Enhanced viability and neuronal differentiation of neural progenitors by chromaffin cell co-culture

Stemness enhancement of human neural stem cells following bone marrow MSC coculture

Rapid loss of stemness capacity in purified prototype neural stem cells (NSCs) remains a serious challenge to basic and clinical studies aiming to repair the central nervous system. Based on the essential role of mesodermal guidance in the process of neurulation, we hypothesized that coculture of human NSCs (hNSCs) with human bone marrow-derived mesenchymal stromal stem cells (hMSCs) could enhance the stemness of hNSCs through Notch-1 signaling. We have now tested the hypothesis by assessing behaviors of hNSCs and hMSCs under systematically designed coculture conditions relative to monocultures, with or without Notch-1 manipulation in vitro. Our data demonstrate that expression levels of Notch-1 and Hes-1 as determined by immunocytochemistry are significantly higher in hNSCs cocultured with hMSCs than those of controls. Furthermore, coculturing significantly increases immunoreactivity of CD15, a neural stemness marker, but decreases CD24, a marker of neural/neuronal commitment in hNSCs. The effect is independent from the physical status of cell growth since coculture and notch signaling actually promotes hNSC adhesion. Importantly, coculture with hMSCs markedly augments hNSC proliferation rate (e.g., higher yield in G2/M phase subpopulation in a notch-dependent manner detected by flow cytometry) without diminishing their lineage differentiation capabilities. The results suggest that coculture of hNSCs with hMSCs enhances stemness biology of hNSCs partially via activation of Notch-1 signal transduction. Our finding sheds new light on mesoderm-ectoderm cell fate determination via contact-based hMSC-hNSC interactions and provides mechanistic leads for devising effective regimens to sustain and augment stemness of in vitro established hNSC and hMSC lines for basic science, translational and clinical applications.

Combined extrinsic and intrinsic manipulations exert complementary neuronal enrichment in embryonic rat neural precursor cultures: an in vitro and in vivo analysis

Numerous central nervous system (CNS) disorders share a common pathology in dysregulation of gamma-aminobutyric acid (GABA) inhibitory signaling. Transplantation of GABA-releasing cells at the site of disinhibition holds promise for alleviating disease symptoms with fewer side effects than traditional drug therapies. We manipulated fibroblast growth factor (FGF)-2 deprivation and mammalian achaete-scute homolog (MASH)1 transcription factor levels in an attempt to amplify the default GABAergic neuronal fate in cultured rat embryonic neural precursor cells (NPCs) for use in transplantation studies. Naïve and MASH1 lentivirus-transduced NPCs were maintained in FGF-2 or deprived of FGF-2 for varying lengths of time. Immunostaining and quantitative analysis showed that GABA- and beta-III-tubulin-immunoreactive cells generally decreased through successive passages, suggesting a loss of neurogenic potential in rat neurospheres expanded in vitro. However, FGF-2 deprivation resulted in a small, but significantly increased population of GABAergic cells derived from passaged neurospheres. In contrast to naïve and GFP lentivirus-transduced clones, MASH1 transduction resulted in increased bromodeoxyuridine (BrdU) incorporation and clonal colony size. Western blotting showed that MASH1 overexpression and FGF-2 deprivation additively increased beta-III-tubulin and decreased cyclic nucleotide phosphodiesterase (CNPase) expression, whereas FGF-2 deprivation alone attenuated glial fibrillary acidic protein (GFAP) expression. These results suggest that low FGF-2 signaling and MASH1 activity can operate in concert to enrich NPC cultures for a GABA neuronal phenotype. When transplanted into the adult rat spinal cord, this combination also yielded GABAergic neurons. These findings indicate that, even for successful utilization of the default GABAergic neuronal precursor fate, a combination of both extrinsic and intrinsic manipulations will likely be necessary to realize the full potential of NSC grafts in restoring function.

Neuronal gene expression and function in the growth-stimulated R28 retinal precursor cell line

PURPOSE

Proliferative retinal progenitor cells that express neuronal characteristics are potentially useful for developmental studies and as experimental graft material. The continuously-growing R28 retinal cell line has been distributed to over 60 laboratories for a variety of studies, yet has not been fully characterized. In this study, we tested the hypothesis that the proliferative R28 retinal cell line contains subpopulations of cells that express neuronal mRNAs and proteins characteristic of CNS neurons.

METHODS

To this end, we sought to determine the potential retinal, neuronal, and growth-related characteristics of this retinal cell line through gene expression profiling, coupled with confirmatory immunocytochemistry and electrophysiology.

RESULTS

Despite expression of growth-stimulatory oncogenes and growth-promoting factors, subpopulations of R28 cells express abundant retinal and neuronal markers, as well as the functional capacity to respond to specific neurotransmitters such as dopamine, acetylcholine, serotonin, and glycine.

CONCLUSION

Proliferative R28 cells retain functional neuronal properties that may prove useful in future studies of neuronal differentiation and development.

Effect of thyroid hormone T3 on myosin-Va expression in the central nervous system

Thyroid hormones (THs) are essential for brain development, where they regulate gliogenesis, myelination, cell proliferation and protein synthesis. Hypothyroidism severely affects neuronal growth and establishment of synaptic connections. Triiodothyronine (T3), the biologically active form of TH, has a central function in these activities. So, Myosin-Va (Myo-Va), a molecular motor protein involved in vesicle and RNA transport, is a good candidate as a target for T3 regulation. Here, we analyzed Myo-Va expression in euthyroid and hypothyroid adult rat brains and synaptosomes. We observed a reduction of Myo-Va expression in cultured neural cells from newborn hypothyroid rat brain, while immunocytochemical experiments showed a punctate distribution of this protein in the cytoplasm of cells. Particularly, Myo-Va co-localized with microtubules in neurites, especially in their varicosities. Myo-Va immunostaining was stronger in astrocytes and neurons of controls when compared with hypothyroid brains. In addition, supplementation of astrocyte cultures with T3 led to increased expression of Myo-Va in cells from both euthyroid and hypothyroid animals, suggesting that T3 modulates Myo-Va expression in neural cells both in vivo and in vitro. We have further analyzed Myo-Va expression in U373 cells, a human glioblastoma line, and found the same punctate cytoplasmic protein localization. As in normal neural cells, this expression was also increased by T3, suggesting that the modulatory mechanism exerted by T3 over Myo-Va remains active on astrocyte tumor cells. These data, coupled with the observation that Myo-Va is severely affected in hypothyroidism, support the hypothesis that T3 activity regulates neural motor protein expression, taking Myo-Va as a model. As a consequence, reduced T3 activity could supposedly affect axonal transport and synaptic function, and could therefore explain disturbances seen in the hypothyroid brain.

Enhanced differentiation of embryonic stem cells using co-cultivation with hepatocytes

We examined the effects of co-cultivated hepatocytes on the hepatospecific differentiation of murine embryonic stem (ES) cells. Utilizing an established mouse ES cell line expressing high or low levels of E-cadherin, that we have previously shown to be responsive to hepatotrophic growth factor stimulation (Dasgupta et al., 2005. Biotechnol Bioeng 92(3):257-266), we compared co-cultures of cadherin-expressing ES (CE-ES) cells with cultured rat hepatocytes, allowing for either paracrine interactions (indirect co-cultures) or both juxtacrine and paracrine interactions (direct co-cultures, random and patterned). Hepatospecific differentiation of ES cells was evaluated in terms of hepatic-like cuboidal morphology, heightened gene expression of late maturation marker, glucose-6-phosphatase in relation to early marker, alpha-fetoprotein (AFP), and the intracellular localization of albumin. Hepatocytes co-cultured with growth factor primed CE-ES cells markedly enhanced ES cell differentiation toward the hepatic lineage, an effect that was reversed through E-cadherin blockage and inhibited in control ES cells with reduced cadherin expression. Comparison of single ES cell cultures versus co-cultures show that direct contact co-cultures of hepatocytes and CE-ES cells maximally promoted ES cell commitment towards hepatodifferentiation, suggesting cooperative effects of cadherin-based juxtacrine and paracrine interactions. In contrast, E-cadherin deficient mouse ES (CD-ES) cells co-cultured with hepatocytes failed to show increased G6P expression, confirming the role of E-cadherin expression. To establish whether albumin expression in CE-ES cells was spatially regulated by co-cultured hepatocytes, we co-cultivated CE-ES cells around micropatterned, pre-differentiated rat hepatocytes. Albumin localization was enhanced "globally" within CE-ES cell colonies and was inhibited through E-cadherin antibody blockage in all but an interfacial band of ES cells. Thus, stem cell based cadherin presentation may be an effective tool to induce hepatotrophic differentiation by leveraging both distal/paracrine and contact/juxtacrine interactions with primary cells of the liver.

Enhanced tyrosine hydroxylase expression in PC12 cells co-cultured with feline mesenchymal stem cells

Mesenchymal stem cells (MSCs) secrete a variety of neuroregulatory molecules, such as nerve growth factor, brain-derived neurotrophic factor, and glial cell-derived neurotrophic factor, which upregulate tyrosine hydroxylase (TH) gene expression in PC12 cells. Enhancing TH gene expression is a critical step for treatment of Parkinson's disease (PD). The objective of this study was to assess the effects of co-culturing PC12 cells with MSCs from feline bone marrow on TH protein expression. We divided the study into three groups: an MSC group, a PC12 cell group, and the combined MSC + PC12 cell group (the co-culture group). All cells were cultured in DMEM-HG medium supplemented with 10% fetal bovine serum for three days. Thereafter, the cells were examined using western blot analysis and immunocytochemistry. In western blots, the co-culture group demonstrated a stronger signal at 60 kDa than the PC12 cell group (p<0.001). TH was not expressed in the MSC group, either in western blot or immunocytochemistry. Thus, the MSCs of feline bone marrow can up-regulate TH expression in PC12 cells. This implies a new role for MSCs in the neurodegenerative disease process.

Characterization of human skin-derived mesenchymal stem cell proliferation rate in different growth conditions

This study investigated conditions for optimal in vitro propagation of human skin-derived mesenchymal stem cells (S-MSC). Forty primary skin-derived precursor cell (SKP) cultures were established from both male and female donors (age 29-65 years) and eight of them were randomly selected for in-depth characterization. Effects of basic fibroblast growth factor (FGF-2), epidermal growth factor (EGF), leukemia inhibiting factor (LIF) and dibutyryl-cyclic adenosine monophosphate (db-cAMP) on S-MSC proliferation were investigated. Primary SKP cultures were >95% homogenous for CD90, CD73, and CD105 marker expression enabling to classify these cells as S-MSC. FGF-2 dose-dependent stimulation was observed in low serum medium only, whereas EGF neither stimulated S-MSC proliferation nor potentates the effect of FGF-2. Pronounced donor to donor differences among S-MSC cultures were observed in 3-day proliferation assay. This study demonstrates that homogenous S-MSC populations can be reproducibly isolated from individual donors of different age. Optimal cell culture conditions for in vitro propagation of S-MSC are B27 supplemented or low serum media with FGF-2 (4 ng/ml). EGF and LIF as well as db-cAMP are dispensable for S-MSC proliferation.

Zuckerkandl's organ improves long-term survival and function of neural stem cell derived dopaminergic neurons in Parkinsonian rats

Transplantation of neural stem cells (NSC) derived dopamine (DA) neurons has emerged as an alternative approach to fetal neural cell transplantation in Parkinson's disease (PD). However, similar to fetal neural cell, survival of these neurons following transplantation is also limited due to limited striatal reinnervation (graft with dense neuronal core), limited host-graft interaction, poor axonal outgrowth, lack of continuous neurotrophic factors supply and principally an absence of cell adhesion molecules mediated appropriate developmental cues. In the present study, an attempt has been made to increase survival and function of NSC derived DA neurons, by co-grafting with Zuckerkandl's organ (a paraneural organ that expresses neurotrophic factors as well as cell adhesion molecules); to provide continuous NTF support and developmental cues to transplanted DA neurons in the rat model of PD. 24 weeks post transplantation, a significant number of surviving functional NSC derived DA neurons were observed in the co-transplanted group as evident by an increase in the number of tyrosine hydroxylase immunoreactive (TH-IR) neurons, TH-IR fiber density, TH-mRNA expression and TH-protein level at the transplantation site (striatum). Significant behavioral recovery (amphetamine induced stereotypy and locomotor activity) and neurochemical recovery (DA-D2 receptor binding and DA and DOPAC levels at the transplant site) were also observed in the NSC+ZKO co-transplanted group as compared to the NSC or ZKO alone transplanted group. In vivo results were further substantiated by in vitro studies, which suggest that ZKO increases the NSC derived DA neuronal survival, differentiation, DA release and neurite outgrowth as well as protects against 6-OHDA toxicity in co-culture condition. The present study suggests that long-term and continuous NTF support provided by ZKO to the transplanted NSC derived DA neurons, helped in their better survival, axonal arborization and integration with host cells, leading to long-term functional restoration in the rat model of PD.

Cell therapy of pain: Characterization of human fetal chromaffin cells at early adrenal medulla development

Adult adrenal chromaffin cells are being utilized for therapeutic transplantation. With the prospect of using fetal chromaffin cells in pain therapy, we studied their phenotype, proliferative power, function, and growth in vitro and in situ in order to determine the optimal time for implantation. Between 7 and 10 gestational weeks (GW), we isolated, in vitro, two types of chromaffin cells with a noradrenergic phenotype akin to that observed, in situ. Among the adherent chromaffin cells first observed in vitro, only a few samples expressed met-enkephalin, whereas almost all the neurosphere-like colonies, which appeared later, expressed it. However, neither of the two types of populations expressed an adrenergic phenotype in line with that observed in situ. At the upper limits of the voluntary abortion period authorized in France, this phenotype (12 GW) and met-enkephalin expression (13 GW) were evidenced in situ. For the first time in man, we demonstrate the secretion of noradrenaline in vitro by the two populations of cells. Consistent with this result, we also noted dopamine beta hydroxylase (DbetaH) mRNA expression in vitro and in situ within this period. These observations on the expression of these biological factors indicate that 9-10 GW would be the best stage for sampling these cells for preclinical transplantation experiments.

Improved neural progenitor cell survival when cografted with chromaffin cells in the rat striatum

Transplantation of stem and neural progenitor cells hold great promise in the repair of neuronal tissue lost due to injury or disease. However, survival following transplantation to the adult CNS has been poor, likely due to a lack of neurotrophic factors, such as basic fibroblast growth factor (FGF-2), that are used to maintain and expand these cells in culture. Chromaffin cells produce several neurotrophic agents, including FGF-2, which may aid in both neuroprotection following injury and progenitor cell proliferation and survival. In addition, increased CNS catecholamines have been shown to improve functional recovery following insult. Thus, cotransplants of neural progenitor cells and chromaffin cells may be a useful clinical strategy. To address this, the survival of rat cortical progenitors transplanted to the adult rat striatum with and without bovine chromaffin cell cografts was assessed. Progenitors obtained from E14 embryos were prelabeled with bromodeoxyuridine (BrdU) before transplantation to enable later identification. Transplants were made both unilaterally and bilaterally, where animals received a monograft (progenitor cells alone) on one side and a cograft (progenitors + chromaffin cells) on the other. Histological results after 7, 17, and 30 days posttransplant revealed greatly improved survival of BrdU-labeled cells in the cografts and also less infiltration of presumptive immune cells. In addition, perivascular cuffing was seen in the monografts. In vitro progenitor cohorts stained positive for nestin, GFAP, and beta-tubulin III, but in vivo very few cells were found that were double labeled with BrdU and one of these markers. Thus, in contrast to in vitro findings, chromaffin cells did not enhance differentiation of progenitors in vivo during the 30 days posttransplantation. The results of these studies suggest that chromaffin cells may provide neurotrophic support to enhance survival, but not differentiation, of cortical progenitor grafts in the adult CNS.

Direct cell-cell contact required for neurotrophic effect of chromaffin cells on neural progenitor cells

Previous studies showed that neural progenitor cultures could be maintained without exogenously added FGF-2 when co-cultured with chromaffin cells. In addition, progenitor cells displayed dramatically increased neuronal differentiation in the presence of chromaffin cells. These findings suggested an approach to improved neural progenitor transplant outcomes using co-transplantation or administration of chromaffin cell-derived factors. The aim of this study was to determine whether the observed survival and differentiation effects were due to diffusible factors or required direct cell-cell contact (DC). Rat neural progenitors were cultured under six different conditions: (1) Standard N2 media with FGF-2; (2) N2 without FGF-2; (3) N2 with FGF+conditioned media (CM) from chromaffin cultures; (4) N2 without FGF-2+CM; (5) Transwells (TW), progenitor+chromaffin cells grown together but separated by a membrane allowing movement of diffusible agents but preventing direct contact; (6) direct contact co-cultures of progenitors and chromaffin cells. Cultures were evaluated for survival, proliferation, and differentiation. Cultures with FGF-2 proliferated and formed floating neurospheres while those grown in N2 without FGF-2 failed to thrive. Those grown either with CM or in transwells showed significantly improved survival. Survival was comparable to the exogenous FGF groups when progenitors were allowed direct contact with chromaffin cells. Proliferation was low in all cultures except those receiving exogenous FGF-2. Direct contact co-cultures exhibited a marked increase in beta-tubulin III+ processes compared to all other groups, indicating differentiation towards a neuronal phenotype. The results of this study suggest that diffusible agents produced by chromaffin cells can sustain viable progenitor cells in vitro even in the absence of added FGF-2 but that the effects on progenitor cell neuronal differentiation require direct cell-cell contact.

Interactions between human adipose stromal cells and mouse neural stem cells in vitro

Transplantation of adult mesenchymal stem cells (MSCs) into adult rat brain has been known to reduce functional deficits associated with stroke and traumatic brain injury. However, in injured brains, there is no evidence that transplanted MSCs replace lost host brain tissue. In this study, we determined in vitro interaction between human adipose tissue stromal cells (hATSCs), a kind of MSC, and neural stem cells (NSCs). hATSCs were isolated and proliferated from human adipose tissues, and NSCs from the subventricular zone of postnatal mice. When NSCs were cultured on mitomycin-treated hATSC monolayers, their proliferation was decreased, but neuronal differentiation was significantly induced. The percentage of neurons significantly increased in 7 days in cultures of NSCs on hATSCs feeder as compared to NSCs cultured on laminin-coated dishes. When the duration of the cultures was extended to 14 days, hATSCs supported the survival of neurons derived from NSCs. To determine the role of soluble factors from hATSCs, NSCs were cultured with hATSCs conditioned medium or co-cultured with permeable filter on which hATSCs were grown. Although proliferation of NSCs significantly decreased and glial differentiation increased under these experimental conditions, their neuronal differentiation was not affected, indicating that direct physical contact between hATSCs and NSCs is required for induction of neuronal differentiation. These data indicate that hATSCs may provide supportive roles on endogenous neural stem cells, when they are transplanted into damaged brain.