Human adipose tissue-derived mesenchymal stem cells improve postnatal neovascularization in a mouse model of hindlimb ischemia

Low-molecular weight heparin protamine complex augmented the potential of adipose-derived stromal cells to ameliorate limb ischemia

BACKGROUND AND AIMS

Heparin/protamine micro/nanoparticles (LH/P-MPs) were recently developed as low-molecular weight, biodegradable carriers for adipose-derived stromal cells (ADSCs). These particles can be used for a locally delivered stem cell therapy that promotes angiogenesis. LH/P-MPs bind to the cell surface of ADSCs and promote cell-to-cell interaction and aggregation of ADSCs. Cultured ADSC/LH/P-MP aggregates remain viable. Here, we examined the ability of these aggregates to rescue limb loss in a mouse model of hindlimb ischemia.

METHODS

Unilateral hindlimb ischemia was induced in adult male BALB/c mice by ligation of the iliac artery and hindlimb vein. For allotransplantation of ADSCs from the same inbred strain, we injected ADSC alone or ADSC/LH/P-MP aggregates or control medium (sham-treated) directly into the ischemic muscles. Ischemic limb blood perfusion, vessel density, and vessel area were recorded. The extent of ischemic limb necrosis or limb loss was assessed on postoperative days 2, 7, and 14.

RESULTS

Compared with the sham-treatment control, treatment with ADSCs alone showed modest effects on blood perfusion recovery and increased the number of α-SMA-positive vessels. Response to ADSC/LH/P-MP aggregates was significantly greater than ADSCs alone for every endpoint. ADSC/LH/P-MP aggregates more effectively prevented the loss of ischemic hindlimbs than ADSCs alone or the sham-treatment.

CONCLUSION

The LH/P-MPs augmented the effects of ADSCs on angiogenesis and reversal of limb ischemia. Use of ADSC/LH/P-MP aggregates offers a novel and convenient treatment method and potentially represents a promising new therapeutic approach to inducing angiogenesis in ischemic diseases.

Serially Transplanted Nonpericytic CD146(-) Adipose Stromal/Stem Cells in Silk Bioscaffolds Regenerate Adipose Tissue In Vivo

Progenitors derived from the stromal vascular fraction (SVF) of white adipose tissue (WAT) possess the ability to form clonal populations and differentiate along multiple lineage pathways. However, the literature continues to vacillate between defining adipocyte progenitors as "stromal" or "stem" cells. Recent studies have demonstrated that a nonpericytic subpopulation of adipose stromal cells, which possess the phenotype, CD45(-) /CD31(-) /CD146(-) /CD34(+) , are mesenchymal, and suggest this may be an endogenous progenitor subpopulation within adipose tissue. We hypothesized that an adipose progenitor could be sorted based on the expression of CD146, CD34, and/or CD29 and when implanted in vivo these cells can persist, proliferate, and regenerate a functional fat pad over serial transplants. SVF cells and culture expanded adipose stromal/stem cells (ASC) ubiquitously expressing the green fluorescent protein transgene (GFP-Tg) were fractionated by flow cytometry. Both freshly isolated SVF and culture expanded ASC were seeded in three-dimensional silk scaffolds, implanted subcutaneously in wild-type hosts, and serially transplanted. Six-week WAT constructs were removed and evaluated for the presence of GFP-Tg adipocytes and stem cells. Flow cytometry, quantitative polymerase chain reaction, and confocal microscopy demonstrated GFP-Tg cell persistence, proliferation, and expansion, respectively. Glycerol secretion and glucose uptake assays revealed GFP-Tg adipose was metabolically functional. Constructs seeded with GFP-Tg SVF cells or GFP-Tg ASC exhibited higher SVF yields from digested tissue, and higher construct weights, compared to nonseeded controls. Constructs derived from CD146(-) CD34(+) -enriched GFP-Tg ASC populations exhibited higher hemoglobin saturation, and higher frequency of GFP-Tg cells than unsorted or CD29(+) GFP-Tg ASC counterparts. These data demonstrated successful serial transplantation of nonpericytic adipose-derived progenitors that can reconstitute adipose tissue as a solid organ. These findings have the potential to provide new insights regarding the stem cell identity of adipose progenitor cells.

Thromboxane Governs the Differentiation of Adipose-Derived Stromal Cells Toward Endothelial Cells In Vitro and In Vivo

RATIONALE

Autologous adipose-derived stromal cells (ASCs) offer great promise as angiogenic cell therapy for ischemic diseases. Because of their limited self-renewal capacity and pluripotentiality, the therapeutic efficacy of ASCs is still relatively low. Thromboxane has been shown to play an important role in the maintenance of vascular homeostasis. However, little is known about the effects of thromboxane on ASC-mediated angiogenesis.

OBJECTIVE

To explore the role of the thromboxane-prostanoid receptor (TP) in mediating the angiogenic capacity of ASCs in vivo.

METHODS AND RESULTS

ASCs were prepared from mouse epididymal fat pads and induced to differentiate into endothelial cells (ECs) by vascular endothelial growth factor. Cyclooxygenase-2 expression, thromboxane production, and TP expression were upregulated in ASCs on vascular endothelial growth factor treatment. Genetic deletion or pharmacological inhibition of TP in mouse or human ASCs accelerated EC differentiation and increased tube formation in vitro, enhanced angiogenesis in in vivo Matrigel plugs and ischemic mouse hindlimbs. TP deficiency resulted in a significant cellular accumulation of β-catenin by suppression of calpain-mediated degradation in ASCs. Knockdown of β-catenin completely abrogated the enhanced EC differentiation of TP-deficient ASCs, whereas inhibition of calpain reversed the suppressed angiogenic capacity of TP re-expressed ASCs. Moreover, TP was coupled with Gαq to induce calpain-mediated suppression of β-catenin signaling through calcium influx in ASCs.

CONCLUSION

Thromboxane restrained EC differentiation of ASCs through TP-mediated repression of the calpain-dependent β-catenin signaling pathway. These results indicate that TP inhibition could be a promising strategy for therapy utilizing ASCs in the treatment of ischemic diseases.

Transplantation of Immortalized CD34+ and CD34- Adipose-Derived Stem Cells Improve Cardiac Function and Mitigate Systemic Pro-Inflammatory Responses

Adipose-derived stem cells (ADSCs) have the potential to differentiate into various cell lineages and they are easily obtainable from patients, which makes them a promising candidate for cell therapy. However, a drawback is their limited life span during in vitro culture. Therefore, hTERT-immortalized CD34+ and CD34- mouse ADSC lines (mADSCs^hTERT) tagged with GFP were established. We evaluated the proliferation capacity, multi-differentiation potential, and secretory profiles of CD34+ and CD34- mADSCs^hTERTin vitro, as well as their effects on cardiac function and systemic inflammation following transplantation into a rat model of acute myocardial infarction (AMI) to assess whether these cells could be used as a novel cell source for regeneration therapy in the cardiovascular field. CD34+ and CD34- mADSCs^hTERT demonstrated phenotypic characteristics and multi-differentiation potentials similar to those of primary mADSCs. CD34+ mADSCs^hTERT exhibited a higher proliferation ability compared to CD34- mADSCs^hTERT, whereas CD34- mADSCs^hTERT showed a higher osteogenic differentiation potential compared to CD34+ mADSCs^hTERT. Primary mADSCs, CD34+, and CD34- mADSCs^hTERT primarily secreted EGF, TGF-β1, IGF-1, IGF-2, MCP-1, and HGFR. CD34+ mADSCs^hTERT had higher secretion of VEGF and SDF-1 compared to CD34- mADSCs^hTERT. IL-6 secretion was severely reduced in both CD34+ and CD34- mADSCs^hTERT compared to primary mADSCs. Transplantation of CD34+ and CD34- mADSCs^hTERT significantly improved the left ventricular ejection fraction and reduced infarct size compared to AMI-induced rats after 28 days. At 28 days after transplantation, engraftment of CD34+ and CD34- mADSCs^hTERT was confirmed by positive Y chromosome staining, and differentiation of CD34+ and CD34- mADSCs^hTERT into endothelial cells was found in the infarcted myocardium. Significant decreases were observed in circulating IL-6 levels in CD34+ and CD34- mADSCs^hTERT groups compared to the AMI-induced control group. Transplantation of CD34- mADSCs^hTERT significantly reduced circulating MCP-1 levels compared to the AMI control and CD34+ mADSCs^hTERT groups. GFP-tagged CD34+ and CD34- mADSCs^hTERT are valuable resources for cell differentiation studies in vitro as well as for regeneration therapy in vivo.

Evaluation of the clinical relevance and limitations of current pre-clinical models of peripheral artery disease

Peripheral artery disease (PAD) has recognized treatment deficiencies requiring the discovery of novel interventions. This article describes current animal models of PAD and discusses their advantages and disadvantages. There is a need for models which more directly simulate the characteristics of human PAD, such as acute-on-chronic presentation, presence of established risk factors and impairment of physical activity.

Effects of Intracoronary Administration of Autologous Adipose Tissue-Derived Stem Cells on Acute Myocardial Infarction in a Porcine Model

PURPOSE

Adipose-derived stem cells (ADSCs) are known to be potentially effective in regeneration of damaged tissue. We aimed to assess the effectiveness of intracoronary administration of ADSCs in reducing the infarction area and improving function after acute transmural myocardial infarction (MI) in a porcine model.

MATERIALS AND METHODS

ADSCs were obtained from each pig's abdominal subcutaneous fat tissue by simple liposuction. After 3 passages of 14-days culture, 2 million ADSCs were injected into the coronary artery 30 min after acute transmural MI. At baseline and 4 weeks after the ADSC injection, 99mTc methoxyisobutylisonitrile-single photon emission computed tomography (MIBISPECT) was performed to evaluate the left ventricular volume, left ventricular ejection fraction (LVEF; %), and perfusion defects as well as the myocardial salvage (%) and salvage index. At 4 weeks, each pig was sacrificed, and the heart was extracted and dissected. Gross and microscopic analyses with specific immunohistochemistry staining were then performed.

RESULTS

Analysis showed improvement in the perfusion defect, but not in the LVEF in the ADSC group (n=14), compared with the control group (n=14) (perfusion defect, -13.0±10.0 vs. -2.6±12.0, p=0.019; LVEF, -8.0±15.4 vs. -15.9±14.8, p=0.181). There was a tendency of reducing left ventricular volume in ADSC group. The ADSCs identified by stromal cell-derived factor-1 (SDF-1) staining were well co-localized by von Willebrand factor and Troponin T staining.

CONCLUSION

Intracoronary injection of cultured ADSCs improved myocardial perfusion in this porcine acute transmural MI model.

Characterization of the Cellular Output of a Point-of-Care Device and the Implications for Addressing Critical Limb Ischemia

Critical limb ischemia (CLI) is a terminal disease with high morbidity and healthcare costs due to limb loss. There are no effective medical therapies for patients with CLI to prevent amputation. Cell-based therapies are currently being investigated to address this unmet clinical need and have shown promising preliminary results. The purpose of this study was to characterize the output of a point-of-care cell separator (MarrowStim P.A.D. Kit), currently under investigation for the treatment of CLI, and compare its output with Ficoll-based separation. The outputs of the MarrowStim P.A.D. Kit and Ficoll separation were characterized using an automated hematology analyzer, colony-forming unit (CFU) assays, and tubulogenesis assays. Hematology analysis indicated that the MarrowStim P.A.D. Kit concentrated the total nucleated cells, mononuclear cells, and granulocytes compared with baseline bone marrow aspirate. Cells collected were positive for VEGFR-2, CD3, CD14, CD34, CD45, CD56, CD105, CD117, CD133, and Stro-1 antigen. CFU assays demonstrated that the MarrowStim P.A.D. Kit output a significantly greater number of mesenchymal stem cells and hematopoietic stem cells compared with cells output by Ficoll separation. There was no significant difference in the number of endothelial progenitor cells output by the two separation techniques. Isolated cells from both techniques formed interconnected nodes and microtubules in a three-dimensional cell culture assay. This information, along with data currently being collected in large-scale clinical trials, will help instruct how different cellular fractions may affect the outcomes for CLI patients.

Therapeutic Potential of Adipose-Derived Therapeutic Factor Concentrate for Treating Critical Limb Ischemia

Transplantation of adipose-derived stem cells (ADSCs) is an emerging therapeutic option for addressing intractable diseases such as critical limb ischemia (CLI). Evidence suggests that therapeutic effects of ADSCs are primarily mediated through paracrine mechanisms rather than transdifferentiation. These secreted factors can be captured in conditioned medium (CM) and concentrated to prepare a therapeutic factor concentrate (TFC) composed of a cocktail of beneficial growth factors and cytokines that individually and in combination demonstrate disease-modifying effects. The ability of a TFC to promote reperfusion in a rabbit model of CLI was evaluated. A total of 27 adult female rabbits underwent surgery to induce ischemia in the left hindlimb. An additional five rabbits served as sham controls. One week after surgery, the ischemic limbs received intramuscular injections of either (1) placebo (control medium), (2) a low dose of TFC, or (3) a high dose of TFC. Limb perfusion was serially assessed with a Doppler probe. Blood samples were analyzed for growth factors and cytokines. Tissue was harvested postmortem on day 35 and assessed for capillary density by immunohistochemistry. At 1 month after treatment, tissue perfusion in ischemic limbs treated with a high dose of TFC was almost double (p < 0.05) that of the placebo group [58.8 ± 23 relative perfusion units (RPU) vs. 30.7 ± 13.6 RPU; mean ± SD]. This effect was correlated with greater capillary density in the affected tissues and with transiently higher serum levels of the angiogenic and prosurvival factors vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). The conclusions from this study are that a single bolus administration of TFC demonstrated robust effects for promoting tissue reperfusion in a rabbit model of CLI and that a possible mechanism of revascularization was promotion of angiogenesis by TFC. Results of this study demonstrate that TFC represents a potent therapeutic cocktail for patients with CLI, many of whom are at risk for amputation of the affected limb.

Human Adipose-Derived Mesenchymal Stem Cells in Cell Therapy: Safety and Feasibility in Different "Hospital Exemption" Clinical Applications

Based on immunomodulatory, osteogenic, and pro-angiogenic properties of adipose-derived stem cells (ASCs), this study aims to assess the safety and efficacy of ASC-derived cell therapies for clinical indications. Two autologous ASC-derived products were proposed to 17 patients who had not experienced any success with conventional therapies: (1) a scaffold-free osteogenic three-dimensional graft for the treatment of bone non-union and (2) a biological dressing for dermal reconstruction of non-healing chronic wounds. Safety was studied using the quality control of the final product (genetic stability, microbiological/mycoplasma/endotoxin contamination) and the in vivo evaluation of adverse events after transplantation. Feasibility was assessed by the ability to reproducibly obtain the final ASC-based product with specific characteristics, the time necessary for graft manufacturing, the capacity to produce enough material to treat the lesion, the surgical handling of the graft, and the ability to manufacture the graft in line with hospital exemption regulations. For 16 patients (one patient did not undergo grafting because of spontaneous bone healing), in-process controls found no microbiological/mycoplasma/endotoxin contamination, no obvious deleterious genomic anomalies, and optimal ASC purity. Each type of graft was reproducibly obtained without significant delay for implantation and surgical handling was always according to the surgical procedure and the implantation site. No serious adverse events were noted for up to 54 months. We demonstrated that autologous ASC transplantation can be considered a safe and feasible therapy tool for extreme clinical indications of ASC properties and physiopathology of disease.

Does adipose tissue-derived stem cell therapy improve graft quality in freshly grafted ovaries?

BACKGROUND

A major concern in ovarian transplants is substantial follicle loss during the initial period of hypoxia. Adipose tissue-derived stem cells (ASCs) have been employed to improve angiogenesis when injected into ischemic tissue. This study evaluated the safety and efficacy of adipose tissue-derived stem cells (ASCs) therapy in the freshly grafted ovaries 30 days after injection.

METHODS

Rat ASCs (rASCs) obtained from transgenic rats expressing green fluorescent protein (GFP)-(5 × 10(4) cells/ovary) were injected in topic (intact) or freshly grafted ovaries of 30 twelve-week-old adult female Wistar rats. The whole ovary was grafted in the retroperitoneum without vascular anastomosis, immediately after oophorectomy. Vaginal smears were performed daily to assess the resumption of the estrous cycle. Estradiol levels, grafts morphology and follicular viability and density were analyzed. Immunohistochemistry assays were conducted to identify and quantify rASC-GFP(+), VEGF tissue expression, apoptosis (cleaved caspase-3 and TUNEL), and cell proliferation (Ki-67). Quantitative gene expression (qPCR) for VEGF-A, Bcl2, EGF and TGF-β1 was evaluated using RT-PCR and a double labeling immunofluorescence assay for GFP and Von Willebrand Factor (VWF) was performed.

RESULTS

Grafted ovaries treated with rASC-GFP(+) exhibited earlier resumption of the estrous phase (p < 0.05), increased VEGF-A expression (11-fold in grafted ovaries and 5-fold in topic ovaries vs. control) and an increased number of blood vessels (p < 0.05) in ovarian tissue without leading to apoptosis or cellular proliferation (p > 0.05). Estradiol levels were similar among groups (p > 0.05). rASC-GFP(+) were observed in similar quantities in the topic and grafted ovaries (p > 0.05), and double-labeling for GFP and vWF was observed in both injected groups.

CONCLUSION

rASC therapy in autologous freshly ovarian grafts could be feasible and safe, induces earlier resumption of the estrous phase and enhances blood vessels in rats. This pilot study may be useful in the future for new researches on frozen-thawed ovarian tissue.

Adipose tissue-derived stem cells as a therapeutic tool for cardiovascular disease

Adipose tissue-derived stem cells (ADSCs) are adult stem cells that can be easily harvested from subcutaneous adipose tissue. Many studies have demonstrated that ADSCs differentiate into vascular endothelial cells (VECs), vascular smooth muscle cells (VSMCs), and cardiomyocytes in vitro and in vivo. However, ADSCs may fuse with tissue-resident cells and obtain the corresponding characteristics of those cells. If fusion occurs, ADSCs may express markers of VECs, VSMCs, and cardiomyocytes without direct differentiation into these cell types. ADSCs also produce a variety of paracrine factors such as vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor-1 that have proangiogenic and/or antiapoptotic activities. Thus, ADSCs have the potential to regenerate the cardiovascular system via direct differentiation into VECs, VSMCs, and cardiomyocytes, fusion with tissue-resident cells, and the production of paracrine factors. Numerous animal studies have demonstrated the efficacy of ADSC implantation in the treatment of acute myocardial infarction (AMI), ischemic cardiomyopathy (ICM), dilated cardiomyopathy, hindlimb ischemia, and stroke. Clinical studies regarding the use of autologous ADSCs for treating patients with AMI and ICM have recently been initiated. ADSC implantation has been reported as safe and effective so far. Therefore, ADSCs appear to be useful for the treatment of cardiovascular disease. However, the tumorigenic potential of ADSCs requires careful evaluation before their safe clinical application.

Effect of autologous adipose tissue-derived mesenchymal stem cells on neovascularization of artificial equine tendon lesions

AIMS

To investigate whether autologous adipose tissue-derived mesenchymal stem cells (AT-MSCs) treatment of tendon lesions increases neovascularization during tendon healing.

MATERIALS & METHODS

A standardized surgical model was used to create lesions in both front limb superficial digital flexor tendons (SDFTs) of nine horses. Either AT-MSCs or control substance was injected intralesionally 2 weeks post-surgery. Color Doppler ultrasonography of SDFTs was performed at regular intervals. Horses were euthanized 22 weeks post-treatment and SDFTs were harvested for histology.

RESULTS

The color Doppler ultrasonography signal was significantly more extensive at 2 weeks post-treatment and the number of vessels counted on histologic slides was significantly higher at 22 weeks post-treatment in AT-MSC-treated SDFTs.

CONCLUSION

Our findings indicate that AT-MSC treatment has a beneficial effect on neovascularization of healing tendons.

Peripheral Nerve Repair: Multimodal Comparison of the Long-Term Regenerative Potential of Adipose Tissue-Derived Cells in a Biodegradable Conduit

Tissue engineering is a popular topic in peripheral nerve repair. Combining a nerve conduit with supporting adipose-derived cells could offer an opportunity to prevent time-consuming Schwann cell culture or the use of an autograft with its donor site morbidity and eventually improve clinical outcome. The aim of this study was to provide a broad overview over promising transplantable cells under equal experimental conditions over a long-term period. A 10-mm gap in the sciatic nerve of female Sprague-Dawley rats (7 groups of 7 animals, 8 weeks old) was bridged through a biodegradable fibrin conduit filled with rat adipose-derived stem cells (rASCs), differentiated rASCs (drASCs), human (h)ASCs from the superficial and deep abdominal layer, human stromal vascular fraction (SVF), or rat Schwann cells, respectively. As a control, we resutured a nerve segment as an autograft. Long-term evaluation was carried out after 12 weeks comprising walking track, morphometric, and MRI analyses. The sciatic functional index was calculated. Cross sections of the nerve, proximal, distal, and in between the two sutures, were analyzed for re-/myelination and axon count. Gastrocnemius muscle weights were compared. MRI proved biodegradation of the conduit. Differentiated rat ASCs performed significantly better than undifferentiated rASCs with less muscle atrophy and superior functional results. Superficial hASCs supported regeneration better than deep hASCs, in line with published in vitro data. The best regeneration potential was achieved by the drASC group when compared with other adipose tissue-derived cells. Considering the ease of procedure from harvesting to transplanting, we conclude that comparison of promising cells for nerve regeneration revealed that particularly differentiated ASCs could be a clinically translatable route toward new methods to enhance peripheral nerve repair.

Role of transforming growth factor-activated kinase-1 on tumor necrosis factor-α actions in human adipose tissue-derived stromal cells

Tumor necrosis factor-α (TNF-α) has multiple effects on proliferation and differentiation of human mesenchymal stem cells. Transforming growth factor-activated kinase-1 (TAK1) mediates the activation of nuclear factor-kappa B (NF-κB), c-Jun N-terminal kinase (JNK), and p38 pathways in response to TNF-α. However, the role of TAK1 in TNF-α-induced effects in human adipose-derived stem cells (hADSCs) and its signaling pathway has not been clearly defined. Therefore, this study was designated to clarify the role of TAK1 in TNF-α-induced actions on proliferation and differentiation of hADSCs and its downstream signaling pathway. Inhibiting TAK1 expression inhibited the TNF-α-induced increase in osteogenic differentiation and basal osteogenic differentiation without affecting the TNF-α-induced effect on proliferation and adipogenic differentiation of hADSCs. A western blot analysis showed that TNF-α treatment induced degradation of IκB, but that TAK1 small interfering RNA (siRNA) transfection did not protect against TNF-α-induced IκB degradation. The transfection of TAK1 siRNA also did not affect TNF-α-induced IκB phosphorylation or ERK1/2 phosphorylation. However, downregulating TAK1 inhibited this TNF-α-induced S536 phosphorylation of the p65 subunit. TNF-α treatment induced p38 phosphorylation, which was inhibited by the transfection of TAK1 siRNA. Adding p38 inhibitor inhibited TNF-α-induced p65 phosphorylation, NF-κB promoter activity, and TNF-α-induced increase in hADSC osteogenic differentiation. These data indicate that TAK1 is involved in the TNF-α-induced activation of p38 kinase, which subsequently phosphorylates the NF-κB p65 subunit, and increases the transactivation potential of p65 and osteogenic differentiation in hADSCs.

Potential of mesenchymal stem cell in stabilization of abdominal aortic aneurysm sac

BACKGROUND

In their origin, abdominal aortic aneurysms (AAAs) are related to an inflammatory reaction within the aortic wall, which can lead to weakness and degeneration of this structure. One of the most widely accepted treatment modalities for AAAs is the placement of stent grafts. Nevertheless, in some patients blood re-enters the aneurysm sac, creating so-called leaks, which constitute a renewed risk of rupture and death.This study explores the possibility of filling aneurysm sacs treated by endovascular aneurysm repair with adipose tissue-derived mesenchymal stem cells (ASCs) in a porcine model.

METHODS

We developed a porcine model using 22 animals by creating an artificial AAA made with a Dacron patch. AAAs were then treated with a coated stent that isolated the aneurysm sac, after which we introduced allogeneic ASC into the sac. Animals were followed-up for up to 3 mo. The experiment consisted of the aforementioned surgical procedure performed first, followed by computed tomography and echo-Doppler imaging during the follow-up, and finally, after sacrificing the animals, histologic analysis of tissue samples from the site of cell implantation by a blinded observer and the detection of implanted cells by immunofluorescence detection of the Y chromosome.

RESULTS

Our findings demonstrate the survival of ASCs over the 3 mo after implantation and histologic changes associated with this treatment. Treated animals had less acute and chronic inflammation throughout the study period, and we observed increasing fibrosis of the aneurysm sac, no accumulation of calcium, and a regeneration of elastic fibers in the artery.

CONCLUSIONS

The combination of endovascular aneurysm repair and cell therapy on AAAs has promising results for the stabilization of the sac, resulting in the generation of living tissue that can secure the stent graft and even showing some signs of wall regeneration. The therapeutic value of such cell-based therapy will require further investigation.

Concentrated Hypoxia-Preconditioned Adipose Mesenchymal Stem Cell-Conditioned Medium Improves Wounds Healing in Full-Thickness Skin Defect Model

In recent years, the bioactive factors were utilized in exercise and athletic skin injuries. In this research, the concentrated conditioned medium of hypoxia-preconditioned adipose mesenchymal stem cells, which is rich in bioactive factor, is applied in full-thickness skin defect model to evaluate the therapeutic efficacy. Adipose mesenchymal stem cells were harvested from the abdominal subcutaneous adipose tissues. The surface markers and the potential of differentiation were analyzed. The conditioned medium of hypoxia-preconditioned stem cells was collected and freeze-dried and then applied on the rat full-thickness skin defect model, and the healing time of each group was recorded. Haematoxylin and eosin staining of skin was assessed by microscope. The characteristics of adipose mesenchymal stem cells were similar to those of other mesenchymal stem cells. The concentration of protein in freeze-dried conditioned medium in 1 mL water was about 15 times higher than in the normal condition medium. In vivo, the concentrated hypoxia-preconditioned conditioned medium can reduce the wound size and accelerate the skin wound healing. The concentrated hypoxia-preconditioned adipose mesenchymal stem cell-conditioned medium has great effect on rat model of wound healing, and it would be an ideal agent for wound care in clinical application.

Concentration-Dependent Vascularization of Adipose Stromal Vascular Fraction Cells

Adipose-derived stromal vascular fraction (SVF) cells have been shown to self-associate to form vascular structures under both in vitro and in vivo conditions. The angiogenic (new vessels from existing vessels) and vasculogenic (new vessels through self-assembly) potential of the SVF cell population may provide a cell source for directly treating (i.e., point of care without further cell isolation) ischemic tissues. However the correct dosage of adipose SVF cells required to achieve a functional vasculature has not been established. Accordingly, in vitro and in vivo dose response assays were performed evaluating the SVF cell vasculogenic potential. Serial dilutions of freshly isolated rat adipose SVF cells were plated on growth factor reduced Matrigel and vasculogenesis, assessed as cellular tube-like network assembly, was quantified after 3 days of culture. This in vitro vasculogenesis assay indicated that rat SVF cells reached maximum network length at a concentration of 2.5 × 10(5) cells/ml and network maintained at the higher concentrations tested. The same concentrations of rat and human SVF cells were used to evaluate vasculogenesis in vivo. SVF cells were incorporated into collagen gels and subcutaneously implanted into Rag1 immunodeficient mice. The 3D confocal images of harvested constructs were evaluated to quantify dose dependency of SVF cell vasculogenesis potential. Rat- and human-derived SVF cells yielded a maximum vasculogenic potential at 1 × 10(6) and 4 × 10(6) cells/ml, respectively. No adverse reactions (e.g., toxicity, necrosis, tumor formation) were observed at any concentration tested. In conclusion, the vasculogenic potential of adipose-derived SVF cell populations is dose dependent.

Neurogenic differentiation from adipose-derived stem cells and application for autologous transplantation in spinal cord injury

Mesenchymal stem cells derived from adipose tissue have the capacity to differentiate into endodermal, mesoderm and ectodermal cell lineages in vitro, which are an ideal engraft in tissue-engineered repair. In this study, mouse adipose-derived stem cells (ADSCs) were isolated from subcutaneous fat. The markers of ADSCs, CD13, CD29, CD44, CD71, CD73, CD90, CD105, CD166, Nestin, GFAP and MAP-2 were detected by immunofluorescence assays. The ADSCs were cultured in cocktail factors (including ATRA, GGF-2, bFGF, PDGF and forskolin) for neurogenic differentiation. The neurogenic cells markers, Nestin, GFAP and MAP-2 were analyzed using immunofluorescence and real-time PCR after dramatic changes in morphology. Neurogenic cells from ADSCs were autologous transplanted into the mouse of spinal cord injury for observation neurogenic cells colonization in spinal cord. The result demonstrated that the mouse ADSCs were positive for the CD13, CD29, CD44, CD71, CD73, CD90, CD105 and CD166 but negative for neurogenic cell markers, MAP-2, GFAP and Nestin. After neurogenic differentiation, the neurogenic cells were positive for neurogenic cell special markers, gene expression level showed a time-lapse increase, and the cells were successful colonized into spinal cord. In conclusion, our research shows that a population of neuronal cells can be specifically generated from ADSCs and that induced cells may allow for participation in tissue-repair.

Phase I trial: the use of autologous cultured adipose-derived stroma/stem cells to treat patients with non-revascularizable critical limb ischemia

BACKGROUND AIMS

Non-revascularizable critical limb ischemia (CLI) is the most severe stage of peripheral arterial disease, with no therapeutic option. Extensive preclinical studies have demonstrated that adipose-derived stroma cell (ASC) transplantation strongly improves revascularization and tissue perfusion in ischemic limbs. This study, named ACellDREAM, is the first phase I trial to evaluate the feasibility and safety of intramuscular injections of autologous ASC in non-revascularizable CLI patients.

METHODS

Seven patients were consecutively enrolled, on the basis of the following criteria: (i) lower-limb rest pain or ulcer; (ii) ankle systolic oxygen pressure <50 or 70 mm Hg for non-diabetic and diabetic patients, respectively, or first-toe systolic oxygen pressure <30 mm Hg or 50 mm Hg for non-diabetic and diabetic patients, respectively; (iii) not suitable for revascularization. ASCs from abdominal fat were grown for 2 weeks and were then characterized.

RESULTS

More than 200 million cells were obtained, with almost total homogeneity and no karyotype abnormality. The expressions of stemness markers Oct4 and Nanog were very low, whereas expression of telomerase was undetectable in human ASCs compared with human embryonic stem cells. ASCs (10(8)) were then intramuscularly injected into the ischemic leg of patients, with no complication, as judged by an independent committee. Trans-cutaneous oxygen pressure tended to increase in most patients. Ulcer evolution and wound healing showed improvement.

CONCLUSIONS

These data demonstrate the feasibility and safety of autologous ASC transplantation in patients with objectively proven CLI not suitable for revascularization. The improved wound healing also supports a putative functional efficiency.

SIRT1 inhibition affects angiogenic properties of human MSCs

Human mesenchymal stem cells (hMSCs) are attractive for clinical and experimental purposes due to their capability of self-renewal and of differentiating into several cell types. Autologous hMSCs transplantation has been proven to induce therapeutic angiogenesis in ischemic disorders. However, the molecular mechanisms underlying these effects remain unclear. A recent report has connected MSCs multipotency to sirtuin families, showing that SIRT1 can regulate MSCs function. Furthermore, SIRT1 is a critical modulator of endothelial angiogenic functions. Here, we described the generation of an immortalized human mesenchymal bone marrow-derived cell line and we investigated the angiogenic phenotype of our cellular model by inhibiting SIRT1 by both the genetic and pharmacological level. We first assessed the expression of SIRT1 in hMSCs under basal and hypoxic conditions at both RNA and protein level. Inhibition of SIRT1 by sirtinol, a cell-permeable inhibitor, or by specific sh-RNA resulted in an increase of premature-senescence phenotype, a reduction of proliferation rate with increased apoptosis. Furthermore, we observed a consistent reduction of tubule-like formation and migration and we found that SIRT1 inhibition reduced the hypoxia induced accumulation of HIF-1α protein and its transcriptional activity in hMSCs. Our findings identify SIRT1 as regulator of hypoxia-induced response in hMSCs and may contribute to the development of new therapeutic strategies to improve regenerative properties of mesenchymal stem cells in ischemic disorders through SIRT1 modulation.

Stem cell therapy for dermal wound healing

The use of cellular therapy in the treatment of dermal wounds is currently an active area of investigation. Multipotent adult stem cells are an attractive choice for cell therapy because they have a large proliferative potential, the ability to differentiate into different cell types and produce a variety cytokines and growth factors important to wound healing. This review focused on the roles of adult stem cells such as endothelial progenitor cells, bone marrow and adipose-derived mesenchymal stem cells, during dermal wound healing process and their therapeutic potentials for the treatment of chronic wounds, which remain a major clinical problem, especially in diabetic patients.

Isolation, characterization, differentiation, and application of adipose-derived stem cells

While bone marrow-derived mesenchymal stem cells are known and have been investigated for a long time, mesenchymal stem cells derived from the adipose tissue were identified as such by Zuk et al. in 2001. However, as subcutaneous fat tissue is a rich source which is much more easily accessible than bone marrow and thus can be reached by less invasive procedures, adipose-derived stem cells have moved into the research spotlight over the last 8 years.Isolation of stromal cell fractions involves centrifugation, digestion, and filtration, resulting in an adherent cell population containing mesenchymal stem cells; these can be subdivided by cell sorting and cultured under common conditions.They seem to have comparable properties to bone marrow-derived mesenchymal stem cells in their differentiation abilities as well as a favorable angiogenic and anti-inflammatory cytokine secretion profile and therefore have become widely used in tissue engineering and clinical regenerative medicine.

The current landscape of adipose-derived stem cells in clinical applications

Adipose-derived stem cells (ASCs) are considered a great alternative source of mesenchymal stem cells (MSCs). Unlike bone marrow stem cells (BMSCs), ASCs can be retrieved in high numbers from lipoaspirate, a by-product of liposuction procedures. Given that ASCs represent an easily accessible and abundant source of multipotent cells, ASCs have garnered attention and curiosity from both scientific and clinical communities for their potential in clinical applications. Furthermore, their unique immunobiology and secretome are attractive therapeutic properties. A decade since the discovery of a stem cell reservoir residing within adipose tissue, ASC-based clinical trials have grown over the years around the world along with assessments made on their safety and efficacy. With the progress of ASCs into clinical applications, the aim towards producing clinical-grade ASCs becomes increasingly important. Several countries have recognised the growing industry of cell therapies and have developed regulatory frameworks to assure their safety. With more research efforts made to understand their effects in both scientific and clinical settings, ASCs hold great promise as a future therapeutic strategy in treating a wide variety of diseases. Therefore, this review seeks to highlight the clinical applicability of ASCs as well as their progress in clinical trials across various medical disciplines.

Performance of an in situ formed bioactive hydrogel dressing from a PEG-based hyperbranched multifunctional copolymer

Hydrogel dressings have been widely used for wound management due to their ability to maintain a hydrated wound environment, restore the skin's physical barrier and facilitate regular dressing replacement. However, the therapeutic functions of standard hydrogel dressings are restricted. In this study, an injectable hybrid hydrogel dressing system was prepared from a polyethylene glycol (PEG)-based thermoresponsive hyperbranched multiacrylate functional copolymer and thiol-modified hyaluronic acid in combination with adipose-derived stem cells (ADSCs). The cell viability, proliferation and metabolic activity of the encapsulated ADSCs were studied in vitro, and a rat dorsal full-thickness wound model was used to evaluate this bioactive hydrogel dressing in vivo. It was found that long-term cell viability could be achieved for both in vitro (21days) and in vivo (14days) studies. With ADSCs, this hydrogel system prevented wound contraction and enhanced angiogenesis, showing the potential of this system as a bioactive hydrogel dressing for wound healing.

The stem cell adjuvant with Exendin-4 repairs the heart after myocardial infarction via STAT3 activation

The poor survival of cells in ischaemic myocardium is a major obstacle for stem cell therapy. Exendin-4 holds the potential of cardioprotective effect based on its pleiotropic activity. This study investigated whether Exendin-4 in conjunction with adipose-derived stem cells (ADSCs) could improve the stem cell survival and contribute to myocardial repairs after infarction. Myocardial infarction (MI) was induced by the left anterior descending artery ligation in adult male Sprague-Dawley rats. ADSCs carrying double-fusion reporter gene [firefly luciferase and monomeric red fluorescent protein (fluc-mRFP)] were quickly injected into border zone of MI in rats treated with or without Exendin-4. Exendin-4 enhanced the survival of transplanted ADSCs, as demonstrated by the longitudinal in vivo bioluminescence imaging. Moreover, ADSCs adjuvant with Exendin-4 decreased oxidative stress, apoptosis and fibrosis. They also improved myocardial viability and cardiac function and increased the differentiation rates of ADSCs into cardiomyocytes and vascular smooth muscle cells in vivo. Then, ADSCs were exposed to hydrogen peroxide/serum deprivation (H₂O₂/SD) to mimic the ischaemic environment in vitro. Results showed that Exendin-4 decreased the apoptosis and enhanced the paracrine effect of ADSCs. In addition, Exendin-4 activated signal transducers and activators of transcription 3 (STAT3) through the phosphorylation of Akt and ERK1/2. Furthermore, Exendin-4 increased the anti-apoptotic protein Bcl-2, but decreased the pro-apoptotic protein Bax of ADSCs. In conclusion, Exendin-4 could improve the survival and therapeutic efficacy of transplanted ADSCs through STAT3 activation via the phosphorylation of Akt and ERK1/2. This study suggests the potential application of Exendin-4 for stem cell–based heart regeneration.

Microchip-based engineering of super-pancreatic islets supported by adipose-derived stem cells

Type 1 diabetes mellitus (T1DM) is a chronic disorder characterized by targeted autoimmune-mediated destruction of the β cells of Langerhans within pancreatic islets. Currently, islet transplantation is the only curative therapy; however, donor shortages and cellular damage during the isolation process critically limit the use of this approach. Here, we describe a method for creating viable and functionally potent islets for successful transplantation by co-culturing single primary islet cells with adipose-derived stem cells (ADSCs) in concave microwells. We observed that the ADSCs segregated from the islet cells, eventually yielding purified islet spheroids in the three-dimensional environment. Thereafter, the ADSC-exposed islet spheroids showed significantly different ultrastructural morphologies, higher viability, and enhanced insulin secretion compared to mono-cultured islet spheroids. This suggests that ADSCs may have a significant potential to protect islet cells from damage during culture, and may be employed to improve islet cell survival and function prior to transplantation. In vivo experiments involving xenotransplantation of microfiber-encapsulated spheroids into a mouse model of diabetes revealed that co-culture-transplanted mice maintained their blood glucose levels longer than mono-culture-transplanted mice, and required less islet mass to reverse diabetes. This method for culturing islet spheroids could potentially help overcome the cell shortages that have limited clinical applications and could possibly be developed into a bioartificial pancreas.

Mesenchymal stem/stromal cells as a pharmacological and therapeutic approach to accelerate angiogenesis

Mesenchymal stem cells or multipotent stromal cells (MSCs) have initially captured attention in the scientific world because of their differentiation potential into osteoblasts, chondroblasts and adipocytes and possible transdifferentiation into neurons, glial cells and endothelial cells. This broad plasticity was originally hypothesized as the key mechanism of their demonstrated efficacy in numerous animal models of disease as well as in clinical settings. However, there is accumulating evidence suggesting that the beneficial effects of MSCs are predominantly caused by the multitude of bioactive molecules secreted by these remarkable cells. Numerous angiogenic factors, growth factors and cytokines have been discovered in the MSC secretome, all have been demonstrated to alter endothelial cell behavior in vitro and induce angiogenesis in vivo. As a consequence, MSCs have been widely explored as a promising treatment strategy in disorders caused by insufficient angiogenesis such as chronic wounds, stroke and myocardial infarction. In this review, we will summarize into detail the angiogenic factors found in the MSC secretome and their therapeutic mode of action in pathologies caused by limited blood vessel formation. Also the application of MSC as a vehicle to deliver drugs and/or genes in (anti-)angiogenesis will be discussed. Furthermore, the literature describing MSC transdifferentiation into endothelial cells will be evaluated critically.

Mesenchymal stem cell delivery strategies to promote cardiac regeneration following ischemic injury

Myocardial infarction (MI) is one of the leading causes of mortality worldwide and is associated with irreversible cardiomyocyte death and pathological remodeling of cardiac tissue. In the past 15 years, several animal models have been developed for pre-clinical testing to assess the potential of stem cells for functional tissue regeneration and the attenuation of left ventricular remodeling. The promising results obtained in terms of improved cardiac function, neo-angiogenesis and reduction in infarct size have motivated the initiation of clinical trials in humans. Despite the potential, the results of these studies have highlighted that the effective delivery and retention of viable cells within the heart remain significant challenges that have limited the therapeutic efficacy of cell-based therapies for treating the ischemic myocardium. In this review, we discuss key elements for designing clinically translatable cell-delivery approaches to promote myocardial regeneration. Key topics addressed include cell selection, with a focus on mesenchymal stem cells derived from the bone marrow (bMSCs) and adipose tissue (ASCs), including a discussion of their potential mechanisms of action. Natural and synthetic biomaterials that have been investigated as injectable cell delivery vehicles for cardiac applications are critically reviewed, including an analysis of the role of the biomaterials themselves in the therapeutic scheme.

Postischemic revascularization: from cellular and molecular mechanisms to clinical applications

After the onset of ischemia, cardiac or skeletal muscle undergoes a continuum of molecular, cellular, and extracellular responses that determine the function and the remodeling of the ischemic tissue. Hypoxia-related pathways, immunoinflammatory balance, circulating or local vascular progenitor cells, as well as changes in hemodynamical forces within vascular wall trigger all the processes regulating vascular homeostasis, including vasculogenesis, angiogenesis, arteriogenesis, and collateral growth, which act in concert to establish a functional vascular network in ischemic zones. In patients with ischemic diseases, most of the cellular (mainly those involving bone marrow-derived cells and local stem/progenitor cells) and molecular mechanisms involved in the activation of vessel growth and vascular remodeling are markedly impaired by the deleterious microenvironment characterized by fibrosis, inflammation, hypoperfusion, and inhibition of endogenous angiogenic and regenerative programs. Furthermore, cardiovascular risk factors, including diabetes, hypercholesterolemia, hypertension, diabetes, and aging, constitute a deleterious macroenvironment that participates to the abrogation of postischemic revascularization and tissue regeneration observed in these patient populations. Thus stimulation of vessel growth and/or remodeling has emerged as a new therapeutic option in patients with ischemic diseases. Many strategies of therapeutic revascularization, based on the administration of growth factors or stem/progenitor cells from diverse sources, have been proposed and are currently tested in patients with peripheral arterial disease or cardiac diseases. This review provides an overview from our current knowledge regarding molecular and cellular mechanisms involved in postischemic revascularization, as well as advances in the clinical application of such strategies of therapeutic revascularization.

A novel three-dimensional adipose-derived stem cell cluster for vascular regeneration in ischemic tissue

BACKGROUND AIMS

Stem cells are one of the most powerful tools in regeneration medicine. However, many limitations remain regarding the use of adult stem cells in clinical applications, including poor cell survival and low treatment efficiency. We describe an innovative three-dimensional cell mass (3DCM) culture that is based on cell adhesion (basic fibroblast growth factor-immobilized substrate) and assess the therapeutic potential of 3DCMs composed of human adipose tissue-derived stromal cells (hASCs).

METHODS

For formation of a 3DCM, hASCs were cultured on a substrate with immobilized fibroblast growth factor-2. The angiogenic potential of 3DCMs was determined by immunostaining, fluorescence-activated cell sorting and protein analysis. To evaluate the vasculature ability and improved treatment efficacy of 3DCMs, the 3DCMs were intramuscularly injected into the ischemic limbs of mice.

RESULTS

The 3DCMs released various angiogenic factors (eg, vascular endothelial growth factor and interleukin-8) and differentiated into vascular cells within 3 days in normal medium. Blood vessel and tissue regeneration was clearly observed through visual inspection in the 3DCM-injected group. hASC injection slowed limb necrosis after treatment, but 50% of the mice ultimately had limb loss within 28 days. Most mice receiving 3DCMs had limb salvage (89%) or mild limb necrosis (11%).

CONCLUSIONS

3DCM culture promotes the efficient vascular differentiation of stem cells, and 3DCM transplantation results in the direct vascular regeneration of the injected cells and an improved therapeutic efficacy.

Identical effects of VEGF and serum-deprivation on phenotype and function of adipose-derived stromal cells from healthy donors and patients with ischemic heart disease

BACKGROUND

Adipose-derived stromal cells (ASCs) stimulated with vascular endothelial growth factor (VEGF) and serum-deprived, are applied in the first in-man double-blind placebo-controlled MyStromalCell Trial, as a novel therapeutic option for treatment of ischemic heart disease (IHD). This in vitro study explored the effect of VEGF and serum deprivation on endothelial differentiation capacity of ASCs from healthy donors and IHD patients.

METHODS

ASCs stimulated with rhVEGF(A165) in serum-deprived medium for one to three weeks were compared with ASCs in serum-deprived (2% fetal bovine serum) or complete medium (10% fetal bovine serum). Expression of VEGF receptors, endothelial and stem cell markers was measured using qPCR, flow cytometry and immunocytochemistry. In vitro tube formation and proliferation was also measured.

RESULTS

ASCs from VEGF-stimulated and serum-deprived medium significantly increased transcription of transcription factor FOXF1, endothelial marker vWF and receptor VEGFR1 compared with ASCs from complete medium. ASCs maintained stem cell characteristics in all conditions. Tube formation of ASCs occurred in VEGF-stimulated and serum-deprived medium. The only difference between healthy and patient ASCs was a variation in proliferation rate.

CONCLUSIONS

ASCs from IHD patients and healthy donors proved equally inclined to differentiate in endothelial direction by serum-deprivation, however with no visible additive effect of VEGF stimulation. The treatment did not result in complete endothelial differentiation, but priming towards endothelial lineage.

[Interests and potentials of adipose tissue in scleroderma]

Systemic sclerosis is a disorder involving the connective tissue, arterioles and microvessels. It is characterized by skin and visceral fibrosis and ischemic phenomena. Currently, therapy is limited and no antifibrotic treatment has proven its efficacy. Beyond some severe organ lesions (pulmonary arterial hypertension, pulmonary fibrosis, scleroderma renal crisis), which only concern a minority of patients, the skin sclerosis of hands and face and the vasculopathy lead to physical and psychological disability in most patients. Thus, functional improvement of hand motion and face represents a priority for patient therapy. Due to its easy obtention by fat lipopaspirate and adipocytes survival, re injection of adipose tissue is a common therapy used in plastic surgery for its voluming effect. Identification and characterization of the adipose tissue-derived stroma vascular fraction, mainly including mesenchymal stem cells, have revolutionized the science showing that adipose tissue is a valuable source of multipotent stem cells, able to migrate to site of injury and to differentiate according to the receiver tissue's needs. Due to easy harvest by liposuction, its abundance in mesenchymal cells far higher that the bone marrow, and stroma vascular fraction's ability to differentiate and secrete growth angiogenic and antiapoptotic factors, the use of adipose tissue is becoming more attractive in regenerative medicine. We here present the interest of adipose tissue use in the treatment of the hands and face in scleroderma.

Stem cells of the lower limb: Their role and potential in management of critical limb ischemia

Peripheral arterial occlusive disease (PAOD) contributes to decreased exercise tolerance, poor balance, impaired proprioception, muscle atrophy and weakness, with advanced cases resulting in critical limb ischemia (CLI) where the viability of the limb is threatened. Patients with a diagnosis of CLI have a poor life expectancy due to concomitant cardio and cerebrovascular diseases. The current treatment options to avoid major amputation by re-establishing a blood supply to the limb generally have poor outcomes. Human skeletal muscle contains both multipotent stem cells and progenitor cells and thus has a capacity for regeneration. Phase I and II studies involving transplantation of bone marrow-derived progenitor cells into CLI limbs show positive effects on wound healing and angiogenesis; the increase in quiescent satellite cell numbers observed in CLI muscle may also provide a sufficient in vivo source of resident stem cells. These indigenous cells have been shown to be capable of forming multiple mesodermal cell lineages aiding the repair and regeneration of chronically ischemic muscle. They may also serve as a repository for autologous transplantation. The behavior and responses of the stem cell population in CLI is poorly understood and this review tries to elucidate the potential of these cells and their future role in the management of CLI.

Modulation of physical environment makes placental mesenchymal stromal cells suitable for therapy

Low level of oxygen at the site of injury is likely to affect the viability and proliferation of the transplanted mesenchymal stromal cells (MSCs). Hence there is a need to understand the effect of the physical environment on transplanted stromal cells. Therefore, we have studied the effect of the duration of hypoxic exposure alone or in combination with normoxia on placenta derived mesenchymal stem cell (PDMSCs). PDMSCs and bone marrow MSCs (BMMSCs) were analysed under four different culture conditions, exposure to direct normoxia (N), direct hypoxia (H) and intermittent normoxia followed by hypoxia (NH) and intermittent hypoxia followed by normoxia (HN). The effect on morphology, proliferation, metabolic activity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) and viability by 7AAD (7-amino-actinomycin D) were assayed, along with markers for MSCs and HLADR. No change in morphology, marker expression or HLADR was detected in N, H, NH or HN. An increase in proliferation rate, decrease in population doubling-time (PDT) and a relative increase in metabolic activity was strongly noted in the order: NH, N/HN and H. No significant difference was observed in the viability between N, H, NH or HN. A similar pattern was also observed in BMMSCS, indicating comparable suitability of PDMSCs in therapeutic applications. Thus we conclude that intermittent exposure to normoxia prior to hypoxic exposure is a better option than direct exposure to hypoxia. This may have clinical relevance in that they probably mirror the in vivo scenario of systemic delivery (NH) of cells as opposed to local delivery (H), thereby suggesting that systemic delivery is better than local delivery.

Thymus fat as an attractive source of angiogenic factors in elderly subjects with myocardial ischemia

Aging negatively affects angiogenesis which is found to be linked to declined vascular endothelial growth factor (VEGF) production. Adult human thymus degenerates into fat tissue (thymus adipose tissue (TAT)). Recently, we described that TAT from cardiomyopathy ischemic subjects has angiogenic properties. The goal of our study was to analyze whether aging could also impair angiogenic properties in TAT as in other adipose tissue such as subcutaneous (subcutaneous adipose tissue (SAT)). SAT and TAT specimens were obtained from 35 patients undergoing cardiac surgery, making these tissues readily available as a prime source of adipose tissue. Patients were separated into two age-dependent groups; middle-aged (n = 18) and elderly (n = 17). Angiogenic, endothelial, and adipogenic expression markers were analyzed in both tissues from each group and correlations were examined between these parameters and also with age. There were no significant differences in subjects from either group in clinical or biological variables. Angiogenic markers VEGF-A, B, C, and D and adipogenic parameters, peroxisome proliferator-activated receptors (PPARγ2), FABP4, and ADRP showed elevated expression levels in TAT from elderly patients compared to the middle-aged group, while in SAT, expression levels of these isoforms were significantly decreased in elderly patients. VEGF-R1, VEGF-R2, VEGF-R3, Thy1, CD31, CD29, and VLA1 showed increased levels in TAT from the elderly compared to the middle-aged, while in SAT these levels displayed a decline with aging. Also, in TAT, angiogenic and endothelial parameters exhibited strong positive correlations with age. TAT appears to be the most appropriate source of angiogenic and endothelial factors in elderly cardiomyopathy subjects compared to SAT.

A comparison of the reparative and angiogenic properties of mesenchymal stem cells derived from the bone marrow of BALB/c and C57/BL6 mice in a model of limb ischemia

Introduction

BALB/c mice and C57/BL6 mice have different abilities to recover from ischemia. C57/BL6 mice display increased vessel collateralization and vascular endothelial growth factor expression with a consequent rapid recovery from ischemia compared with BALB/c mice. Mesenchymal stem cells (MSCs) are one of the main cell types that contribute to the recovery from ischemia because, among their biological activities, they produce several proangiogenic paracrine factors and differentiate into endothelial cells. The objective of this study was to evaluate whether the MSCs of these two mouse strains have different inductive capacities for recovering ischemic limbs.

Methods

MSCs from these two strains were obtained from the bone marrow, purified and characterized before being used for in vivo experiments. Limb ischemia was surgically induced in BALB/c mice, and MSCs were injected on the fifth day. The evolution of limb necrosis was evaluated over the subsequent month. Muscle strength was assessed on the 30th day after the injection, and then the animals were sacrificed to determine the muscle mass and perform histological analyses to detect cellular infiltration, capillary and microvessel densities, fibrosis, necrosis and tissue regeneration.

Results

The MSCs from both strains promoted high level of angiogenesis similarly, resulting in good recovery from ischemia. However, BALB/c MSCs promoted more muscle regeneration (57%) than C57/BL6 MSCs (44%), which was reflected in the increased muscle strength (0.79 N versus 0.45 N).

Conclusion

The different genetic background of MSCs from BALB/c mice and C57/BL6 mice was not a relevant factor in promoting angiogenesis of limb ischemia, because both cells showed a similar angiogenic activity. These cells also showed a potential myogenic effect, but the stronger effect promoted by BALB/c MSCs indicates that the different genetic background of MSCs was more relevant in myogenesis than angiogesis.

Mutual effect of subcutaneously transplanted human adipose-derived stem cells and pancreatic islets within fibrin gel

While subcutaneous tissue has been proposed as a potential site for pancreatic islet transplantation, concern remains that the microvasculature of subcutaneous tissue is too poor to support transplanted islets. In an effort to overcome this limitation, we evaluated whether fibrin gel with human adipose-derived stem cells (hADSCs) and rat pancreatic islets could cure diabetes mellitus when transplanted into the subcutaneous space of diabetic mice. Subcutaneously co-transplanted islets and hADSCs showed normalization of the diabetic recipient's blood glucose levels. The result was enhanced by co-treatment of fibroblast growth factor-2 (FGF2) in the fibrin gel. The hADSCs enhanced islet viability after transplantation by secreting various growth factors that can protect islets from hypoxic damage. Afterward, hADSCs could maintain islet viability by recruiting new microvasculature nearby the transplanted islets via overexpression of vascular endothelial growth factor (VEGF). The hADSCs did not directly differentiate into endothelial cells (no detection of biomarkers of human endothelial cells), but showed evidence of differentiation toward insulin-secreting cells (detection of human insulin). Mice receiving islet transplantation alone did not become normoglycemic. Collectively, co-transplantation of fibrin gel with islets and hADSCs will expand the indications for islet transplant therapy and the potential clinical application of cell-based therapy.

Enhanced wound vascularization using a dsASCs seeded FPEG scaffold

The bioengineering of autologous vascular networks is of great importance in wound healing. Adipose-derived stem cells (ASCs) are of interest due to their ability to differentiate toward various cell types, including vascular. We hypothesized that adult human ASCs embedded in a three-dimensional PEG-fibrin (FPEG) gel have the ability to modulate vascularization of a healing wound. Initial in vitro characterization of ASCs isolated from discarded burn skin samples (dsASCs) and embedded in FPEG gels indicated they could express such pericyte/smooth muscle cell markers as α-smooth muscle actin, platelet-derived growth factor receptor-β, NG2 proteoglycan, and angiopoietin-1, suggesting that these cells could potentially be involved in a supportive cell role (i.e., pericyte/mural cell) for blood vessels. Using a rat skin excision model, wounds treated with dsASCs-FPEG gels showed earlier collagen deposition and wound remodeling compared to vehicle FPEG treated wounds. Furthermore, the dsASCs-seeded gels increased the number of vessels in the wound per square millimeter by day 16 (~66.7 vs. ~36.9/mm(2)) in these same studies. dsASCs may support this increase in vascularization through their trophic contribution of vascular endothelial growth factor, as determined by in vitro analysis of mRNA and the protein levels. Immunohistochemistry showed that dsASCs were localized to the surrounding regions of large blood-perfused vessels. Human dsASCs may play a supportive role in the formation of vascular structures in the healing wound through direct mechanisms as well as indirect trophic effects. The merging of autologous grafts or bioengineered composites with the host's vasculature is critical, and the use of autologous dsASCs in these procedures may prove to be therapeutic.

Notch signalling inhibits the adipogenic differentiation of single-cell-derived mesenchymal stem cell clones isolated from human adipose tissue

ADSCs (adipose-derived mesenchymal stem cells) are candidate adult stem cells for regenerative medicine. Notch signalling participates in the differentiation of a heterogeneous ADSC population. We have isolated, human adipose tissue-derived single-cell clones using a cloning ring technique and characterized for their stem cell characteristics. The role of Notch signalling in the differentiation capacity of these adipose-derived single-cell-clones has also been investigated. All 14 clones expressed embryonic and mesenchymal stem cell marker genes. These clones could differentiate into both osteogenic and adipogenic lineages. However, the differentiation potential of each clone was different. Low adipogenic clones had significantly higher mRNA expression levels of Notch 2, 3 and 4, Jagged1, as well as Delta1, compared with those of high adipogenic clones. In contrast, no changes in expression of Notch signalling component mRNA between low and high osteogenic clones was found. Notch receptor mRNA expression decreased with the adipogenic differentiation of both low and high adipogenic clones. The γ-secretase inhibitor, DAPT (N-[N-(3,5-difluorophenacetyl)-l-alanyl]-(S)-phenylglycine t-butyl ester), enhanced adipogenic differentiation. Correspondingly, cells seeded on a Notch ligand (Jagged1) bound surface showed lower intracellular lipid accumulation. These results were noted in both low and high adipogenic clones, indicating that Notch signalling inhibited the adipogenic differentiation of adipose ADSC clones, and could be used to identify an adipogenic susceptible subpopulation for soft-tissue augmentation application.

Adipose tissue dysfunction contributes to obesity related metabolic diseases

Obesity significantly increases the risk of developing type 2 diabetes, hypertension, coronary heart disease, stroke, fatty liver disease, dementia, obstructive sleep apnea and several types of cancer. Adipocyte and adipose tissue dysfunction represent primary defects in obesity and may link obesity to metabolic and cardiovascular diseases. Adipose tissue (AT) dysfunction manifests by a proinflammatory adipokine secretion pattern that mediate auto/paracrine and endocrine communication and by inflammatory cell infiltration, particularly in intra-abdominal fat. Impaired AT function is caused by the interaction of genetic, behavioral and environmental factors which lead to adipocyte hypertrophy, ectopic fat accumulation, hypoxia, AT stresses, impaired AT mitochondrial function and inflammatory processes within adipose tissue. Recently, increased autophagy has been linked to obesity and AT dysfunction and may represent a mechanism to compensate for AT stresses. A better understanding of mechanisms causing or maintaining AT dysfunction may provide new therapeutic strategies in the treatment of obesity-induced metabolic diseases.

Adipose-derived mesenchymal stem cells and regenerative medicine

Adipose tissue-derived mesenchymal stem cells (ADSCs) are multipotent and can differentiate into various cell types, including osteocytes, adipocytes, neural cells, vascular endothelial cells, cardiomyocytes, pancreatic β-cells, and hepatocytes. Compared with the extraction of other stem cells such as bone marrow-derived mesenchymal stem cells (BMSCs), that of ADSCs requires minimally invasive techniques. In the field of regenerative medicine, the use of autologous cells is preferable to embryonic stem cells or induced pluripotent stem cells. Therefore, ADSCs are a useful resource for drug screening and regenerative medicine. Here we present the methods and mechanisms underlying the induction of multilineage cells from ADSCs.

Adipose-Derived Stem Cells in Tissue Regeneration: A Review

In 2001, researchers at the University of California, Los Angeles, described the isolation of a new population of adult stem cells from liposuctioned adipose tissue. These stem cells, now known as adipose-derived stem cells or ADSCs, have gone on to become one of the most popular adult stem cells populations in the fields of stem cell research and regenerative medicine. As of today, thousands of research and clinical articles have been published using ASCs, describing their possible pluripotency in vitro, their uses in regenerative animal models, and their application to the clinic. This paper outlines the progress made in the ASC field since their initial description in 2001, describing their mesodermal, ectodermal, and endodermal potentials both in vitro and in vivo, their use in mediating inflammation and vascularization during tissue regeneration, and their potential for reprogramming into induced pluripotent cells.

Adipose stem cell tissue-engineered construct used to treat large anterior mandibular defect: a case report and review of the clinical application of good manufacturing practice-level adipose stem cells for bone regeneration

PURPOSE

Large mandibular resection defects historically have been treated using autogenous bone grafts and reconstruction plates. However, a major drawback of large autogenous bone grafts is donor-site morbidity.

PATIENTS AND METHODS

This report describes the replacement of a 10-cm anterior mandibular ameloblastoma resection defect, reproducing the original anatomy of the chin, using a tissue-engineered construct consisting of β-tricalcium phosphate (β-TCP) granules, recombinant human bone morphogenetic protein-2 (BMP-2), and Good Manufacturing Practice-level autologous adipose stem cells (ASCs). Unlike prior reports, 1-step in situ bone formation was used without the need for an ectopic bone-formation step. The reconstructed defect was rehabilitated with a dental implant-supported overdenture. An additive manufactured medical skull model was used preoperatively to guide the prebending of patient-specific hardware, including a reconstruction plate and titanium mesh. A subcutaneous adipose tissue sample was harvested from the anterior abdominal wall of the patient before resection and simultaneous reconstruction of the parasymphysis. ASCs were isolated and expanded ex vivo over the next 3 weeks. The cell surface marker expression profile of ASCs was similar to previously reported results and ASCs were analyzed for osteogenic differentiation potential in vitro. The expanded cells were seeded onto a scaffold consisting of β-TCP and BMP-2 and the cell viability was evaluated. The construct was implanted into the parasymphyseal defect.

RESULTS

Ten months after reconstruction, dental implants were inserted into the grafted site, allowing harvesting of bone cores. Histologic examination and in vitro analysis of cell viability and cell surface markers were performed and prosthodontic rehabilitation was completed.

CONCLUSION

ASCs in combination with β-TCP and BMP-2 offer a promising construct for the treatment of large, challenging mandibular defects without the need for ectopic bone formation and allowing rehabilitation with dental implants.

VEGF microsphere technology to enhance vascularization in fat grafting

Vascularization is crucial for implantation of engineered tissues in reconstructive surgery. Polypeptides encapsulated in microspheres can be efficiently transported to their site of action and released in a sustained dosage. We evaluated the effect of delivering vascular endothelial growth factor (VEGF)-encapsulated microspheres in a lipoaspirate scaffold on vascularization and tissue survival. The VEGF-loaded (n=6) and empty (n=6) poly(lactic-co-glycolic acid) microspheres in human lipoaspirate and the human lipoaspirate alone (n=6) were injected subcutaneously into the flanks of athymic nude mice. Three mice from each group were killed, and grafts were explanted at weeks 3 and 6. Increases in mass and volume of VEGF samples, as well as decreases in empty and lipoaspirate-only samples, were observed at 3 and 6 weeks, reaching statistical significance at 6 weeks. Hematoxylin and eosin and CD31+ imaging demonstrated significantly greater vascularization in VEGF samples than in both the empty and lipoaspirate-only groups at both 3 and 6 weeks.

Adipose-derived stem cells on the healing of ischemic colitis: a therapeutic effect by angiogenesis

BACKGROUND

There has been no specific treatment for ischemic colitis. We verified the effects of adipose-derived stem cells (ASCs) on ischemia-induced colitis in a rat model.

METHODS

Forty male Sprague-Dawley rats (10 weeks old; weight, 350 ± 20 g) were divided into two groups: a control group (only fibrinogen and thrombin injected, n = 20) and an ASC group (local implantation of ASCs mixed with thrombin and fibrinogen, n = 20). An ischemic colitis model was established by modifying Nagahata's methods with double-blind randomization. ASCs (1 × 10(6) cells) were implanted intramurally into the ischemic area using a fibrin glue mixture. The severity of adhesion, degree of ileus, the number and size of the ulcers, Wallace macroscopic and microscopic scores, and microvascular density were measured.

RESULTS

The degree of ileus was significantly lower, and significantly fewer and smaller ulcerations were found in the ASC group than those in the control group. Wallace macroscopic and microscopic scores were lower in the ASC group than in the control group (1.90 ± 1.22 versus 3.25 ± 1.83, p < 0.01 and 1.55 ± 1.88 versus 2.84 ± 1.89, p < 0.05, respectively). Microvascular density was higher in the ASC group than in the control (54.45 ± 19.45 versus 26.54 ± 13.14, p < 0.01, respectively).

CONCLUSIONS

Local implantation of ASCs into an ischemic-injured colonic wall reduced the grade of ischemic injury and enhanced tissue healing by promoting angiogenesis.

Paracrine release from nonviral engineered adipose-derived stem cells promotes endothelial cell survival and migration in vitro

Stem cells hold great potential for therapeutic angiogenesis due to their ability to directly contribute to new vessel formation or secrete paracrine signals. Adipose-derived stem cells (ADSCs) are a particularly attractive autologous cell source for therapeutic angiogenesis due to their ease of isolation and relative abundance. Gene therapy may be used to further enhance the therapeutic efficacy of ADSCs by overexpressing desired therapeutic factors. Here, we developed vascular endothelial growth factor (VEGF)-overexpressing ADSCs utilizing poly(β-amino esters) (PBAEs), a hydrolytically biodegradable polymer, and examined the effects of paracrine release from nonviral modified ADSCs on the angiogenic potential of human umbilical vein endothelial cells (HUVECs) in vitro. PBAE polymeric vectors delivered DNA into ADSCs with high efficiency and low cytotoxicity, leading to an over 3-fold increase in VEGF production by ADSCs compared with Lipofectamine 2000. Paracrine release from PBAE/VEGF-transfected ADSCs enhanced HUVEC viability and decreased HUVEC apoptosis under hypoxia. Further, paracrine release from PBAE/VEGF-transfected ADSCs significantly enhanced HUVEC migration and tube formation, two critical cellular processes for effective angiogenesis. Our results demonstrate that genetically engineered ADSCs using biodegradable polymeric nanoparticles may provide a promising autologous cell source for therapeutic angiogenesis in treating cardiovascular diseases.