The Survival Condition and Immunoregulatory Function of Adipose Stromal Vascular Fraction (SVF) in the Early Stage of Nonvascularized Adipose Transplantation

Introduction

Adipose tissue transplantation is one of the standard procedures for soft-tissue augmentation, reconstruction, and rejuvenation. However, it is unknown as to how the graft survives after transplantation. We thus seek out to investigate the roles of different cellular components in the survival of graft.

Materials & Methods

The ratios of stromal vascular fraction (SVF) cellular components from human adipose tissue were evaluated using flow cytometry. Human liposuction aspirates that were either mixed with marked SVF cells or PBS were transplanted into nude mice. The graft was harvested and stained on days 1,4,7 and 14. The inflammation level of both SVF group and Fat-only group were also evaluated.

Results

Flow cytometric analysis showed SVF cells mainly contained blood-derived cells, adipose-derived stromal cells (ASCs), and endothelial cells. Our study revealed that most cells are susceptible to death after transplantation, although CD34+ ASCs can remain viable for 14 days. Notably, we found that ASCs migrated to the peripheral edge of the graft. Moreover, the RT-PCR and the immuno-fluorescence examination revealed that although the SVF did not reduce the number of infiltrating immune cells (macrophages) in the transplant, it does have an immunoregulatory function of up-regulating the expression of CD163 and CD206 and down-regulating that of IL-1β, IL-6.

Conclusions

Our study suggests that the survival of adipose tissue after nonvascularized adipose transplantation may be due to the ASCs in SVF cells. Additionally, the immunoregulatory function of SVF cells may be indirectly contributing to the remolding of adipose transplant, which may lead to SVF-enriched adipose transplantation.     

Plasticity of human adipose stem cells to perform adipogenic and endothelial differentiation

Recent research findings postulate that adipocytes and endothelial cells (EC) may share a common progenitor. However, the interlinking pathways between adipose tissue and endothelium, and the differentiation potential of cells to convert from one tissue into the other via progenitor cells have not been elucidated and are therefore the focus of this study. Stromal vascular fraction (SVF) cells were isolated from liposuction aspirates or excised adipose tissue and separated into CD31+ and CD31- populations by magnet-assisted cell sorting. Differentiation to fat tissue was induced in both CD31 fractions after expansion by insulin, dexamethasone, isobutylmethylxanthine, triiodothyronine, pioglitazone, and transferrin. Differentiation was assayed enzymatically and by cell counting. Maturation to endothelium was performed with vascular endothelial growth factor (VEGF), insulin-like growth factor-1 plus 2% fetal calf serum, and confirmed by flow cytometry and tube formation assays on Matrigel. Our results show that the SVF contains a CD31-, S100+ cell type that can differentiate into adipocytes and EC. The SVF also comprises CD31+ cells that, although they have an endothelial phenotype, can be converted into mature adipocytes. These findings demonstrate the potency of SVF cells to perform both adipogenic and endothelial differentiation. Further, they reveal the plasticity of mature cells of mesenchymal origin to undergo conversion from endothelium to adipose tissue and vice versa.     

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.     

Purification and growth of endothelial progenitor cells from murine bone marrow mononuclear cells

This study reports the culture and purification of murine bone marrow endothelial progenitor cells (EPCs) using endothelial cell-conditioned medium (EC-CM). Endothelial-like cells appeared at day 5 in culture of bone marrow mononuclear cells in the presence of EC-CM in the culture system, and these cells incorporated acetylated low-density lipoproteins (Ac-LDL) and reacted with endothelial-specific Ulex Europaeus Lectin. Continued incubation of these cells at low density with EC-CM for longer than 10 days resulted in the formation of endothelial cell colonies which gave rise to colonies of endothelial progeny and can be passed for many generations in the EC-CM culture system. Cells derived from these colonies expressed endothelial cell markers such as vWF and CD31, incorporated Dil-Ac-LDL, stained positive for Ulex Europaeus Lectin, formed capillary-like structures on Matrigel, and demonstrated a high proliferative capacity in culture. These bone marrow-derived adherent cells were identified as EPCs. The purification and the formation of EPC colonies by using EC-CM were associated with the cytokines secreted in the EC-CM. VEGF, bFGF, and GM-CSF in the EC-CM stimulated the proliferation and growth of EPCs, whereas AcSDKP (tetrapeptide NAc-Ser-Asp-Lys-Pro) in EC-CM suppressed the growth of mesenchymal stem cells (MSC) and fibroblasts. This approach is efficient for isolation/purification and outgrowth of bone marrow EPCs in vitro, a very important cell source in angiogenic therapies and regenerative medicine.     

In vitro neovasculogenic potential of resident adipose tissue precursors

Adipose tissue development is associated with neovascularization, which might be exploited therapeutically. We investigated the neovasculogenesis antigenic profile and kinetics in adipose tissue-derived stromal cells (ADSCs) to understand the potential of ADSCs to generate new vessels. Murine and human visceral adipose tissues were processed with collagenase to obtain ADSCs from the stromal vascular fraction. Freshly isolated murine and human ADSCs featured the expression of early markers of endothelial differentiation [uptake of DiI-labeled acetylated LDL, CD133, CD34, kinase insert domain receptor (KDR)], but not markers for more mature endothelial cells (CD31 and von Willebrand factor). In methylcellulose medium, multilocular cells positive for Oil Red O staining appeared after 6 days. After 10 days, clusters of ADSCs spontaneously formed branched tubelike structures, which were strongly positive for CD34 and CD31, while losing their ability to undergo adipocyte differentiation. In Matrigel, in the presence of endothelial growth factors ADSCs formed branched tubelike structures. By clonal assays in methylcellulose we also determined the frequency of granulocyte-macrophage (CFU-GM) and erythroid (BFU-E) colony-forming units from ADSCs, compared with bone marrow-derived stromal cells (BMSCs) used as a positive control. After 4-14 days, BMSCs formed 8 +/- 3 BFU-E and 40 +/- 10 CFU-GM, while ADSCs never produced colonies of myeloid progenitors. The developing adipose tissue has neovasculogenic potential, based on the recruitment of local rather than circulating progenitors. Adipose tissue might therefore be a viable autonomous source of cells for postnatal neovascularization.     

Overexpression of osteopontin induces angiogenesis of endothelial progenitor cells via the avβ3/PI3K/AKT/eNOS/NO signaling pathway in glioma cells

Angiogenesis, a hallmark of tumor growth, is regulated by various angiogenic factors. Recent studies have shown that osteopontin (OPN) is a secreted, integrin-binding protein that contributes to glioma progression. However, its effect on the angiogenesis of gliomas is not fully understood. To elucidate the role of OPN in the process of glioma angiogenesis, endothelial progenitor cells (EPCs) were treated with conditioned media of human glioma SHG44 cells overexpressing OPN. Here, we identified that OPN secreted by glioma cells accelerated EPCs angiogenesis in vitro, including proliferation, migration, and tube formation. OPN also induced the activation of AKT and endothelial nitric oxide synthase (eNOS) and increased NO production without affecting the expression of VEGF, VEGFR-1, or VEGFR-2. Moreover, the avβ3 antibody, the PI3-K inhibitor LY294002 and the eNOS inhibitor NMA suppressed the OPN-mediated increase in NO production and angiogenesis in EPCs. Taken together, these results demonstrate that OPN directly stimulates angiogenesis via the avβ3/PI3-K/AKT/eNOS/NO signaling pathway and may play an important role in tumorigenesis by enhancing angiogenesis in gliomas.     

Correction of Diabetic Erectile Dysfunction with Adipose Derived Stem Cells Modified with the Vascular Endothelial Growth Factor Gene in a Rodent Diabetic Model

The aim of this study was to determine whether adipose derived stem cells (ADSCs) expressing vascular endothelial growth factor (VEGF) gene can improve endothelial function, recover the impaired VEGF signaling pathway and enhance smooth muscle contents in a rat diabetic erectile dysfunction (DED) model. DED rats were induced via intraperitoneal injection of streptozotocin (40 mg/kg), and then screened by apomorphine (100 µg/kg). Five groups were used (n = 12/group)–Group 1 (G1): intracavernous injection of lentivirus-VEGF; G2: ADSCs injection; G3: VEGF-expressing ADSCs injection; G4: Phosphate buffered saline injection; G1–G4 were DED rats; G5: normal rats. The mean arterial pressure (MAP) and intracavernosal pressure (ICP) were measured at days 7 and 28 after the injections. The components of the VEGF system, endothelial, smooth muscle, pericytes markers in cavernoursal tissue were assessed. On day 28 after injection, the group with intracavernosum injection of ADSCs expressing VEGF displayed more efficiently and significantly raised ICP and ICP/MAP (p<0.01) than those with ADSCs or lentivirus-VEGF injection. Western blot and immunofluorescent analysis demonstrated that improved erectile function by ADSCs-VEGF was associated with increased expression of endothelial markers (VEGF, VEGF R1, VEGF R2, eNOS, CD31 and vWF), smooth muscle markers (a-actin and smoothelin), and pericyte markers (CD146 and NG2). ADSCs expressing VEGF produced a therapeutic effect and restored erectile function in diabetic rats by enhancing VEGF-stimulated endothelial function and increasing the contents of smooth muscle and pericytes.     

Human adipose stromal vascular cell delivery in a fibrin spray

Background aimsAdipose tissue represents a practical source of autologous mesenchymal stromal cells (MSCs) and vascular-endothelial progenitor cells, available for regenerative therapy without in vitro expansion. One of the problems confronting the therapeutic application of such cells is how to immobilize them at the wound site. We evaluated in vitro the growth and differentiation of human adipose stromal vascular fraction (SVF) cells after delivery through the use of a fibrin spray system.MethodsSVF cells were harvested from four human adult patients undergoing elective abdominoplasty, through the use of the LipiVage system. After collagenase digestion, mesenchymal and endothelial progenitor cells (pericytes, supra-adventitial stromal cells, endothelial progenitors) were quantified by flow cytometry before culture. SVF cells were applied to culture vessels by means of the Tisseel fibrin spray system. SVF cell growth and differentiation were documented by immunofluorescence staining and photomicrography.ResultsSVF cells remained viable after application and were expanded up to 3 weeks, when they reached confluence and adipogenic differentiation. Under angiogenic conditions, SVF cells formed endothelial (vWF+, CD31+ and CD34+) tubules surrounded by CD146+ and α-smooth muscle actin+ perivascular/stromal cells.ConclusionsHuman adipose tissue is a rich source of autologous stem cells, which are readily available for regenerative applications such as wound healing, without in vitro expansion. Our results indicate that mesenchymal and endothelial progenitor cells, prepared in a closed system from unpassaged lipoaspirate samples, retain their growth and differentiation capacity when applied and immobilized on a substrate using a clinically approved fibrin sealant spray system.     

Dimethyloxaloylglycine Improves Angiogenic Activity of Bone Marrow Stromal Cells in the Tissue-Engineered Bone

One of the big challenges in tissue engineering for treating large bone defects is to promote the angiogenesis of the tissue-engineered bone. Hypoxia inducible factor-1α (HIF-1α) plays an important role in angiogenesis-osteogenesis coupling during bone regeneration, and can activate a broad array of angiogenic factors. Dimethyloxaloylglycine (DMOG) can activate HIF-1α expression in cells at normal oxygen tension. In this study, we explored the effect of DMOG on the angiogenic activity of bone mesenchymal stem cells (BMSCs) in the tissue-engineered bone. The effect of different concentrations of DMOG on HIF-1a expression in BMSCs was detected with western blotting, and the mRNA expression and secretion of related angiogenic factors in DMOG-treated BMSCs were respectively analyzed using qRT-PCR and enzyme linked immunosorbent assay. The tissue-engineered bone constructed with β-tricalcium phosphate (β-TCP) and DMOG-treated BMSCs were implanted into the critical-sized calvarial defects to test the effectiveness of DMOG in improving the angiogenic activity of BMSCs in the tissue-engineered bone. The results showed DMOG significantly enhanced the mRNA expression and secretion of related angiogenic factors in BMSCs by activating the expression of HIF-1α. More newly formed blood vessels were observed in the group treated with β-TCP and DMOG-treated BMSCs than in other groups. And there were also more bone regeneration in the group treated with β-TCP and DMOG-treated BMSCs. Therefore, we believed DMOG could enhance the angiogenic activity of BMSCs by activating the expression of HIF-1α, thereby improve the angiogenesis of the tissue-engineered bone and its bone healing capacity.     

NEU1 Sialidase Regulates the Sialylation State of CD31 and Disrupts CD31-driven Capillary-like Tube Formation in Human Lung Microvascular Endothelia

The highly sialylated vascular endothelial surface undergoes changes in sialylation upon adopting the migratory/angiogenic phenotype. We recently established endothelial cell (EC) expression of NEU1 sialidase (Cross, A. S., Hyun, S. W., Miranda-Ribera, A., Feng, C., Liu, A., Nguyen, C., Zhang, L., Luzina, I. G., Atamas, S. P., Twaddell, W. S., Guang, W., Lillehoj, E. P., Puché, A. C., Huang, W., Wang, L. X., Passaniti, A., and Goldblum, S. E. (2012) NEU1 and NEU3 sialidase activity expressed in human lung microvascular endothelia. NEU1 restrains endothelial cell migration whereas NEU3 does not. J. Biol. Chem. 287, 15966–15980). We asked whether NEU1 might regulate EC capillary-like tube formation on a Matrigel substrate. In human pulmonary microvascular ECs (HPMECs), prior silencing of NEU1 did not alter tube formation. Infection of HPMECs with increasing multiplicities of infection of an adenovirus encoding for catalytically active WT NEU1 dose-dependently impaired tube formation, whereas overexpression of either a catalytically dead NEU1 mutant, NEU1-G68V, or another human sialidase, NEU3, did not. NEU1 overexpression also diminished EC adhesion to the Matrigel substrate and restrained EC migration in a wounding assay. In HPMECs, the adhesion molecule, CD31, also known as platelet endothelial cell adhesion molecule-1, was sialylated via α2,6-linkages, as shown by Sambucus nigra agglutinin lectin blotting. NEU1 overexpression increased CD31 binding to Arachis hypogaea or peanut agglutinin lectin, indicating CD31 desialylation. In the postconfluent state, when CD31 ectodomains are homophilically engaged, NEU1 was recruited to and desialylated CD31. In postconfluent ECs, CD31 was desialylated compared with subconfluent cells, and prior NEU1 silencing completely protected against CD31 desialylation. Prior CD31 silencing and the use of CD31-null ECs each abrogated the NEU1 inhibitory effect on EC tube formation. Sialyltransferase 6 GAL-I overexpression increased α2,6-linked CD31 sialylation and dose-dependently counteracted NEU1-mediated inhibition of EC tube formation. These combined data indicate that catalytically active NEU1 inhibits in vitro angiogenesis through desialylation of its substrate, CD31.     

Human subcutaneous adipose tissue subjected to cold shock as a source of viable cellular population with characteristics of multipotent mesenchymal stromal cells

Cellular population with characteristics of multipotent mesenchymal stromal cells (MMSCs) was isolated from subcutaneous adipose tissue frozen without any cryoprotectant at -70 degrees C. Under critical for the adipose tissue condition, the cells retained their viability in vitro and ability of adhesion to plastic. Cellular population was homogeneous and represented by small cells (d - 7 microm) with fibroblast-like morphology. Cells were positively stained with Abs for the Abs: CD29, CD44, CD49a, b, d, CD73, CD90, CD105, CD166, HLA ABC. Cells were negative for CD34, CD45--markers of hematopoietic cells, CD31--marker of endothelial cells, Stro-1, as well as for HLA DR, DP, DQ (flow cytometer analysis). Being induced to differentiate in vitro, the cells were able to differentiate into cells similar to cells of bone, adipose and cartilage tissue. Karyological assay of the cells isolated from human adipose tissue subjected to cold shock revealed diploid set of chromosomes, 46, XX, without aneuploidy and structural reconstructions of chromosomes. Thus, it has been established that, under extreme condition for the organism, the population of cells with a phenotype similar to miltipotent mesenchymal stromal cells is preserved in subcutaneous adipose tissue.     

Thymosin beta10 inhibits cell migration and capillary-like tube formation of human coronary artery endothelial cells

Thymosin beta10 is a cytoplasm G-actin sequestering protein whose functions are largely unknown. To determine the direct effects of exogenous thymosin beta10 on angiogenic potentials as endothelial cell migration and capillary-like tube formation, human coronary artery endothelial cells (HCAECs) were incubated with increasing doses of thymosin beta10 (25-100 ng/ml). By using a modified Boyden chamber assay, thymosin beta10 inhibited cell migration in a dose- and time-dependent manner with the maximal effect being a 36% reduction at 100 ng/ml as compared to controls (P < 0.01). In addition, thymosin beta10 (100 ng/ml) significantly inhibited the capillary-like tube-formation of HCAECs on Matrigel, showing a 21% reduction of the total tube length as compared to negative controls (P < 0.01). Furthermore, by using real time PCR analysis, thymosin beta10 significantly decreased mRNA levels of vascular endothelial growth factor (VEGF), VEGF receptor-1 (VEGFR-1) and integrin alphaV after 24 h treatment in HCAECs. By contrast, thymosin beta4 significantly increased HCAEC migration. These results indicate that thymosin beta10, but not thymosin beta4, have direct inhibitive effects on endothelial migration and tube formation that might be mediated via downregulation of VEGF, VEGFR-1 and integrin alphaV in HCAECs. This study suggests a potential therapeutic application of thymosin beta10 to the diseases with excessive angiogenesis such as cancer.     

Bone tissue engineering using adipose‐derived stem cells and endothelial cells: Effects of the cell ratio

The microvascular endothelial network is essential for bone formation and regeneration. In this context, endothelial cells not only support vascularization but also influence bone physiology via cell contact‐dependent mechanisms. In order to improve vascularization and osteogenesis in tissue engineering applications, several strategies have been developed. One promising approach is the coapplication of endothelial and adipose derived stem cells (ADSCs). In this study, we aimed at investigating the best ratio of human umbilical vein endothelial cells (HUVECs) and osteogenic differentiated ADSCs with regard to proliferation, apoptosis, osteogenesis and angiogenesis. For this purpose, cocultures of ADSCs and HUVECs with ratios of 25%:75%, 50%:50% and 75%:25% were performed. We were able to prove that cocultivation supports proliferation whereas apoptosis was unidirectional decreased in cocultured HUVECs mediated by a p‐BAD‐dependent mechanism. Moreover, coculturing ADSCs and HUVECs stimulated matrix mineralization and the activity of alkaline phosphatase (ALP). Increased gene expression of the proangiogenic markers eNOS, Flt, Ang2 and MMP3 as well as sprouting phenomena in matrigel assays proved the angiogenic potential of the coculture. In summary, coculturing ADSCs and HUVECs stimulates proliferation, cell survival, osteogenesis and angiogenesis particularly in the 50%:50% coculture.     

Hypoxia-Induced Endothelial Progenitor Cell Function Is Blunted in Angiotensinogen Knockout Mice

Angiotensinogen (AGT), the precursor of angiotensin I, is known to be involved in tumor angiogenesis and associated with the pathogenesis of coronary atherosclerosis. This study was undertaken to determine the role played by AGT in endothelial progenitor cells (EPCs) in tumor progression and metastasis. It was found that the number of EPC colonies formed by AGT heterozygous knockout (AGT^+/−) cells was less than that formed by wild-type (WT) cells, and that the migration and tube formation abilities of AGT^+/− EPCs were significantly lower than those of WT EPCs. In addition, the gene expressions of vascular endothelial growth factor (VEGF), Flk1, angiopoietin (Ang)-1, Ang-2, Tie-2, stromal derived factor (SDF)-1, C-X-C chemokine receptor type 4 (CXCR4), and of endothelial nitric oxide synthase (eNOS) were suppressed in AGT^+/− EPCs. Furthermore, the expressions of hypoxia-inducible factor (HIF)-1α and -2α were downregulated in AGT^+/− early EPCs under hypoxic conditions, suggesting a blunting of response to hypoxia. Moreover, the activation of Akt/eNOS signaling pathways induced by VEGF, epithelial growth factor (EGF), or SDF-1α were suppressed in AGT^+/− EPCs. In AGT^+/− mice, the incorporation of EPCs into the tumor vasculature was significantly reduced, and lung tumor growth and melanoma metastasis were attenuated. In conclusion, AGT is required for hypoxia-induced vasculogenesis.     

Inhibition of Lymphangiogenesis of Endothelial Progenitor Cells with VEGFR-3 siRNA Delivered with PEI-alginate Nanoparticles

Lymphangiogenesis is implicated in lymphatic metastasis of tumor cells. Recently, growing evidences show that endothelial progenitor cells (EPCs) are involved in lymphangiogenesis. This study has investigated effects of VEGF-C/VEGFR-3 (vascular endothelial growth factor receptor-3) signaling pathway on EPC differentiation and effectiveness of inhibiting lymphatic formation of EPCs with VEGFR-3 siRNA delivered in PEI (polyethylenimine)-alginate nanoparticles. CD34⁺VEGFR-3⁺ EPCs were sorted from mononuclear cells of human cord blood. Under induction with VEGF-C, the cells differentiated toward lymphatic endothelial cells. The nanoparticles were formulated with 25 kDa branched PEI and alginate. The size and surface charge of PEI-alginate nanoparticles loading VEGFR-3 siRNA (N/P = 16) are 139.1 nm and 7.56 mV respectively. VEGFR-3 siRNA specifically inhibited expression of VEGFR-3 mRNA in the cells. After treatment with PEI-alginate/siRNA nanocomplexes, EPCs could not differentiate into lymphatic endothelial cells, and proliferation, migration and lymphatic formation of EPC-derived cells were suppressed significantly. These results demonstrate that VEGFR-3 signaling plays an important role in differentiation of CD34⁺VEGFR-3⁺ EPCs. VEGFR-3 siRNA delivered with PEI-alginate nanoparticles can effectively inhibit differentiation and lymphangiogenesis of EPCs. Inhibiting VEGFR-3 signaling with siRNA/nanocomplexes would be a potential therapy for suppression of tumor lymphangiogenesis and lymphatic metastasis.     

Histological changes induced by Polyglycolic-Acid (PGA) scaffolds seeded with autologous adipose or muscle-derived stem cells when implanted on rabbit bladder

Purpose: To evaluate the morphological and histological changes induced by PGA scaffold seeded with autologous adipose or muscle derived stem cells implanted on rabbit bladder wall. Material and Methods: Adipose derived stem cells (ADSCs) were obtained from the inguinal fat of eight rabbits and muscle derived stem cells (MDSCs) from the anterior tibial muscle of other eight rabbits. After culture and isolation, the cells were stained with Vybrant Red CM DiI and then implanted at third passage. Two PGA scaffolds were implanted on the bladder submucosa of each animal. On the right bladder side was implanted unseeded PGA scaffold while on the left side was implanted ADSCs or skeletal MDSCs seeded PGA scaffold. ADSCs were implanted in eight animals and MDSC in other eight animals. The animals were sacrificed at four and eight weeks. Histological evaluation was performed with Hematoxylin and Eosin, Masson's Trichrome and smooth muscle α-actin. Results: We observed a mild inflammatory response in all the three groups. Seeded scaffolds induced higher lymphocytes and lower polimorphonuclear migration than controls. Fibrosis was more pronounced in the control groups. Smooth muscle α-actin was positive only in ADSC and MDSC seeded scaffolds. At four and eight weeks ADCSs and skeletal MDSCs labeled cells were found at the implant sites. Conclusions: The implantation of PGA scaffolds seeded with ADSC and MDSC induced less fibrosis than control and smooth muscle regeneration.     

Three specific antigens to isolate endothelial progenitor cells from human liposuction material

Background aimsHuman endothelial progenitor cells (EPC) play an important role in regenerative medicine and contribute to neovascularization on vessel injury. They are usually enriched from peripheral blood, cord blood and bone marrow. In human fat tissue, EPC are rare and their isolation remains a challenge.MethodsFat tissue was prepared by collagenase digestion, and the expression of specific marker proteins was evaluated by flow cytometry in the stromal vascular fraction (SVF). For enrichment, magnetic cell sorting was performed with the use of CD133 microbeads and EPC were cultured until colonies appeared. A second purification was performed with CD34; additional isolation steps were performed with the use of a combination of CD34 and CD31 microbeads. Enriched cells were investigated by flow cytometry for the expression of endothelial specific markers, by Matrigel assay and by the uptake of acetylated low-density lipoprotein.ResultsThe expression pattern confirmed the heterogeneous nature of the SVF, with rare numbers of CD133+ detectable. EPC gained from the SVF by magnetic enrichment showed cobblestone morphology of outgrowth endothelial cells and expressed the specific markers CD31, CD144, vascular endothelial growth factor (VEGF)R2, CD146, CD73 and CD105. Functional integrity was confirmed by uptake of acetylated low-density lipoprotein and the formation of tube-like structures on Matrigel.ConclusionsRare EPC can be enriched from human fat tissue by magnetic cell sorting with the use of a combination of microbeads directed against CD133, an early EPC marker, CD34, a stem cell marker, and CD31, a typical marker for endothelial cells. In culture, they differentiate into EC and hence could have the potential to contribute to neovascularization in regenerative medicine.     

Pleiotrophin induces angiogenesis: involvement of the phosphoinositide-3 kinase but not the nitric oxide synthase pathways

Pleiotrophin (PTN) is a developmentally regulated protein that has been shown to be involved in tumor growth and metastasis presumably by activating tumor angiogenesis. To clarify the potential angiogenic activity of PTN and to analyze the signaling pathways involved in this process, we used an in vitro model of Human Umbilical Vein Endothelial Cells (HUVEC). We show that PTN was mitogenic toward a variety of endothelial cells including HUVEC, stimulated HUVEC migration across a reconstituted basement membrane and induced the formation of capillary-like structures by HUVEC grown as 3D-cultures in Matrigel or collagen. The signaling pathways triggered following endothelial cell stimulation by PTN were studied by using pharmacological inhibitors of the Phosphoinositide-3 kinase (PI3K) and endothelial Nitric Oxide Synthase (eNOS), two enzymes that have been shown to be crucial in the angiogenic response to Vascular Endothelial Growth Factor (VEGF). Whereas wortmannin (a PI3K inhibitor) and L-NAME (an eNOS inhibitor) dramatically reduced HUVEC growth induced by VEGF, only the former inhibitor reduced the growth induced by PTN and to a lesser extent that stimulated by basic Fibroblast Growth Factor. Thus, our results indicate that PTN induces angiogenesis and utilizes PI3K- but not eNOS-dependent pathways for its angiogenic activity.     

Evaluation of CD49f as a novel surface marker to identify functional adipose‐derived mesenchymal stem cell subset

ObjectivesCD49f is expressed on a variety of stem cells and has certain effects on their cytological functions, such as proliferation and differentiation potential. However, whether CD49f is expressed on the surface of adipose tissue‐derived mesenchymal stem cells (ADSCs) and its effect on ADSCs has not been clarified.Materials and methodsThe effects of in vitro culture passage and inflammatory factor treatment on CD49f expression and the adhesion ability of ADSCs from mice and rats were investigated. CD49f⁺ cells were selected from rat ADSCs (rADSCs) by magnetic‐activated cell sorting (MACS), and the cellular functions of CD49f⁺ ADSCs and unsorted ADSCs, including their clonogenic, proliferation, adipogenic and osteogenic differentiation, migration and anti‐apoptotic capacities, were compared.ResultsCD49f expression and the adhesion ability of ADSCs decreased with increasing in vitro culture passage number. TNF‐α and IFN‐γ treatment decreased CD49f expression but increased the adhesion ability of ADSCs. After CD49f was blocked with an anti‐CD49f antibody, the adhesion ability of ADSCs was decreased. No significant difference in clonogenic activity was observed between unsorted ADSCs and CD49f⁺ ADSCs. CD49f⁺ ADSCs had greater proliferation, adipogenic and osteogenic differentiation, migration and anti‐apoptotic capacities than unsorted ADSCs.ConclusionIn the current study, the expression of CD49f on ADSCs was identified for the first time. The expression of CD49f on ADSCs was influenced by in vitro culture passage number and inflammatory factor treatment. Compared with unsorted ADSCs, CD49f ⁺ ADSCs exhibited superior cellular functions, thus may have great application value in mesenchymal stem cell (MSC)‐based therapies.