Immuno-electron microscopy characterization of human bone marrow stromal cells with anti-NGFR antibodies

Correlations Between the Expression of Stromal Cell Activation Related Biomarkers, L-NGFR, Phospho-ERK1-2 and CXCL12, and Primary Myelofibrosis Progression

In myelofibrosis, pathologically enhanced extracellular matrix production due to aberrant cytokine signalling and clonal megakaryocyte functions result(s) in impaired hemopoiesis. Disease progression is still determined by detecting reticulin and collagen fibrosis with Gomori’s silver impregnation. Here, we tested whether the expression growth related biomarkers L-NGFR/CD271, phospho-ERK1-2 and CXCL12 can be linked to the functional activation of bone marrow stromal cells during primary myelofibrosis progression. Immunoscores for all tested biomarkers showed varying strength of positive statistical correlation with the silver impregnation based myelofibrosis grades. The intimate relationship between spindle shaped stromal cells positive for all three markers and aberrant megakaryocytes was likely to reflect their functional cooperation. L-NGFR reaction was restricted to bone marrow stromal cells and revealed the whole length of their processes. Also, L-NGFR positive cells showed the most intersections, the best statistical correlations with myelofibrosis grades and the strongest interrater agreements. CXCL12 reaction highlighted stromal cell bodies and a weak extracellular staining in line with its constitutive release. Phospho-ERK1-2 reaction showed a similar pattern to CXCL12 in stromal cells with an additional nuclear staining in agreement with its role as a transcription factor. Both p-ERK1-2 and CXCL12 were also expressed at a moderate level in sinus endothelial cells. Connexin 43 gap junction communication channels, known to be required for CXCL12 release to maintain stem cell niche, were also expressed progressively in the myelofibrotic stromal network as a support of compartmental functions. Our results suggest that, diverse growth related pathways are activated in the functionally coupled bone marrow stromal cells during myelofibrosis progression. L-NGFR expression can be a useful biological marker of stromal cell activation which deserves diagnostic consideration for complementing Gomori’s silver impregnation.

Neurological Regulation of the Bone Marrow Niche

The bone marrow (BM) hematopoietic niche is the microenvironment where in the adult hematopoietic stem and progenitor cells (HSPCs) are maintained and regulated. This regulation is tightly controlled through direct cell-cell interactions with mesenchymal stromal stem (MSCs) and reticular cells, adipocytes, osteoblasts and endothelial cells, through binding to extracellular matrix molecules and through signaling by cytokines and hematopoietic growth factors. These interactions provide a healthy environment and secure the maintenance of the HSPC pool, their proliferation, differentiation and migration. Recent studies have shown that innervation of the BM and interactions with the peripheral sympathetic neural system are important for maintenance of the hematopoietic niche, through direct interactions with HSCPs or via interactions with other cells of the HSPC microenvironment. Signaling through adrenergic receptors (ARs), opioid receptors (ORs), endocannabinoid receptors (CRs) on HSPCs and MSCs has been shown to play an important role in HSPC homeostasis and mobilization. In addition, a wide range of neuropeptides and neurotransmitters, such as Neuropeptide Y (NPY), Substance P (SP) and Tachykinins, as well as neurotrophins and neuropoietic growth factors have been shown to be involved in regulation of the hematopoietic niche. Here, a comprehensive overview is given of their role and interactions with important cells in the hematopoietic niche, including HSPCs and MSCs, and their effect on HSPC maintenance, regulation and mobilization.

Beyond the Niche: Myelodysplastic Syndrome Topobiology in the Laboratory and in the Clinic

We review the murine and human microenvironment and hematopoietic stem cell niche in the context of intact bone marrow architecture in man and mouse, both in normal and in myelodysplastic syndrome marrow. We propose that the complexity of the hematopoietic stem cell niche can usefully be approached in the context of its topobiology, and we provide a model that incorporates in vitro and in vivo models as well as in situ findings from intact human marrow to explain the changes seen in myelodysplastic syndrome patients. We highlight the clinical application of the study of the bone marrow microenvironment and its topobiology in myelodysplastic syndromes.

Nuclear factor-erythroid 2, nerve growth factor receptor, and CD34-microvessel density are differentially expressed in primary myelofibrosis, polycythemia vera, and essential thrombocythemia

Because of the presence of various overlapping findings, the discrimination of polycythemia vera (PV) from prefibrotic/fibrotic primary myelofibrosis (PF/F-PMF) and essential thrombocythemia (ET) may be challenging, particularly in suboptimal bone marrow biopsy specimens. In this study, we assessed whether differences in the expression of nuclear factor-erythroid 2 (NF-E2), nerve growth factor receptor (NGFR; CD271), CD34, CD68, p53, CD3, CD20, and CD138 by immunohistochemistry could be useful in separating among them. Higher frequencies of nuclear positive erythroblasts with NF-E2 were observed in ET and PV cases (50% ± 13.3% and 41.5% ± 9.4%, respectively) when compared with both PF-PMF (21% ± 11.7%) and F-PMF (28.5% ± 10.8%). We found that with a cutoff level of at least 30% nuclear staining for NF-E2 in erythroblasts, we could reliably exclude the possibility of PMF. Conversely, NGFR+ stromal cells per high-power field (HPF) was significantly increased in F-PMF (53.5 ± 19.1/HPF) and PF-PMF (13.5 ± 3.8/HPF) compared with ET (4.4 ± 2.2/HPF) and PV (6.6 ± 3.3/HPF). Similarly, differences in CD34-microvessel density was remarkable in F-PMF and PF-PMF cases in comparison with PV and ET (49.9 ± 12.1/HPF, 29.3 ± 12.4/HPF, 13.7 ± 4.6/HPF, and 11.9 ± 5.1/HPF, respectively). Thus, the assessment of NF-E2 and NGFR expression and the evaluation of CD34-microvessel density may provide additional support in reaching a correct diagnosis in these cases of myeloproliferative neoplasms.

NGF in Early Embryogenesis, Differentiation, and Pathology in the Nervous and Immune Systems

The physiology of NGF is extremely complex, and although the study of this neurotrophin began more than 60 years ago, it is far from being concluded. NGF, its precursor molecule pro-NGF, and their different receptor systems (i.e., TrkA, p75NTR, and sortilin) have key roles in the development and adult physiology of both the nervous and immune systems. Although the NGF receptor system and the pathways activated are similar for all types of cells sensitive to NGF, the effects exerted during embryonic differentiation and in committed mature cells are strikingly different and sometimes opposite. Bearing in mind the pleiotropic effects of NGF, alterations in its expression and synthesis, as well as variations in the types of receptor available and in their respective levels of expression, may have profound effects and play multiple roles in the development and progression of several diseases. In recent years, the use of NGF or of inhibitors of its receptors has been prospected as a therapeutic tool in a variety of neurological diseases and injuries. In this review, we outline the different roles played by the NGF system in various moments of nervous and immune system differentiation and physiology, from embryonic development to aging. The data collected over the past decades indicate that NGF activities are highly integrated among systems and are necessary for the maintenance of homeostasis. Further, more integrated and multidisciplinary studies should take into consideration these multiple and interactive aspects of NGF physiology in order to design new therapeutic strategies based on the manipulation of NGF and its intracellular pathways.

Distinctive contact between CD34+ hematopoietic progenitors and CXCL12+ CD271+ mesenchymal stromal cells in benign and myelodysplastic bone marrow

Mesenchymal stromal cells (MSCs) support hematopoiesis and are cytogenetically and functionally abnormal in myelodysplastic syndrome (MDS), implying a possible pathophysiologic role in MDS and potential utility as a diagnostic or risk-stratifying tool. We have analyzed putative MSC markers and their relationship to CD34+ hematopoietic stem/progenitor cells (HSPCs) within intact human bone marrow in paraffin-embedded bone marrow core biopsies of benign, MDS and leukemic (AML) marrows using tissue microarrays to facilitate scanning, image analysis and quantitation. We found that CD271+, ALP+ MSCs formed an extensive branching perivascular, periosteal and parenchymal network. Nestin was brightly positive in capillary/arteriolar endothelium and occasional subendothelial cells, whereas CD146 was most brightly expressed in SMA+ vascular smooth muscle/pericytes. CD271+ MSCs were distinct by double immunofluorescence from CD163+ macrophages and were in close contact with but distinct from brightly nestin+ and from brightly CD146+ vascular elements. Double immunofluorescence revealed an intimate spatial relationship between CD34+ HSPCs and CD271+ MSCs; remarkably, 86% of CD34+ HSPCs were in direct contact with CD271+ MSCs across benign, MDS and AML marrows, predominantly in a perivascular distribution. Expression of the intercrine chemokine CXCL12 was strong in the vasculature in both benign and neoplastic marrow, but was also present in extravascular parenchymal cells, particularly in MDS specimens. We identified these parenchymal cells as MSCs by ALP/CXCL12 and CD271/CXCL12 double immunofluorescence. The area covered by CXCL12+ ALP+ MSCs was significantly greater in MDS compared with benign and AML marrow (P=0.021, Kruskal-Wallis test). The preservation of direct CD271+ MSC/CD34+ HSPC contact across benign and neoplastic marrow suggests a physiologically important role for the CD271+ MSC/CD34+ HSPC relationship and possible abnormal exposure of CD34+ HSPCs to increased MSC CXCL12 expression in MDS.

Effects of resveratrol on enrichment of adipose-derived stem cells and their differentiation to osteoblasts in two-and three-dimensional cultures

The goal of this study was to develop a method for increasing the yield of multipotent adipose-derived mesenchymal stem cells (ASCs) and osteoprogenitor cells (OPCs) from subcutaneous fat. After removing mature adipocytes and haematopoietic cells from rat inguinal fat, ASCs in the remaining cell population were verified by their attachment to plastic, surface marker profile (CD271(+), CD73(+) and CD45(-)) and ability to differentiate into adipocytes, chondrocytes and osteoblasts. OPCs were defined as E11(+) and OCN(+). Adherent cells were cultured in growth medium (GM) or osteogenic medium (OM) and treated with resveratrol (0, 12.5, and 25 µM) for 7 days; ASCs and OPCs were assessed by flow cytometry. Osteogenic potential was determined in two-dimensional (2D) cultures as a function of alkaline phosphatase-specific activity and osteocalcin production. In addition, cells were seeded onto three-dimensional (3D) poly-ε-caprolactone scaffolds and cultured under dynamic conditions; mineralization was quantified by micro-CT at 4, 8 and 12 weeks. Resveratrol increased the percentage of ASCs in the population (population%) and number of ASCs in both GM and OM, but increased only the number of OPCs in GM. In both media types resveratrol increased alkaline phosphatase activity and osteocalcin levels. In 3D cultures, resveratrol-treated cells significantly increased mineralized matrix volume at early time points. Resveratrol exerted a biphasic effect on adherent cells by enriching the ASC and OPC populations and enhancing osteogenic differentiation. Resveratrol pretreatment induced more mineralization at earlier time points and represents a clinically viable technique for orthopaedic and dental applications for autologous stem cell therapy.

Thrombopoietin receptor agonist therapy in primary immune thrombocytopenia is associated with bone marrow hypercellularity and mild reticulin fibrosis but not other stromal abnormalities

Primary immune thrombocytopenia is an acquired autoimmune disorder characterized by platelet count of <100 × 10(9)/l in the absence of other causes of thrombocytopenia. Primary immune thrombocytopenia is defined as 'chronic' when it has been present for more than 12 months without spontaneous remission or maintenance of complete response to therapy. Recently, thrombopoietin receptor agonists became available for treatment of chronic primary immune thrombocytopenia. Anecdotal reports have raised concerns about a possible association between therapy with thrombopoietin receptor agonists and an increase in bone marrow fibrosis. To investigate this association we studied eight patients with primary immune thrombocytopenia in detail comparing fibrosis and other morphological features in pre-therapy and on-therapy bone marrow biopsies, with the longest follow-up reported to date. A slight but significant increase to MF-1 in reticulin fibrosis was observed during therapy, but collagen was never present. On-therapy bone marrows were hypercellular due to panmyelosis with increased trilineage hematopoiesis. Megakaryocytes were increased in number, with acquisition of evident pleomorphism, nuclear hyperlobulation and tendency in some cases to form clusters. The overall picture of the on-therapy marrows was characterized by myeloproliferative neoplasm-like features, resembling essential thrombocythemia or occasionally early primary myelofibrosis. As thrombopoietin receptor agonists are becoming a mainstream treatment for primary immune thrombocytopenia, general pathologists and especially hematopathologists need to be aware of the characteristic morphological changes associated with use of these therapeutic agents, in order to avoid misdiagnosis of a myeloid neoplasm.

Neurotrophins regulate bone marrow stromal cell IL-6 expression through the MAPK pathway

BACKGROUND

The host's response to infection is characterized by altered levels of neurotrophins and an influx of inflammatory cells to sites of injured tissue. Progenitor cells that give rise to the differentiated cellular mediators of inflammation are derived from bone marrow progenitor cells where their development is regulated, in part, by cues from bone marrow stromal cells (BMSC). As such, alteration of BMSC function in response to elevated systemic mediators has the potential to alter their function in biologically relevant ways, including downstream alteration of cytokine production that influences hematopoietic development.

METHODOLOGY/PRINCIPAL FINDINGS

In the current study we investigated BMSC neurotrophin receptor expression by flow cytometric analysis to determine differences in expression as well as potential to respond to NGF or BDNF. Intracellular signaling subsequent to neurotrophin stimulation of BMSC was analyzed by western blot, microarray analysis, confocal microscopy and real-time PCR. Analysis of BMSC Interleukin-6 (IL-6) expression was completed using ELISA and real-time PCR.

CONCLUSION

BMSC established from different individuals had distinct expression profiles of the neurotrophin receptors, TrkA, TrkB, TrkC, and p75(NTR). These receptors were functional, demonstrated by an increase in Akt-phosphorylation following BMSC exposure to recombinant NGF or BDNF. Neurotrophin stimulation of BMSC resulted in increased IL-6 gene and protein expression which required activation of ERK and p38 MAPK signaling, but was not mediated by the NFkappaB pathway. BMSC response to neurotrophins, including the up-regulation of IL-6, may alter their support of hematopoiesis and regulate the availability of inflammatory cells for migration to sites of injury or infection. As such, these studies are relevant to the growing appreciation of the interplay between neurotropic mediators and the regulation of hematopoiesis.

Bone regeneration: the stem/progenitor cells point of view

After bone injuries, several molecular mechanisms establish bone repair from stem/progenitor cells. Inflammation factors attract regenerative cells which expand and differentiate in order to build up a bone highly similar to that before injury. Bone marrow (BM) mesenchymal stem cells (MSCs) as skeletal stem cells and endothelial progenitors (EPCs) are at the origin of such reparation mechanisms. However, discrepancies exist about their identities. Although cultured MSCs are extensively described, their in vivo native forms are poorly known. In addition, recent experiments show that several types of EPC exist. We therefore review up-to-date data on the characterization of such stem/progenitor cells and propose a new point of view of their function in bone regeneration.

The stromal composition of mast cell aggregates in systemic mastocytosis

Systemic mastocytosis is a stem cell disorder characterized histologically by the presence of multifocal compact aggregates of mast cells in at least one extracutaneous organ with or without evidence of skin lesions. The mast cell aggregates are accompanied by fibrosis, which is often significant. However, in spite of its frequent occurrence and severity, little is known about its characteristics. In this study, we evaluated the composition of the fibrotic mast cell aggregates by studying eight bone marrow biopsies and two spleens involved by systemic mastocytosis, and compared the findings with those observed in other fibrotic bone marrow disorders such as primary myelofibrosis and metastatic malignancy. Histochemistry and immunohistochemistry were used to evaluate: (a) extracellular matrix (reticulin, trichrome, collagen IV, laminin); (b) stromal reticulum cells (low-affinity nerve growth factor receptor); (c) presence of myofibroblastic differentiation (smooth muscle actin) and (d) microvessel density (CD34). We found that all cases showed marked reticulin and collagen fibrosis. However, unlike primary myelofibrosis and metastatic malignancy, which are usually associated with increased low-affinity nerve growth factor receptor positivity, its expression was low in all cases of systemic mastocytosis. Myofibroblastic differentiation was only focally detected in two of eight bone marrow biopsies. In all cases, the systemic mastocytosis lesions were largely devoid of type IV collagen and laminin. The latter findings were in contrast with those seen in cases of primary myelofibrosis and metastatic malignancy where smooth muscle actin, collagen IV and laminin were expressed in most cases. Also in contrast with the other two conditions, only minimal vascularity was detectable within the fibrotic mast cell lesions. These findings indicate that systemic mastocytosis exhibits a distinct pattern of stromal change, and suggest that the fibrogenetic mechanism in systemic mastocytosis is most likely different from that of other bone marrow neoplasms which are also associated with fibrosis.

Bone marrow stromal cells reduce axonal loss in experimental autoimmune encephalomyelitis mice

We investigated the ability of human bone marrow stromal cell (hBMSC) treatment to reduce axonal loss in experimental autoimmune encephalomyelitis (EAE) mice. EAE was induced in SJL/J mice by injection with proteolipid protein (PLP). Mice were injected intravenously with hBMSCs or PBS on the day of clinical onset, and neurological function was measured daily (score 0-5) until 45 weeks after onset. Mice were sacrificed at week 1, 10, 20, 34, and 45 after clinical onset. Bielshowsky silver was used to identify axons. Immunohistochemistry was performed to measure the expression of nerve growth factor (NGF) and MAB1281, a marker of hBMSCs. hBMSC treatment significantly reduced the mortality, the disease severity, and the number of relapses in EAE mice compared with PBS treatment. Axonal density and NGF(+) cells in the EAE brain were significantly increased in the hBMSC group compared with the PBS group at 1, 10, 20, 34, and 45 weeks. Disease severity was significantly correlated with decreased axonal density and decreased NGF, and increased axonal density was significantly correlated with reduced loss of NGF expression after hBMSC treatment. Most of the NGF(+) cells are brain parenchymal cells. Under 5% of MAB1281(+) cells colocalized with NG2(+), a marker of oligodendrocyte progenitor cells. Nearly 10% of MAB1281(+) cells colocalized with GFAP, a marker of astrocytes, and MAP-2, a marker of neurons. Our findings indicate that hBMSCs improve functional recovery and may provide a potential therapy aimed at axonal protection in EAE mice, in which NGF may play a vital role.

Neurotrophins and the immune system

The neurotrophins are a family of polypeptide growth factors that are essential for the development and maintenance of the vertebrate nervous system. In recent years, data have emerged indicating that neurotrophins could have a broader role than their name might suggest. In particular, the putative role of NGF and its receptor TrkA in immune system homeostasis has become a much studied topic, whereas information on the other neurotrophins is scarce in this regard. This paper reviews what is known about the expression and possible functions of neurotrophins and their receptors in different immune tissues and cells, as well as recent data obtained from studies of transgenic mice in our laboratory. Results from studies to date support the idea that neurotrophins may regulate some immune functions. They also play an important role in the development of the thymus and in the survival of thymocytes.

Isolation and characterization of bone marrow multipotential mesenchymal progenitor cells

OBJECTIVE

There is an increased interest in rheumatology in mesenchymal progenitor/stem cells (MPCs) and their roles in rheumatic diseases, but little is known about the phenotype of these cells in vivo. The aim of this study was to isolate and characterize human bone marrow (BM) MPCs.

METHODS

Fluorescence microscopy was used to identify putative MPCs among adherent BM cells. To purify them, a positive selection with antifibroblast microbeads was used, combined with fluorescence-activated cell sorting (FACS) for microbead+,CD45(low) cells. A more detailed phenotype of these cells was determined using 4-color flow cytometry, and standard chondrogenic, osteogenic, and adipogenic assays were used to investigate their differentiation potentials.

RESULTS

Putative MPCs microscopically identified as large, fibroblast-like, D7-FIB+ cells were purified using positive selection with D7-FIB-conjugated (antifibroblast) microbeads followed by FACS for specifically bound microbead+,CD45(low) cells. These cells represented 0.01% of mononuclear cells in the BM. They were uniformly positive for CD105, LNGFR, HLA-DR, CD10, CD13, CD90, STRO-1, and bone morphogenetic protein receptor type IA (BMPRIA) and were negative for CD14, CD34, CD117, and CD133. Only cells with this phenotype could proliferate and produce adherent cell monolayers capable of chondrogenic, osteogenic, and adipogenic differentiation. D7-FIB- cells in the BM lacked any MPC activity. Uncultured skin fibroblasts had a phenotype similar to that of BM MPCs, but were negative for LNGFR, STRO-1, HLA-DR, and BMPRIA.

CONCLUSION

This study shows the distinct phenotype, morphology, and method of isolation of BM MPCs. The findings may have implications for defining the physiologic roles of MPCs in arthritis, bone diseases, and joint regeneration.

Neural and marrow-derived stromal cell sphere transplantation in a rat model of traumatic brain injury

OBJECT

This study was designed to investigate the effect of treatment with a novel composite material consisting of embryonic neurospheres and bone marrow-derived stromal cell spheres (NMSCSs) in a rat model of traumatic brain injury (TBI).

METHODS

The NMSCS composite was injected into the TBI contusion site 24 hours after injury, and all rats were killed on Day 14 after the transplantation. The Rotarod test and the neurological severity score were used to evaluate neurological function. The transplanted NMSCS was analyzed in recipient rat brains by using histological staining and laser scanning confocal microscopy. The lesion volumes in the brains were also calculated using computer image analysis.

CONCLUSIONS

Rats that received NMSCS transplants had reduced lesion volume and showed improved motor and neurological function when compared with control groups 14 days after the treatment. These results suggest that transplantation of this novel biological material (NMSCS) may be useful in the treatment of TBI.

Human bone marrow stromal cell cultures conditioned by traumatic brain tissue extracts: growth factor production

Treatment of traumatic brain injury (TBI) with bone marrow stromal cells (MSCs) improves functional outcome in the rat. However, the specific mechanisms by which introduced MSCs provide benefit remain to be elucidated. Currently, the ability of therapeutically transplanted MSCs to replace injured parenchymal CNS tissue appears limited at best. Tissue replacement, however, is not the only possible compensatory avenue in cell transplantation therapy. Various growth factors have been shown to mediate the repair and replacement of damaged tissue, so trophic support provided by transplanted MSCs may play a role in the treatment of damaged tissue. We therefore investigated the temporal profile of various growth factors, brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and hepatocyte growth factor (HGF), within cultures of human MSCs (hMSCs) conditioned with cerebral tissue extract from TBI. hMSCs were cultured with TBI extracts of rat brain in vitro and quantitative sandwich enzyme-linked immunosorbent assays (ELISAs) were performed. TBI-conditioned hMSCs cultures demonstrated a time-dependent increase of BDNF, NGF, VEGF, and HGF, indicating a responsive production of these growth factors by the hMSCs. The ELISA data suggest that transplanted hMSCs may provide therapeutic benefit via a responsive secretion of an array of growth factors that can foster neuroprotection and angiogenesis.

Isolation of bone marrow mesenchymal stem cells by anti-nerve growth factor receptor antibodies

OBJECTIVE

Mesenchymal stem cells (MSCs) are a population of multipotent cells that can proliferate and differentiate into multiple mesodermal tissues. We previously reported that monoclonal antibodies to the low-affinity nerve growth factor receptor (alpha-LNGFR) stain bone marrow (BM) mesenchymal cells. We now show that LNGFR antibodies label primitive MSCs with high specificity and purity in adult BM, and compare these cells to those isolated by plastic adherence (PA) and CD45(-)anti-glycophorin A(-) selection.

MATERIALS AND METHODS

Low-density mononuclear cells (LD-MNCs) from normal BM were separated by PA or immunomagnetic selection for NGFR(+) or CD45(-)alpha-glycophorin A(-) cells. The three fractions were grown in Iscove's modified Dulbecco medium + 20% fetal bovine serum +/- basic fibroblast growth factor (bFGF) in order to assess their proliferative capacity and evaluate their phenotype during culture. The clonogenic potential of the MSCs was assessed using a colony-forming unit fibroblast (CFU-F) assay, whereas multipotential differentiation was determined after culture in adipocytic and osteoblastic conditioned media.

RESULTS

The NGFR(+) mesenchymal cells grown without growth factors showed persistent NGFR expression (rapidly down-regulated after the addition of bFGF) and persistent CFU-F activity. The NGFR(+) fractions were rich in clonogenic precursors: CFU-F median frequency was 1584/1 x 10(6) cells (range 325-13,793) in the NGFR(+) cells and 35/1 x 10(6) cells (range 27-112) in the LD-MNCs. The NGFR(-) fraction never showed any residual CFU-F activity. Compared with the other two fractions, the NGFR(+) cells (+/- bFGF) showed a 1 to 3 log greater expansion in the number of fibroblastic cells and a greater capacity to give rise to adipocyte colonies and induce osteoblastic differentiation, and they had similar effects in supporting the growth of hematopoietic precursors.

CONCLUSION

The data suggest that positive selection using low-affinity NGFR antibodies makes it possible to obtain homogeneous multipotent MSCs.

The stromal composition of malignant lymphoid aggregates in bone marrow: variations in architecture and phenotype in different B-cell tumours

We present evidence that different B-cell tumours, in bone marrow, have different relationships to stroma. Marrow core biopsies from 46 patients with B-cell tumours were immunostained with antibodies for distinct stromal cells. Cases included follicular lymphoma (FL), chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL), mantle cell lymphoma (MCL), lymphoplasmacytic lymphoma (LPL), and nodal, extranodal and splenic marginal zone lymphoma (NMZL, MALT, SMZL). In normal marrow, low-affinity nerve growth factor receptor (LNGFR) highlighted a fine network of adventitial reticular cells (ARC). The nodular aggregates of CLL/SLL, NMZL, MALT and SMZL were characterized by distortion of the ARC network and downregulation of LNGFR. In contrast, the aggregates of FL, LPL and MCL were composed of linear arrays of ARC in tight association with individual tumour cells. LNFGR+ was upregulated in ARC associated with the aggregates in FL, LPL and focally in MCL. Upregulation of CD35, vascular cell adhesion molecule (VCAM-1) and CD40 on ARC was noted exclusively in FL. Marrow lymphoid aggregates in CLL/SLL, NMZL, MALT and SMZL probably grow by displacing the pre-existing marrow stroma, while FL and LPL maintain a close association with the ARC network. In FL, expression of follicular dendritic cell-associated markers is modulated in pre-existing marrow stromal cells.

Therapeutic benefit of intracerebral transplantation of bone marrow stromal cells after cerebral ischemia in rats

We tested the hypothesis that bone marrow stromal cells (MSCs) transplanted into the ischemic boundary zone, survive, differentiate and improve functional recovery after middle cerebral artery occlusion (MCAo). MSCs were harvested from adult rats and cultured with or without nerve growth factor (NGF). For cellular identification, MSCs were prelabeled with bromodeoxyuridine (BrdU). Rats (n=24) were subjected to 2 h of MCAo, received grafts at 24 h and were euthanized at 14 days after MCAo. Test groups consisted of: (1) control-MCAo alone (n=8); (2) intracerebral transplantation of MSCs (n=8); (3) intracerebral transplantation of MSCs cultured with NGF (n=8). Immunohistochemistry was used to identify cells from MSCs. Behavioral tests (rotarod, adhesive-removal and modified neurological severity score [NSS]) were performed before and after MCAo. The data demonstrate that MSCs survive, migrate and differentiate into phenotypic neural cells. Significant recovery of somatosensory behavior (p<0.05) and NSS (p<0.05) were found in animals transplanted with MSCs compared with control animals. Animals that received MSCs cultured with NGF displayed significant recovery in motor (p<0.05), somatosensory (p<0.05) and NSS (p<0.05) behavioral tests compared with control animals. Our data suggest that intracerebral transplantation of MSCs may provide a powerful autoplastic therapy for stroke.

Intracranial bone marrow transplantation after traumatic brain injury improving functional outcome in adult rats

OBJECT

The authors tested the hypothesis that intracranial bone marrow (BM) transplantation after traumatic brain injury (TBI) in rats provides therapeutic benefit.

METHODS

Sixty-six adult Wistar rats, weighing 275 to 350 g each, were used for the experiment. Bone marrow prelabeled with bromodeoxyuridine (BrdU) was harvested from tibias and femurs of healthy adult rats. Other animals were subjected to controlled cortical impact, and BM was injected adjacent to the contusion 24 hours after the impact. The animals were killed at 4, 7, 14, or 28 days after transplantation. Motor function was evaluated both before and after the injury by using the rotarod test. After the animals had been killed, brain sections were examined using hemotoxylin and eosin and immunohistochemical staining methods. Histological examination revealed that, after transplantation, BM cells survived, proliferated, and migrated toward the injury site. Some of the BrdU-labeled BM cells were reactive, with astrocytic (glial fibrillary acid protein) and neuronal (NeuN and microtubule-associated protein) markers. Transplanted BM expressed proteins phenotypical of intrinsic brain cells, that is, neurons and astrocytes. A statistically significant improvement in motor function in rats that underwent BM transplantation, compared with control rats, was detected at 14 and 28 days posttransplantation.

CONCLUSIONS

On the basis of their findings, the authors assert that BM transplantation improves neurological outcome and that BM cells survive and express nerve cell proteins after TBI.

Nerve growth factor control of neuronal expression of angiogenetic and vasoactive factors

In postnatal tissues, angiogenesis occurs in nontumoral conditions on appropriate stimuli. In the nervous tissue, hypoxia, neural graft, increased neural function, and synaptic activity are associated with neoangiogenesis. We have investigated the occurrence of neoangiogenesis in the superior cervical ganglia (scg) of newborn rats treated for 8--21 days with 6-hydroxy-dopamine (6-OHDA), nerve growth factor (NGF), or 6-OHDA + NGF. The two latter treatments induced a significant increase in scg size. However, the increase after combined treatment far exceeded that of NGF alone. Similarly, histological and histochemical analysis revealed neuronal hypertrophy and endothelial cell hyperplasia associated with stromal hypertrophy (as described by laminin immunostaining) and increased vascular bed (as revealed by platelet/endothelial cell adhesion molecule-1 immunostaining) in 6-OHDA + NGF-treated pups. NGF, either alone or associated with 6-OHDA, also induced a significant up-regulation of NADPH diaphorase, neuronal nitric oxide synthase, and vascular endothelial growth factor expression in scg neurons. The present investigation suggests that the increase of scg size induced by NGF and 6-OHDA + NGF is associated with neoangiogenesis, and that the induction of vasoactive and angiogenic factors in neurons represents a further and previously undisclosed effect of NGF.

Adult bone marrow stromal cells administered intravenously to rats after traumatic brain injury migrate into brain and improve neurological outcome

To measure effect of bone marrow stromal cells (MSCs) administered i.v. on rats subjected to traumatic brain injury (TBI), we injected MSCs labeled by BrdU into the tail vein 24 h after TBI and sacrificed rats 15 days later. The neurological severity score (NSS) and the Rotarod test were used to evaluate neurological function. The distribution of the donor cells in brain, heart, lung, kidney, liver and spleen were analyzed in recipient rats using immunohistochemical staining. MSCs injected i.v. significantly reduced motor and neurological deficits compared with control groups by day 15 after TBI. The cells preferentially entered and migrated into the parenchyma of the injured brain and expressed the neuronal marker NeuN and the astrocytic marker GFAP. MSCs were also found in other organs and primarily localized to the vascular structures, without any obvious adverse effects. Our data suggest that i.v. administration of MSCs may be useful in the treatment of TBI.

Marrow stromal cells migrate throughout forebrain and cerebellum, and they differentiate into astrocytes after injection into neonatal mouse brains

Stem cells are a valuable resource for treating disease, but limited access to stem cells from tissues such as brain restricts their utility. Here, we injected marrow stromal cells (MSCs) into the lateral ventricle of neonatal mice and asked whether these multipotential mesenchymal progenitors from bone marrow can adopt neural cell fates when exposed to the brain microenvironment. By 12 days postinjection, MSCs migrated throughout the forebrain and cerebellum without disruption to the host brain architecture. Some MSCs within the striatum and the molecular layer of the hippocampus expressed glial fibrillary acidic protein and, therefore, differentiated into mature astrocytes. MSCs also populated neuron rich regions including the Islands of Calleja, the olfactory bulb, and the internal granular layer of the cerebellum. A large number of MSCs also were found within the external granular layer of the cerebellum. In addition, neurofilament positive donor cells were found within the reticular formation of the brain stem, suggesting that MSCs also may have differentiated into neurons. Therefore, MSCs are capable of producing differentiated progeny of a different dermal origin after implantation into neonatal mouse brains. These results suggest that MSCs are potentially useful as vectors for treating a variety of central nervous system disorders.

Further characterization of cells expressing STRO-1 in cultures of adult human bone marrow stromal cells

Primitive cells of the osteoblast lineage are not well characterized but are known to be present within the STRO-1+ fraction of adult human bone and marrow. A survey of human osteosarcoma cell lines revealed that STRO-1 is expressed by MG-63 but not SaOS-2. Among murine cell lines tested, expression of STRO-1 was detected in the bipotential (adipocyte/osteoblast) line BMS-2 but not the committed osteoblast precursor MC3T3-E1. A proportion of cultured adult human bone marrow stromal cells (BMSCs) consistently expressed the STRO-1 antigen. The expression of a range of cell surface antigens was studied in relation to STRO-1 by flow cytometry and several, including the bone/liver/kidney isoform of alkaline phosphatase (ALP), were found to subtype the STRO-1+ population of BMSCs. Further, BMSCs dual-labeled with antibodies recognizing STRO-1 and ALP could be assigned to one of four fractions: STRO-1-/ALP-, STRO-1+/ALP-, STRO-1+/ALP+, and STRO-1-/ALP+. Cells from each fraction could be isolated in high purity and, when recultured, remained viable and exhibited a limited degree of phenotypic stability. Using reverse transcriptase-polymerase chain reaction, cells in the four fractions were found to express different levels of transcripts for the parathyroid hormone receptor (PTHr) and bone sialoprotein (BSP). The expression of transcripts for the nuclear transcription factor core-binding factor alpha 1/osteoblast-specific factor-2 (CBFA1/OSF2) was restricted to those fractions expressing STRO-1 and/or ALP. Treatment with 10 nM dexamethasone consistently increased the proportion of cells present in those fractions which expressed the highest levels of transcripts for PTHr and BSP (STRO-1+/ALP+ and STRO-1-/ALP+) while simultaneously decreasing the proportion present in the STRO-1+/ALP- fraction. In conclusion, the expression of STRO-1 in vitro remains a characteristic of less well differentiated cells of the osteoblast lineage; in cultures of BMSCs and in established human osteosarcoma cell lines, there is an inverse association between the expression of STRO-1 and ALP; dual labeling of BMSCs with monoclonal antibodies recognizing STRO-1 and ALP permits the identification and isolation of cells of the osteoblast lineage at different stages of differentiation.

Nerve growth factor: a neurotrophin with activity on cells of the immune system

Numerous studies published in the last two decades provide evidence that nerve growth factor (NGF), a polypeptide originally discovered because of its neurotrophic activity, acts on a variety of cells of the immune system, including mast cells, eosinophils, and B and T lymphocytes. NGF has been shown to increase during inflammatory responses, autoimmune disorders, parasitic infections, and allergic diseases. Moreover, stress, which is characterized also by activation of a variety of immune cells, causes a significant increase in basal plasma NGF levels. Recently published studies reveal that hematopoietic progenitor cells seem to be able to produce and/or respond to NGF. We report these data and discuss the hypothesis of the possible implication of NGF on the functional activities of immune cells.

[Immune thrombocytopenia and HIV-1 infection. Response to splenectomy]

Background

The stromal vascular fraction (SVF) is a heterogeneous cell population derived from the adipose tissue. There is still a lack of information concerning the characterization of the cell subpopulations constituting the SVF as well as its mesenchymal and haematopoietic potential. Furthermore there are great variations in its phenotypical characterization.

Methods

Composition of SVF was investigated by FACS analysis, cytological and "in vitro" assays. We studied CD34+ population by combining FACS with human CFC (colony-forming-cell haematopoietic assay). The endothelial fraction was investigated by quantifying the co-expression of specific markers (CD146, CD105, CD31 and UEA-1). Mesenchymal potential was assessed by CFU-F assay and cultured AT-MSC were characterized by a 5-color FACS analysis. The multipotent differentiation potential (osteogenic, adipogenic and chondrogenic) was investigated both at cellular and molecular level.

Results

We identified in the SVF two CD34+ populations with a marked difference in the intensity of antigen expression, the majority of the cells expressing CD34 at low intensity. Moreover, two CD146+ cell populations were clearly distinguishable in the SVF:a CD146 dim accounting for 9.9% of the total SVF cells and a CD146+ bright cell population accounting for about 39.3%. The frequency of CFC clones was comparable with the one reported for peripheral blood. Endothelial cells account for about 7.7% of the SVF cells. AT-MSC differenced in the osteogenic adipogenic and chondrogenic lineage.

Conclusion

The SVF is not a homogeneous cell population, and its final composition could be influenced both by the flow cytometric technique analysis and the SVF extraction steps. The CFU-F frequency in the SVF was 1/4880, a value about seven times greater than the data reported for bone marrow. The antigenic profile of AT-MSC was comparable with bone-marrow derived MSC. AT-MSC were able to differentiate along the osteogenic adipogenic and chondrogenic lineages. The data here reported, further contribute to the characterization of SVF, a tissue providing an alternative as a source of MSC for clinical applications.