Chemotaxis and differentiation of human adipose tissue CD34+/CD31- progenitor cells: role of stromal derived factor-1 released by adipose tissue capillary endothelial cells

Mesenchymal stromal cell migration: possibilities to improve cellular therapy

Mesenchymal stromal cells (MSC) represent a type of multipotent cells that can be isolated from several human tissues and that can be expanded ex vivo for clinical application. The regenerative and immune modulatory capacities of MSC have raised hopes for clinical applications of MSC. At the moment, many clinical trials applying MSC for treatment of multiple diseases are being set up. Currently, extensive expansion (3-6 weeks) is required to obtain enough cells for transplantation. However, culture-expanded MSC have almost completely lost their engraftment potential. MSC expansion cultures are initiated with a heterogeneous, poorly defined cell population. It is unknown which MSC populations are expanded and how this affects homing capacity. Thus, understanding MSC migration will offer perspectives to modulate the expansion protocols to obtain cells that maintain migration and homing capacities. This review highlights our current understanding of MSC migration with particular emphasis on the possibilities to improve MSC-based therapy.

Nuclear receptors Nur77 and Nurr1 modulate mesenchymal stromal cell migration

Detailed understanding of mesenchymal stromal cells (MSC) migration is imperative for future cellular therapies. To identify genes involved in the process of MSC migration, we generated gene expression profiles of migrating and nonmigrating fetal bone marrow MSC (FBMSC). Only 12 genes showed differential expression in migrating versus nonmigrating FBMSC. The nuclear receptors Nur77 and Nurr1 showed the highest expression in migratory MSC. Nur77 and Nurr1 are members of NR4A nuclear orphan receptor family, and we found that their expression is rapidly increased upon exposure of FBMSC to the migratory stimuli stromal-derived factor-1α (SDF-1α) and platelet-derived growth factor-BB. Lentiviral expression of Nur77 or Nurr1 resulted in enhanced migration of FBMSC toward SDF-1α compared with mock-transduced FBMSC. Analysis of the cell cycle, known to be involved in MSC migration, revealed that expression of Nur77 and Nurr1 decreases the proportion of cells in S-phase compared with control cells. Further, gain-of-function experiments showed increased hepatocyte growth factor expression and interleukin (IL)-6 and IL-8 production in MSC. Despite the altered cytokine profile, FBMSC expressing Nur77 or Nurr1 maintained the capacity to inhibit T-cell proliferation in a mixed lymphocyte reaction. Our results demonstrate that Nur77 and Nurr1 promote FBMSC migration. Modulation of Nur77 and Nurr1 activity may therefore offer perspectives to enhance the migratory potential of FBMSC which may specifically regulate the local immune response.

Engineering of large osteogenic grafts with rapid engraftment capacity using mesenchymal and endothelial progenitors from human adipose tissue

We investigated whether the maintenance in culture of endothelial and mesenchymal progenitors from the stromal vascular fraction (SVF) of human adipose tissue supports the formation of vascular structures in vitro and thereby improves the efficiency and uniformity of bone tissue formation in vivo within critically sized scaffolds. Freshly-isolated human SVF cells were seeded and cultured into hydroxyapatite scaffolds (1 cm-diameter, 1 cm-thickness) using a perfusion-based bioreactor system, which resulted in maintenance of CD34(+)/CD31(+) endothelial lineage cells. Monolayer-expanded isogenic adipose stromal cells (ASC) and age-matched bone marrow stromal cells (BMSC), both lacking vasculogenic cells, were used as controls. After 5 days in vitro, SVF-derived endothelial and mesenchymal progenitors formed capillary networks, which anastomosed with the host vasculature already 1 week after ectopic nude rat implantation. As compared to BMSC and ASC, SVF-derived cells promoted faster tissue ingrowth, more abundant and uniform bone tissue formation, with ossicles reaching a 3.5 mm depth from the scaffold periphery after 8 weeks. Our findings demonstrate that maintenance of endothelial/mesenchymal SVF cell fractions is crucial to generate osteogenic constructs with enhanced engraftment capacity. The single, easily accessible cell source and streamlined, bioreactor-based process makes the approach attractive towards manufacturing of clinically relevant sized bone substitute grafts.

Distinct stem cells subpopulations isolated from human adipose tissue exhibit different chondrogenic and osteogenic differentiation potential

Recently adipose tissue has become a research topic also for the searching for an alternative stem cells source to use in cell based therapies such as tissue engineer. In fact Adipose Stem Cells (ASCs) exhibit an important differentiation potential for several cell lineages such as chondrogenic, osteogenic, myogenic, adipogenic and endothelial cells. ASCs populations isolated using standard methodologies (i.e., based on their adherence ability) are very heterogeneous but very few studies have analysed this aspect. Consequently, several questions are still pending, as for example, on what regard the existence/ or not of distinct ASCs subpopulations. The present study is originally aimed at isolating selected ASCs subpopulations, and to analyse their behaviour towards the heterogeneous population regarding the expression of stem cell markers and also regarding their osteogenic and chondrogenic differentiation potential. Human Adipose derived Stem Cells (hASCs) subpopulations were isolated using immunomagnetic beads coated with several different antibodies (CD29, CD44, CD49d, CD73, CD90, CD 105, Stro-1 and p75) and were characterized by Real Time RT-PCR in order to assess the expression of mesenchymal stem cells markers (CD44, CD73, Stro-1, CD105 and CD90) as well as known markers of the chondrogenic (Sox 9, Collagen II) and osteogenic lineage (Osteopontin, Osteocalcin). The obtained results underline the complexity of the ASCs population demonstrating that it is composed of several subpopulations, which express different levels of ASCs markers and exhibit distinctive differentiation potentials. Furthermore, the results obtained clearly evidence of the advantages of using selected populations in cell-based therapies, such as bone and cartilage regenerative medicine approaches.

Immune cells in adipose tissue: key players in metabolic disorders

Obesity, defined as the excess development of adipose tissue, is an important risk factor for metabolic and cardiovascular diseases such as type 2 diabetes, hypertension and atherosclerosis. Over the past few years, metabolic inflammation has emerged as a major process underlying the link between obesity and its associated pathologies. Adipose tissue appears to play a primary and crucial role as a source and site of inflammation. Accumulation of immune cells within adipose tissue occurs in obese conditions. The present review focuses on the relationship between adipose tissue and immune cells, including macrophages, dendritic cells, T and B lymphocytes, and natural killer cells, in both the physiological state and under obese conditions. The factors involved in the accumulation of both myeloid and lymphoid cells in adipose tissue are also described. In addition, the role of adipose-tissue immune cells on adipocyte metabolism and cells of the adipose tissue stromal-vascular fraction are discussed, with particular emphasis on the cross-talk between macrophages and adipocytes, together with recent reports of T lymphocytes in adipose tissue.

Native human adipose stromal cells: localization, morphology and phenotype

Objectives:

Beside having roles in energy homeostasis and endocrine modulation, adipose tissue (AT) is now considered a promising source of mesenchymal stromal cells (adipose-derived stromal cells or ASCs) for regenerative medicine. Despite numerous studies on cultured ASCs, native human ASCs are rarely investigated. Indeed, the phenotype of ASCs in their native state, their localization within AT and comparison with bone marrow-derived mesenchymal stromal cells (BM-MSCs) has been poorly investigated.

Design:

To address these issues, the stroma vascular fraction (SVF) of human AT was extracted and native cell subtypes were isolated by immunoselection to study their clonogenic potential in culture. Immunohistology on samples of human AT in combination with reconstruction of confocal sections were performed in order to localize ASCs.

Results:

Compared with BM-MNCs, all native ASCs were found in the CD34⁺ cell fraction of the AT-SVF. Native ASCs expressed classical mesenchymal markers described for BM-MSCs. Interestingly, CD34 expression decreased during ASC cell culture and was negatively correlated with cell proliferation rate. Immunohistological analysis revealed that native ASCs exhibited specific morphological features with protrusions. They were found scattered in AT stroma and did not express in vivo pericytic markers such as NG2, CD140b or alpha-smooth muscle actin, which appeared during the culture process. Finally, ASCs spontaneous commitment to adipocytic lineage was enhanced in AT from obese humans.

Conclusions:

The use of complementary methodological approaches to study native human ASCs revealed their immunophenotype, their specific morphology, their location within AT and their stemness. Furthermore, our data strongly suggest that human ASCs participate in adipogenesis during AT development.

Adipose tissue remodeling under ischemia: death of adipocytes and activation of stem/progenitor cells

BACKGROUND

Following various types of plastic surgery, such as adipose grafting and flap elevation, adipose tissue undergoes ischemia, leading to hypoxia and nutrient depletion. However, few studies have examined ischemic and/or hypoxic changes in adipose tissue.

METHODS

The authors established surgically induced ischemia models by severing blood vessels supplying the inguinal fat pads in mice. The partial pressure of oxygen in adipose tissue was measured with an oxygen monitor, and ischemic changes were analyzed by whole-mount staining, immunohistochemistry, flow cytometry, and Western blotting. The authors also examined cell survival under a hypoxic condition in vitro.

RESULTS

Models for three degrees (mild, intermediate, and severe) of ischemia showed approximately 75, 55, and 20 percent of the partial pressure of oxygen level in normal adipose tissue (50.5±1.3 mm Hg), respectively. Adipose tissue atrophy with substantial fibrosis on day 28 was seen, depending on the severity of ischemia. Intermediate and severe ischemia induced elevated expression of hypoxia-inducible factor 1α and fibroblast growth factor 2 on day 1 and degenerative changes (i.e., apoptosis, necrosis, and macrophage infiltration and phagocytosis) in adipose tissue. Dead cells included adipocytes, vascular endothelial cells, and blood-derived cells, but not adipose-derived stem/progenitor cells. Subsequent to degenerative changes, regenerative changes were seen, including angiogenesis, adipogenesis, and proliferation of cells (adipose-derived stem/progenitor cells, vascular endothelial cells, and blood cells). The authors found that, in vitro, the experimentally differentiated adipocytes underwent apoptosis and/or necrosis under severe hypoxia, but adipose-derived stem/progenitor cells remained viable.

CONCLUSIONS

Severe ischemia/hypoxia induces degenerative changes in adipose tissue and subsequent adaptive tissue remodeling. Adipocytes die easily under ischemic conditions, whereas adipose-derived stem/progenitor cells are activated and contribute to adipose tissue repair.

Human adipose-derived stromal cells accelerate diabetic wound healing: impact of cell formulation and delivery

Human adipose-derived stromal cells (ASCs) have been shown to possess therapeutic potential in a variety of settings, including cutaneous wound healing; however, it is unknown whether the regenerative properties of this cell type can be applied to diabetic ulcers. ASCs collected from elective surgical procedures were used to treat full-thickness dermal wounds in leptin receptor-deficient (db/db) mice. Cells were delivered either as multicellular aggregates or as cell suspensions to determine the impact of cell formulation and delivery methods on biological activity and in vivo therapeutic effect. After treatment with ASCs that were formulated as multicellular aggregates, diabetic wounds experienced a significant increase in the rate of wound closure compared to wounds treated with an equal number of ASCs delivered in suspension. Analysis of culture supernatant and gene arrays indicated that ASCs formulated as three-dimensional aggregates produce significantly more extracellular matrix proteins (e.g., tenascin C, collagen VI alpha3, and fibronectin) and secreted soluble factors (e.g., hepatocyte growth factor, matrix metalloproteinase-2, and matrix metalloproteinase-14) compared to monolayer culture. From these results, it is clear that cell culture, formulation, and delivery method have a large impact on the in vitro and in vivo biology of ASCs.

Hepatocyte growth factor mobilizes and recruits hematopoietic progenitor cells into liver through a stem cell factor-mediated mechanism

AIMS

Although bone marrow cells are reported to migrate to the liver under circumstances of severe liver injury, the bone marrow cell type and the mechanisms in this process, remain to be clarified. We examined the involvement of hepatocyte growth factor (HGF) in this process and the cell type of migrated hematopoietic cells by HGF.

METHODS

The CD34(+) cells and colony forming cells in the peripheral blood were examined in HGF transgenic, recombinant HGF-administered, and HGF-expressing adenovirus-administered mice. The cell type mobilized by HGF was examined by the percentages of donor cells in the peripheral blood of the recipient mice transplanted with Lin(-)c-kit(+)Sca-1(+)CD34(+) cells and those with Lin(-)c-kit(+)Sca-1(+)CD34(-) cells. Expression of stem cell factor (SCF) was examined after the addition of HGF in MS-5 stromal cells. The numbers of the cells which were mobilized from bone marrow and recruited into liver by HGF were assessed using green fluorescence fluorescent (GFP)-chimera mice.

RESULTS

Mobilized CD34+ cells and colony forming cells in the peripheral blood were increased by HGF treatment. The cells mobilized by HGF were mostly Lin(-)c-kit(+)Sca-1(+)CD34(+) cells. Recruitment of bone marrow cells into liver was not suppressed in MMP-9-/- mice. Expression of SCF was induced by HGF in MS-5 stromal cells. However, expression of CXCR4, SDF-1, MMP-9 or VCAM-1 was not changed. The numbers of GFP-positive cells in liver 1 month after treatment by HGF was greater than that by G-CSF.

CONCLUSION

The results of the present study suggest that HGF mobilizes and recruits hematopoietic progenitor cells from bone marrow into the liver through SCF-mediated mechanism.

Effects of transplantation of adipose tissue-derived stem cells on prostate tumor

BACKGROUND

Obesity is a risk factor for prostate cancer development, but the underlying mechanism is unknown. The present study tested the hypothesis that stromal cells of the adipose tissue might be recruited by cancer cells to help tumor growth.

METHODS

PC3 prostate cancer cells were transplanted into the subcutaneous space of the right flank of athymic mice. One week later, adipose tissue-derived stromal or stem cells (ADSC) or phosphate-buffered saline (PBS, as control) was transplanted similarly to the left flank. Tumor size was monitored for the next 34 days; afterwards, the mice were sacrificed and their tumors harvested for histological examination. The ability of PC3 cells to attract ADSC was tested by migration assay. The involvement of the CXCL12/CXCR4 axis was tested by migration assay in the presence of a specific inhibitor AMD3100.

RESULTS

Throughout the entire course, the average size of PC3 tumors in ADSC-treated mice was larger than in PBS-treated mice. ADSC were identified inside the tumors of ADSC-treated mice; CXCR4 expression was also detected. Migration assay indicated the involvement of the CXCL12/CXCR4 axis in the migration of ADSC toward PC3 cells. Capillary density was twice as high in the tumors of ADSC-treated mice than in the tumors of PBS-treated mice. VEGF expression was similar but FGF2 expression was significantly higher in tumors of ADSC-treated mice than in the tumors of PBS-tread mice.

CONCLUSION

Prostate cancer cells recruited ADSC by the CXCL12/CXCR4 axis. ADSC helps tumor growth by increasing tumor vascularity, and which was mediated by FGF2.

Mapping of the fibroblast growth factors in human white adipose tissue

CONTEXT

Fibroblast growth factors (FGFs) regulate the development of white adipose tissue (WAT). However, the secretion and cellular origin of individual FGFs in WAT as well as the influence of obesity are unknown.

OBJECTIVE

Our objective was to map FGFs in human sc WAT, the cellular source, and association with obesity.

DESIGN

Secretion, mRNA, and circulatory levels of FGFs in human abdominal sc WAT from nonobese and obese donors were examined by microarray, real-time quantitative PCR, and ELISA. The activity of FGFs in cultured human adipocytes was determined by phosphorylation assays.

RESULTS

Expression of five FGFs (FGF1, FGF2, FGF7, FGF9, and FGF18) and FGF homologous factor (FHF2) was identified in WAT. Only FGF1 was released in a time-dependent manner from sc WAT, and fat cells were the major source of FGF1 secretion. FGF1 expression increased and FGF2 decreased during adipocyte differentiation. Furthermore, FGF1 was not secreted into the circulation. Although FGF1 levels were 2-fold increased in obesity, they were unaltered by weight reduction. Only FGF1 and FGF2 induced a marked concentration-dependent phosphorylation of p44/42 in cultured human adipocytes.

CONCLUSIONS

Of the investigated FGFs, only FGF1 is secreted from sc WAT and predominantly so from the adipocyte fraction. The activity in adipocyte cultures and lack of secretion into the circulation suggest that FGF1 acts as an auto- or paracrine factor. FGF1 levels are increased in obesity but unaffected by weight reduction, suggesting a primary defect in obese individuals. In conclusion, FGF1 may play a superior role among the FGFs in sc WAT and obesity development.

Endothelial progenitor cells: their potential in the placental vasculature and related complications

Endothelial progenitor cells (EPCs) have received significant attention in recent times. A role for EPCs has been suggested in a range of pathologies and some recent studies of EPCs in pregnancy have been published. This review provides a guide to the confusing field of EPCs. Attention is paid to their phenotyping, as although elementary this remains a highly debated topic. The current understanding of different subtypes and physiological role of EPCs in the placenta, fetus and adult are also considered. An overview is given as to role of EPC's in the pathophysiology of different disease states and the possible therapeutic and diagnostic applications expected from EPC-related research in obstetrics.

Commitment of stem cells into functional hepatocytes

Liver transplants represent the only way to treat patients suffering from terminal liver failure, but they are associated with numerous problems, including a chronic shortage of donors, high cost, rejection, and side effects for the donor. It is anticipated that regenerative medicine will provide an alternative to liver transplants for such patients. Regenerative medicine refers to the academic field of eliciting the inherent capacity of organisms for self-regeneration to the greatest possible extent in order to develop new methods of treatment for intractable disorders. From this perspective, much is expected from the use of human embryonic stem cells (ES cells) or induced pluripotent stem cells (iPS cells), and the vigorous development of technology to induce the differentiation of such stem cells into cells possessing hepatic functions is underway. Clinical applications of these human stem cells, however, have yet to reach even the earliest stages of implementation. Facing off against these versatile ES cells are stem cells derived from somatic cells present within organisms, which are attracting attention owing to their superiority in terms of ethics and safety, with many research institutes now in the process of elucidating the details of stem cell separation and identification as well as their plasticity and pluripotency. Bone marrow cells are the best-known somatic-cell-derived stem cells, but the use of mesenchymal stem cells (MSCs) found in adipose tissue has also recently attracted attention. This paper will review the differentiation ability and mechanisms of these various stem cell types to hepatocytes and their application to liver regeneration and the future outlook.

Cell cycle and tissue of origin contribute to the migratory behaviour of human fetal and adult mesenchymal stromal cells

Mesenchymal stromal cells (MSC) are potential cells for cellular therapies, in which the recruitment and migration of MSC towards injured tissue is crucial. Our data show that culture-expanded MSC from fetal lung and bone marrow, adult bone marrow and adipose tissue contained a small percentage of migrating cells in vitro, but the optimal stimulus was different. Overall, fetal lung-MSC had the highest migratory capacity. As fetal bone marrow-MSC had lower migratory potential than fetal lung-MSC, the tissue of origin may determine the migratory capacity of MSC. No additive effect in migration towards combined stimuli was observed, which suggests only one migratory MSC fraction. Interestingly, actin rearrangement and increased paxillin phosphorylation were observed in most MSC upon stromal cell-derived factor-1alpha or platelet-derived growth factor-BB stimulation, indicating that this mechanism involved in responding to migratory cues is not restricted to migratory MSC. Migratory MSC maintained differentiation and migration potential, and contained significantly less cells in S- and G2/M-phase than their non-migrating counterpart. In conclusion, our results suggest that MSC from various sources have different migratory capacities, depending on the tissue of origin. Similar to haematopoietic stem cells, cell cycle contributes to MSC migration, which offers perspectives for modulation of MSC to enhance efficacy of future cellular therapies.

Human CD34/CD90 ASCs are capable of growing as sphere clusters, producing high levels of VEGF and forming capillaries

Background

Human adult adipose tissue is an abundant source of mesenchymal stem cells (MSCs). Moreover, it is an easily accessible site producing a considerable amount of stem cells.

Methodology/Principal Findings

In this study, we have selected and characterized stem cells within the stromal vascular fraction (SVF) of human adult adipose tissue with the aim of understanding their differentiation capabilities and performance. We have found, within the SVF, different cell populations expressing MSC markers – including CD34, CD90, CD29, CD44, CD105, and CD117 – and endothelial-progenitor-cell markers – including CD34, CD90, CD44, and CD54. Interestingly, CD34⁺/CD90⁺ cells formed sphere clusters, when placed in non-adherent growth conditions. Moreover, they showed a high proliferative capability, a telomerase activity that was significantly higher than that found in differentiated cells, and contained a fraction of cells displaying the phenotype of a side population. When cultured in adipogenic medium, CD34⁺/CD90⁺ quickly differentiated into adipocytes. In addition, they differentiated into endothelial cells (CD31⁺/VEGF⁺/Flk-1⁺) and, when placed in methylcellulose, were capable of forming capillary-like structures producing a high level of VEGF, as substantiated with ELISA tests.

Conclusions/Significance

Our results demonstrate, for the first time, that CD34⁺/CD90⁺ cells of human adipose tissue are capable of forming sphere clusters, when grown in free-floating conditions, and differentiate in endothelial cells that form capillary-like structures in methylcellulose. These cells might be suitable for tissue reconstruction in regenerative medicine, especially when patients need treatments for vascular disease.

Characterization of human adult stem-cell populations isolated from visceral and subcutaneous adipose tissue

Adipose tissue is a dynamic endocrine organ with a central role in metabolism regulation. Functional differences in adipose tissue seem associated with the regional distribution of fat depots, in particular in subcutaneous and visceral omental pads. Here, we report for the first time the isolation of human adipose-derived adult stem cells from visceral omental and subcutaneous fat (V-ASCs and S-ASCs, respectively) from the same subject. Immunophenotyping shows that plastic culturing selects homogeneous cell populations of V-ASCs and S-ASCs from the corresponding stromal vascular fractions (SVFs), sharing typical markers of mesenchymal stem cells. Electron microscopy and electrophysiological and real-time RT-PCR analyses confirm the mesenchymal stem nature of both V-ASCs and S-ASCs, while no significant differences in a limited pattern of cytokine/chemokine expression can be detected. Similar to S-ASCs, V-ASCs can differentiate in vitro toward adipogenic, osteogenic, chondrogenic, muscular, and neuronal lineages, as demonstrated by histochemical, immunofluorescence, real-time RT-PCR, and electrophysiological analyses, suggesting the multipotency of such adult stem cells. Our data demonstrate that both visceral and subcutaneous adipose tissues are a source of pluripotent stem cells with multigermline potential. However, the visceral rather than the subcutaneous ASC could represent a more appropriate in vitro cell model for investigating the molecular mechanisms implicated in the pathophysiology of metabolic disorders such as obesity.

Platelet lysate as a serum substitute for 2D static and 3D perfusion culture of stromal vascular fraction cells from human adipose tissue

Fetal bovine serum (FBS) and fibroblast growth factor (FGF)-2 are key supplements for the culture of stromal vascular fraction (SVF) cells from adipose tissue, both for typical monolayer (2D) expansion and for streamlined generation of osteogenic-vasculogenic grafts in 3D perfusion culture. The present study investigates whether factors present in human platelet lysate (PL) could substitute for FBS and FGF-2 in 2D and 3D culture models of SVF cells from human lipoaspirates. SVF cells were grown in medium supplemented with 10% FBS+FGF-2 or with 5% PL. In 2D cultures, PL initially supported SVF cell proliferation, but resulted in growth arrest shortly after the first passage. Freshly isolated SVF cells cultured with both media under perfusion for 5 days within 3D ceramic scaffolds induced bone formation after subcutaneous implantation in nude mice. However, blood vessels of donor origin were generated only using FBS+FGF-2-cultured cells. This was unexpected, because the proportion of CD34+/CD31+ endothelial lineage cells was significantly higher with PL than that of FBS+FGF-2 (33% vs. 3%, respectively). These results support the use of PL as a substitute of FBS+FGF-2 for short-term culture of human SVF cells, and indicate that more specific serum-free formulations are required to maintain a functionally vasculogenic fraction of SVF cells expanded under 3D perfusion.

Proangiogenic contribution of adiponectin toward mammary tumor growth in vivo

PURPOSE

Adipocytes represent one of the most abundant constituents of the mammary gland. They are essential for mammary tumor growth and survival. Metabolically, one of the more important fat-derived factors ("adipokines") is adiponectin (APN). Serum concentrations of APN negatively correlate with body mass index and insulin resistance. To explore the association of APN with breast cancer and tumor angiogenesis, we took an in vivo approach aiming to study its role in the mouse mammary tumor virus (MMTV)-polyoma middle T antigen (PyMT) mammary tumor model.

EXPERIMENTAL DESIGN

We compared the rates of tumor growth in MMTV-PyMT mice in wild-type and APN-null backgrounds.

RESULTS

Histology and micro-positron emission tomography imaging show that the rate of tumor growth is significantly reduced in the absence of APN at early stages. PyMT/APN knockout mice exhibit a reduction in their angiogenic profile resulting in nutrient deprivation of the tumors and tumor-associated cell death. Surprisingly, in more advanced malignant stages of the disease, tumor growth develops more aggressively in mice lacking APN, giving rise to a larger tumor burden, an increase in the mobilization of circulating endothelial progenitor cells, and a gene expression fingerprint indicative of more aggressive tumor cells.

CONCLUSIONS

These observations highlight a novel important contribution of APN in mammary tumor development and angiogenesis, indicating that APN has potent angio-mimetic properties in tumor vascularization. However, in tumors deprived of APN, this antiangiogenic stress results in an adaptive response that fuels tumor growth through mobilization of circulating endothelial progenitor cells and the development of mechanisms enabling massive cell proliferation despite a chronically hypoxic microenvironment.

Gene expression profiling of human mesenchymal stem cells chemotactically induced with CXCL12

In situ tissue engineering is a promising approach in regenerative medicine, with the possibility that adult stem or progenitor cells will be guided chemotactically to a tissue defect and subsequently differentiate into the surrounding tissue type. Mesenchymal stem cells (MSC) represent attractive candidate cells. Chemokines such as CXCL12 (SDF-1alpha) chemoattract MSC, but little is known about the molecular processes involved in the chemotaxis and migration of MSC. In this study, MSC recruitment by CXCL12 was investigated by genome-wide microarray analysis. The dose-dependent migration potential of bone-marrow-derived MSC toward CXCL12 was measured in an in vitro assay, with a maximum being recorded at a concentration of 1,000 nM CXCL12. Microarray analysis of MSC stimulated with CXCL12 and non-stimulated controls showed 30 differentially expressed genes (24 induced and six repressed). Pathway analysis revealed 11 differentially expressed genes involved in cellular movement and cytokine-cytokine receptor interaction, including those for migratory inducers such as the chemokines CXCL8 and CCL26, the leukocyte inhibitory factor, secretogranin II, and prostaglandin endoperoxide synthase 2. These results were confirmed by real-time polymerase chain reaction for selected genes. The obtained data provide further insights into the molecular mechanisms involved in chemotactic processes in cell migration and designate CXCL12 as a promising candidate for in situ recruitment in regenerative therapies.

Acceleration of spinal fusion using syngeneic and allogeneic adult adipose derived stem cells in a rat model

Posterolateral spinal fusion is the standard treatment for lumbar compression fractures. Adult adipose tissue-derived stem cells (ASCs) promote osteogenesis in vivo and in vitro. The hypothesis tested in this study was that syngeneic and allogeneic ASCs on a biomaterial scaffold composed of tricalcium phosphate and collagen I will accelerate spinal fusion in a rat model. ASCs from male Fischer or ACI rats were loaded onto scaffolds (53,571 cells/mm(3)) and cultured in stromal media for 48 h. Male Fisher rats were assigned to 4 cohorts (n = 14/cohort) after bilateral decortication of the L4 and L5 transverse processes: (1) No treatment; (2) scaffold only; (3) scaffold + syngeneic ASCs; or (4) scaffold + allogeneic ASCs. Half of each cohort was harvested 4 or 8 weeks after surgery. Spinal fusion was evaluated with radiographs, microcomputed tomography, and light microscopy. Callus did not form in spines without scaffolds. There were no significant differences in callus formation among scaffold cohorts 4 weeks after surgery. Callus formation was more mature in both ASC cohorts versus scaffold alone 8 weeks after surgery based on microstructure as well as radiographic and microcomputed tomographic evidence of active bone formation. Inflammatory cell infiltrate was significantly lower in both ASC cohorts (syngeneic = 18.3 +/- 0.85%; allogeneic = 23.5 +/- 2.33%) versus scaffold alone (46.8 +/- 11.8%) 4 weeks after surgery. Results of this study support syngeneic and allogeneic ASC acceleration of posterior lumbar spinal fusion in a rat model.

Human adipose-derived stem cells as future tools in tissue regeneration: osteogenic differentiation and cell-scaffold interaction

Tissue engineering is now contributing to new developments in several clinical fields, and mesenchymal stem cells derived from adipose tissue (hASCs) may provide a novel opportunity to replace, repair and promote the regeneration of diseased or damaged musculoskeletal tissue. Our interest was to characterize and differentiate hASCs isolated from twenty-three donors. Proliferation, CFU-F, cytofluorimetric and histochemistry analyses were performed. HASCs differentiate into osteogenic, chondrogenic, and adipogenic lineages, as assessed by tissue-specific markers such as alkaline phosphatase, osteopontin expression and deposition of calcium matrix, lipid-vacuoles formation and Glycosaminoglycans production. We also compared osteo-differentiated hASCs cultured on monolayer and loaded on biomaterials routinely used in the clinic, such as hydroxyapatite, cancellous human bone fragments, deproteinized bovine bone granules, and titanium. Scaffolds loaded with pre-differentiated hASCs do not affect cell proliferation and no cellular toxicity was observed. HASCs tightly adhere to scaffolds and differentiated-hASCs on human bone fragments and bovine bone granules produced, respectively, 3.4- and 2.1-fold more calcified matrix than osteo-differentiated hASCs on monolayer. Moreover, both human and deproteinized bovine bone is able to induce osteogenic differentiation of CTRL-hASCs. Although our in vitro results need to be confirmed in in vivo bone regeneration models, our data suggest that hASCs may be considered suitable biological tools for the screening of innovative scaffolds that would be useful in tissue engineering.

Identification of a rare subset of adipose tissue-resident progenitor cells, which express CD133 and TRPC3 as a VEGF-regulated Ca2+ entry channel

VEGF-induced Ca2+ signalling was investigated in CD133+/VEGFR-2+ progenitor cells isolated from human adipose stroma. Colonies derived from CD133+ immunoselected cells displayed inhomogenous Ca2+ signals, with variable magnitude of VEGF-induced Ca2+ entry, which positively correlated with expression of the Ca2+ channel protein TRPC3. High levels of VEGF-induced Ca2+ entry and TRPC3 expression were preferentially detected in rim areas of expanding colonies. Dominant negative suppression of TRPC3 inhibited VEGF-induced Ca2+ entry into CD133+ cells. Our results identify TRPC3 as a key Ca2+ entry channel in a subset of CD133+ stem cells. We suggest TRPC3 as an essential determinant of cell fate in CD133+ progenitor-derived colonies.

IFATS collection: The role of human adipose-derived stromal cells in inflammatory microvascular remodeling and evidence of a perivascular phenotype

A growing body of literature suggests that human adipose-derived stromal cells (hASCs) possess developmental plasticity both in vitro and in vivo, and might represent a viable cell source for therapeutic angiogenesis and tissue engineering. We investigate their phenotypic similarity to perivascular cell types, ability to contribute to in vivo microvascular remodeling, and ability to modulate vascular stability. We evaluated hASC surface expression of vascular and stem/progenitor cell markers in vitro, as well as any effects of platelet-derived growth factor B chain (PDGF-BB) and vascular endothelial growth factor 165 on in vitro hASC migration. To ascertain in vivo behavior of hASCs in an angiogenic environment, hASCs were isolated, expanded in culture, labeled with a fluorescent marker, and injected into adult nude rat mesenteries that were stimulated to undergo microvascular remodeling. Ten, 30, and 60 days after injection, tissues from anesthetized animals were harvested and processed with immunohistochemical techniques to determine hASC quantity, positional fate in relation to microvessels, and expression of endothelial and perivascular cell markers. After 60 days, 29% of hASCs exhibited perivascular morphologies compared with 11% of injected human lung fibroblasts. hASCs exhibiting perivascular morphologies also expressed markers characteristic of vascular pericytes: smooth muscle alpha-actin (10%) and neuron-glia antigen 2 (8%). In tissues treated with hASCs, vascular density was significantly increased over age-matched controls lacking hASCs. This study demonstrates that hASCs express pericyte lineage markers in vivo and in vitro, exhibit increased migration in response to PDGF-BB in vitro, exhibit perivascular morphology when injected in vivo, and contribute to increases in microvascular density during angiogenesis by migrating toward vessels. Disclosure of potential conflicts of interest is found at the end of this article.