Generation of bone marrow-derived neural cells in serum-free monolayer culture

HipOP mesenchymal population has high potential for repairing injured peripheral nerves

Bone marrow stromal cells (BMSCs) are reportedly a heterogeneous population of mesenchymal stem cells (MSCs). Recently, we developed a simple strategy for the enrichment of MSCs with the capacity to differentiate into osteoblasts, chondrocytes, and adipocytes. On transplantation, the progenitor-enriched fractions can regenerate the bone with multiple lineages of donor origin and are thus called "highly purified osteoprogenitors" (HipOPs). Although our previous studies have demonstrated that HipOPs are enriched with MSCs and exhibit a higher potential to differentiate into osteoblasts, adipocytes, and chondrocytes than BMSCs, their potential to differentiate into neural cells has not been clarified. In this study, we evaluated the efficacy of HipOPs as a resource of neural stem cells. The neurosphere assay showed that neurospheres formed by HipOPs exhibited self-renewal ability and their size was generally larger than that of neurospheres formed by BMSCs. A limiting dilution assay was used to evaluate the frequency of neural progenitors in BMSCs and HipOPs. The results demonstrated that the frequency of neural progenitors in HipOPs was 120-fold higher than that in BMSCs. Furthermore, to investigate the in vivo regenerative potential of the peripheral nerve, we modified a murine peripheral nerve injury experimental model and demonstrated that HipOPs exhibit a higher efficacy in repairing injured peripheral nerves. These findings suggest that HipOPs are a useful cell resource for regenerative therapies such as that in case of peripheral nerve injury.

Bone marrow stromal cells as replacement cells for Parkinson's disease: generation of an anatomical but not functional neuronal phenotype

The focus of cell replacement therapies (CRTs) for Parkinson's disease has been on delivering dopamine-producing cells to the striatum. Fetal grafts have proven the feasibility of this approach, but an appropriate source of replacement cells has restricted the clinical translation. Bone marrow stromal cells (BMSCs) have been heralded as an ideal source of dopaminergic (DAergic) replacement cells, as they are viewed as ethically acceptable, easily procured, and readily expanded. It is known that they confer functional benefits, particularly in stroke models, through the release of neurotrophic factors, but their transdifferentiation into neurons is still under contention. We sought to evaluate the neuronal phenotype and functional capacity of adult rat BMSCs after exposure to a novel multistep in vitro differentiation protocol compared with cells exposed to other reported neuronal differentiation conditions. We employed a systematic, comprehensive method of assessment to determine the neuronal differentiation capacity of BMSCs. Our fluorescence-activated cell sorting, immunofluorescent and semiquantitative polymerase chain reaction results confirmed that undifferentiated BMSCs isolated based on their adherence to plastic are of mesenchymal origin and express a range of lineage markers. After exposure to preinduction and neuronal induction steps, BMSCs down-regulate markers of other lineages but fail, as assessed by patch clamp, to differentiate into functional neurons. Thus, for BMSCs to be considered a source of DAergic neuronal replacement cells, their ability to transdifferentiate terminally along a neuronal lineage first must be clarified before attempting to direct more complex specification process required for them to be used in Parkinson's-disease-focused CRTs.

Analysis of mesenchymal stem cell differentiation in vitro using classification association rule mining

In this paper, data mining is used to analyze the data on the differentiation of mammalian Mesenchymal Stem Cells (MSCs), aiming at discovering known and hidden rules governing MSC differentiation, following the establishment of a web-based public database containing experimental data on the MSC proliferation and differentiation. To this effect, a web-based public interactive database comprising the key parameters which influence the fate and destiny of mammalian MSCs has been constructed and analyzed using Classification Association Rule Mining (CARM) as a data-mining technique. The results show that the proposed approach is technically feasible and performs well with respect to the accuracy of (classification) prediction. Key rules mined from the constructed MSC database are consistent with experimental observations, indicating the validity of the method developed and the first step in the application of data mining to the study of MSCs.

Chemokine CXC receptor 4--mediated glioma tumor tracking by bone marrow--derived neural progenitor/stem cells

Malignant gliomas manifest frequent tumor recurrence after surgical resection and/or other treatment because of their nature of invasiveness and dissemination. The recognized brain tumor-tracking property of neural progenitor/stem cells opened the possibility of targeting malignant brain tumors using neural progenitor/stem cells. We and others have previously shown that fetal neural progenitor/stem cells can be used to deliver therapeutic molecules to brain tumors. Our recent work has further shown that gene delivery by bone marrow-derived neural progenitor/stem cells achieves therapeutic effects in a glioma model. In this study, we isolate and characterize bone marrow-derived neural progenitor/stem cells, which also express the chemokine receptor chemokine CXC receptor 4 (CXCR4). We show that CXCR4 is required for their chemotaxis and extracellular matrix invasion against a gradient of glioma soluble factors. Furthermore, beta-galactosidase-labeled bone marrow-derived neural progenitor/stem cells implanted in the contralateral side of the brain were shown to track gliomas as early as day 1 and increased through days 3 and 7. Intracranial glioma tracking by bone marrow-derived neural progenitor/stem cells is significantly inhibited by preincubation of bone marrow-derived neural progenitor/stem cells with a blocking anti-CXCR4 antibody, suggesting a CXCR4-dependent tracking mechanism. Glioma tracking bone marrow-derived neural progenitor/stem cells were found to express progenitor/stem cell markers, as well as CXCR4. Although bromodeoxyuridine incorporation assays and proliferating antigen staining indicated that tumor tracking bone marrow-derived neural progenitor/stem cells were mostly nonproliferating, these cells survive in the local tumor environment with little apoptosis. Elucidating the molecular mechanism of brain tumor tracking by adult source stem cells may provide basis for the development of future targeted therapy for malignant brain tumors.

Formation of neurons by non-neural adult stem cells: potential mechanism implicates an artifact of growth in culture

Trans-differentiation is a mechanism proposed to explain how tissue-specific stem cells could generate cells of other organs, thus supporting the emerging concept of enhanced adult stem cell plasticity. Although spontaneous cell fusion rather than trans-differentiation may explain some unexpected cell fate changes in vivo, such a mechanism does not explain potential trans-differentiation events in vitro, including the generation of neural cell types from cultured bone marrow-derived stem cells. Here we present evidence that shows that cultured bone marrow-derived stem cells express neural proteins and form structures resembling neurons under defined growth conditions. We demonstrate that these changes in cell structure and neural protein expression are not consistent with typical neural development. Furthermore, the ability of bone marrow-derived stem cells to adopt a neural phenotype in vitro may occur as a result of cellular stress in response to removing cells from their niche and their growth in alternative environmental conditions. These findings suggest a potential explanation for the growth behavior of cultured bone marrow-derived stem cells and highlight the need to carefully validate the plasticity of stem cell differentiation.

Spontaneous expression of neural phenotype and NGF, TrkA, TrkB genes in marrow stromal cells

Marrow stromal cells (MSCs) have the ability to provide growth factors and differentiate into neural-like cells on treating with EGF, bFGF and other factors. We wanted to explore whether growth factors secreted by MSCs itself could induce self-differentiation into neural-like cells. Here, we show that even in the absence of inducing factors, rMSCs spontaneously differentiate into neural-like cells expressing neural markers, such as nestin, beta-tubulin III, Doublecortin (DCX), microtubule-associated protein 2 (MAP2) and neuron-specific enolase (NSE). Furthermore, some cells become neurosphere-like growing in suspension. Compared with control and neural-like rMSCs induced by epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF), we found using real-time PCR that self-differentiating rMSCs (SDrMSCs) expressed significantly higher levels of neurotrophic high-affinity receptors (TrkA and TrkB). Coincident with neural marker expression, nerve growth factor (NGF) mRNA was significantly higher than controls despite lower protein levels in the supernatant. Our study suggests that rMSCs have the potential to differentiate into neural cells spontaneously in culture and may contribute towards the natural function of MSCs for neural system in vivo.

Differentiation assays of bone marrow-derived Multipotent Adult Progenitor Cell (MAPC)-like cells towards neural cells cannot depend on morphology and a limited set of neural markers

There are accumulating studies that report a neurogenic potential of bone marrow-derived cells both in vitro as well as in vivo. Most claims of neural "transdifferentiation" have based their conclusions on morphology and neural gene expression. Recently, doubts have been raised about the validity of both outcome parameters since non-neural cells can extend neurites and show aberrant neural gene expression as a response to stress inducing factors. In this study, we compared bone marrow-derived Multipotent Adult Progenitor Cell (MAPC)-like cells and neural stem cells (NSC) in their morphology and neural gene expression profile after neural differentiation using three differentiation protocols. We evaluated the expression of five neuroglial antigens [neurofilament 200 (NF200); beta III tubulin (beta3 tub); tau; Glial Fibrillary Acidic Protein (GFAP); Myelin Basic Protein (MBP) and RIP antigen] using real-time PCR (RT-PCR) and immunocytochemistry (ICC). MAPC-like cells adopted a neural-like morphology in one protocol but a fibroblast-like morphology in the two other protocols. RT-PCR and ICC show that MAPC-like cells already express the neural antigens beta III tubulin and NF200 at baseline, but no upregulation of these genes after exposure to three distinct differentiation protocols was seen. In contrast, NSC adopt neural and glial morphologies with a clear increase in expression of all neuroglial genes in all differentiation protocols used. In conclusion, our data demonstrate that neural-like morphology and expression of a limited set of neural marker genes by MAPC-like cells after differentiation are not absolute proof of neural transdifferentiation because MAPC-like cells only partially meet the criteria which are fulfilled by NSC after neural differentiation.

Comparative analysis of differentiation and behavior of human neural and mesenchymal stem cells In Vitro and In Vivo

Comparative analysis of differentiation of human neural and mesenchymal stem cells in tissue culture and after transplantation into the brain was carried out using the same antibody set. Neural stem cells differentiated into all types of neural cells, are retained after transplantation, migrate, and form reciprocal relationships with the recipient brain. Mesenchymal stem cells were incapable of neural development under conditions of common culturing or after transplantation and retained the fibroblast-like status. Recipient filaments grew into mesenchymal stem cell transplants containing no neural cells due to local changes in the extracellular matrix at the site of transplantation.