. Therefore, the need for novel models to study its pathogenesis and therapeutic strategies is evident, as the brain poorly recovers after injury and neurodegenerative diseases and can neither replace dead neurons nor reinnervate target structures. Recently, mesenchymal stem cells (MSCs), particularly those from the human olfactory mucous membrane referred to as the olfactory ecto-MSCs (OE-MSCs), have emerged as a potential avenue to explore in modeling AD and developing therapeutics for the disease due to their lifelong regeneration potency and facile accessibility. This review provides a comprehensive summary of the current literature on isolating OE-MSCs and delves into whether they could be reliable models for studying AD pathogenesis. It also explores whether healthy individual-derived OE-MSCs could be therapeutic agents for the disease. Despite being a promising tool in modeling and developing therapies for AD, some significant issues remain, which are also discussed in the review.

Transplantation of olfactory mucosa mesenchymal stromal cells repairs spinal cord injury by inducing microglial polarization

STUDY DESIGN

Animal studies OBJECTIVES: To evaluate the therapeutic effect of olfactory mucosa mesenchymal stem cell (OM-MSCs) transplantation in mice with spinal cord injury (SCI) and to explore the mechanism by which OM-MSCs inhibit neuroinflammation and improve SCI.

SETTING

Xiangya Hospital, Central South University; Affiliated Hospital of Guangdong Medical University.

METHODS

Mice (C57BL/6, female, 6-week-old) were randomly divided into sham, SCI, and SCI + OM-MSC groups. The SCI mouse model was generated using Allen's method. OM-MSCs were immediately delivered to the lateral ventricle after SCI using stereotaxic brain injections. One day prior to injury and on days 1, 5, 7, 14, 21, and 28 post-injury, the Basso Mouse Scale and Rivlin inclined plate tests were performed. Inflammation and microglial polarization were evaluated using histological staining, immunofluorescence, and qRT-PCR.

RESULTS

OM-MSCs originating from the neuroectoderm have great potential in the management of SCI owing to their immunomodulatory effects. OM-MSCs administration improved motor function, alleviated inflammation, promoted the transformation of the M1 phenotype of microglia into the M2 phenotype, facilitated axonal regeneration, and relieved spinal cord injury in SCI mice.

CONCLUSIONS

OM-MSCs reduced the level of inflammation in the spinal cord tissue, protected neurons, and repaired spinal cord injury by regulating the M1/M2 polarization of microglia.

Features of Remyelination after Transplantation of Olfactory Ensheathing Cells with Neurotrophic Factors into Spinal Cord Cysts

This paper shows for the first time that co-transplantation of human olfactory ensheathing cells with neurotrophin-3 into spinal cord cysts is more effective for activation of remyelination than transplantation of cells with brain-derived neurotrophic factor and a combination of these two factors. The studied neurotrophic factors do not affect proliferation and migration of ensheathing cells in vitro. It can be concluded that the maximum improvement of motor function in rats receiving ensheathing cells with neurotrophin-3 is largely determined by activation of remyelination.

Development of Good Manufacturing Practice-Compatible Isolation and Culture Methods for Human Olfactory Mucosa-Derived Mesenchymal Stromal Cells

Demyelination in the central nervous system (CNS) resulting from injury or disease can cause loss of nerve function and paralysis. Cell therapies intended to promote remyelination of axons are a promising avenue of treatment, with mesenchymal stromal cells (MSCs) a prominent candidate. We have previously demonstrated that MSCs derived from human olfactory mucosa (hOM-MSCs) promote myelination to a greater extent than bone marrow-derived MSCs (hBM-MSCs). However, hOM-MSCs were developed using methods and materials that were not good manufacturing practice (GMP)-compliant. Before considering these cells for clinical use, it is necessary to develop a method for their isolation and expansion that is readily adaptable to a GMP-compliant environment. We demonstrate here that hOM-MSCs can be derived without enzymatic tissue digestion or cell sorting and without culture antibiotics. They grow readily in GMP-compliant media and express typical MSC surface markers. They robustly produce CXCL12 (a key secretory factor in promoting myelination) and are pro-myelinating in in vitro rodent CNS cultures. GMP-compliant hOM-MSCs are comparable in this respect to those grown in non-GMP conditions. However, when assessed in an in vivo model of demyelinating disease (experimental autoimmune encephalitis, EAE), they do not significantly improve disease scores compared with controls, indicating further pre-clinical evaluation is necessary before their advancement to clinical trials.

IGF-1 Mediated Neuroprotective Effects of Olfactory-Derived Mesenchymal Stem Cells on Auditory Hair Cells

IMPORTANCE

Mesenchymal stem cells (MSCs) have the capability of providing ongoing paracrine support to degenerating tissues. Since MSCs can be extracted from a broad range of tissues, their specific surface marker profiles and growth factor secretions can be different. We hypothesized that MSCs derived from different sources might also have different neuroprotective potential.

OBJECTIVE

In this study, we extracted MSCs from rodent olfactory mucosa and compared their neuroprotective effects on auditory hair cell survival with MSCs extracted from rodent adipose tissue.

METHODS

Organ of Corti explants were dissected from 41 cochlea and incubated with olfactory mesenchymal stem cells (OMSCs) and adipose mesenchymal stem cells (AMSCs). After 72 hours, Corti explants were fixed, stained, and hair cells counted. Growth factor concentrations were determined in the supernatant and cell lysate using Enzyme-Linked Immunosorbent Assay (ELISA).

RESULTS

Co-culturing of organ of Corti explants with OMSCs resulted in a significant increase in inner and outer hair cell stereocilia survival, compared to control. Comparisons between both stem cell lines, showed that co-culturing with OMSCs resulted in superior inner and outer hair cell stereocilia survival rates over co-culturing with AMSCs. Assessment of growth factor secretions revealed that the OMSCs secrete significant amounts of insulin-like growth factor 1 (IGF-1). Co-culturing OMSCs with organ of Corti explants resulted in a 10-fold increase in IGF-1 level compared to control, and their secretion was 2 to 3 times higher compared to the AMSCs.

CONCLUSIONS

This study has shown that OMSCs may mitigate auditory hair cell stereocilia degeneration. Their neuroprotective effects may, at least partially, be ascribed to their enhanced IGF-1 secretory abilities compared to AMSCs.

Cultured Mesenchymal Cells from Nasal Turbinate as a Cellular Model of the Neurodevelopmental Component of Schizophrenia Etiology

The study of neurodevelopmental molecular mechanisms in schizophrenia requires the development of adequate biological models such as patient-derived cells and their derivatives. We previously utilized cell lines with neural progenitor properties (CNON) derived from the superior or middle turbinates of patients with schizophrenia and control groups to study schizophrenia-specific gene expression. In this study, we analyzed single-cell RNA seq data from two CNON cell lines (one derived from an individual with schizophrenia (SCZ) and the other from a control group) and two biopsy samples from the middle turbinate (MT) (also from an individual with SCZ and a control). We compared our data with previously published data regarding the olfactory neuroepithelium and demonstrated that CNON originated from a single cell type present both in middle turbinate and the olfactory neuroepithelium and expressed in multiple markers of mesenchymal cells. To define the relatedness of CNON to the developing human brain, we also compared CNON datasets with scRNA-seq data derived from an embryonic brain and found that the expression profile of the CNON closely matched the expression profile one of the cell types in the embryonic brain. Finally, we evaluated the differences between SCZ and control samples to assess the utility and potential benefits of using CNON single-cell RNA seq to study the etiology of schizophrenia.

Low sulfated heparan sulfate mimetic differentially affects repair in immune-mediated and toxin-induced experimental models of demyelination

There is an urgent need for therapies that target the multicellular pathology of central nervous system (CNS) disease. Modified, nonanticoagulant heparins mimic the heparan sulfate glycan family and are known regulators of multiple cellular processes. In vitro studies have demonstrated that low sulfated modified heparin mimetics (LS-mHeps) drive repair after CNS demyelination. Herein, we test LS-mHep7 (an in vitro lead compound) in experimental autoimmune encephalomyelitis (EAE) and cuprizone-induced demyelination. In EAE, LS-mHep7 treatment resulted in faster recovery and rapidly reduced inflammation which was accompanied by restoration of animal weight. LS-mHep7 treatment had no effect on remyelination or on OLIG2 positive oligodendrocyte numbers within the corpus callosum in the cuprizone model. Further in vitro investigation confirmed that LS-mHep7 likely mediates its pro-repair effect in the EAE model by sequestering inflammatory cytokines, such as CCL5 which are upregulated during immune-mediated inflammatory attacks. These data support the future clinical translation of this next generation modified heparin as a treatment for CNS diseases with active immune system involvement.

Cultured Mesenchymal Cells from Nasal Turbinate as a Cellular Model of the Neurodevelopmental Component of Schizophrenia Etiology

Study of the neurodevelopmental molecular mechanisms of schizophrenia requires the development of adequate biological models such as patient-derived cells and their derivatives. We previously used cell lines with neural progenitor properties (CNON) derived from superior or middle turbinates of patients with schizophrenia and control groups to study gene expression specific to schizophrenia. In this study, we compared single cell-RNA seq data from two CNON cell lines, one derived from an individual with schizophrenia (SCZ) and the other from a control group, with two biopsy samples from the middle turbinate (MT), also from an individual with SCZ and a control. In addition, we compared our data with previously published data from olfactory neuroepithelium (1). Our data demonstrated that CNON originated from a single cell type which is present both in middle turbinate and olfactory neuroepithelium. CNON express multiple markers of mesenchymal cells. In order to define relatedness of CNON to the developing human brain, we also compared CNON datasets with scRNA-seq data of embryonic brain (2) and found that the expression profile of CNON very closely matched one of the cell types in the embryonic brain. Finally, we evaluated differences between SCZ and control samples to assess usability and potential benefits of using single cell RNA-seq of CNON to study etiology of schizophrenia.

Prospects for the use of olfactory mucosa cells in bioprinting for the treatment of spinal cord injuries

The review focuses on the most important areas of cell therapy for spinal cord injuries. Olfactory mucosa cells are promising for transplantation. Obtaining these cells is safe for patients. The use of olfactory mucosa cells is effective in restoring motor function due to the remyelination and regeneration of axons after spinal cord injuries. These cells express neurotrophic factors that play an important role in the functional recovery of nerve tissue after spinal cord injuries. In addition, it is possible to increase the content of neurotrophic factors, at the site of injury, exogenously by the direct injection of neurotrophic factors or their delivery using gene therapy. The advantages of olfactory mucosa cells, in combination with neurotrophic factors, open up wide possibilities for their application in three-dimensional and four-dimensional bioprinting technology treating spinal cord injuries.

Mesenchymal Stromal Cell Therapy in Spinal Cord Injury: Mechanisms and Prospects

Spinal cord injury (SCI) often leads to severe motor, sensory, and autonomic dysfunction in patients and imposes a huge economic cost to individuals and society. Due to its complicated pathophysiological mechanism, there is not yet an optimal treatment available for SCI. Mesenchymal stromal cells (MSCs) are promising candidate transplant cells for use in SCI treatment. The multipotency of MSCs, as well as their rich trophic and immunomodulatory abilities through paracrine signaling, are expected to play an important role in neural repair. At the same time, the simplicity of MSCs isolation and culture and the bypassing of ethical barriers to stem cell transplantation make them more attractive. However, the MSCs concept has evolved in a specific research context to encompass different populations of cells with a variety of biological characteristics, and failure to understand this can undermine the quality of research in the field. Here, we review the development of the concept of MSCs in order to clarify misconceptions and discuss the controversy in MSCs neural differentiation. We also summarize a potential role of MSCs in SCI treatment, including their migration and trophic and immunomodulatory effects, and their ability to relieve neuropathic pain, and we also highlight directions for future research.

Human olfactory mesenchymal stromal cell transplantation ameliorates experimental autoimmune encephalomyelitis revealing an inhibitory role for IL16 on myelination

One of the therapeutic approaches for the treatment of the autoimmune demyelinating disease, multiple sclerosis (MS) is bone marrow mesenchymal stromal cell (hBM-MSCs) transplantation. However, given their capacity to enhance myelination in vitro, we hypothesised that human olfactory mucosa-derived MSCs (hOM-MSCs) may possess additional properties suitable for CNS repair. Herein, we have examined the efficacy of hOM-MSCs versus hBM-MSCs using the experimental autoimmune encephalomyelitis (EAE) model. Both MSC types ameliorated disease, if delivered during the initial onset of symptomatic disease. Yet, only hOM-MSCs improved disease outcome if administered during established disease when animals had severe neurological deficits. Histological analysis of spinal cord lesions revealed hOM-MSC transplantation reduced blood–brain barrier disruption and inflammatory cell recruitment and enhanced axonal survival. At early time points post-hOM-MSC treatment, animals had reduced levels of circulating IL-16, which was reflected in both the ability of immune cells to secrete IL-16 and the level of IL-16 in spinal cord inflammatory lesions. Further in vitro investigation revealed an inhibitory role for IL-16 on oligodendrocyte differentiation and myelination. Moreover, the availability of bioactive IL-16 after demyelination was reduced in the presence of hOM-MSCs. Combined, our data suggests that human hOM-MSCs may have therapeutic benefit in the treatment of MS via an IL-16-mediated pathway, especially if administered during active demyelination and inflammation.

Designing Olfactory Ensheathing Cell Transplantation Therapies: Influence of Cell Microenvironment

Olfactory ensheathing cell (OEC) transplantation is emerging as a promising treatment option for injuries of the nervous system. OECs can be obtained relatively easily from nasal biopsies, and exhibit several properties such as secretion of trophic factors, and phagocytosis of debris that facilitate neural regeneration and repair. But a major limitation of OEC-based cell therapies is the poor survival of transplanted cells which subsequently limit their therapeutic efficacy. There is an unmet need for approaches that enable the in vitro production of OECs in a state that will optimize their survival and integration after transplantation into the hostile injury site. Here, we present an overview of the strategies to modulate OECs focusing on oxygen levels, stimulating migratory, phagocytic, and secretory properties, and on bioengineering a suitable environment in vitro.

Human Olfactory Mesenchymal Stem Cells Are a Novel Candidate for Neurological Autoimmune Disease

Background: Human olfactory mesenchymal stem cells (OMSC) have become a novel therapeutic option for immune disorder or demyelinating disease due to their immunomodulatory and regenerative potentials. However, the immunomodulatory effects of OMSC still need to be elucidated, and comparisons of the effects of different MSCs are also required in order to select an optimal cell source for further applications. Results: In animal experiments, we found neural functional recovery and delayed EAE attack in the OMSC treatment group. Compared with umbilical cord-derived mesenchymal stem cells (UMSC) treatment group and the control group, the OMSC treatment group had a better neurological improvement, lower serum levels of IFN-γ, and a lower proportion of CD4+IFN-γ+ T splenic lymphocyte. We also observed OMSC effectively suppressed CD4+IFN-γ+ T cell proportion in vitro when co-cultured with human peripheral blood-derived lymphocytes. The OMSC-mediated immunosuppressive effect on human CD4+IFN-γ+ T cells was attenuated by blocking cyclooxygenase activity. Conclusion: Our results suggest that OMSC treatment delayed the onset and promoted the neural functional recovery in the EAE mouse model possibly by suppressing CD4+IFN-γ+ T cells. OMSC transplantation might become an alternative therapeutic option for neurological autoimmune disease.

Considering the Cellular Composition of Olfactory Ensheathing Cell Transplants for Spinal Cord Injury Repair: A Review of the Literature

Olfactory ensheathing cells (OECs) are specialized glia cells of the olfactory system that support the continual regeneration of olfactory neurons throughout adulthood. Owing to their pro-regenerative properties, OECs have been transplanted in animal models of spinal cord injuries (SCI) and trialed in clinical studies on SCI patients. Although these studies have provided convincing evidence to support the continued development of OEC transplantation as a treatment option for the repair of SCI, discrepancies in the reported outcome has shown that OEC transplantation requires further improvement. Much of the variability in the reparative potential of OEC transplants is due to the variations in the cell composition of transplants between studies. As a result, the optimal cell preparation is currently a subject of debate. Here we review, the characterization as well as the effect of the cell composition of olfactory cell transplantation on therapeutic outcome in SCI. Firstly, we summarize and review the cell composition of olfactory cell preparations across the different species studied prior to transplantation. Since the purity of cells in olfactory transplants might affect the study outcome we also examine the effect of the proportions of OECs and the different cell types identified in the transplant on neuroregeneration. Finally, we consider the effect of the yield of cells on neuroregeneration by assessing the cell dose of transplants on therapeutic outcome.

Human adipose-derived mesenchymal stromal cells from face and abdomen undergo replicative senescence and loss of genetic integrity after long-term culture

Body fat depots are heterogeneous concerning their embryonic origin, structure, exposure to environmental stressors, and availability. Thus, investigating adipose-derived mesenchymal stromal cells (ASCs) from different sources is essential to standardization for future therapies. In vitro amplification is also critical because it may predispose cell senescence and mutations, reducing regenerative properties and safety. Here, we evaluated long-term culture of human facial ASCs (fASCs) and abdominal ASCs (aASCs) and showed that both met the criteria for MSCs characterization but presented differences in their immunophenotypic profile, and differentiation and clonogenic potentials. The abdominal tissue yielded more ASCs, and these had higher proliferative potential, but facial cells displayed fewer mitotic errors at higher passages. However, both cell types reduced clonal efficiency over time and entered replicative senescence around P12, as evaluated by progressive morphological alterations, reduced proliferative capacity, and SA-β-galactosidase expression. Loss of genetic integrity was detected by a higher proportion of cells showing nuclear alterations and γ-H2AX expression. Our findings indicate that the source of ASCs can substantially influence their phenotype and therefore should be carefully considered in future cell therapies, avoiding, however, long-term culture to ensure genetic stability.

Therapeutic Potential of Niche-Specific Mesenchymal Stromal Cells for Spinal Cord Injury Repair

The use of mesenchymal stem/stromal cells (MSCs) for transplant-mediated repair represents an important and promising therapeutic strategy after spinal cord injury (SCI). The appeal of MSCs has been fuelled by their ease of isolation, immunosuppressive properties, and low immunogenicity, alongside the large variety of available tissue sources. However, despite reported similarities in vitro, MSCs sourced from distinct tissues may not have comparable biological properties in vivo. There is accumulating evidence that stemness, plasticity, immunogenicity, and adaptability of stem cells is largely controlled by tissue niche. The extrinsic impact of cellular niche for MSC repair potential is therefore important, not least because of its impact on ex vivo expansion for therapeutic purposes. It is likely certain niche-targeted MSCs are more suited for SCI transplant-mediated repair due to their intrinsic capabilities, such as inherent neurogenic properties. In addition, the various MSC anatomical locations means that differences in harvest and culture procedures can make cross-comparison of pre-clinical data difficult. Since a clinical grade MSC product is inextricably linked with its manufacture, it is imperative that cells can be made relatively easily using appropriate materials. We discuss these issues and highlight the importance of identifying the appropriate niche-specific MSC type for SCI repair.

Promoting motor functions in a spinal cord injury model of rats using transplantation of differentiated human olfactory stem cells: A step towards future therapy

Human olfactory ecto-mesenchymal stem cells (hOE-MSCs) derived from the human olfactory mucosa (OM) can be easily isolated and expanded in cultures while their immense plasticity is maintained. To mitigate ethical concerns, the hOE-MSCs can be also transplanted across allogeneic barriers, making them desirable cells for clinical applications. The main purpose of this study was to evaluate the effects of administering the hOE-MSCs on a spinal cord injury (SCI) model of rats. These cells were accordingly isolated and cultured, and then treated in the neurobasal medium containing serum-free Dulbecco's Modified Essential Medium (DMEM) and Ham's F-12 Medium (DMEM/F12) with 2% B27 for two days. Afterwards, the pre-induced cells were incubated in N2B27 with basic fibroblast growth factor (bFGF), fibroblast growth factor 8b (FGF8b), sonic hedgehog (SHH), and ascorbic acid (vitamin C) for six days. The efficacy of the induced cells was additionally evaluated using immunocytochemistry (ICC) and real-time polymerase chain reaction (RT-PCR). The differentiated cells were similarly transplanted into the SC contusions. Functional recovery was further conducted on a weekly basis for eight consecutive weeks. Moreover, cell integration was assessed via conventional histology and ICC, whose results revealed the expression of choline acetyltransferase (ChAT) marker at the induction stage. According to the RT-PCR findings, the highest expression level of insulin gene-enhancer protein (islet-1), oligodendrocyte transcription factor (Olig2), and homeobox protein HB9 was observed at the induction stage. The number of engraftment cells also rose (approximately by 2.5 % ± 0.1) in the motor neuron-like cells derived from the hOE-MSCs-grafted group compared with the OE-MSCs-grafted one. The functional analysis correspondingly revealed that locomotor and sensory scores considerably improved in the rats in the treatment group. These findings suggested that motor neuron-like cells derived from the hOE-MSCs could be utilized as an alternative cell-based therapeutic strategy for SCI.

Human foreskin-derived dermal stem/progenitor cell-conditioned medium combined with hyaluronic acid promotes extracellular matrix regeneration in diabetic wounds

BACKGROUND

Diabetic wounds remain a challenging clinical problem, which requires further treatment development. Published data showed that dermis-derived stem/progenitor cells (DSPCs) display superior wound healing in vitro. The beneficial effects of DSPCs are mediated through paracrine secretion, which can be obtained from conditioned medium (CM). Hyaluronic acid (HA) is especially suitable for skin regeneration and delivering bioactive molecules in CM. This study investigated the effect of human foreskin-derived dermal stem/progenitor cell (hFDSPC)-CM combined with HA on a diabetic mouse model and relevant mechanism in vitro.

METHODS

hFDSPCs and human adipose-derived stem cells (hADSCs) were identified, and the respective CM was prepared. PBS, HA, hFDSPC-CM combined with HA, or hADSC-CM combined with HA was topically applied to mice. HE, CD31, CD68, CD86, and CD206 staining was performed to evaluate gross wound condition, angiogenesis, and inflammation, respectively. Masson and Picrosirius red staining was performed to evaluate collagen deposition and maturation. The effects of hFDSPC-CM and hADSC-CM on human keratinocyte cells (HaCaT) and fibroblasts were evaluated in vitro using CCK-8 and EdU assays to determine cell viability and proliferation, respectively. The scratch assay was performed to evaluate cell migration. Tube formation assay was performed on human umbilical vein endothelial cells (HUVECs) to confirm angiogenesis. Extracellular matrix (ECM) metabolic balance-related genes and proteins, such as collagen I (COL 1), collagen III (COL 3), fibronectin (FN), α-SMA, matrix metalloproteinases 1 (MMP-1), matrix metalloproteinases 3 (MMP-3), and transforming growth factor-beta 1 (TGF-β1), were analysed.

RESULTS

hFDSPC-CM combined with HA showed superior wound closure rate over hADSC-CM. Histologically, the hFDSPC-CM combined with HA group showed significantly improved re-epithelialisation, angiogenesis, anti-inflammation, collagen regeneration, and maturation compared to hADSC-CM combined with HA group. In vitro assays revealed that hFDSPC-CM displayed significant advantages on cell proliferation, migration, and ECM regeneration through a TGF-β/Smad signalling pathway compared with hADSC-CM.

CONCLUSIONS

hFDSPC-CM combined with HA was superior for treating diabetic wounds. The underlying mechanism may promote proliferation and migration of epidermal cells with fibroblasts, thus leading to ECM deposition and remodelling. Reduced inflammation may be due to the above-mentioned mechanism.

Combined Use of Chitosan and Olfactory Mucosa Mesenchymal Stem/Stromal Cells to Promote Peripheral Nerve Regeneration In Vivo

Peripheral nerve injury remains a clinical challenge with severe physiological and functional consequences. Despite the existence of multiple possible therapeutic approaches, until now, there is no consensus regarding the advantages of each option or the best methodology in promoting nerve regeneration. Regenerative medicine is a promise to overcome this medical limitation, and in this work, chitosan nerve guide conduits and olfactory mucosa mesenchymal stem/stromal cells were applied in different therapeutic combinations to promote regeneration in sciatic nerves after neurotmesis injury. Over 20 weeks, the intervened animals were subjected to a regular functional assessment (determination of motor performance, nociception, and sciatic indexes), and after this period, they were evaluated kinematically and the sciatic nerves and cranial tibial muscles were evaluated stereologically and histomorphometrically, respectively. The results obtained allowed confirming the beneficial effects of using these therapeutic approaches. The use of chitosan NGCs and cells resulted in better motor performance, better sciatic indexes, and lower gait dysfunction after 20 weeks. The use of only NGGs demonstrated better nociceptive recoveries. The stereological evaluation of the sciatic nerve revealed identical values in the different parameters for all therapeutic groups. In the muscle histomorphometric evaluation, the groups treated with NGCs and cells showed results close to those of the group that received traditional sutures, the one with the best final values. The therapeutic combinations studied show promising outcomes and should be the target of new future works to overcome some irregularities found in the results and establish the combination of nerve guidance conduits and olfactory mucosa mesenchymal stem/stromal cells as viable options in the treatment of peripheral nerves after injury.

On the in vivo origin of human nasal mesenchymal stem cell cultures

OBJECTIVES

Mesenchymal stem cells (MSCs), classically expanded in culture from bone marrow, are of broad interest to the regenerative medicine community. Human nasal turbinate mesenchymal-like stem cell cultures have also been described, defined by an in vitro phenotype similar to bone marrow MSCs. Nonetheless, the identity in vivo of the cells that give rise to nasal MSC-like cultures remains unclear, and these cells are often suggested to be related to olfactory lineages. Here, we sought to define the in vivo phenotype of human nasal MSC-like cells.

METHODS

Human turbinate tissue samples were used for RNA and immunohistochemical analysis. We also analyzed a recently published single cell RNA-sequencing dataset from adult human olfactory and respiratory mucosa samples from our lab, to focus on cell populations expressing MSC markers. Immunochemistry was performed to stain turbinate sections and nasal MSC cultures for selected markers.

RESULTS

While there is no single MSC-specific gene, we identified a human nasal mucosal cell population in vivo that uniquely expressed transcripts characteristic of typical MSC cultures, including ENG (CD105), NES, and CD34, and lacked expression of other transcripts associated with surface epithelia. The expression of transcription factors such as SOX17, EBF1, and FOXP1 suggests cells in the MSC-like cluster maintain an ability to direct cell fate, consistent with the behavior of nasal MSC-like cells in vitro. SOX17 was found to be uniformly expressed by nasal MSC cultures, consistent with the in vivo data. Immunohistochemistry of human nasal tissue samples indicated that ENG, CD34, and SOX17 expression localized selectively to cells surrounding blood vessels in the lamina propria.

CONCLUSION

Our findings provide evidence that the in vivo origin of nasal MSC-like cultures is likely a vascular or pericyte population, rather than cells related to the olfactory neuronal lineage.

LEVEL OF EVIDENCE

NA.

Microcarrier expansion of c-MycERTAM -modified human olfactory mucosa cells for neural regeneration

Human olfactory mucosa cells (hOMCs) have potential as a regenerative therapy for spinal cord injury. In our earlier work, we derived PA5 cells, a polyclonal population that retains functional attributes of primary human OMCs. Microcarrier suspension culture is an alternative to planar two-dimensinal culture to produce cells in quantities that can meet the needs of clinical development. This study aimed to screen the effects of 10 microcarriers on PA5 hOMCs yield and phenotype. Studies performed in well plates led to a 2.9-fold higher cell yield on plastic compared to plastic plus microcarriers with upregulation of neural markers β-III tubulin and nestin for both conditions. Microcarrier suspension culture resulted in concentrations of 1.4 × 10⁵ cells/ml and 4.9 × 10⁴ cells/ml for plastic and plastic plus, respectively, after 7 days. p75^NTR transcript was significantly upregulated for PA5 hOMCs grown on Plastic Plus compared to Plastic. Furthermore, coculture of PA5 hOMCs grown on Plastic Plus with a neuronal cell line (NG108-15) led to increased neurite outgrowth. This study shows successful expansion of PA5 cells using suspension culture on microcarriers, and it reveals competing effects of microcarriers on cell expansion versus functional attributes, showing that designing scalable bioprocesses should not only be driven by cell yields.

Altered Secretome and ROS Production in Olfactory Mucosa Stem Cells Derived from Friedreich's Ataxia Patients

Friedreich’s ataxia is the most common hereditary ataxia for which there is no cure or approved treatment at present. However, therapeutic developments based on the understanding of pathological mechanisms underlying the disease have advanced considerably, with the implementation of cellular models that mimic the disease playing a crucial role. Human olfactory ecto-mesenchymal stem cells represent a novel model that could prove useful due to their accessibility and neurogenic capacity. Here, we isolated and cultured these stem cells from Friedreich´s ataxia patients and healthy donors, characterizing their phenotype and describing disease-specific features such as reduced cell viability, impaired aconitase activity, increased ROS production and the release of cytokines involved in neuroinflammation. Importantly, we observed a positive effect on patient-derived cells, when frataxin levels were restored, confirming the utility of this in vitro model to study the disease. This model will improve our understanding of Friedreich´s ataxia pathogenesis and will help in developing rationally designed therapeutic strategies.

Insight into the proteomic profiling of exosomes secreted by human OM-MSCs reveals a new potential therapy

Mesenchymal stromal cells (MSCs) have been used for the treatment of neuronal injury and neurodegenerative diseases. Their underlying mechanism may involve increased secretion of paracrine factors, which promotes tissue repair. Presently, exosomes have been regarded as important components of paracrine secretion and paracrine factors. MSC exosomes represent a promising opportunity to develop novel cell-free therapy approaches. In this study, exosomes from nasal olfactory mucosa MSCs (OM-MSCs) were extracted and purified using ultracentrifugation, resulting in exosome diameters of 40-130 nm. Similar to other exosomes, OM-MSC exosomes were CD63- and CD81-positive and calnexin-negative. Functionally, OM-MSC exosomes promoted human brain microvascular endothelial cell (HBMEC) proliferation and migration. The present study analyzed the OM-MSC exosome paracrine proteome. A total of 304 exosome-associated proteins were identified by LC-MS/MS, including plasminogen activator inhibitor 1 (SERPINE 1), insulin-like growth factor binding protein family members (IGFBP 4 and 5), epidermal growth factor receptor (EGFR), neurogenic locus notch homolog protein 2 (NOTCH 2), apolipoprotein E (APOE), and heat shock protein HSP90-beta (HSP90AB1). These molecules are known to be important in neurotrophic, angiogenesis, cell growth, differentiation, apoptosis, and inflammation and are highly correlated with the mechanism of tissue repair and neural restoration. These observations may provide a basis for further evaluation of OM-MSC exosome potential as a novel therapeutic modality.

A scoping review of trials for cell-based therapies in human spinal cord injury

INTRODUCTION

Spinal cord injury (SCI) is associated with significant and life-long disability. Yet, despite decades of research, no regenerative treatment has reached clinical practice. Cell-based therapies are one possible regenerative strategy beginning to transfer to human trials from a more extensive pre-clinical basis.

METHODS

We therefore conducted a scoping review to synthesise all cell-based trials in SCI to consider the current state of the field and the cell transplant type or strategy with greatest promise. A search strategy of MEDLINE returned 1513 results. All clinical trials including adult human patients with acute or chronic, compete or incomplete SCI and a recorded ASIA score were sought. Exclusion criteria included non-traumatic SCI, paediatric patients and animal studies. A total of 43 studies, treating 1061 patients, were identified. Most trials evaluated cells from the bone marrow (22 papers, 660 patients) or the olfactory bulb (10 papers, 245 patients).

RESULTS

Cell transplantation does appear to be safe, with no serious adverse effects being reported in the short-term. 86% of trials described efficacy as a primary outcome. However, varying degrees of outcome reporting prevented meta-analysis. No emerging cell type or technique was identified. The majority of trials, 53%, took place in developing countries, which may suggest more stringent regulatory requirements within Western countries.

CONCLUSION

We believe cell-based transplantation translation remains in its infancy and that, although further robust clinical research is required, it is an important strategy to consider in the treatment of SCI.

Human olfactory mesenchymal stromal cells co-expressing horizontal basal and ensheathing cell proteins in culture

Introduction:

The olfactory neuro-epithelium has an intrinsic capability of renewal during lifetime provided by the existence of globose and horizontal olfactory precursor cells. Additionally, mesenchymal stromal olfactory cells also support the homeostasis of the olfactory mucosa cell population. Under in vitro culture conditions with Dulbecco modified eagle/F12 medium supplemented with 10% fetal bovine serum, tissue biopsies from upper turbinate have generated an adherent population of cells expressing mainly mesenchymal stromal phenotypic markers. A closer examination of these cells has also found co-expression of olfactory precursors and ensheathing cell phenotypic markers. These results were suggestive of a unique property of olfactory mesenchymal stromal cells as potentially olfactory progenitor cells.

Objective:

To study whether the expression of these proteins in mesenchymal stromal cells is modulated upon neuronal differentiation.

Materials and methods:

We observed the phenotype of olfactory stromal cells under DMEM/F12 plus 10% fetal bovine serum in comparison to cells from spheres induced by serum-free medium plus growth factors inducers of neural progenitors.

Results:

The expression of mesenchymal stromal (CD29+, CD73+, CD90+, CD45-), horizontal basal (ICAM-1/CD54+, p63+, p75NGFr+), and ensheathing progenitor cell (nestin+, GFAP+) proteins was determined in the cultured population by flow cytometry. The determination of Oct 3/4, Sox-2, and Mash-1 transcription factors, as well as the neurotrophins BDNF, NT3, and NT4 by RT-PCR in cells, was indicative of functional heterogeneity of the olfactory mucosa tissue sample.

Conclusions:

Mesenchymal and olfactory precursor proteins were downregulated by serum-free medium and promoted differentiation of mesenchymal stromal cells into neurons and astroglial cells.

Multi-target approaches to CNS repair: olfactory mucosa-derived cells and heparan sulfates

Spinal cord injury (SCI) remains one of the biggest challenges in the development of neuroregenerative therapeutics. Cell transplantation is one of numerous experimental strategies that have been identified and tested for efficacy at both preclinical and clinical levels in recent years. In this Review, we briefly discuss the state of human olfactory cell transplantation as a therapy, considering both its current clinical status and its limitations. Furthermore, we introduce a mesenchymal stromal cell derived from human olfactory tissue, which has the potential to induce multifaceted reparative effects in the environment within and surrounding the lesion. We argue that no single therapy will be sufficient to treat SCI effectively and that a combination of cell-based, rehabilitation and pharmaceutical interventions is the most promising approach to aid repair. For this reason, we also introduce a novel pharmaceutical strategy based on modifying the activity of heparan sulfate, an important regulator of a wide range of biological cell functions. The multi-target approach that is exemplified by these types of strategies will probably be necessary to optimize SCI treatment.

Rat Olfactory Mucosa Mesenchymal Stem/Stromal Cells (OM-MSCs): A Characterization Study

Stem/stromal cell-based therapies are a branch of regenerative medicine and stand as an attractive option to promote the repair of damaged or dysfunctional tissues and organs. Olfactory mucosa mesenchymal stem/stromal cells have been regarded as a promising tool in regenerative therapies because of their several favorable properties such as multipotency, high proliferation rate, helpful location, and few associated ethical issues. These cells are easily accessible in the nasal cavity of most mammals, including the rat, can be easily applied in autologous treatments, and do not cope with most of the obstacles associated with the use of other stem cells. Despite this, its application in preclinical trials and in both human and animal patients is still limited because of the small number of studies performed so far and to the nonexistence of a standard and unambiguous protocol for collection, isolation, and therapeutic application. In the present work a validation of a protocol for isolation, culture, expansion, freezing, and thawing of olfactory mucosa mesenchymal stem/stromal cells was performed, applied to the rat model, as well as a biological characterization of these cells. To investigate the therapeutic potential of OM-MSCs and their eventual safe application in preclinical trials, the main characteristics of OMSC stemness were addressed.

Priming TLR3 and TLR4 in human adipose- and olfactory mucosa-derived mesenchymal stromal cells and comparison of their cytokine secretions

Mesenchymal stromal cells (MSCs) have potent immunomodulatory abilities to regulate most of the immune cells. Not only the tissue origin of MSCs can affect their functions, but also their microenvironment can strongly influence their biology, particularly through toll-like receptors (TLR)/ligands interaction. In the present study, we compared MSCs derived from two different sources, i.e. human olfactory ecto-mesenchymal stem cells (OE-MSCs) and adipose tissue (AT-MSCs), in terms of their immunosuppressive effects before and after TLR3 and TLR4 stimulation through low-level and short-term TLR-priming protocol. After isolation and characterization of OE-MSCs and AT-MSCs, flow cytometry analyses were used to assess the expression of TLR3, TLR4 by MSCs. Secretion and expression levels of immune-related genes were analyzed using ELISA and RT-qPCR techniques. Based on the results, the proliferation potential of OE-MSCs was significantly higher than that of AT-MSCs. The gene expression and also protein levels of both TLR3 and TLR4 were significantly higher in OE-MSCs, compared to AT-MSCs. Among the examined cytokines and chemokines, OE-MSCs exhibited significantly higher levels of CCL5, IL-8, and TGF-β production, in comparison with AT-MSCs. However, IL-6 secretion by AT-MSCs was considerably more than that by OE-MSCs. OE-MSCs were only affected by the TLR4 ligand, and IL-8 and IL-6 production levels increased after LPS treatment. However, only IL-8 significantly increased after adding LPS or Poly (I:C) to the AT-MSC media. According to the obtained data, OE-MSCs exhibited a higher proliferative potential and greater expression levels of TLR3 and TLR4 genes, compared to AT-MSCs. However, unlike AT-MSCs, the expression of TLR3 by OE-MSCs was nonfunctional. Finally, based on our findings, OE-MSCs have a stronger secretion of immunosuppressive cytokines both before and after LPS or PIC treatment, compared to AT-MSCs.

Generation of c-MycERTAM-transduced human late-adherent olfactory mucosa cells for potential regenerative applications

Human olfactory mucosa cells (hOMCs) have been transplanted to the damaged spinal cord both pre-clinically and clinically. To date mainly autologous cells have been tested. However, inter-patient variability in cell recovery and quality, and the fact that the neuroprotective olfactory ensheathing cell (OEC) subset is difficult to isolate, means an allogeneic hOMC therapy would be an attractive "off-the-shelf" alternative. The aim of this study was to generate a candidate cell line from late-adherent hOMCs, thought to contain the OEC subset. Primary late-adherent hOMCs were transduced with a c-MycERTAM gene that enables cell proliferation in the presence of 4-hydroxytamoxifen (4-OHT). Two c-MycERTAM-derived polyclonal populations, PA5 and PA7, were generated and expanded. PA5 cells had a normal human karyotype (46, XY) and exhibited faster growth kinetics than PA7, and were therefore selected for further characterisation. PA5 hOMCs express glial markers (p75NTR, S100ß, GFAP and oligodendrocyte marker O4), neuronal markers (nestin and ß-III-tubulin) and fibroblast-associated markers (CD90/Thy1 and fibronectin). Co-culture of PA5 cells with a neuronal cell line (NG108-15) and with primary dorsal root ganglion (DRG) neurons resulted in significant neurite outgrowth after 5 days. Therefore, c-MycERTAM-derived PA5 hOMCs have potential as a regenerative therapy for neural cells.

The Use of Myelinating Cultures as a Screen of Glycomolecules for CNS Repair

In vitro cell-based assays have been fundamental in modern drug discovery and have led to the identification of novel therapeutics. We have developed complex mixed central nervous system (CNS) cultures, which recapitulate the normal process of myelination over time and allow the study of several parameters associated with CNS damage, both during development and after injury or disease. In particular, they have been used as a reliable screen to identify drug candidates that may promote (re)myelination and/or neurite outgrowth. Previously, using these cultures, we demonstrated that a panel of low sulphated heparin mimetics, with structures similar to heparan sulphates (HSs), can reduce astrogliosis, and promote myelination and neurite outgrowth. HSs reside in either the extracellular matrix or on the surface of cells and are thought to modulate cell signaling by both sequestering ligands, and acting as co-factors in the formation of ligand-receptor complexes. In this study, we have used these cultures as a screen to address the repair potential of numerous other commercially available sulphated glycomolecules, namely heparosans, ulvans, and fucoidans. These compounds are all known to have certain characteristics that mimic cellular glycosaminoglycans, similar to heparin mimetics. We show that the N-sulphated heparosans promoted myelination. However, O-sulphated heparosans did not affect myelination but promoted neurite outgrowth, indicating the importance of structure in HS function. Moreover, neither highly sulphated ulvans nor fucoidans had any effect on remyelination but CX-01, a low sulphated porcine intestinal heparin, promoted remyelination in vitro. These data illustrate the use of myelinating cultures as a screen and demonstrate the potential of heparin mimetics as CNS therapeutics.

In vitro comparative study of human mesenchymal stromal cells from dermis and adipose tissue for application in skin wound healing

Novel strategies combining cell therapy, tissue engineering, and regenerative medicine have been developed to treat major skin wounds. Although mesenchymal stromal cells (MSCs) from different tissues have similar stem cell features, such as self-renewing mesodermal differentiation potential and expression of immunophenotypic markers, they also have distinct characteristics. Therefore, we aimed to characterize the application of MSCs derived from the dermis and adipose tissue (DSCs and ASCs, respectively) in cutaneous wound healing by in vitro approaches. Human DSC and ASC were obtained and evaluated for their isolation efficiency, stemness, proliferative profile, and genetic stability over time in culture. The ability of wound closure was first assessed by direct cell scratch assay. The paracrine effects of DSC- and ASC-conditioned medium in dermal fibroblasts and keratinocytes and in the induction of tubule formation were also investigated. Although the ASC isolation procedures resulted in 100 times more cells than DSC, the latter had a higher proliferation rate in culture. Both presented low frequency of nuclear alterations over time in culture and showed similar characteristics of stem cells, such as expression of immunophenotypic markers and differentiation potential. DSCs showed increased healing capacity, and their conditioned media had greater paracrine effect in closing the wound of dermal fibroblasts and keratinocytes and in inducing angiogenesis. In conclusion, the therapeutic potential of MSCs is influenced by the obtainment source. Both ASCs and DSCs are applicable for skin wound healing; however, DSCs have an improved potential and should be considered for future applications in cell therapy.

Differentiation of human mesenchymal stem cells (MSC) to dopaminergic neurons: A comparison between Wharton's Jelly and olfactory mucosa as sources of MSCs

The generation of dopaminergic neurons from stem cells is a potential therapeutic approach to treat neurodegenerative disorders, such as Parkinson's disease. The current study aims to investigate the potential of two different types of mesenchymal stem cells derived from human Wharton's jelly and nasal cavity for differentiation into dopaminergic neurons. The differentiation capacities of both cell types were evaluated using real-time PCR, immunocytochemistry, flow cytometry and HPLC. Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) are noted for their capability to differentiate into mesodermal and non-mesodermal cells, including neurons. However, it was demonstrated that having the same neuroectodermal origin as the nervous system, the olfactory ectomesenchymal stem cells (OE-MSCs) expressed the neural marker MAP2 as well as dopaminergic markers such as tyrosine hydroxylase (TH), dopamine transporter (DAT) and PITX3 to a greater extent than the WJ-MSCs both at the level of mRNA and protein. Furthermore, quantitative flow cytometric evaluation of these markers at 12 days post-induction supported the above-mentioned results. Finally, the assessment of the functionality of differentiated cells and their ability to synthesize dopamine measured by HPLC revealed that the OE-MSC-derived dopaminergic cells released almost the same amount of dopamine as that secreted by WJ-MSC-derived cells. Thus it showed the difference in their functionality to be negligible. Overall, it may be concluded that higher proliferation and differentiation capacity of OE-MSCs, along with their easier harvestability and autologous transplantability compared with WJ-MSCs, makes them a better cell source for stem cell therapy of neurodegenerative disorders which are caused by degeneration of dopaminergic neurons.

Secretomes from Mesenchymal Stem Cells against Acute Kidney Injury: Possible Heterogeneity

A kidney has the ability to regenerate itself after a variety of renal injuries. Mesenchymal stem cells (MSCs) have been shown to ameliorate tissue damages during renal injuries and diseases. The regenerations induced by MSCs are primarily mediated by the paracrine release of soluble factors and extracellular vesicles, including exosomes and microvesicles. Extracellular vesicles contain proteins, microRNAs, and mRNAs that are transferred into recipient cells to induce several repair signaling pathways. Over the past few decades, many studies identified trophic factors from MSCs, which attenuate renal injury in a variety of animal acute kidney injury models, including renal ischemia-reperfusion injury and drug-induced renal injury, using microarray and proteomic analysis. Nevertheless, these studies have revealed the heterogeneity of trophic factors from MSCs that depend on the cell origins and different stimuli including hypoxia, inflammatory stimuli, and aging. In this review article, we summarize the secretomes and regenerative mechanisms induced by MSCs and highlight the possible heterogeneity of trophic factors from different types of MSC and different circumstances for renal regeneration.

The olfactory mucosa: a potential source of stem cells for hearing regeneration

The olfactory mucosa contains cells that enable it to generate new neurons and other supporting cells throughout life, allowing it to replace cells of the mucosa that have been damaged by exposure to various insults. In this article, we discuss the different types of stem cell found within the olfactory mucosa and their properties. In particular, the mesenchymal-like cells found within the lamina propria will be reviewed in detail. In addition, we discuss potential applications of olfactory-derived stem cells toward hearing regeneration secondary to either inner hair cell loss or primary or secondary auditory nerve degeneration.

The Nasal Cavity of the Rat and Mouse-Source of Mesenchymal Stem Cells for Treatment of Peripheral Nerve Injury

The nasal cavity performs several crucial functions in mammals, including rodents, being involved in respiration, behavior, reproduction, and olfaction. Its anatomical structure is complex and divided into several regions, including the olfactory recess where the olfactory mucosa (OM) is located and where the capture and interaction with the environmental odorants occurs. Among the cells of this region are the OM mesenchymal stem cells (MSCs), whose location raises the possibility that these cells could be involved in the peculiar ability of the olfactory nerve to regenerate continuously throughout life, although this relationship has not yet been confirmed. These cells, like all MSCs, present functional characteristics that make them candidates in new therapies associated with regenerative medicine, namely to promote the regeneration of the peripheral nerve after injury. The availability of stem cells to be therapeutically applied essentially depends on their collection in the tissue of origin. In the case of mice and rat's OM-MSCs, knowledge about the anatomy and histology of their nasal cavity is essential in establishing effective collection protocols. The present article describes the morphological characteristics of rodent's OM and establishes an alternative protocol for access to the olfactory recess and collection of the OM. Anat Rec, 301:1678-1689, 2018. © 2018 Wiley Periodicals, Inc.

Mesenchymal Stem Cell-Macrophage Choreography Supporting Spinal Cord Repair

Spinal cord injury results in destructive events that lead to tissue loss and functional impairments. A hallmark of spinal cord injury is the robust and persistent presence of inflammatory macrophages. Mesenchymal stem cells (MSCs) are known to benefit repair of the damaged spinal cord often associated with improved functional recovery. Transplanted MSCs immediately encounter the abundance of inflammatory macrophages in the injury site. It is known that MSCs interact closely and reciprocally with macrophages during tissue healing. Here, we will review the roles of (transplanted) MSCs and macrophages in spinal cord injury and repair. Molecular interactions between MSCs and macrophages and the deficiencies in our knowledge about the underlying mechanisms will be reviewed. We will discuss possible ways to benefit from the MSC-macrophage choreography for developing repair strategies for the spinal cord.

Olfactory Ensheathing Cells for Spinal Cord Injury: Sniffing Out the Issues

Olfactory ensheathing cells (OECs) are glia reported to sustain the continuous axon extension and successful topographic targeting of the olfactory receptor neurons responsible for the sense of smell (olfaction). Due to this distinctive property, OECs have been trialed in human cell transplant therapies to assist in the repair of central nervous system injuries, particularly those of the spinal cord. Though many studies have reported neurological improvement, the therapy remains inconsistent and requires further improvement. Much of this variability stems from differing olfactory cell populations prior to transplantation into the injury site. While some studies have used purified cells, others have used unpurified transplants. Although both preparations have merits and faults, the latter increases the variability between transplants received by recipients. Without a robust purification procedure in OEC transplantation therapies, the full potential of OECs for spinal cord injury may not be realised.

Cell therapy for spinal cord injury with olfactory ensheathing glia cells (OECs)

The prospects of achieving regeneration in the central nervous system (CNS) have changed, as most recent findings indicate that several species, including humans, can produce neurons in adulthood. Studies targeting this property may be considered as potential therapeutic strategies to respond to injury or the effects of demyelinating diseases in the CNS. While CNS trauma may interrupt the axonal tracts that connect neurons with their targets, some neurons remain alive, as seen in optic nerve and spinal cord (SC) injuries (SCIs). The devastating consequences of SCIs are due to the immediate and significant disruption of the ascending and descending spinal pathways, which result in varying degrees of motor and sensory impairment. Recent therapeutic studies for SCI have focused on cell transplantation in animal models, using cells capable of inducing axon regeneration like Schwann cells (SchCs), astrocytes, genetically modified fibroblasts and olfactory ensheathing glia cells (OECs). Nevertheless, and despite the improvements in such cell-based therapeutic strategies, there is still little information regarding the mechanisms underlying the success of transplantation and regarding any secondary effects. Therefore, further studies are needed to clarify these issues. In this review, we highlight the properties of OECs that make them suitable to achieve neuroplasticity/neuroregeneration in SCI. OECs can interact with the glial scar, stimulate angiogenesis, axon outgrowth and remyelination, improving functional outcomes following lesion. Furthermore, we present evidence of the utility of cell therapy with OECs to treat SCI, both from animal models and clinical studies performed on SCI patients, providing promising results for future treatments.

Recent achievements in stem cell-mediated myelin repair

PURPOSE OF REVIEW

Following the establishment of a number of successful immunomodulatory treatments for multiple sclerosis, current research focuses on the repair of existing damage.

RECENT FINDINGS

Promotion of regeneration is particularly important for demyelinated areas with degenerated or functionally impaired axons of the central nervous system's white and gray matter. As the protection and generation of new oligodendrocytes is a key to the re-establishment of functional connections, adult oligodendrogenesis and myelin reconstitution processes are of primary interest. Moreover, understanding, supporting and promoting endogenous repair activities such as mediated by resident oligodendroglial precursor or adult neural stem cells are currently thought to be a promising approach toward the development of novel regenerative therapies.

SUMMARY

This review summarizes recent developments and findings related to pharmacological myelin repair as well as to the modulation/application of stem cells with the aim to restore defective myelin sheaths.

Human mesenchymal factors induce rat hippocampal- and human neural stem cell dependent oligodendrogenesis

The generation of new oligodendrocytes is essential for adult brain repair in diseases such as multiple sclerosis. We previously identified the multifunctional p57kip2 protein as a negative regulator of myelinating glial cell differentiation and as an intrinsic switch of glial fate decision in adult neural stem cells (aNSCs). In oligodendroglial precursor cells (OPCs), p57kip2 protein nuclear exclusion was recently found to be rate limiting for differentiation to proceed. Furthermore, stimulation with mesenchymal stem cell (MSC)-derived factors enhanced oligodendrogenesis by yet unknown mechanisms. To elucidate this instructive interaction, we investigated to what degree MSC secreted factors are species dependent, whether hippocampal aNSCs respond equally well to such stimuli, whether apart from oligodendroglial differentiation also tissue integration and axonal wrapping can be promoted and whether the oligodendrogenic effect involved subcellular translocation of p57kip2. We found that CC1 positive oligodendrocytes within the hilus express nuclear p57kip2 protein and that MSC dependent stimulation of cultured hippocampal aNSCs was not accompanied by nuclear p57kip2 exclusion as observed for parenchymal OPCs after spontaneous differentiation. Stimulation with human MSC factors was observed to equally promote rat stem cell oligodendrogenesis, axonal wrapping and tissue integration. As forced nuclear shuttling of p57kip2 led to decreased CNPase- but elevated GFAP expression levels, this indicates heterogenic oligodendroglial mechanisms occurring between OPCs and aNSCs. We also show for the first time that dominant pro-oligodendroglial factors derived from human fetal MSCs can instruct human induced pluripotent stem cell-derived NSCs to differentiate into O4 positive oligodendrocytes.

Isolation of putative stem cells present in human adult olfactory mucosa

The olfactory mucosa (OM) has the unique characteristic of performing an almost continuous and lifelong neurogenesis in response to external injuries, due to the presence of olfactory stem cells that guarantee the maintenance of the olfactory function. The easy accessibility of the OM in humans makes these stem cells feasible candidates for the development of regenerative therapies. In this report we present a detailed characterization of a patient-derived OM, together with a description of cell cultures obtained from the OM. In addition, we present a method for the enrichment and isolation of OM stem cells that might be used for future translational studies dealing with neuronal plasticity, neuro-regeneration or disease modeling.

Human olfactory mesenchymal stromal cell transplants promote remyelination and earlier improvement in gait co-ordination after spinal cord injury

Autologous cell transplantation is a promising strategy for repair of the injured spinal cord. Here we have studied the repair potential of mesenchymal stromal cells isolated from the human olfactory mucosa after transplantation into a rodent model of incomplete spinal cord injury. Investigation of peripheral type remyelination at the injury site using immunocytochemistry for P0, showed a more extensive distribution in transplanted compared with control animals. In addition to the typical distribution in the dorsal columns (common to all animals), in transplanted animals only, P0 immunolabelling was consistently detected in white matter lateral and ventral to the injury site. Transplanted animals also showed reduced cavitation. Several functional outcome measures including end‐point electrophysiological testing of dorsal column conduction and weekly behavioural testing of BBB, weight bearing and pain, showed no difference between transplanted and control animals. However, gait analysis revealed an earlier recovery of co‐ordination between forelimb and hindlimb stepping in transplanted animals. This improvement in gait may be associated with the enhanced myelination in ventral and lateral white matter, where fibre tracts important for locomotion reside. Autologous transplantation of mesenchymal stromal cells from the olfactory mucosa may therefore be therapeutically beneficial in the treatment of spinal cord injury. GLIA 2017 GLIA 2017;65:639–656

Are nestin-positive mesenchymal stromal cells a better source of cells for CNS repair?

In recent years there has been a great deal of research within the stem cell field which has led to the definition and classification of a range of stem cells from a plethora of tissues and organs. Stem cells, by classification, are considered to be pluri- or multipotent and have both self-renewal and multi-differentiation capabilities. Presently there is a great deal of interest in stem cells isolated from both embryonic and adult tissues in the hope they hold the therapeutic key to restoring or treating damaged cells in a number of central nervous system (CNS) disorders. In this review we will discuss the role of mesenchymal stromal cells (MSCs) isolated from human olfactory mucosa, with particular emphasis on their potential role as a candidate for transplant mediated repair in the CNS. Since nestin expression defines the entire population of olfactory mucosal derived MSCs, we will compare these cells to a population of neural crest derived nestin positive population of bone marrow-MSCs.

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Human olfactory mucosa is a new source of mesenchymal stromal cells (MSCs).

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Some bone marrow MSCs are nestin-positive, neural crest derived and regulate hematopoietic stem cell activation.

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Human olfactory mucosa contains a population of nestin-positive MSCs that secrete CXCL12 and may have promote CNS repair.

Comparative miRNA-Based Fingerprinting Reveals Biological Differences in Human Olfactory Mucosa- and Bone-Marrow-Derived Mesenchymal Stromal Cells

Previously we reported that nestin-positive human mesenchymal stromal cells (MSCs) derived from the olfactory mucosa (OM) enhanced CNS myelination in vitro to a greater extent than bone-marrow-derived MSCs (BM-MSCs). miRNA-based fingerprinting revealed the two MSCs were 64% homologous, with 26 miRNAs differentially expressed. We focused on miR-146a-5p and miR-140-5p due to their reported role in the regulation of chemokine production and myelination. The lower expression of miR-140-5p in OM-MSCs correlated with higher secretion of CXCL12 compared with BM-MSCs. Addition of CXCL12 and its pharmacological inhibitors to neural co-cultures supported these data. Studies on related miR-146a-5p targets demonstrated that OM-MSCs had lower levels of Toll-like receptors and secreted less pro-inflammatory cytokines, IL-6, IL-8, and CCL2. OM-MSCs polarized microglia to an anti-inflammatory phenotype, illustrating potential differences in their inflammatory response. Nestin-positive OM-MSCs could therefore offer a cell transplantation alternative for CNS repair, should these biological behaviors be translated in vivo.

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OM-MSCs share 64% miRNA homology to BM-MSCs and differentially express 26 miRNAs

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CXCL12 promotes CNS myelination and is negatively regulated by miR-140-5p in BM-MSCs

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miR-146a-5p negatively regulates IL-6, IL-8, TLR2, and TLR4 on OM-MSCs

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These properties make OM-MSCs a suitable candidate for transplant-mediated CNS repair

Co-transplantation of autologous OM-MSCs and OM-OECs: a novel approach for spinal cord injury

Spinal cord injury (SCI) is a disastrous injury that leads to motor and sensory dysfunctions in patients. In recent years, co-transplantation has become an increasingly used therapeutic treatment for patients with SCI. Both mesenchymal stem cells (MSCs) and olfactory-ensheathing cells (OECs) have been adopted to ameliorate SCI, with promising outcomes. Remarkable effects on the rehabilitation of patients with SCI have been achieved using MSCs. Olfactory mucosa (OM) MSCs from human OM are one of the most ideal cell resources for auto-transplantation in clinical application owing to their a high proliferation rate and multipotent capability. In addition, OECs derived from OM have been used to improve functional recovery of SCI and resulted in promising functional recovery in years. Accordingly, co-transplantation of OM-MSCs coupled with OM-OECs has been adopted to improve the recovery of SCI. Here we reviewed the reported applications of OM-MSCs and OM-OECs for SCI treatment and proposed that a novel combined strategy using both autologous OM-MSCs and OM-OECs would achieve a better approach for the treatment of SCI.

Olfactory mucosa: a rich source of cell therapy for central nervous system repair

Damage to the brain and spinal cord leads to permanent functional disability because of the very limited capacity of the central nervous system (CNS) for repair. Cell therapy is thought to be a promising strategy for CNS repair. The proper cell type of transplantation for CNS repair has not been identified until now, but autologous transplantation would be advantageous. The olfactory mucosa (OM), from the olfactory system, in which the neurosensory cells are replaced throughout adult life, is thought to be a rich source of cell therapy for CNS repair. The OM is a heterogeneous tissue composed of a variety of cells supporting both normal function and regenerative capacity, in which many studies focused on four major types of cells, including horizontal basal cells (HBCs), globose basal cells (GBC), mesenchymal stem cells (MSCs), and olfactory ensheathing cells (OECs). Here, we review the four major types of cells in the OM and shed light on the potential of the OM for CNS repair.

Olfactory ecto-mesenchymal stem cells possess immunoregulatory function and suppress autoimmune arthritis

Recent studies have identified olfactory ecto-mesenchymal stem cells (OE-MSCs) as a new type of resident stem cell in the olfactory lamina propria. However, it remains unclear whether OE-MSCs possess any immunoregulatory functions. In this study, we found that mouse OE-MSCs expressed higher transforming growth factor-beta and interleukin-10 levels than bone marrow-derived MSCs. In culture, OE-MSCs exerted their immunosuppressive capacity via directly suppressing effector T-cell proliferation and increasing regulatory T (Treg) cell expansion. In mice with collagen-induced arthritis, adoptive transfer of OE-MSCs markedly suppressed arthritis onset and disease severity, which was accompanied by increased Treg cells and reduced Th1/Th17 cell responses in vivo. Taken together, our findings identified a novel function of OE-MSCs in regulating T-cell responses, indicating that OE-MSCs may represent a new cell therapy for the treatment of rheumatoid arthritis and other autoimmune diseases.

Isolation of human adult olfactory sphere cells as a cell source of neural progenitors

Olfactory stem cells are generated from olfactory mucosa. Various culture conditions generate olfactory stem cells that differ according to species and developmental stage and have different progenitor or stem cell characteristics. Olfactory spheres (OSs) are clusters of progenitor or stem cells generated from olfactory mucosa in suspension culture. In this study, adult human OSs were generated and their characteristics analyzed. Human OSs were adequately produced from olfactory mucosa with area over 40 mm(2). Immunocytochemistry (ICC) and fluorescence-activated cell sorting showed that human OSs were AN2 and A2B5-positive. Immunofluorescence analysis of cell type-specific ICC indicated that the number of Tuj1-positive OS cells was significantly elevated. Tuj1-positive cells displayed typical neuronal soma and dendritic morphology. Human OS cells were also immunopositive for MAP2. By contrast, few RIP-, O4-, and GFAP-positive cells were present. These RIP, O4, and GFAP-positive cells did not resemble bona fide oligodendrocytes and astrocytes morphologically. In culture to induce differentiation of oligodendrocytes, human OS cells also expressed neuronal markers, but neither oligodendrocyte or astrocyte markers. These findings suggest that human OS cells autonomously differentiate into neurons in our culture condition and have potential to be used as a cell source of neural progenitors for their own regenerative grafts, avoiding the need for immunosuppression and ethical controversies.

Olfactory sphere cells are a cell source for γ-aminobutyric acid-producing neurons

Olfactory sphere cells (OSCs) are stem cells generated by culturing olfactory mucosa. Adult rat OSCs express oligodendrocyte progenitor cell (OPC) markers and differentiate into mature oligodendrocytes. Although OSCs also express nestin, a marker of neural stem cells (NSCs), it remains unclear whether adult rat OSCs are multipotent and capable of giving rise to neurons as well as oligodendrocytes. Valproic acid (VPA) is a histone deacetylase inhibitor that has the contradictory capacity to induce both differentiation of NSCs and dedifferentiation of OPCs. This study investigates a potential role for VPA in inducing either differentiation or dedifferentiation of adult rat OSCs. Treatment of OSCs with VPA induced hyperacetylation of histones and decreased cell proliferation in the absence of changes in the number of nestin-positive cells. Furthermore, VPA promoted the genesis of γ-aminobutyric acid (GABA)-producing neurons identified by expression of Tuj1/GAD67/GABA while repressing oligodendrocyte production. These findings suggest that OSCs treated with VPA did not exhibit stem cell properties indicative of dedifferentiation but rather switched to a neuronal identity during their terminal differentiation. OSCs were then transplanted into the hippocampus of rats with kainic acid-induced temporal lobe epilepsy and were systemically given VPA. Although grafted OSCs expressed Tuj1 and GAD67, these cells did not sufficiently inhibit epileptic activity. These results suggest that OSCs are a transplantable cell source for GABA-producing neurons that can be modulated by VPA. However, further investigation is required to develop them for clinical applications.