On the track of a human circulating mesenchymal stem cell of neural crest origin

Granulocyte-colony stimulating factor enhances bone fracture healing

BACKGROUND

Circulating mesenchymal stem cells contribute to bone repair. Their incorporation in fracture callus is correlated to their bioavailability. In addition, Granulocyte-colony stimulating factor induces the release of vascular and mesenchymal progenitors. We hypothesized that this glycoprotein stimulates fracture healing, and analyzed the effects of its administration at low doses on bone healing.

METHODS

27 adult male Sprague-Dawley rats underwent mid-femur osteotomy stabilized by centromedullar pinning. In a post (pre) operative group, rats were subcutaneously injected with 5 μg/kg per day of Granulocyte-colony stimulating factor for 5 days after (before) surgery. In a control group, rats were injected with saline solution for 5 days immediately after surgery. A radiographic consolidation score was calculated. At day 35, femurs were studied histologically and underwent biomechanical tests.

FINDINGS

5 weeks after surgery, mean radiographic scores were significantly higher in the Preop group 7.75 (SD 0.42) and in the Postop group 7.67 (SD 0.52) than in the control group 6.75 (SD 0.69). Biomechanical tests showed femur stiffness to be more than three times higher in both the Preop 109.24 N/mm (SD 51.86) and Postop groups 100.05 N/mm (SD 60.24) than in control 32.01 N/mm (SD 15.78). Mean maximal failure force was twice as high in the Preop group 68.66 N (SD 27.78) as in the control group 34.21 N (SD 11.79). Histological results indicated a later consolidation process in control than in treated groups.

INTERPRETATION

Granulocyte-colony stimulating factor injections strongly stimulated early femur fracture healing, indicating its potential utility in human clinical situations such as programmed osteotomy and fracture.

Schwann cell precursors in health and disease

Schwann cell precursors (SCPs) are frequently regarded as neural crest-derived cells (NCDCs) found in contact with axons during nerve formation. Nevertheless, cells with SCPs properties can be found up to the adulthood. They are well characterized with regard to both gene expression profile and cellular behavior -for instance, proliferation, migratory capabilities and survival requirements-. They differ in origin regarding their anatomic location: even though most of them are derived from migratory NCCs, there is also contribution of the boundary cap neural crest cells (bNCCs) to the skin and other tissues. Many functions are known for SCPs in normal development, including nerve fasciculation and target innervation, arterial branching patterning and differentiation, and other morphogenetic processes. In addition, SCPs are now known to be a source of many neural (glia, endoneural fibroblasts, melanocytes, visceral neurons, and chromaffin cells) and non-neural-like (mesenchymal stromal cells, able e.g., to generate dentine-producing odontoblasts) cell types. Until now no reports of endoderm-like derivatives were reported so far. Interestingly, in the Schwann cell lineage only early SCPs are likely able to differentiate into melanocytes and bone marrow mesenchymal stromal cells. We have also herein discussed the literature regarding their role in repair as well as in disease mechanisms, such as in diverse cancers. Moreover, many caveats in our knowledge of SCPs biology are highlighted all through this article. Future research should expand more into the relevance of SCPs in pathologies and in other regenerative mechanisms which might bring new unexpected clinically-relevant knowledge.

Rat Nasal Respiratory Mucosa-Derived Ectomesenchymal Stem Cells Differentiate into Schwann-Like Cells Promoting the Differentiation of PC12 Cells and Forming Myelin In Vitro

Schwann cell (SC) transplantation as a cell-based therapy can enhance peripheral and central nerve repair experimentally, but it is limited by the donor site morbidity for clinical application. We investigated weather respiratory mucosa stem cells (REMSCs), a kind of ectomesenchymal stem cells (EMSCs), isolated from rat nasal septum can differentiate into functional Schwann-like cells (SC-like cells). REMSCs proliferated quickly in vitro and expressed the neural crest markers (nestin, vimentin, SOX10, and CD44). Treated with a mixture of glial growth factors for 7 days, REMSCs differentiated into SC-like cells. The differentiated REMSCs (dREMSCs) exhibited a spindle-like morphology similar to SC cells. Immunocytochemical staining and Western blotting indicated that SC-like cells expressed the glial markers (GFAP, S100β, Galc, and P75) and CNPase. When cocultured with dREMSCs for 5 days, PC12 cells differentiated into mature neuron-like cells with long neurites. More importantly, dREMSCs could form myelin structures with the neurites of PC12 cells at 21 days in vitro. Our data indicated that REMSCs, a kind of EMSCs, could differentiate into SC-like cells and have the ability to promote the differentiation of PC12 cells and form myelin in vitro.

Neural crest as the source of adult stem cells

Recent studies suggest that adult stem cells can cross germ layer boundaries. For example, bone marrow-derived stem cells appear to differentiate into neurons and glial cells, as well as other types of cells. How can stem cells from bone marrow, pancreas, skin, or fat become neurons and glia; in other words, what molecular and cellular events direct mesodermal cells to a neural fate? Transdifferentiation, dediffereniation, and fusion of donor adult stem cells with fully differentiated host cells have been proposed to explain the plasticity of adult stem cells. Here we review the origin of select adult stem cell populations and propose a unifying hypothesis to explain adult stem cell plasticity. In addition, we outline specific experiments to test our hypothesis. We propose that peripheral, tissue-derived, or adult stem cells are all progeny of the neural crest.

Human Mesenchymal Stem Cells Express Neural Genes, Suggesting a Neural Predisposition

Because of their unique attributes of plasticity and accessibility, bone marrow-derived mesenchymal stem cells (MSCs) may find use for therapy of neurodegenerative disorders. Our previous studies of adult human MSCs demonstrated that these cells express an extensive assortment of neural genes at a low but clearly detectable level. Here, we report expression of 12 neural genes, 8 genes related to the neuro-dopaminergic system, and 11 transcription factors with neural significance by human MSCs. Our results suggest that, as opposed to cells that do not express neural genes, human MSCs are predisposed to differentiate to neuronal and glial lineages, given the proper conditions. Our findings add a new dimension in which to view adult stem cell plasticity, and may explain the relative ease with which MSCs, transplanted into the central nervous system (CNS) differentiate to a variety of functional neural cell types. Our results further promote the possibility that adult human MSCs are promising candidates for cell-based therapy of neurodegenerative diseases.

In search of adult renal stem cells

The therapeutic potential of adult stem cells in the treatment of chronic degenerative diseases has becoming increasingly evident over the last few years. Significant attention is currently being paid to the development of novel treatments for acute and chronic kidney diseases too. To date, promising sources of stem cells for renal therapies include adult bone marrow stem cells and the kidney precursors present in the early embryo. Both cells have clearly demonstrated their ability to differentiate into the kidney's specialized structures. Adult renal stem cells have yet to be identified, but the papilla is where the stem cell niche is probably located. Now we need to isolate and characterize the fraction of papillary cells that constitute the putative renal stem cells. Our growing understanding of the cellular and molecular mechanisms behind kidney regeneration and repair processes - together with a knowledge of the embryonic origin of renal cells - should induce us, however, to bear in mind that in the kidney, as in other mesenchymal tissues, the need for a real stem cell compartment might be less important than the phenotypic flexibility of tubular cells. Thus, by displaying their plasticity during kidney maintenance and repair, terminally differentiated cells may well function as multipotent stem cells despite being at a later stage of maturation than adult stem cells. One of the major tasks of Regenerative Medicine will be to disclose the molecular mechanisms underlying renal tubular plasticity and to exploit its biological and therapeutic potential.

Aspects cellulaires de la régénération osseuse

Bone regeneration is only possible if stem cells give rise to progenitors of osteoblasts, chondroblasts or chondroidocytes. Stem cells and osteogenic progenitors were evidenced in bone marrow while only progenitors can be found in periosteum. Bone marrow stem cells did show an amazing plasticity and some cells of the bone surrounding tissues such as perivascular cells, adipocytes, muscle cells or even circulating cells are able to transdifferentiate in osteoblasts when submitted to an osteogenic environment. We have shown that the destruction of both bone marrow and periost impairs the bone healing. It indicates that the periost and bone marrow destruction removes the predetermined osteogenic cells and the informative factors able to induce the transdifferenciation of the cells contained in the peri-osseous tissues.

Neuronal differentiation of murine bone marrow Thy-1- and Sca-1-positive cells

Recent evidence suggests that cells from bone marrow can acquire neuroectodermal phenotypes in cell culture or after transplantation in animal models and in the human brain. However, isolation of the bone marrow cell subpopulation with neuronal differentiation potential remains a challenge. To isolate and expand neural progenitors from whole murine bone marrow, bone marrow was obtained from hind limb bone of C57BL6 mice and plated in culture with neuronal medium with basic fibroblast growth factor and epidermal growth factor. After 5-7 days in culture, cellular spheres similar to brain neurospheres appeared either floating or attached to culture dishes. These spheres were collected, dissociated, and expanded. The bone marrow-derived spheres were positive for nestin as assessed by immunocytochemistry and by reverse transcriptase polymerase chain reaction. Thy-1- and Sca-1-positive bone marrow cells selected by magnetic cell sorting resulted in a higher yield of nestin-positive spheres. After exposure to neuronal differentiative medium retinoic acid with and without Sonic hedgehog, cells positive for neuronal markers tubulin III (TuJ-1) and neurofilament (NF) were detected. The mRNA profile of these cells included the expression of TuJ-1, neuronal-specific enolase (NSE), and NF-light chain. To evaluate the in vivo behavior of these cells, spheres derived from bone marrow-derived cells of transgenic green fluorescent protein (GFP) mice were transplanted into newborn mouse brain. Two months later, the mouse neural cortex contained a minor proportion of GFP(+) cells co-expressing neuronal markers (TuJ-1, NF, MAP-2, NeuN). Although cell fusion phenomena with the host cells could not be ruled out, bone marrow-derived neurosphere transplantation could be a strategy for cellular mediated gene therapy.

Generation of Neuroprogenitor-like Cells from Adult Mammalian Bone Marrow Stromal Cells In Vitro

Recently, it has been proposed that bone marrow stromal cells (BMSCs) have a broader capacity for differentiation than previously contemplated. In vitro studies have indicated that BMSCs may have the capacity to differentiate into neuroectodermal-like cells in response to various growth conditions, including those commonly used to maintain and differentiate cultures of primary neural stem cells (NSCs). Interpreting the wealth of data on this subject has been difficult because of variation in the starting cell population and the differences between the methods used to induce their differentiation. Here we evaluate how cultures of expanded BMSCs with a consistent immunophenotype respond to a variety of growth conditions and induction agents and review their ability to form neural-like derivatives. In addition, we report on some modifications to previously published techniques for the generation of neural-like cells from BMSCs in vitro.

Do hematopoietic cells exposed to a neurogenic environment mimic properties of endogenous neural precursors?

Hematopoietic progenitors are cells, which under challenging experimental conditions can develop unusual phenotypic properties, rather distant from their original mesodermal origin. As previously reported, cells derived from human umbilical cord blood (HUCB) or human bone marrow (BM) under certain in vivo or in vitro conditions can manifest neural features that resemble features of neural-derived cells, immunocytochemically and in some instances also morphologically. The present study explored how hematopoietic-derived cells would respond to neurogenic signals from the subventricular zone (SVZ) of adult and aged (6 and 16 months old) rats. The mononuclear fraction of HUCB cells was transplanted into the SVZ of immunosuppressed (single cyclosporin or three-drug treatment) animals. The triple-suppression paradigm allowed us to protect transplanted human cells within the brain and to explore further their phenotypic and migratory properties. One week after implantation, many surviving HUCB cells were located within the SVZ and the vertical limb of the rostral migratory stream (RMS). The migration of HUCB cells was restricted exclusively to the pathway leading to the olfactory bulb. In younger animals, grafted cells navigated almost halfway through the vertical limb, whereas, in the older animals, the migration was less pronounced. The overall cell survival was greater in younger animals than in older ones. Immunocytochemistry for surface CD antigen expression showed that many HUCB cells, either cultured or within the brain parenchyma, retained their hematopoietic identity. A few cells, identified by using human-specific antibodies (anti-human nuclei, or mitochondria) expressed nestin and doublecortin, markers of endogenous neural progenitors. Therefore, it is believed that the environment of the neurogenic SVZ, even in aged animals, was able to support survival, "neuralization," and migratory features of HUCB-derived cells.

Mid-trimester fetal blood-derived adherent cells share characteristics similar to mesenchymal stem cells but full-term umbilical cord blood does not

Stem cell transplantation is a promising treatment for many conditions. Although stem cells can be isolated from many tissues, blood is the ideal source of these cells due to the ease of collection. Mesenchymal stem cells (MSCs) have been paid increased attention because of their powerful proliferation and pluripotent differentiating ability. But whether MSCs reside in blood (newborn umbilical cord blood and fetal or adult peripheral blood) is also debatable. The present study showed that MSC-like cells could be isolated and expanded from 16-26 weeks fetal blood but were not acquired efficiently from full-term infants' umbilical cord blood (UCB). Adherent cells separated from postnatal UCB were heterogeneous in cell morphology. Their proliferation capacity was limited and they were mainly CD45+, which indicated their haematopoietic derivation. On the contrary, MSC-like cells shared a similar phenotype to bone marrow MSCs. They were CD34- CD45- CD44+ CD71+ CD90+ CD105+. They could be induced to differentiate into osteogenic, adipogenic and neural lineage cells. Single cell clones also showed similar phenotype and differentiation ability. Our results suggest that early fetal blood is rich in MSCs but term UCB is not.

Aldosteronomas: experience with superselective adrenal arterial embolization in 33 cases

PURPOSE

To evaluate the effectiveness and long-term follow-up results of superselective adrenal arterial embolization (SAAE) of aldosteronomas.

MATERIALS AND METHODS

Thirty-three patients with unilateral aldosteronomas were treated with SAAE. A 0.2-7.0-mL dose of high-concentration ethanol (HCE) was selectively infused into the feeding arterial branches of the aldosteronoma through a microcatheter by using a coaxial technique. Hormone, electrolyte, and blood pressure levels were evaluated after SAAE. The influence of background factors on SAAE success rate and the influence of age on hypertension in the patients in whom SAAE was successful were assessed with the Fisher exact test and a logistic regression model.

RESULTS

SAAE was successful in 27 (82%) of 33 patients. SAAE success rate was not influenced by sex, age, hypertension duration, family history of hypertension, adenoma site, type of ethanol used, or number of embolized arteries. The destructive effects of SAAE continued for the 6-94-month (mean, 45 months) follow-up period in all patients in whom SAAE was successful. In one patient, aldosteronoma recurred 15 months after SAAE and the second SAAE was successful. Blood pressure decreased in all 11 (100%) patients aged 45 years or younger and in eight (50%) of 16 patients older than 45 years (P =.008). Blood pressure decreased within 4 weeks after SAAE in 15 (79%) of these 19 patients. The rate of blood pressure reduction after SAAE decreased with increasing age, and the correlation was significant (P =.022). None of the 33 patients had severe complications.

CONCLUSION

SAAE with HCE is an effective therapy for aldosteronoma.

Crosstalk between neurokinin receptors is relevant to hematopoietic regulation: cloning and characterization of neurokinin-2 promoter

Neurokinin (NK)-1 and NK-2 receptors regulate hematopoiesis by interacting with neurotransmitters that belong to the tachykinin. This report studies the relationship between NK-1 and NK-2 in primary human bone marrow (BM) stroma, which supports hematopoiesis. Use of NK receptor antagonists and deficient stromal cells indicate that the neurotransmitter, substance P (SP), could exert dual hematopoietic effects (inhibitory or stimulatory), depending on the interacting receptor and crosstalk between NK-1 and NK-2. Cloning and identification of the minimal promoter for NK-2 and comparison with NK-1 promoter showed that the hematopoietic functions of NK receptors involve receptor crosstalk and the particular cytokine (IL-3, GM-CSF, TGF-beta or IL-1alpha). Crosstalk between NK-1 and NK-2 adds to communication within neural-hematopoietic axis.

Adult bone marrow stromal stem cells express germline, ectodermal, endodermal, and mesodermal genes prior to neurogenesis

Bone marrow stromal stem cells (MSCs) normally differentiate into mesenchymal derivatives but recently have also been converted into neurons, classical ectodermal cells. To begin defining underlying mechanisms, we extended our characterization of MSCs and the differentiated neurons. In addition to expected mesodermal mRNAs, populations and clonal lines of MSCs expressed germinal, endodermal, and ectodermal genes. Thus, the MSCs are apparently "multidifferentiated" in addition to being multipotent. Conversely, the differentiating neurons derived from populations and clonal lines of MSCs expressed the specific markers beta-III tubulin, tau, neurofilament-M, TOAD-64, and synaptophysin de novo. The transmitter enzymes tyrosine hydroxylase and choline acetyltransferase were localized to neuronal subpopulations. Our observations suggest that MSCs are already multidifferentiated and that neural differentiation comprises quantitative modulation of gene expression rather than simple on-off switching of neural-specific genes.

Regulation by phagic T-lymphocytes of a (pluripotent?) organ stem cell present in adult human blood. A beneficial exception to self-tolerance

Stem cells isolated from adult human blood are able to give rise to several different kinds of cell types such as mesenchymal cells, including striated muscle cells, hepatocytes, and endothelial-cells. Because independently studied by authors whose interests focused on particular tissue types, these stem cells have been described as different. However, they might well represent one unique population of pluripotent stem cells in homeostatic equilibrium with the 'reserve' stem cells buried in organs. In the blood, these stem cells have a monocytic phenotype. In in vitro culture, once they have adhered, they spontaneously differentiate into diverse types of cells reminiscent of embryonic stem cells in culture. Normally, they are almost quiescent cells. But under precise circumstances such as wound-healing, they may proliferate and migrate to the right organ to give rise there to the right type of cells, in order to participate in the repair process. Indeed, such a powerful stem cell needs to be tightly controlled. We illustrate here, by time-lapse videocinematography, how a special subpopulation of T-lymphocytes, for which we coined the name 'phagic T-lymphocytes' (PTLs), destroys these stem cells as soon as they differentiate in vitro, i.e., without the purpose of a repair. These stem cells express constitutively HLA-DR molecules and therefore can act as antigen-presenting cells able to activate phagic T-lymphocytes. The targets of these activated phagic T-lymphocytes are the differentiated stem cell themselves. Phagic T-lymphocytes are attracted by the stem cells, circulate around them, then penetrate and circulate inside them until the latter 'explode'. This mechanism of destruction by phagic T-lymphocytes is unique and seems to be normally restricted to stem cells. It represents a beneficial exception in self-tolerance since it avoids the accumulation of these stem cells out of healing purposes. Interestingly, in disorders such as fibrosis and/or some malignant proliferations, these stem cells proliferate, escape destruction by phagic T-lymphocytes and, as a consequence, accumulate, giving rise to a 'tissue' when cultured in vitro.