Performance and mechanism of neuroleukin in the growth and survival of sertoli cell-induced neurons in a coculture system

Cerebrospinal fluid levels of the neurotrophic factor neuroleukin are increased in early Alzheimer's disease, but not in cerebral amyloid angiopathy

Background

Neuroleukin (NLK) is a protein with neurotrophic properties and is present in a proportion of senile plaques and amyloid laden vessels. It has been suggested that NLK is part of a neuroprotective response to amyloid β-induced cell death. The aim of our study was to investigate the value of cerebrospinal fluid (CSF) NLK levels as a biomarker of vascular amyloid deposition in patients with cerebral amyloid angiopathy (CAA) and in patients with amnestic mild cognitive impairment (aMCI) and Alzheimer’s disease (AD).

Methods

CSF NLK levels were quantified by ELISA in CAA patients (n = 25) and controls (n = 27) and in two independent samples of aMCI patients, AD patients, and controls: (1) From the Radboud University Medical Center (Nijmegen), we included n = 19 aMCI patients, n = 40 AD patients, and n = 32 controls. (2) From the Hospital of Sant Pau (Barcelona), we included n = 33 aMCI patients, n = 17 AD patients, and n = 50 controls.

Results

CSF NLK levels were similar in CAA patients and controls (p = 0.95). However, we found an elevated CSF concentration of NLK in aMCI (p < 0.0001) and AD patients (p < 0.0001) compared to controls in both samples sets. In addition, we found a correlation of CSF NLK with CSF YKL-40 (age-adjusted-spearman-rank-coefficient = 0.82, p < 0.0001) in aMCI/AD patients, a well-known glial marker of neuro-inflammation.

Conclusions

We found that CSF NLK levels are elevated in aMCI and AD patients compared to controls, but are not increased in CAA patients. CSF NLK levels may be related to an increased neuroinflammatory state in early stages of AD, given its association with YKL-40.

Inducing Non-genetically Modified Induced Embryonic Sertoli Cells Derived From Embryonic Stem Cells With Recombinant Protein Factors

Embryonic Sertoli cells (eSCs) possess multiple supporting functions and research value in gonadal development and sex determination. However, the limitation of acquiring quality eSCs had hindered the further application. Herein, we successfully derived non-genetically modified (non-GM)-induced embryonic Sertoli-like cells (eSLCs) from mouse embryonic stem cells (ESCs) with a TM4 cell-derived conditioned medium containing recombinant endogenous protein factors Sry, Sox9, Sf1, Wt1, Gata4, and Dmrt1. These eSLCs were determined through morphology; transcriptional expression levels of stage-specific, epithelial, and mesenchymal marker genes; flow cytometry, immunofluorescence; and immunocytochemistry and functionally determined by coculture with spermatogonia stem cells. Results indicated that these eSLCs performed similarly to eSCs in specific biomarkers and expression of marker genes and supported the maturation of spermatogonia. The study induced eSLCs from mouse ESCs by defined protein factors. However, the inducing efficiency of the non-GM method was still lower than that of the lentiviral transduction method. Thus, this work established a foundation for future production of non-GM eSLCs for clinical applications and fundamental theory research.

GRP78-Mediated Signaling Contributes to Axonal Growth Resulting in Motor Function Recovery in Spinal Cord-Injured Mice

Promoting axonal growth is essential for repairing damaged neuronal connections and motor function in spinal cord injury (SCI). Neuroleukin (NLK) exerts axonal growth activity in vitro and in vivo, but the mechanism remains unclear. This study reveals that the 78-kDa glucose-regulated protein (GRP78) is a NLK neuronal receptor that contributes to recovery from SCI. Binding and immunoprecipitation assays indicated that NLK binds to GRP78. Pretreatment to cultured neurons with a GRP78-neutralizing antibody suppressed NLK-induced axonal growth. Blocking cell surface GRP78 inhibited neuronal NLK-induced Akt activation. Treatment with an Akt inhibitor suppressed NLK-induced axonal growth. Continuous administration of NLK into the lateral ventricle of SCI mice increased axonal density in the injured region and restored motor function, which was not observed when NLK was simultaneously administered with a GRP78-neutralizing antibody. These results indicate that GRP78 regulates the NLK-induced axonal growth activity; NLK-GRP78 signaling promotes motor function recovery in SCI, presenting as a potential therapeutic target.

The Effect of Sertoli Cells on Xenotransplantation and Allotransplantation of Ventral Mesencephalic Tissue in a Rat Model of Parkinson's Disease

Intra-striatal transplantation of fetal ventral mesencephalic (VM) tissue has a therapeutic effect on patients with Parkinson’s disease (PD). Sertoli cells (SCs) possess immune-modulatory properties that benefit transplantation. We hypothesized that co-graft of SCs with VM tissue can attenuate rejection. Hemi-parkinsonian rats were generated by injecting 6-hydroxydopamine into the right medial forebrain bundle of Sprague Dawley (SD) rats. The rats were then intrastriatally transplanted with VM tissue from rats or pigs (rVM or pVM), with/without a co-graft of SCs (rVM+SCs or pVM+SCs). Recovery of dopaminergic function and survival of the grafts were evaluated using the apomorphine-induced rotation test and small animal-positron emission tomography (PET) coupled with [¹⁸F] DOPA or [¹⁸F] FE-PE2I, respectively. Immunohistochemistry (IHC) examination was used to determine the survival of the grafted dopaminergic neurons in the striatum and to investigate immune-modulatory effects of SCs. The results showed that the rVM+SCs and pVM+SCs groups had significantly improved drug-induced rotational behavior compared with the VM alone groups. PET revealed a significant increase in specific uptake ratios (SURs) of [¹⁸F] DOPA and [¹⁸F] FE-PE2I in the grafted striatum of the rVM+SCs and pVM+SCs groups as compared to that of the rVM and pVM groups. SC and VM tissue co-graft led to better dopaminergic (DA) cell survival. The co-grafted groups exhibited lower populations of T-cells and activated microglia compared to the groups without SCs. Our results suggest that co-graft of SCs benefit both xeno- and allo-transplantation of VM tissue in a PD rat model. Use of SCs enhanced the survival of the grafted dopaminergic neurons and improved functional recovery. The enhancement may in part be attributable to the immune-modulatory properties of SCs. In addition, [¹⁸F]DOPA and [¹⁸F]FE-PE2I coupled with PET may provide a feasible method for in vivo evaluation of the functional integrity of the grafted DA cell in parkinsonian rats.

Differentiation roadmap of embryonic Sertoli cells derived from mouse embryonic stem cells

Background

Embryonic Sertoli cells (eSCs) play an important role in sex determination and in male gonad development which makes them a very useful cell type for therapeutic applications. However, the deriving mechanism of Sertoli cells has been unclear and challenging to create a large number of quality eSCs. Therefore, this study aimed to create the eSCs induced from mouse embryonic stem (mES) cells by regulating defined factors and to explore the relevant regulatory mechanism.

Methods

Six inducing factors, Sry, Sox9, SF1, WT1, GATA4, and Dmrt1, were respectively transduced into mES cells by lentiviral infection according to the experimental design. The test groups were identified by development stage-specific markers, AMH, Emx2, SF1, and FasL, using flow cytometry. Induced eSCs were determined by FasL and AMH biomarkers under immunofluorescence, immunocytochemistry, and flow cytometry. Moreover, the pluripotency markers, gonad development-related markers, epithelial markers and mesenchymal markers in test groups were transcriptionally determined by qPCR.

Results

In this study, the co-overexpression of all the six factors effectively produced a large population of eSCs from mES cells in 35 days of culturing. These eSCs were capable of forming tubular-like and ring-like structures with functional performance. The results of flow cytometry indicated that the upregulation of GATA4 and WT1 contributed to the growth of somatic cells in the coelomic epithelium regarded as the main progenitor cells of eSCs. Whereas, SF1 facilitated the development of eSC precursor cells, and Sry and Sox9 promoted the determination of male development. Moreover, the overexpression of Dmrt1 was essential for the maintenance of eSCs and some of their specific surface biomarkers such as FasL. The cellular morphology, biomarker identification, and transcriptomic analysis aided in exploring the regulatory mechanism of deriving eSCs from mES cells.

Conclusion

Conclusively, we have elucidated a differentiation roadmap of eSCs derived from mES cells with a relevant regulatory mechanism. Through co-overexpression of all these six factors, a large population of eSCs was successfully induced occupying 24% of the whole cell population (1 × 10⁵ cells/cm²). By adopting this approach, a mass of embryonic Sertoli cells can be generated for the purpose of co-culture technique, organ transplantation, gonadal developmental and sex determination researches.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1180-6) contains supplementary material, which is available to authorized users.

Extracellular Neuroleukin Enhances Neuroleukin Secretion From Astrocytes and Promotes Axonal Growth in vitro and in vivo

Under pathological conditions in the central nervous system (CNS), including spinal cord injury, astrocytes show detrimental effects against neurons. It is also known that astrocytes sometimes exert beneficial effects, such as neuroprotection and secretion of axonal growth factors. If beneficial effects of astrocytes after injury could be induced, dysfunction of the injured CNS may improve. However, a way of promoting beneficial functions in astrocytes has not been elucidated. In the current study, we focused on neuroleukin (NLK), which is known to have axonal growth activities in neurons. Although NLK is secreted from astrocytes, the function of NLK in astrocytes is poorly understood. We aimed to clarify the mechanism of NLK secretion in astrocytes and the functional significance of secreted NLK from astrocytes. Stimulation of cultured astrocytes with recombinant NLK significantly elevated the secretion of NLK from astrocytes. Furthermore, astrocyte conditioned medium treated with NLK increased axonal density in cultured cortical neurons. Recombinant NLK itself directly increased axonal density in cultured neurons. These results indicated that NLK secreted from astrocytes acted as an axonal growth factor and that secretion was stimulated by extracellular NLK. To elucidate a direct binding molecule of NLK on astrocytes, drug affinity responsive target stability (DARTS) analysis was performed. A 78 kDa glucose regulated protein (GRP78) was identified as a receptor for NLK, which was related to the secretion of NLK from astrocytes. When NLK was injected into the lesion site of spinal cord injured mice, axonal density in the injured region was significantly increased and hindlimb motor function improved. These results suggested that NLK-GRP78 signalling was important for the beneficial effects of astrocytes. This study strengthens the potential of astrocytes for use as therapeutic targets in CNS traumatic injury.

In Vitro Derivation of Functional Sertoli-Like Cells from Mouse Embryonic Stem Cells

Sertoli cells (SCs) in the mammalian testes are well known as supporting cells of spermatogenesis, but have recently become an attractive source of cell therapy because of their capacity for immune modulation and trophic effects. In order to increase their applicable efficacy, we demonstrate a novel differentiation method for mouse embryonic stem cell (ESC)-derived Sertoli-like cells (SLCs) via the intermediate mesoderm (IM). We show that IM derived from an induction of 6 days expressed markers such as Wt1, Lhx1, Pax2 and Osr1, and that a sequential induction of 6 days resulted in ESC-SLCs. The SLCs expressed their marker genes ( Sf1, Sox9, Gata4, Wt1, Fshr and Scf), but the pluripotency-marker gene Oct4 was decreased. After sorting by FSHR expression, high-purity (> 90%) SLCs were collected that showed distinct characteristics of SCs such as high phagocytic and immune modulation activities as well as the expression of immune-related genes. In addition, when transplanted into the seminiferous tubule of busulfan-treated mice, SLCs re-located and were maintained in the basal region of the tubule. These results demonstrated that our robust sequential differentiation system produced functional SLCs from mouse ESCs in vitro.

Emerging Strategies for Stem Cell Lineage Commitment in Tissue Engineering and Regenerative Medicine

Stem cells have transformed the fields of tissue engineering and regenerative medicine, and their potential to further advance these fields cannot be overstated. The stem cell niche is a dynamic microenvironment that determines cell fate during development and tissue repair following an injury. Classically, stem cells were studied in isolation of their microenvironment; however, contemporary research has produced a myriad of evidence that shows the importance of multiple aspects of the stem cell niche in regulating their processes. In the context of tissue engineering and regenerative medicine studies, the niche is an artificial environment provided by culture conditions. In vitro culture conditions may involve coculturing with other cell types, developing specific biomaterials, and applying relevant forces to promote the desired lineage commitment. Considerable advance has been made over the past few years toward directed stem cell differentiation; however, the unspecific differentiation of stem cells yielding a mixed population of cells has been a challenge. In this review, we provide a systematic review of the emerging strategies used for lineage commitment within the context of tissue engineering and regenerative medicine. These strategies include scaffold pore-size and pore-shape gradients, stress relaxation, sonic and electromagnetic effects, and magnetic forces. Finally, we provide insights and perspectives into future directions focusing on signaling pathways activated during lineage commitment using external stimuli.

Oxidation Resistance 1 Modulates Glycolytic Pathways in the Cerebellum via an Interaction with Glucose-6-Phosphate Isomerase

Glucose metabolism is essential for the brain: it not only provides the required energy for cellular function and communication but also participates in balancing the levels of oxidative stress in neurons. Defects in glucose metabolism have been described in neurodegenerative disease; however, it remains unclear how this fundamental process contributes to neuronal cell death in these disorders. Here, we investigated the molecular mechanisms driving the selective neurodegeneration in an ataxic mouse model lacking oxidation resistance 1 (Oxr1) and discovered an unexpected function for this protein as a regulator of the glycolytic enzyme, glucose-6-phosphate isomerase (GPI/Gpi1). Initially, we present a dysregulation of metabolites of glucose metabolism at the pre-symptomatic stage in the Oxr1 knockout cerebellum. We then demonstrate that Oxr1 and Gpi1 physically and functionally interact and that the level of Gpi1 oligomerisation is disrupted when Oxr1 is deleted in vivo. Furthermore, we show that Oxr1 modulates the additional and less well-understood roles of Gpi1 as a cytokine and neuroprotective factor. Overall, our data identify a new molecular function for Oxr1, establishing this protein as important player in neuronal survival, regulating both oxidative stress and glucose metabolism in the brain.

Identification of Sertoli cell-specific transcripts in the mouse testis and the role of FSH and androgen in the control of Sertoli cell activity

Background

The Sertoli cells act to induce testis differentiation and subsequent development in fetal and post-natal life which makes them key to an understanding of testis biology. As a major step towards characterisation of factors involved in Sertoli cell function we have identified Sertoli cell-specific transcripts in the mouse testis and have used the data to identify Sertoli cell-specific transcripts altered in mice lacking follicle-stimulating hormone receptors (FSHRKO) and/or androgen receptors (AR) in the Sertoli cells (SCARKO).

Results

Adult iDTR mice were injected with busulfan to ablate the germ cells and 50 days later they were treated with diphtheria toxin (DTX) to ablate the Sertoli cells. RNAseq carried out on testes from control, busulfan-treated and busulfan + DTX-treated mice identified 701 Sertoli-specific transcripts and 4302 germ cell-specific transcripts. This data was mapped against results from microarrays using testicular mRNA from 20 day-old FSHRKO, SCARKO and FSHRKO.SCARKO mice. Results show that of the 534 Sertoli cell-specific transcripts present on the gene chips, 85% were altered in the FSHRKO mice and 94% in the SCARKO mice (mostly reduced in both cases). In the FSHRKO.SCARKO mice additive or synergistic effects were seen for most transcripts. Age-dependent studies on a selected number of Sertoli cell-specific transcripts, showed that the marked effects in the FSHRKO at 20 days had largely disappeared by adulthood although synergistic effects of FSHR and AR knockout were seen.

Conclusions

These studies have identified the Sertoli cell-specific transcriptome in the mouse testis and have shown that most genes in the transcriptome are FSH- and androgen-dependent at puberty although the importance of FSH diminishes towards adulthood.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4357-3) contains supplementary material, which is available to authorized users.

Cryopreserved CD90+ cells obtained from mobilized peripheral blood in sheep: a new source of mesenchymal stem cells for preclinical applications

Mobilized peripheral blood (MPB) bone marrow cells possess the potential to differentiate into a variety of mesenchymal tissue types and offer a source of easy access for obtaining stem cells for the development of experimental models with applications in tissue engineering. In the present work, we aimed to isolate by magnetic activated cell sorting CD90+ cells from MPB by means of the administration of Granulocyte-Colony Stimulating Factor and to evaluate cell proliferation capacity, after thawing of the in vitro culture of this population of mesenchymal stem cells (MSCs) in sheep. We obtained a median of 8.2 ± 0.6 million of CD90+ cells from the 20-mL MPB sample. After thawing, at day 15 under in vitro culture, the mean CD90+ cells determined by flow cytometry was 92.92 ± 1.29 % and cell duplication time determined by crystal violet staining was 47.59 h. This study describes for the first time the isolation, characterization, and post-in vitro culture thawing of CD90+ MSCs from mobilized peripheral blood in sheep. This population can be considered as a source of MSCs for experimental models in tissue engineering research.