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

A Recombinant Peptide Device Combined with Adipose Tissue-Derived Stem Cells Enhances Subcutaneous Islet Engraftment

Subcutaneous space has been considered an attractive site for islet graft transplantation; however, the oxygen tension and vascularization are insufficient for islet graft survival. We investigated whether subcutaneous pre-implantation of a recombinant peptide (RCP) device with adipose tissue-derived stem cells (ADSCs) enhanced subcutaneous islet engraftment. RCP devices with/without syngeneic ADSCs were pre-implanted into the subcutaneous space of C57BL/6 mice. Syngeneic islets (300 or 120 islet equivalents (IEQs)) were transplanted into the pre-treated space after diabetes induction using streptozotocin. The cure rates of groups in which RCP devices were implanted four weeks before transplantation were significantly better than the intraportal transplantation group when 300 IEQs of islets were transplanted (p < 0.01). The blood glucose changes in the RCP+ADSCs-4w group was significantly ameliorated in comparison to the RCP-4w group when 120 IEQs of islets were transplanted (p < 0.01). Immunohistochemical analyses showed the collagen III expression in the islet capsule of the RCP+ADSCs-4w group was significantly enhanced in comparison to the RCP-4w and RCP+ADSCs-d10 groups (p < 0.01, p < 0.01). In addition, the number of von Willebrand factor-positive vessels within islets in the RCP+ADSCs-4w group was significantly higher than the RCP-4w group. These results suggest that using ADSCs in combination with an RCP device could enhance the restoration of the extracellular matrices, induce more efficient prevascularization within islets, and improve the graft function.

Bioengineering Cell Therapy for Treatment of Peripheral Artery Disease

Peripheral artery disease is an atherosclerotic disease associated with limb ischemia that necessitates limb amputation in severe cases. Cell therapies comprised of adult mononuclear or stromal cells have been clinically tested and show moderate benefits. Bioengineering strategies can be applied to modify cell behavior and function in a controllable fashion. Using mechanically tunable or spatially controllable biomaterials, we highlight examples in which biomaterials can increase the survival and function of the transplanted cells to improve their revascularization efficacy in preclinical models. Biomaterials can be used in conjunction with soluble factors or genetic approaches to further modulate the behavior of transplanted cells and the locally implanted tissue environment in vivo. We critically assess the advances in bioengineering strategies such as 3-dimensional bioprinting and immunomodulatory biomaterials that can be applied to the treatment of peripheral artery disease and then discuss the current challenges and future directions in the implementation of bioengineering strategies.

The comparison of adipose-derived stromal cells (ADSCs) delivery method in a murine model of hindlimb ischemia

BACKGROUND

Adipose-derived stromal cells (ADSCs) demonstrate ability to promote tissue healing and down-regulate excessive inflammation. ADSCs have been used to treat critical limb ischemia in preclinical and clinical trials, but still, there is little known about their optimal delivery strategy. To date, no direct analysis of different methods of ADSCs delivery has been performed in the hindlimb ischemia model. Therefore, in this study we focused on the therapeutic efficacy of different ADSCs delivery methods in a murine model of hindlimb ischemia.

METHODS

For the hADSCs isolation, we used the subcutaneous adipose tissue collected during the surgery. The murine hindlimb ischemia was used as a model. The unilateral femoral artery ligation was performed on 10-12-week-old male C57BL/6. ADSCs were delivered directly into ischemic muscle, into the contralateral muscle or intravenously. 7 and 14 days after the surgery, the gastrocnemius and quadriceps muscles were collected for the immunohistochemical analysis. The results were analyzed with relevant tests using the Statistica software.

RESULTS

Our research revealed that muscle regeneration, angiogenesis, arteriogenesis and macrophage infiltration in murine model of hindlimb ischemia differ depending on ADSCs delivery method. We have demonstrated that intramuscular method (directly into ischemic limb) of ADSCs delivery is more efficient in functional recovery after critical limb ischemia than intravenous or contralateral route.

CONCLUSIONS

We have noticed that injection of ADSCs directly into ischemic limb is the optimal delivery strategy because it increases: (1) muscle fiber regeneration, (2) the number of capillaries and (3) the influx of macrophages F4/80+/CD206+.

A Gelatin Hydrogel Nonwoven Fabric Enhances Subcutaneous Islet Engraftment in Rats

Although subcutaneous islet transplantation has many advantages, the subcutaneous space is poor in vessels and transplant efficiency is still low in animal models, except in mice. Subcutaneous islet transplantation using a two-step approach has been proposed, in which a favorable cavity is first prepared using various materials, followed by islet transplantation into the preformed cavity. We previously reported the efficacy of pretreatment using gelatin hydrogel nonwoven fabric (GHNF), and the length of the pretreatment period influenced the results in a mouse model. We investigated whether the preimplantation of GHNF could improve the subcutaneous islet transplantation outcomes in a rat model. GHNF sheets sandwiching a silicone spacer (GHNF group) and silicone spacers without GHNF sheets (control group) were implanted into the subcutaneous space of recipients three weeks before islet transplantation, and diabetes was induced seven days before islet transplantation. Syngeneic islets were transplanted into the space where the silicone spacer was removed. Blood glucose levels, glucose tolerance, immunohistochemistry, and neovascularization were evaluated. The GHNF group showed significantly better blood glucose changes than the control group (p < 0.01). The cure rate was significantly higher in the GHNF group (p < 0.05). The number of vWF-positive vessels was significantly higher in the GHNF group (p < 0.01), and lectin angiography showed the same tendency (p < 0.05). The expression of laminin and collagen III around the transplanted islets was also higher in the GHNF group (p < 0.01). GHNF pretreatment was effective in a rat model, and the main mechanisms might be neovascularization and compensation of the extracellular matrices.

Effect of high cyclic hydrostatic pressure on osteogenesis of mesenchymal stem cells cultured in liquefied micro-compartments

Bone resident cells are constantly subjected to a range of distinct mechanical loadings, which generates a complex microenvironment. In particular, hydrostatic pressure (HP) has a key impact on modulation of cell function and fate determination. Although HP is a constant mechanical stimulus, its role in regulating the osteogenesis process within a defined 3D microenvironment has not been comprehensively elucidated. Perceiving how environmental factors regulate the differentiation of stem cells is essential for expanding their regenerative potential. Inspired by the mechanical environment of bone, this study attempted to investigate the influence of different ranges of cyclic HP on human adipose-derived mesenchymal stem cells (MSCs) encapsulated within a compartmentalized liquefied microenvironment. Taking advantage of the liquefied environment of microcapsules, MSCs were exposed to cyclic HP of 5 or 50 MPa, 3 times/week at 37 °C. Biological tests using fluorescence staining of F-actin filaments showed a noticeable improvement in cell-cell interactions and cellular network formation of MSCs. These observations were more pronounced in osteogenic (OST) condition, as confirmed by fluorescent staining of vinculin. More interestingly, there was a significant increase in alkaline phosphatase activity of MSCs exposed to 50 MPa magnitude of HP, even in the absence of osteoinductive factors. In addition, a greater staining area of both osteopontin and hydroxyapatite was detected in the 50 MPa/OST group. These findings highlight the benefit of hydrostatic pressure to regulate osteogenesis of MSCs as well as the importance of employing simultaneous biochemical and mechanical stimulation to accelerate the osteogenic potential of MSCs for biomedical purposes.

Innovations in Stem Cell Therapy for Diabetic Wound Healing

Significance: The global burden of diabetic wounds, particularly diabetic foot ulcers, continues to have large economic and social impact throughout the world. Current strategies are not sufficient to overcome this burden of disease. Finding newer, more advanced regenerative cell and tissue-based strategies to reduce morbidity remains paramount. Recent Advances: Recent advances in stem cell therapies are discussed. We also highlight the practical issues of translating these advancing technologies into the clinical setting. Critical Issues: We discuss the use of somatic and induced pluripotent stem cells and the stromal vascular fraction, as well as innovations, including the use of 3D bioprinting of skin. We also explore related issues of using regenerative techniques in clinical practice, including the current regulatory landscape and translatability of in vivo research. Future Directions: Advances in stem cell manipulation showcase the best therapeutic resources available to enhance mechanisms of wound healing such as angiogenesis, cell proliferation, and collagen synthesis; potential methods include changing the scaffold microenvironment, including relative oxygen tension, and the use of gene modification and nanotechnology. Secretome engineering, particularly the use of extracellular vesicles, may be another potential cell-derived therapeutic that may enable use of cell-free translational therapy.

In Vivo Photoacoustic Monitoring of Stem Cell Location and Apoptosis with Caspase-3-Responsive Nanosensors

Stem cell therapy has immense potential in a variety of regenerative medicine applications. However, clinical stem cell therapy is severely limited by challenges in assessing the location and functional status of implanted cells in vivo. Thus, there is a great need for longitudinal, noninvasive stem cell monitoring. Here we introduce a multidisciplinary approach combining nanosensor-augmented stem cell labeling with ultrasound guided photoacoustic (US/PA) imaging for the spatial tracking and functional assessment of transplanted stem cell fate. Specifically, our nanosensor incorporates a peptide sequence that is selectively cleaved by caspase-3, the primary effector enzyme in mammalian cell apoptosis; this cleavage event causes labeled cells to show enhanced optical absorption in the first near-infrared (NIR) window. Optimization of labeling protocols and spectral characterization of the nanosensor in vitro showed a 2.4-fold increase in PA signal from labeled cells during apoptosis while simultaneously permitting cell localization. We then successfully tracked the location and apoptotic status of mesenchymal stem cells in a mouse hindlimb ischemia model for 2 weeks in vivo, demonstrating a 4.8-fold increase in PA signal and spectral slope changes in the first NIR window under proapoptotic (ischemic) conditions. We conclude that our nanosensor allows longitudinal, noninvasive, and nonionizing monitoring of stem cell location and apoptosis, which is a significant improvement over current end-point monitoring methods such as biopsies and histological staining of excised tissue.

Development of Hetero-Cell Type Spheroids Via Core-Shell Strategy for Enhanced Wound Healing Effect of Human Adipose-Derived Stem Cells

BACKGROUND

Stem cell-based therapies have been developed to treat various types of wounds. Human adipose-derived stem cells (hADSCs) are used to treat skin wounds owing to their outstanding angiogenic potential. Although recent studies have suggested that stem cell spheroids may help wound healing, their cell viability and retention rate in the wound area require improvement to enhance their therapeutic efficacy.

METHODS

We developed a core-shell structured spheroid with hADSCs in the core and human dermal fibroblasts (hDFs) in the outer part of the spheroid. The core-shell structure was formed by continuous centrifugation and spheroid incubation. After optimizing the method for inducing uniform-sized core-shell spheroids, cell viability, cell proliferation, migration, and therapeutic efficacy were evaluated and compared to those of conventional spheroids.

RESULTS

Cell proliferation, migration, and involucrin expression were evaluated in keratinocytes. Tubular assays in human umbilical vein endothelial cells were used to confirm the improved skin regeneration and angiogenic efficacy of core-shell spheroids. Core-shell spheroids exhibited exceptional cell viability under hypoxic cell culture conditions that mimicked the microenvironment of the wound area.

CONCLUSION

The improvement in retention rate, survival rate, and angiogenic growth factors secretion from core-shell spheroids may contribute to the increased therapeutic efficacy of stem cell treatment for skin wounds.

Novel Approaches Used in Ovarian Tissue Transplantation for Fertility Preservation: Focus on Tissue Engineering Approaches and Angiogenesis Capacity

Due to the impact of the modern lifestyle, female infertility has been reduced because of different reasons. For example, in combined chemotherapeutic therapies, a small fraction of cancer survivors has faced different post-complications and side effects such as infertility. Besides, in modern society, delayed age of childbearing has also affected fertility. Nowadays, ovarian tissue cryopreservation and transplantation (OTC/T) is considered one of the appropriate strategies for the restoration of ovarian tissue and bioactivity in patients with the loss of reproductive function. In this regard, several procedures have been considered to improve the efficacy and safety of OTT. Among them, a surgical approach is used to transplant ovaries into the optimal sites, but the existence of ischemic changes and lack of appropriate revascularization can lead to bulk follicular atresia. Besides, the role of OTC/T is limited in women of advanced maternal age undergoing lifesaving chemo-radiation. As a correlate, the development of de novo approaches with efficacious regenerative outcomes is highly welcomed. Tissue engineering shows high therapeutic potentialities to restore fertility in males and females using the combination of biomaterials, cells, and growth factors. Unfortunately, most synthetic and natural materials are at the experimental stage and only the efficacy has been properly evaluated in limited cases. Along with these descriptions, strategies associated with the induction of angiogenesis in transplanted ovaries can diminish the injuries associated with ischemic changes. In this review, the authors tried to summarize recent techniques, especially tissue engineering approaches for improving ovarian function and fertility by focusing on angiogenesis and neovascularization.

Development and Validation of a Multiparametric Semiquantitative Scoring System for the Histopathological Assessment of Ischaemia Severity in Skeletal Muscle

Skeletal muscle is one of the most abundant and dynamic tissues of the body, with a strong regenerative capacity. Muscle injuries can occur as a result of a variety of events, including tissue ischaemia. Lower limb ischaemia occurs when there is an insufficient nutrient and oxygen supply, often caused by stenosis of the arteries due to atherosclerosis. The aim of this study was to develop and validate a multiparametric scoring tool for assessing ischaemia severity in skeletal muscle in a commonly used preclinical animal model. Tissue ischaemia was surgically induced in mice by ligation and excision of the femoral artery. Calf muscles were carefully dissected, prepared for histological analysis, and scored for inflammation, fibrosis, necrosis, adipocyte infiltration, and muscle fibre degeneration/regeneration. Kendall’s coefficient of concordance (W) showed a very good agreement between the appraisers when scoring each individual histological feature: inflammation (W = 0.92, $p\le 0.001$ ), fibrosis (W = 0.94, $p\le 0.001$ ), necrosis (W = 0.77, $p\le 0.001$ ), adipocyte infiltration (W = 0.91, $p\le 0.001$ ), and fibre degeneration/regeneration (W = 0.86, $p\le 0.001$ ). Intrarater agreement was also excellent (W = 0.94 or more, $p\le 0.001$ ). There was a statistically significant negative association between the level of muscle ischaemia damage and the calf muscle weight and skeletal muscle fibre diameter. Here, we have developed and validated a new multiparametric, semiquantitative scoring system for assessing skeletal muscle damage due to ischaemia, with excellent inter- and intrarater reproducibility. This scoring system can be used for assessing treatment efficacy in preclinical models of hind limb ischaemia.

Chorioallantoic Membrane Assay at the Cross-Roads of Adipose-Tissue-Derived Stem Cell Research

With a history of more than 100 years of different applications in various scientific fields, the chicken chorioallantoic membrane (CAM) assay has proven itself to be an exceptional scientific model that meets the requirements of the replacement, reduction, and refinement principle (3R principle). As one of three extraembryonic avian membranes, the CAM is responsible for fetal respiration, metabolism, and protection. The model provides a unique constellation of immunological, vascular, and extracellular properties while being affordable and reliable at the same time. It can be utilized for research purposes in cancer biology, angiogenesis, virology, and toxicology and has recently been used for biochemistry, pharmaceutical research, and stem cell biology. Stem cells and, in particular, mesenchymal stem cells derived from adipose tissue (ADSCs) are emerging subjects for novel therapeutic strategies in the fields of tissue regeneration and personalized medicine. Because of their easy accessibility, differentiation profile, immunomodulatory properties, and cytokine repertoire, ADSCs have already been established for different preclinical applications in the files mentioned above. In this review, we aim to highlight and identify some of the cross-sections for the potential utilization of the CAM model for ADSC studies with a focus on wound healing and tissue engineering, as well as oncological research, e.g., sarcomas. Hereby, the focus lies on the combination of existing evidence and experience of such intersections with a potential utilization of the CAM model for further research on ADSCs.

A pilot study to demonstrate the paracrine effect of equine, adult allogenic mesenchymal stem cells in vitro, with a potential for healing of experimentally-created, equine thoracic wounds in vivo

Regenerative biological therapies using mesenchymal stem cells (MSCs) are being studied and used extensively in equine veterinary medicine. One of the important properties of MSCs is the cells' reparative effect, which is brought about by paracrine signaling, which results in the release of biologically active molecules, which in turn, can affect cellular migration and proliferation, thus a huge potential in wound healing. The objective of the current study was to demonstrate the in vitro and in vivo potentials of equine allogenic bone marrow-derived MSCs for wound healing. Equine bone marrow-derived MSCs from one allogenic donor horse were used. Equine MSCs were previously characterized for their in vitro proliferation, expression of cluster-of-differentiation markers, and trilineage differentiation. MSCs were first evaluated for their migration using an in vitro wound healing scratch assay, and subsequently, the conditioned medium was evaluated for their effect on human fibroblast proliferation. Subsequently, allogenic cells were intradermally injected into full-thickness, cutaneous thoracic wounds of 4 horses. Wound healing was assessed by using 3-D digital imaging and by measuring mRNA expression of pro-and anti-inflammatory markers for 30 days. Using human fibroblasts in an in vitro wound healing assay, we demonstrate a significantly higher healing in the presence of conditioned medium collected from proliferating MSCs than in the presence of medium containing fetal bovine serum. The in vitro effect of MSCs did not translate into a detectable effect in vivo. Nonetheless, we proved that molecularly characterized equine allogenic MSCs do not illicit an immunologic response. Investigations using MSCs derived from other sources (adipose tissue, umbilical cord), or a higher number of MSCs or a compromised animal model may be required to prove the efficacy of equine MSCs in wound healing in vivo.

A Comparative Analysis of the Wound Healing-Related Heterogeneity of Adipose-Derived Stem Cells Donors

Adipose-derived Stem cells (ASCs) are on the verge of being available for large clinical trials in wound healing. However, for developing advanced therapy medicinal products (ATMPs), potency assays mimicking the mode of action are required to control the product consistency of the cells. Thus, greater effort should go into the design of product assays. Therefore, we analyzed three ASC-based ATMPs from three different donors with respect to their surface markers, tri-lineage differentiation, proliferation, colony-forming unit capacity, and effect on fibroblast proliferation and migration, endothelial proliferation, migration, and angiogenesis. Furthermore, the transcriptome of all three cell products was analyzed through RNA-sequencing. Even though all products met the criteria by the International Society for Cell and Gene Therapy and the International Federation for Adipose Therapeutics and Science, we found one product to be consistently superior to others when exploring their potency in the wound healing specific assays. Our results indicate that certain regulatory genes associated with extracellular matrix and angiogenesis could be used as markers of a superior ASC donor from which to use ASCs to treat chronic wounds. Having a panel of assays capable of predicting the potency of the product would ensure the patient receives the most potent product for a specific indication, which is paramount for successful patient treatment and acceptance from the healthcare system.

Potency assays for human adipose-derived stem cells as a medicinal product toward wound healing

In pre-clinical studies, human adipose-derived stem cells (hASCs) have shown great promise as a treatment modality for healing of cutaneous wounds. The advantages of hASCs are that they are relatively easy to obtain in large numbers from basic liposuctions, they maintain their characteristics after long-term in vitro culture, and they possess low immunogenicity, which enables the use of hASCs from random donors. It has been hypothesized that hASCs exert their wound healing properties by reducing inflammation, inducing angiogenesis, and promoting fibroblast and keratinocyte growth. Due to the inherent variability associated with the donor-dependent nature of ASC-based products, it appears necessary that the quality of the different products is prospectively certified using a set of most relevant potency assays. In this review, we present an overview of the available methodologies to assess the Mode and the Mechanism of Action of hASCs, specifically in the wound healing scenario. In conclusion, we propose a panel of potential potency assays to include in the future production of ASC-based medicinal products.

Effects of adipose-derived stromal cells and endothelial progenitor cells on adipose transplant survival and angiogenesis

BACKGROUND

A paracrine mechanism is thought to mediate the proangiogenic capacity of adipose-derived stromal/stem cells (ASCs). However, the precise mechanism by which ASCs promote the formation of blood vessels by endothelial progenitor cells (EPCs) is unclear.

METHODS

The EPCs-ASCs cocultures prepared in different ratios were subjected to tube formations assay to verify whether ASCs could directly participate in the tube genesis. The supernatant from cultured ASCs was used to stimulate EPCs to evaluate the effects on the angiogenic property of EPCs, as well as capacity for migration and invasion. A coculture model with transwell chamber were used to explore the regulation of angiogenesis markers expression in EPCs by ASCs. We then mixed ASCs with EPCs and transplanted them with adipose tissue into nude mice to evaluate the effects on angiogenesis in adipose tissue grafts.

RESULTS

In the EPCs-ASCs cocultures, the tube formation was significantly decreased as the relative abundance of ASCs increased, while the ASCs was found to migrate and integrated into the agglomerates formed by EPCs. The supernatant from ASCs cultures promoted the migration and invasion of EPCs and the ability to form capillary-like structures. The expression of multiple angiogenesis markers in EPCs were significantly increased when cocultured with ASCs. In vivo, ASCs combined with EPC promoted vascularization in the fat transplant. Immunofluorescence straining of Edu and CD31 indicated that the Edu labeled EPC did not directly participate in the vascularization inside the fat tissue.

CONCLUSIONS

ADSC can participate in the tube formation of EPC although it cannot form canonical capillary structures. Meanwhile, Soluble factors secreted by ASCs promotes the angiogenic potential of EPCs. ASCs paracrine signaling appears to promote angiogenesis by increasing the migration and invasion of EPCs and simultaneously upregulating the expression of angiogenesis markers in EPCs. The results of in vivo experiments showed that ASCs combined with EPCs significantly promote the formation of blood vessels in the fat implant. Remarkably, EPCs may promote angiogenesis by paracrine regulation of endogenous endothelial cells (ECs) rather than direct participation in the formation of blood vessels.

Area light source-triggered latent angiogenic molecular mechanisms intensify therapeutic efficacy of adult stem cells

Light-based therapy such as photobiomodulation (PBM) reportedly produces beneficial physiological effects in cells and tissues. However, most reports have focused on the immediate and instant effects of light. Considering the physiological effects of natural light exposure in living organisms, the latent reaction period after irradiation should be deliberated. In contrast to previous reports, we examined the latent reaction period after light exposure with optimized irradiating parameters and validated novel therapeutic molecular mechanisms for the first time. we demonstrated an organic light-emitting diode (OLED)-based PBM (OPBM) strategy that enhances the angiogenic efficacy of human adipose-derived stem cells (hADSCs) via direct irradiation with red OLEDs of optimized wavelength, voltage, current, luminance, and duration, and investigated the underlying molecular mechanisms. Our results revealed that the angiogenic paracrine effect, viability, and adhesion of hADSCs were significantly intensified by our OPBM strategy. Following OPBM treatment, significant changes were observed in HIF-1α expression, intracellular reactive oxygen species levels, activation of the receptor tyrosine kinase, and glycolytic pathways in hADSCs. In addition, transplantation of OLED-irradiated hADSCs resulted in significantly enhanced limb salvage ratio in a mouse model of hindlimb ischemia. Our OPBM might serve as a new paradigm for stem cell culture systems to develop cell-based therapies in the future.

Role of Stem Cells in the Ovarian Tissue Cryopreservation and Transplantation for Fertility Preservation

Although the cancer survival rate has increased, cancer treatments, including chemotherapy and radiotherapy, can cause ovarian failure and infertility in women of reproductive age. Preserving fertility throughout cancer treatment is critical for maintaining quality of life. Fertility experts should propose individualized fertility preservation methods based on the patient’s marital status, pubertal status, partner status, and the urgency of treatment. Widely practiced fertility preservation methods, including ovarian transposition and embryo and oocyte cryopreservation, are inappropriate for prepubertal girls or those needing urgent initiation of cancer treatment. Ovarian tissue cryopreservation and transplantation, an emerging new technology, may be a solution for these cancer patients. The use of stem cells in ovarian tissue cryopreservation and transplantation increases oxygenation, angiogenesis, and follicle survival rates. This review discusses the recent advances in ovarian tissue cryopreservation and transplantation with special focus on the use of stem cells to improve fertilization techniques.

Dental Pulp Mesenchymal Stem Cells Attenuate Limb Ischemia via Promoting Capillary Proliferation and Collateral Development in a Preclinical Model

Critical limb ischemia (CLI), an end-stage manifestation of peripheral artery disease (PAD), still lacks effective therapeutic strategies. Recently, dental pulp-derived mesenchymal stem cells (DP-MSCs) have been attracting more and more attentions in therapeutic applications due to their high proliferation ability, powerful osteogenic differentiation potential, and effective anti-inflammatory effects. In this study, we compared the therapeutic effects of MSCs derived from different sources in a femoral artery-ligated preclinical ischemic model. We found that treatments with MSCs, including bone marrow- (BM-), adipose- (AD-), dental pulp- (DP-), and umbilical cord- (UC-) derived MSCs, improved limb functions, reduced inflammatory responses, increased angiogenesis, and promoted regeneration of muscle fiber. Among them, DP-MSCs and BM-MSCs produced much more impressive effects in restoring limb functions and promoting angiogenesis. The flow velocity restored to nearly 20% of the normal level at 3 weeks after treatments with DP-MSCs and BM-MSCs, and obvious capillary proliferation and collateral development could be observed. Although neovascularization was induced in the ischemic limb after ligation, MSCs, especially DP-MSCs, significantly enhanced the angiogenesis. In vitro experiments showed that serum deprivation improved the expression of angiogenic factors, growth factors, and chemokines in DP-MSCs and UC-MSCs, but not in BM-MSCs and AD-MSCs. However, DP-MSCs produced stronger therapeutic responses than UC-MSCs, which might be due to the higher expression of hepatocyte growth factor (HGF) and hypoxia-inducible factor-1 α (HIF-1α). We speculated that DP-MSCs might stimulate angiogenesis and promote tissue repair via expressing and secreting angiogenic factors, growth factors, and chemokines, especially HGF and HIF-1α. In conclusion, DP-MSCs might be a promising approach for treating CLI.

The Use of Mesenchymal Stem Cells and their Derived Extracellular Vesicles in Cardiovascular Disease Treatment

BACKGROUND

Cardiovascular disease (CVD), including disorders of cardiac muscle and vascular, is the major cause of death globally. Many unsuccessful attempts have been made to intervene in the disease's pathogenesis and treatment. Stem cell-based therapies, as a regeneration strategy, cast a new hope for CVD treatment. One of the most well-known stem cells is mesenchymal stem cells (MSCs), classified as one of the adult stem cells and can be obtained from different tissues. These cells have superior properties, such as proliferation and highly specialized differentiation. On the other hand, they have the potential to modulate the immune system and anti-inflammatory activity. One of their most important features is the secreting the extracellular vesicles (EVs) like exosomes (EXOs) as an intercellular communication system mediating the different physiological and pathophysiological affairs.

METHODS

In this review study, the importance of MSC and its secretory exosomes for the treatment of heart disease has been together and specifically addressed and the use of these promising natural and accessible agents is predicted to replace the current treatment modalities even faster than we imagine.

RESULTS

MSC derived EXOs by providing a pro-regenerative condition allowing innate stem cells to repair damaged tissues successfully. As a result, MSCs are considered as the appropriate cellular source in regenerative medicine. In the plethora of experiments, MSCs and MSC-EXOs have been used for the treatment and regeneration of heart diseases and myocardial lesions.

CONCLUSION

Administration of MSCs has been provided a replacement therapeutic option for heart regeneration, obtaining great attention among the basic researcher and the medical doctors.

Ovarian tissue damage after grafting: systematic review of strategies to improve follicle outcomes

Frozen-thawed human ovarian tissue endures large-scale follicle loss in the early post-grafting period, characterized by hypoxia lasting around 7 days. Tissue revascularization occurs progressively through new vessel invasion from the host and neoangiogenesis from the graft. Such reoxygenation kinetics lead to further potential damage caused by oxidative stress. The aim of the present manuscript is to provide a systematic review of proangiogenic growth factors, hormones and various antioxidants administered in the event of ovarian tissue transplantation to protect the follicle pool from depletion by boosting revascularization or decreasing oxidative stress. Although almost all investigated studies revealed an advantage in terms of revascularization and reduction in oxidative stress, far fewer demonstrated a positive impact on follicle survival. As the cascade of events driven by ischaemia after transplantation is a complex process involving numerous players, it appears that acting on specific molecular mechanisms, such as concentrations of proangiogenic growth factors, is not enough to significantly mitigate tissue damage. Strategies exploiting the activated tissue response to ischaemia for tissue healing and remodelling purposes, such as the use of antiapoptotic drugs and adult stem cells, are also discussed in the present review, since they yielded promising results in terms of follicle pool protection.

Modular cell-assembled adipose matrix-derived bead foams as a mesenchymal stromal cell delivery platform for soft tissue regeneration

With the goal of establishing a new clinically-relevant bioscaffold format to enable the delivery of high densities of human adipose-derived stromal cells (ASCs) for applications in soft tissue regeneration, a novel "cell-assembly" method was developed to generate robust 3-D scaffolds comprised of fused networks of decellularized adipose tissue (DAT)-derived beads. In vitro studies confirmed that the assembly process was mediated by remodelling of the extracellular matrix by the seeded ASCs, which were well distributed throughout the scaffolds and remained highly viable after 8 days in culture. The ASC density, sulphated glycosaminoglycan content and scaffold stability were enhanced under culture conditions that included growth factor preconditioning. In vivo testing was performed to compare ASCs delivered within the cell-assembled DAT bead foams to an equivalent number of ASCs delivered on a previously-established pre-assembled DAT bead foam platform in a subcutaneous implant model in athymic nude mice. Scaffolds were fabricated with human ASCs engineered to stably co-express firefly luciferase and tdTomato to enable long-term cell tracking. Longitudinal bioluminescence imaging showed a significantly stronger signal associated with viable human ASCs at timepoints up to 7 days in the cell-assembled scaffolds, although both implant groups were found to retain similar densities of human ASCs at 28 days. Notably, the infiltration of CD31⁺ murine endothelial cells was enhanced in the cell-assembled implants at 28 days. Moreover, microcomputed tomography angiography revealed that there was a marked reduction in vascular permeability in the cell-assembled group, indicating that the developing vascular network was more stable in the new scaffold format. Overall, the novel cell-assembled DAT bead foams represent a promising platform to harness the pro-regenerative paracrine functionality of human ASCs and warrant further investigation as a clinically-translational approach for volume augmentation.

Modulating hypoxia and oxidative stress in human xenografts using adipose tissue-derived stem cells

OBJECTIVE

To investigate whether adipose tissue-derived stem cells (ASCs) modulate hypoxia and oxidative stress in human ovarian tissue transplants.

DESIGN

Prospective experimental study SETTING: Gynecological research unit in a university hospital PATIENT(S): Cryopreserved ovarian cortex from 5 adult women.

INTERVENTION(S)

Thirty mice were grafted with frozen-thawed human ovarian tissue, with or without ASCs (2-step/ASCs+ovarian tissue [OT] group and OT group). The ovarian grafts were retrieved on days 3 (n = 5), 10 (n = 5), and 21 (n = 5). The 10 animals grafted for 21 days underwent in vivo evaluations using microdialysis. One piece of ovarian tissue per patient was fixed for analysis after thawing (non-grafted controls).

MAIN OUTCOME MEASURE(S)

Direct reactive oxygen species were collected every second day after grafting by means of microdialysis. Analyses of ovarian fragments included immunolabeling for double CD34 (revascularization by host and graft components); immunofluorescence for hypoxia-inducible factor 1α (hypoxia-related response), nuclear factor erythroid 2-related factor 2 (oxidative stress-related response), and 8-hydroxy-deoxyguanosine (oxidative stress-related DNA damage); and gene expression (quantitative reverse transcription polymerase chain reaction) for vascular endothelial growth factor-A (neoangiogenesis), superoxide dismutase 2 (antioxidant activity), and nuclear respiratory factor 1 (mitochondrial biogenesis).

RESULT(S)

Reactive oxygen species peaked earlier in the ASC group (day 2) compared with that in the OT group (day 10) after grafting. Total vascularization was stable in the ASC group at all time points, while it was lower in the OT group 3 days after grafting. Hypoxia-inducible factor 1α expression, also detected in non-grafted controls, was significantly lower in the ASC group than in the OT group on days 3 and 10. The increase in VEGF gene expression lasted significantly longer in the ASC group than in the OT group. There was no significant upturn in the oxidative stress-related response (nuclear factor erythroid 2-related factor 2 pathway) or oocyte DNA damage (8-hydroxy-deoxyguanosine) in any of the grafted groups.

CONCLUSION(S)

Use of ASCs allows faster ovarian graft reperfusion and mitigates the hypoxia-related response through rapid revascularization, sustained by prolonged increase in vascular endothelial growth factor after grafting. No evidence of oxidative stress-related damage was detected irrespective of the transplantation strategy.

Cell-based strategies for IVD repair: clinical progress and translational obstacles

Intervertebral disc (IVD) degeneration is a major cause of low back pain, a prevalent and chronic condition that has a striking effect on quality of life. Currently, no approved pharmacological interventions or therapies are available that prevent the progressive destruction of the IVD; however, regenerative strategies are emerging that aim to modify the disease. Progress has been made in defining promising new treatments for disc disease, but considerable challenges remain along the entire translational spectrum, from understanding disease mechanism to useful interpretation of clinical trials, which make it difficult to achieve a unified understanding. These challenges include: an incomplete appreciation of the mechanisms of disc degeneration; a lack of standardized approaches in preclinical testing; in the context of cell therapy, a distinct lack of cohesion regarding the cell types being tested, the tissue source, expansion conditions and dose; the absence of guidelines regarding disease classification and patient stratification for clinical trial inclusion; and an incomplete understanding of the mechanisms underpinning therapeutic responses to cell delivery. This Review discusses current approaches to disc regeneration, with a particular focus on cell-based therapeutic strategies, including ongoing challenges, and attempts to provide a framework to interpret current data and guide future investigational studies.

Comparative analysis of mouse bone marrow and adipose tissue mesenchymal stem cells for critical limb ischemia cell therapy

INTRODUCTION

Critical limb ischemia (CLI) is the most advanced form of peripheral arterial disease (PAD) characterized by ischemic rest pain and non-healing ulcers. Currently, the standard therapy for CLI is the surgical reconstruction and endovascular therapy or limb amputation for patients with no treatment options. Neovasculogenesis induced by mesenchymal stem cells (MSCs) therapy is a promising approach to improve CLI. Owing to their angiogenic and immunomodulatory potential, MSCs are perfect candidates for the treatment of CLI. The purpose of this study was to determine and compare the in vitro and in vivo effects of allogeneic bone marrow mesenchymal stem cells (BM-MSCs) and adipose tissue mesenchymal stem cells (AT-MSCs) on CLI treatment.

METHODS

For the first step, BM-MSCs and AT-MSCs were isolated and characterized for the characteristic MSC phenotypes. Then, femoral artery ligation and total excision of the femoral artery were performed on C57BL/6 mice to create a CLI model. The cells were evaluated for their in vitro and in vivo biological characteristics for CLI cell therapy. In order to determine these characteristics, the following tests were performed: morphology, flow cytometry, differentiation to osteocyte and adipocyte, wound healing assay, and behavioral tests including Tarlov, Ischemia, Modified ischemia, Function and the grade of limb necrosis scores, donor cell survival assay, and histological analysis.

RESULTS

Our cellular and functional tests indicated that during 28 days after cell transplantation, BM-MSCs had a great effect on endothelial cell migration, muscle restructure, functional improvements, and neovascularization in ischemic tissues compared with AT-MSCs and control groups.

CONCLUSIONS

Allogeneic BM-MSC transplantation resulted in a more effective recovery from critical limb ischemia compared to AT-MSCs transplantation. In fact, BM-MSC transplantation could be considered as a promising therapy for diseases with insufficient angiogenesis including hindlimb ischemia.

Stem Cell Therapy for Thromboangiitis Obliterans (Buerger’s Disease)

Buerger’s disease or Thromboangiitis Obliterans (TAO) is a nonatherosclerotic segmental vascular disease which affects small and medium arteries and veins in the upper and lower extremities. Based on pathological findings, TAO can be considered as a distinct form of vasculitis that is most prevalent in young male smokers. There is no definitive cure for this disease as therapeutic modalities are limited in number and efficacy. Surgical bypass has limited utility and 24% of patients will ultimately require amputation. Recently, studies have shown that therapeutic angiogenesis and immunomodulatory approaches through the delivery of stem cells to target tissues are potential options for ischemic lesion treatment. In this review, we summarize the current knowledge of TAO treatment and provide an overview of stem cell-based treatment modalities.

Long-Term Advantages of Ovarian Reserve Maintenance and Follicle Development Using Adipose Tissue-Derived Stem Cells in Ovarian Tissue Transplantation

(1) Background: Ovarian tissue transplantation with adipose tissue-derived stem cells (ASCs) has been shown to enhance graft vascularization and increase follicle survival after a short interval of 7 days. The aim of the present study was to investigate their long-term effects on primordial follicle pool maintenance and follicle development. (2) Methods: A total of 14 severe combined immunodeficient (SCID) mice were grafted with frozen-thawed human ovarian tissue with or without ASCs. Blood was taken monthly in order to quantify the anti-Müllerian hormone (AMH) and estradiol. After 6 months, all the grafts were retrieved and sent for histology and immunolabeling (AMH, AMH receptor II, estrogen receptors α and β, and c-kit/kit ligand). (3) Results: A significant upturn was observed in AMH and estradiol plasma levels 4 months after transplantation in both grafted groups. The primordial follicle pool was better preserved in the ASC group (41.86 ± 28.35) than in the standard transplantation group (9.65 ± 17.6, p < 0.05) compared to non-grafted controls (124.7 ± 140). (4) Conclusions: The use of ASCs prior to ovarian tissue transplantation yielded a larger primordial follicle pool and more physiological follicle distribution after long-term grafting. These findings suggested that ASC use might extend the ovarian tissue lifespan.

Stromal Cells Promote Neovascular Invasion Across Tissue Interfaces

Vascular connectivity between adjacent vessel beds within and between tissue compartments is essential to any successful neovascularization process. To establish new connections, growing neovessels must locate other vascular elements during angiogenesis, often crossing matrix and other tissue-associated boundaries and interfaces. How growing neovessels traverse any tissue interface, whether part of the native tissue structure or secondary to a regenerative procedure (e.g., an implant), is not known. In this study, we developed an experimental model of angiogenesis wherein growing neovessels must interact with a 3D interstitial collagen matrix interface that separates two distinct tissue compartments. Using this model, we determined that matrix interfaces act as a barrier to neovessel growth, deflecting growing neovessels parallel to the interface. Computational modeling of the neovessel/matrix biomechanical interactions at the interface demonstrated that differences in collagen fibril density near and at the interface are the likely mechanism of deflection, while fibril alignment guides deflected neovessels along the interface. Interestingly, stromal cells facilitated neovessel interface crossing during angiogenesis via a vascular endothelial growth factor (VEGF)-A dependent process. However, ubiquitous addition of VEGF-A in the absence of stromal cells did not promote interface invasion. Therefore, our findings demonstrate that vascularization of a tissue via angiogenesis involves stromal cells providing positional cues to the growing neovasculature and provides insight into how a microvasculature is organized within a tissue.

Adipose stem cells from type 2 diabetic mice exhibit therapeutic potential in wound healing

Background

Diabetic patients suffer from impaired wound healing. Mesenchymal stem cell (MSC) therapy represents a promising approach toward improving skin wound healing through the release of soluble growth factors and cytokines that stimulate new vessel formation and modulate inflammation. Whether adipose tissue-derived MSCs (ASCs) from type 2 diabetes (T2D) donors are suitable for skin damage repair remains largely unknown.

Methods

In this study, we compared the phenotype and functionality of ASCs harvested from high-fat diet (HFD) and streptozotocin (STZ)-induced T2D or control mice, and assessed their abilities to promote wound healing in an excisional wound splinting mouse model with T2D.

Results

T2D ASCs expressed similar cellular markers as control ASCs but secreted less hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and transforming growth factor β (TGF-β). T2D ASCs were somewhat less effective in promoting healing of the wound, as manifested by slightly reduced re-epithelialization, cutaneous appendage regeneration, and collagen III deposition in wound tissues. In vitro, T2D ASCs promoted proliferation and migration of skin fibroblasts to a comparable extent as control ASCs via suppression of inflammation and macrophage infiltration.

Conclusions

From these findings, we conclude that, although ASCs from T2D mice are marginally inferior to control ASCs, they possess comparable therapeutic effects in wound healing.

Adipose tissue-derived stromal cells stimulated macrophages-endothelial cells interactions promote effective ischemic muscle neovascularization

Neovascularization, the process of new blood vessels formation in response to hypoxia induced signals, is an essential step during wound healing or ischemia repair. It follows as a cascade of consecutive events leading to new blood vessels formation and their subsequent remodeling to a mature and functional state, enabling tissue regeneration. Any disruption in consecutive stages of neovascularization can lead to chronic wounds or impairment of tissue repair. In the study we try to explain the biological basis of accelerated blood vessels formation in ischemic tissue after adipose tissue-derived stromal cells (ADSCs) administration. Experiments were performed on mouse models of hindlimb ischemia. We have evaluated the level of immune cells (neutrophils, macrophages) infiltration. The novelty of our work was the assessment of bone marrow-derived stem/progenitor cells (BMDCs) infiltration and their contribution to the neovascularization process in ischemic tissue. We have noticed that ADSCs regulated immune response and affected the kinetics and ratio of macrophages population infiltrating ischemic tissue. Our research revealed that ADSCs promoted changes in the morphology of infiltrating macrophages and their tight association with forming blood vessels. We assume that recruited macrophages may take over the role of pericytes and stabilize the new blood vessel or even differentiate into endothelial cells, which in consequence can accelerate vascular formation upon ADSCs administration. Our findings indicate that administration of ADSCs into ischemic muscle influence spatio-temporal distribution of infiltrating cells (macrophages, neutrophils and BMDCs), which are involved in each step of vascular formation, promoting effective ischemic tissue neovascularization.

Locally Transplanted Adipose Stem Cells Reduce Anastomotic Leaks in Ischemic Colorectal Anastomoses: A Rat Model

BACKGROUND

Anastomotic leakage remains a dreaded complication after colorectal surgery. Stem-cell-based therapies have been shown to increase angiogenesis and cell proliferation.

OBJECTIVE

The purpose of this research was to investigate the use of adipose-derived stem cells on the healing of ischemic colonic anastomoses in a rat model.

DESIGN

This is an animal research study using xenotransplantation.

SETTINGS

Male Wistar rats (300-400 g, n = 48) were purchased from a licensed breeder.

PATIENTS

Adipose stem cells were isolated from the subcutaneous fat of healthy human donors.

INTERVENTIONS

The rats underwent laparotomy with creation of an ischemic colorectal anastomosis created by ligation of mesenteric vessels. The animals were divided into 3 groups: control group with an ischemic anastomosis, vehicle-only group in which the ischemic anastomosis was treated with an absorbable gelatin sponge, and a treatment group in which the ischemic anastomosis was treated with an absorbable gelatin sponge plus adipose stem cells. Animals were killed at postoperative days 3 and 7.

MAIN OUTCOME MEASURES

Anastomotic leakage was defined as the finding of feculent peritonitis or perianastomotic abscess on necropsy. Rat mRNA expression was measured using real-time polymerase chain reaction.

RESULTS

Adipose-derived stem cells significantly decreased anastomotic leakage when compared with control at both postoperative days 3 (25.0% vs 87.5%; p = 0.02) and 7 (25.0% vs 87.5%; p = 0.02). The use of an absorbable gelatin sponge alone had no effect on anastomotic leakage when compared with control and postoperative days 3 or 7. We found that stem cell-treated animals had a 5.9-fold and 7.4-fold increase in the expression of vascular endothelial growth factor when compared with control at 3 and 7 days; however, this difference was not statistically significant when compared with the absorbable gelatin sponge group.

LIMITATIONS

This is a preclinical animal research study using xenotransplantation of cultured stem cells.

CONCLUSIONS

Locally transplanted adipose stem cells enhance the healing of ischemic colorectal anastomoses and may be a novel strategy for reducing the risk of anastomotic leakage in colorectal surgery. See Video Abstract at http://links.lww.com/DCR/B203. EL TRANSPLANTE LOCAL DE CÉLULAS MADRE ADIPOSAS REDUCE LA FUGA ANASTOMÓTICA EN LAS SUTURAS COLORRECTALES ISQUÉMICAS: MODELO EN RATAS: Las fugas anastomóticas son una complicación pusilánime después de toda cirugía colorrectal. Se ha demostrado que el tratamiento con células madre aumenta la angiogénesis y la proliferación celular.Investigar el uso de células madre derivadas de tejido adiposo en la cicatrización de una anastomosis colónica isquémica basada en ratas como modelo.Estudio de investigación en animales utilizando xenotrasplantes.Adquisición de típicas ratas de laboratorio raza Wistar, todas machos (300-400 g, n = 48) de un criadero autorizado.Aislamiento de células madre de tipo adiposo del tejido celular subcutáneo en donantes humanos sanos.Las ratas se sometieron a laparotomía con la creación de una anastomosis colorrectal isquémica obtenida mediante ligadura controlada de los vasos mesentéricos correspondientes. Los animales se dividieron en tres grupos: grupo de control con anastomosis isquémica, grupo de vehículo único en el que la anastomosis isquémica se trató con una esponja de gelatina absorbible, y un grupo de tratamiento en el que la anastomosis isquémica se trató con una esponja de gelatina absorbible asociada a un vástago adiposo de células madre. Los animales fueron sacrificados el POD3 y el POD7.La fuga anastomótica fué definida como el hallazgo de peritonitis fecaloidea o absceso perianastomótico a la necropsia. La expresión de RNAm de las ratas se midió usando PCR en tiempo real.Las células madre derivadas de tejido adiposo disminuyeron significativamente la fuga anastomótica en comparación con el grupo control tanto en el POD3 (25% frente a 87.5%, p = 0.02) como en el POD7 (25% frente a 87.5%, p = 0.02). El uso de una esponja de gelatina absorbible sola, no tuvo efecto sobre la fuga anastomótica en comparación con los controles el POD3 o el POD7. Descubrimos que los animales tratados con células madre adiposas tenían un aumento de 5,9 y 7,4 veces en la expresión de VEGF en comparación con el control a los 3 y 7 días, respectivamente; sin embargo, esta diferencia no fue estadísticamente significativa en comparación con el grupo de esponja de gelatina absorbible.Este es un estudio preclínico de investigación en animales que utiliza xenotrasplantes de células madre adiposas cultivadas.Las células madre de tipo adiposo trasplantadas localmente mejoran la cicatrisación en casos de anastomosis colorrectales isquémicas, y podrían convertirse en una nueva estrategia para reducir el riesgo de fugas anastomóticas en casos de cirugía colorrectal. Consulte Video Resumen en http://links.lww.com/DCR/B203. (Traducción-Dr Xavier Delgadillo).

The Proliferation and Differentiation of Adipose-Derived Stem Cells in Neovascularization and Angiogenesis

Neovascularization and angiogenesis are vital processes in the repair of damaged tissue, creating new blood vessel networks and increasing oxygen and nutrient supply for regeneration. The importance of Adipose-derived Mesenchymal Stem Cells (ASCs) contained in the adipose tissue surrounding blood vessel networks to these processes remains unknown and the exact mechanisms responsible for directing adipogenic cell fate remain to be discovered. As adipose tissue contains a heterogenous population of partially differentiated cells of adipocyte lineage; tissue repair, angiogenesis and neovascularization may be closely linked to the function of ASCs in a complex relationship. This review aims to investigate the link between ASCs and angiogenesis/neovascularization, with references to current studies. The molecular mechanisms of these processes, as well as ASC differentiation and proliferation are described in detail. ASCs may differentiate into endothelial cells during neovascularization; however, recent clinical trials have suggested that ASCs may also stimulate angiogenesis and neovascularization indirectly through the release of paracrine factors.

Minicircle-based GCP-2 ex vivo gene therapy enhanced the reepithelialization and angiogenic capacity

Recently, minicircle (MC)-based cell therapy has been emerging as a novel technology for nonviral genetic modification. In this study, we investigated the characteristics of granulocyte chemotactic protein-2 (GCP-2)-overexpressing fibroblasts (GCP-2/MC) using MC microporation technology, as well as its therapeutic mechanism in wound healing. GCP-2 parent plasmid and MC containing GCP-2 were generated. Human dermal fibroblasts (HDF) were transfected with MC containing GCP-2. Quantitative reverse transcription polymerase chain reaction (qRT-PCR), scratch wound assay, and in vivo wound healing assay were performed. Gene and protein expression analysis revealed that GCP-2/MC highly expressed epithelialization growth factor, epidermal growth factor (EGF), chemokines, GCP-2, interleukin (IL)-8, as well as wound healing-associated genes such as insulin growth factor (IGF)-1 and hepatocyte growth factor (HGF). An in vitro scratch wound closure and matrigel tube formation assays demonstrated that the culture medium derived from GCP-2/MC substantially accelerated the wound closure and matrigel network formation. Wounds in nude mice were created by skin excisions followed by injections of GCP-2/MC. Results showed high cell survival potential and that GCP-2/MC transplantation highly accelerated skin wound closure by increasing reepithelialization, capillary density, and enhancing angiogenic factors, suggesting direct benefits for cutaneous closure. Taken together, these data suggest that MC-based GCP-2 overexpression could be a promising alternative strategy for promoting wound healing.

Recent Advance in Source, Property, Differentiation, and Applications of Infrapatellar Fat Pad Adipose-Derived Stem Cells

Infrapatellar fat pad (IPFP) can be easily obtained during knee surgery, which avoids the damage to patients for obtaining IPFP. Infrapatellar fat pad adipose-derived stem cells (IPFP-ASCs) are also called infrapatellar fat pad mesenchymal stem cells (IPFP-MSCs) because the morphology of IPFP-ASCs is similar to that of bone marrow mesenchymal stem cells (BM-MSCs). IPFP-ASCs are attracting more and more attention due to their characteristics suitable to regenerative medicine such as strong proliferation and differentiation, anti-inflammation, antiaging, secreting cytokines, multipotential capacity, and 3D culture. IPFP-ASCs can repair articular cartilage and relieve the pain caused by osteoarthritis, so most of IPFP-related review articles focus on osteoarthritis. This article reviews the anatomy and function of IPFP, as well as the discovery, amplification, multipotential capacity, and application of IPFP-ASCs in order to explain why IPFP-ASC is a superior stem cell source in regenerative medicine.

Secretome of Senescent Adipose-Derived Mesenchymal Stem Cells Negatively Regulates Angiogenesis

Nowadays, paracrine regulation is considered as a major tool of mesenchymal stem cell (MSC) involvement in tissue repair and renewal in adults. Aging results in alteration of tissue homeostasis including neovascularization. In this study, we examined the influence of replicative senescence on the angiogenic potential of adipose-derived MSCs (ASCs). Angiogenic activity of conditioned medium (CM) from senescent and “young” ASCs was evaluated in chorioallantoic membrane (CAM) assay in ovo using Japanese quail embryos. Also, the formation of capillary-like tubes by human umbilical vein endothelial cells (HUVECs) in 3D basement membrane matrix “Matrigel” and HUVEC migration capacity were analyzed. Multiplex, dot-blot and gene expression analysis were performed to characterize transcription and production of about 100 angiogenesis-associated proteins. The results point to decreased angiogenic potential of senescent ASC secretome in ovo. A number of angiogenesis-associated proteins demonstrated elevation in CM after long-term cultivation. Meanwhile, VEGF (key positive regulator of angiogenesis) did not change transcription level and concentration in CM. Increasing both pro- (FGF-2, uPA, IL-6, IL-8 etc.) and antiangiogenic (IL-4, IP-10, PF4, Activin A, DPPIV etc.) factors was observed. Some proangiogenic genes were downregulated (IGF1, MMP1, TGFB3, PDGFRB, PGF). Senescence-associated secretory phenotype (SASP) modifications after long-term cultivation lead to attenuation of angiogenic potential of ASC.

Anastomotic leak in colorectal cancer patients: New insights and perspectives

Anastomotic leak (AL) remains a potentially life-threatening sequela of colorectal surgery impacting on mortality, short- and long-term morbidity, quality of life, local recurrence (LR) and disease-free survival. Despite technical improvements and the identification of several surgery- and patient-related factors associated to the risk of AL, its incidence has not significantly changed over time. In this context, the clarification of the mechanisms underlying anastomotic healing remains an important unmet need, crucial for improving patients' outcomes. This review concentrates on novel key findings in the etiopathogenesis of AL, how they can contribute in determining LR, and measures which may contribute to reducing its incidence. AL results from a complex, dynamic interplay of several factors and biological processes, including host genetics, gut microbiome, inflammation and the immune system. Many of these factors seem to act in concert to drive both AL and LR, even if the exact mechanisms remain to be elucidated. The next generation sequencing technology, including the microbial metagenomics, could lead to tailored bowel preparations targeting only those pathogens that can cause AL. Significant progress is being made in each of the reviewed areas, moving toward translational and targeted therapeutic strategies to prevent the difficult complication of AL.

Targeting Purinergic Signaling and Cell Therapy in Cardiovascular and Neurodegenerative Diseases

Extracellular purines exert several functions in physiological and pathophysiological mechanisms. ATP acts through P2 receptors as a neurotransmitter and neuromodulator and modulates heart contractility, while adenosine participates in neurotransmission, blood pressure, and many other mechanisms. Because of their capability to differentiate into mature cell types, they provide a unique therapeutic strategy for regenerating damaged tissue, such as in cardiovascular and neurodegenerative diseases. Purinergic signaling is pivotal for controlling stem cell differentiation and phenotype determination. Proliferation, differentiation, and apoptosis of stem cells of various origins are regulated by purinergic receptors. In this chapter, we selected neurodegenerative and cardiovascular diseases with clinical trials using cell therapy and purinergic receptor targeting. We discuss these approaches as therapeutic alternatives to neurodegenerative and cardiovascular diseases. For instance, promising results were demonstrated in the utilization of mesenchymal stem cells and bone marrow mononuclear cells in vascular regeneration. Regarding neurodegenerative diseases, in general, P2X7 and A_2A receptors mostly worsen the degenerative state. Stem cell-based therapy, mainly through mesenchymal and hematopoietic stem cells, showed promising results in improving symptoms caused by neurodegeneration. We propose that purinergic receptor activity regulation combined with stem cells could enhance proliferative and differentiation rates as well as cell engraftment.

Therapeutic Angiogenesis with Somatic Stem Cell Transplantation

Therapeutic angiogenesis is an important strategy to rescue ischemic tissues in patients with critical limb ischemia having no other treatment option such as endovascular angioplasty or bypass surgery. Studies indicated so far possibilities of therapeutic angiogenesis using autologous bone marrow mononuclear cells, CD34⁺ cells, peripheral blood mononuclear cells, adipose-derived stem/progenitor cells, and etc. Recent studies indicated that subcutaneous adipose tissue contains stem/progenitor cells that can give rise to several mesenchymal lineage cells. Moreover, these mesenchymal progenitor cells release a variety of angiogenic growth factors including vascular endothelial growth factor, fibroblast growth factor, hepatocyte growth factor and chemokine stromal cell-derived factor-1. Subcutaneous adipose tissues can be harvested by less invasive technique. These biological properties of adipose-derived regenerative cells (ADRCs) implicate that autologous subcutaneous adipose tissue would be a useful cell source for therapeutic angiogenesis in humans. In this review, I would like to discuss biological properties and future perspective of ADRCs-mediated therapeutic angiogenesis.

Adipose-derived stem cells contribute to cardiovascular remodeling

Obesity is an independent risk factor for cardiovascular disease. Adipose tissue was initially thought to be involved in metabolism through paracrine. Recent researches discovered mesenchymal stem cells inside adipose tissue which could differentiate into vascular lineages in vitro and in vivo, participating vascular remodeling. However, there were few researches focusing on distinct characteristics and functions of adipose-derived stem cells (ADSCs) from different regions. This is the first comprehensive review demonstrating the variances of ADSCs from the perspective of their origins.

Combinatorial conditioning of adipose derived-mesenchymal stem cells enhances their neurovascular potential: Implications for intervertebral disc degeneration

BACKGROUND

Mesenchymal stem cells (MSCs) are becoming an increasingly attractive option for regenerative therapies due to their availability, self-renewal capacity, multilineage potential, and anti-inflammatory properties. Clinical trials are underway to test the efficacy of stem cell-based therapies for the repair and regeneration of the degenerate intervertebral disc (IVD), a major cause of back pain. Recently, both bone marrow-derived MSCs and adipose-derived stem cells (ASCs) have been assessed for IVD therapy but there is a lack of knowledge surrounding the optimal cell source and the response of transplanted cells to the low oxygen, pro-inflammatory niche of the degenerate disc. Here, we investigated several neurovascular factors from donor-matched MSCs and ASCs that may potentiate the survival and persistence of sensory nerve fibers and blood vessels present within painful degenerate discs and their regulation by oxygen tensions and inflammatory cytokines.

METHODS

Donor-matched ASCs and MSCs were conditioned with either IL-1β or TNFα under normoxic (21% O2) or hypoxic (5% O2) conditions. Expression and secretion of several potent neurovascular factors were assessed using qRT-PCR and human magnetic Luminex assay.

RESULTS

ASCs and MSCs expressed constitutive levels of key neurotrophic factors; and stimulation of ASCs with hypoxia triggered increased secretion of both angiogenic factors (Ang-2 and VEGF-A) and neurotrophic (NGF and NT-3) compared to MSCs. We also report increased transcriptional regulation of pain-associated neuropeptides in hypoxia stimulated ASCs compared to those in normoxic conditions. We demonstrate transcriptional and translational upregulation of NGF, NT-3, Ang-1, and FGF-2 in response to cytokines in ASCs in 21% and 5% O2.

CONCLUSIONS

This work highlights fundamental differences between the neurovascular secretome of donor-matched ASCs and MSCs, demonstrating the importance of cell-selection for tissue specific regeneration to reduce ectopic sensory nerve and blood vessel survival and improve patient outcomes.

LncRNA TUG1 regulates FGF1 to enhance endothelial differentiation of adipose-derived stem cells by sponging miR-143

Adipose-derived stem cells (ADSCs) have emerged as a cell source for regeneration medicine. ADSCs possess the capacity to differentiate into endothelial cells and serve an essential role in vascular development and function. LncRNA taurine upregulated gene 1 (TUG1) has recently been linked with angiogenesis in hepatoblastoma. However, the roles of TUG1 in endothelial differentiation of ADSCs remain unidentified. Human adipose-derived stem cells (hADSCs) were obtained and characterized by flow cytometry, Oil red O and Alizarin Red staining. HADSCs were maintained in the endothelial differentiation medium and the expressions of TUG1, miR-143, and FGF1 were examined by qRT-PCR. To assess endothelial differentiation, the expressions of CD31, von Willebrand factor (vWF), VE-cadherin were examined by Western blot analysis, qRT-PCR, and immunofluorescence. Tube formation in Matrigel was examined. The interactions between TUG1 and miR-143, miR-143 and FGF1 were validated by luciferase assays. During the endothelial differentiation process, TUG1 and FGF1 were upregulated, whereas miR-143 was downregulated. TUG1 overexpression downregulated miR-143, upregulated FGF1, CD31, vWF, and VE-cadherin, and enhanced capillary tube formation. Luciferase assays showed that TUG1 interacted with miR-143, and FGF1 was a direct target of miR-143. Furthermore, the enhancement of endothelial differentiation induced by TUG1 overexpression was abolished by miR-143 overexpression. Our findings implicated that lncRNA TUG1 promoted endothelial differentiation of ADSCs by regulating the miR-143/FGF1 axis.

Umbilical cord-derived mesenchymal stromal cells in cardiovascular disease: review of preclinical and clinical data

The human umbilical cord has recently emerged as an attractive potential source of mesenchymal stromal cells (MSCs) to be adopted for use in regenerative medicine. Umbilical cord MSCs (UC-MSCs) not only share the same features of all MSCs such as multi-lineage differentiation, paracrine functions and immunomodulatory properties, they also have additional advantages, such as no need for bone marrow aspiration and higher self-renewal capacities. They can be isolated from various compartments of the umbilical cord (UC) and can be used for autologous or allogeneic purposes. In the past decade, they have been adopted in cardiovascular disease and have shown promising results mainly due to their pro-angiogenic and anti-inflammatory properties. This review offers an overview of the biological properties of UC-MSCs describing available pre-clinical and clinical data with respect to their potential therapeutic use in cardiovascular regeneration, with current challenges and future directions discussed.

Critical limb ischemia: Current and novel therapeutic strategies

Critical limb ischemia (CLI) is the advanced stage of peripheral artery disease spectrum and is defined by limb pain or impending limb loss because of compromised blood flow to the affected extremity. Current conventional therapies for CLI include amputation, bypass surgery, endovascular therapy, and pharmacological approaches. Although these conventional therapeutic strategies still remain as the mainstay of treatments for CLI, novel and promising therapeutic approaches such as proangiogenic gene/protein therapies and stem cell-based therapies have emerged to overcome, at least partially, the limitations and disadvantages of current conventional therapeutic approaches. Such novel CLI treatment options may become even more effective when other complementary approaches such as utilizing proper bioscaffolds are used to increase the survival and engraftment of delivered genes and stem cells. Therefore, herein, we address the benefits and disadvantages of current therapeutic strategies for CLI treatment and summarize the novel and promising therapeutic approaches for CLI treatment. Our analyses also suggest that these novel CLI therapeutic strategies show considerable advantages to be used when current conventional methods have failed for CLI treatment.

Monitoring of diffusion properties and transverse relaxation time of mouse ischaemic muscle after administration of human mesenchymal stromal cells derived from adipose tissue

Objectives

Application of non‐invasive imaging methods plays an important role in the assessment of cellular therapy effects in peripheral artery disease. The purpose of this work was to evaluate the kinetics of MRI‐derived parameters characterizing ischaemic hindlimb muscle after administration of human mesenchymal stromal cells derived from adipose tissue (hADSC) in mice.

Materials and methods

MRI experiments were performed on a 9.4T Bruker system. The measurement protocol included transverse relaxation time mapping and diffusion tensor imaging. The monitoring period encompassed 14 days after femoral artery ligation and subsequent cell administration. The effect of hADSC transplantation was compared with the effect of normal human dermal fibroblasts (NHDFs) and phosphate‐buffered saline injection.

Results

The most significant differences between the hADSC group and the remaining ones were observed around day 3 after ischaemia induction (increased transverse relaxation time in the hADSC group in comparison with the control group) and around day 7 (increased transverse relaxation time and decreased third eigenvalue of the diffusion tensor in the hADSC group in comparison with the control and NHDF groups) at the site of hADSC injection. Histologically, it was associated with increased macrophage infiltration at days 3‐7 and with the presence of small regenerating fibres in the ischaemic tissue at day 7.

Conclusions

Our results underscore the important role of macrophages in mediating the therapeutic effects of hADSCs and confirm the huge potential of magnetic resonance imaging in monitoring of cellular therapy effects.

Hypoxia Rapidly Induces the Expression of Cardiomyogenic Factors in Human Adipose-Derived Adherent Stromal Cells

BACKGROUND

The efficacy of interstitial vascular fraction (SVF) transplantation in the treatment of heart disease has been proven in a variety of in vivo studies. In a previous study, we found that bone marrow-derived mesenchymal stem cells (BM-MSCs) altered their expression of several cardiomyogenic factors under hypoxic conditions.

METHODS

We hypothesized that hypoxia may also induce obtained adipose-derived adherent stromal cells (ADASs) from SVFs and adipose-derived stem cells (ASCs) to differentiate into cardiomyocytes and/or cells with comparable phenotypes. We examined the differentiation markers of cell lineages in ADASs and ASCs according to time by hypoxic stress and found that only ADASs expressed cardiomyogenic markers within 24 h under hypoxic conditions in association with the expression of hypoxia-inducible factor 1-α (HIF-1α).

RESULTS

Differentially secreted proteins in a conditioned medium (CM) from ASCs and ADASs under normoxic or hypoxic conditions were detected using an antibody assay and may be associated with a dramatic increase in the expression of cardiomyogenic markers in only ADASs. Furthermore, the cardiomyogenic factors were expressed more rapidly in ADASs than in ASCs under hypoxic conditions in association with the expression of HIF-1α, and angiogenin, fibroblast growth factor-19 (FGF-19) and/or macrophage inhibitory factor (MIF) are related.

CONCLUSIONS

These results provide new insights into the applicability of ADASs preconditioned by hypoxic stress in cardiac diseases.

Adipose-derived stem cells-induced burn wound healing and regeneration of skin appendages in a novel skin island rat model

BACKGROUND

The study of effectiveness of adipose-derived stem cells (ASCs) in treating burn wounds is still a developing field. The process of wound contraction in areas of loose skin is a major confounding factor in the evaluation and study of burn wound healing in animal models.

METHODS

To evaluate the effect of local ASCs administration, deep partial thickness burn wounds were induced by 30 s application of hot copper plates in a novel skin island burn wound rat model to avoid interference from primary wound contraction. Skin islands were divided into two treatment groups-control group (n = 9) injected with PBS and ASCs-treated group (n = 9) injected with 5 × 10 ASCs intradermally. Progress in wound healing was checked at regular intervals after injury (on 1st, 2nd, 3rd, and 4th week) by measuring the mean wound area and analyzing the wound histologically and immunohistochemically, after unstitching the overlaying skin to expose the skin island.

RESULTS

It was found that local intradermal injection of ASCs improved burn wound healing at all given time points when compared with control groups, especially in the first 2 weeks (p < 0.05). The percentage of live follicles increased gradually in the ASCs-treated groups compared with control groups between the 3rd and 4th weeks (p < 0.05). The vascular density and proliferating cell nuclear antigen index were also significantly increased in the ASCs-treated groups.

CONCLUSION

Thus, in this study, a novel burn wound rat model with reduced interference from wound contraction has been put forth to investigate the therapeutic effects of local administration of ASCs on burn wound healing. Local injection of ASCs not only improved burn wound recovery but also enhanced angiogenesis and skin appendage regeneration.

In Vivo Photoacoustic Tracking of Mesenchymal Stem Cell Viability

Adult stem cell therapy has demonstrated improved outcomes for treating cardiovascular diseases in preclinical trials. The development of imaging tools may increase our understanding of the mechanisms of stem cell therapy, and a variety of imaging tools have been developed to image transplanted stem cells in vivo; however, they lack the ability to interrogate stem cell function longitudinally. Here, we report the use of a nanoparticle-based contrast agent that can track stem cell viability using photoacoustic imaging. The contrast agent consists of inert gold nanorods coated with IR775c, a reactive oxygen species (ROS) sensitive near-infrared dye. Upon cell death, stem cells produce ROS to degrade the cell. Using this feature of stem cells, the viability can be measured by comparing the IR775c signal to the ROS insensitive gold nanorod signal, which can also be used to track stem cell location. The nanoprobe was successfully loaded into mesenchymal stem cells (MSCs), and then, MSCs were transplanted into the lower limb of a mouse and imaged using combined ultrasound and photoacoustic imaging. MSC viability was assessed using the nanoprobe and displayed significant cell death within 24 h and an estimated 5% viability after 10 days. This nanoparticle system allows for longitudinal tracking of MSC viability in vivo with high spatial and temporal resolution which other imaging modalities currently cannot achieve.

Recent trends in peripheral nervous regeneration using 3D biomaterials

Mesenchymal stem cells (MSCs) owing their multipotency are known as progenitors for the regeneration of adult tissues including that of neuronal tissue. The repair and/or regeneration of traumatic nerves is still a challenging task for neurosurgeons. It is also a well-established fact that the microenvironment plays a primary role in determining the fate of stem cells to a specific lineage. In recent years, with the advent of nanotechnology and its positive influence on designing and fabrication of various 3D biomaterials have progressed to a greater extent. The production of 3D biomaterials such as nanofibers, conduits and hydrogels are providing a suitable environment for mimicking physiological niche of stem cells. These 3D biomaterials in combination with MSCs have been successfully analyzed for their potential in the regeneration of degenerative neurological disorders. This review primarily highlights the combinatorial effect of multipotent MSCs seeded on various 3D polymeric scaffolds in repair and regeneration of nervous tissue. The elaboration of MSCs from distinct sources reported so far in literature are summarized to understand their role in regeneration processes. Furthermore, we accentuate the application of 3D biomaterials especially the nanofibers, polymeric conduits, hydrogels infiltrated with MSCs harvested from distinct sources in the field of peripheral nerve regeneration studies.

Effect of cell source and osteoblast differentiation on gene expression profiles of mesenchymal stem cells derived from bone marrow or adipose tissue

Mesenchymal stem cells (MSCs) have been used in therapies for bone tissue healing. The aim of this study was to investigate the effect of cell source and osteoblast differentiation on gene expression profiles of MSCs from bone marrow (BM-MSCs) or adipose tissue (AT-MSCs) to contribute for selecting a suitable cell population to be used in cell-based strategies for bone regeneration. BM-MSCs and AT-MSCs were cultured in growth medium to keep MSCs characteristics or in osteogenic medium to induce osteoblast differentiation (BM-OBs and AT-OBs). The transcriptomic analysis was performed by microarray covering the entire rat functional genome. It was observed that cells from bone marrow presented higher expression of genes related to osteogenesis, whereas cells from adipose tissue showed a higher expression of genes related to angiogenesis and adipocyte differentiation, irrespective of cell differentiation. By comparing cells from the same source, MSCs from both sources exhibited higher expression of genes involved in angiogenesis, osteoblast differentiation, and bone morphogenesis than osteoblasts. The clustering analysis showed that AT-OBs exhibited a gene expression profile closer to MSCs from both sources than BM-OBs, suggesting that BM-OBs were in a more advanced stage of differentiation. In conclusion, our results suggest that in cell-based therapies for bone regeneration AT-MSCs could be considered for angiogenic purposes, whereas BM-MSCs and osteoblasts differentiated from either source could be better for osteogenic approaches.