Proliferation, Metabolic Activity, and Adipogenic Differentiation of Human Preadipocytes Exposed to 2 Surfactants In Vitro

Senescence in Adipose-Derived Stem Cells: Biological Mechanisms and Therapeutic Challenges

Adipose tissue-derived stem cells (ADSCs) represent a subset of the mesenchymal stem cells in every adipose compartment throughout the body. ADSCs can differentiate into various cell types, including chondrocytes, osteocytes, myocytes, and adipocytes. Moreover, they exhibit a notable potential to differentiate in vitro into cells from other germinal lineages, including endothelial cells and neurons. ADSCs have a wide range of clinical applications, from breast surgery to chronic wounds. Furthermore, they are a promising cell population for future tissue-engineering uses. Accumulating evidence indicates a decreased proliferation and differentiation potential of ADSCs with an increasing age, increasing body mass index, diabetes mellitus, metabolic syndrome, or exposure to radiotherapy. Therefore, the recent literature thoroughly investigates this cell population's senescence mechanisms and how they can hinder its possible therapeutic applications. This review will discuss the biological mechanisms and the physio-pathological causes behind ADSC senescence and how they can impact cellular functionality. Moreover, we will examine the possible strategies to invert these processes, re-establishing the full regenerative potential of this progenitor population.

Genetic deletion of the cannabinoid receptors CB1 and CB2 enhances inflammation with diverging effects on skin wound healing in mice

AIMS

Inflammation during wound healing is both essential and critical for restoring tissue integrity. Participating cells secrete soluble factors to regulate the inflammatory phase and to induce the adjacent regenerative processes. If pro-inflammatory signals are overexpressed, the wound stagnates in the inflammatory phase, which decelerates regular wound healing. The endocannabinoid system is ascribed great significance in maintenance of tissue homeostasis. It mediates several effects through the cannabinoid receptors CB1 and CB2.

MAIN METHODS

In order to clarify the role of these receptors in wound healing, excisional wounds were created on wildtype and CB1 and CB2 knockout mice. The wound closure was analyzed over a period of 14 days, and cytokine concentrations of tissue homogenisates were measured by ELISA. MSCs were isolated from the animals' subcutaneous adipose tissue and analyzed for viability and differentiation capacity, in vitro.

KEY FINDINGS

Deletion of CB2 increased Interleukin (IL)-6 and tumor necrosis factor (TNF)-α but did not affect tissue regeneration. In CB1-deficient animals, wound closure was delayed during early phases of healing, which was accompanied by increased concentrations of monocyte chemoattractant protein (MCP)-1 and TNF-α. CB1 and CB2 knockout MSCs presented altered viability and differentiation capacity compared to wildtype MSCs. The CB1-deficient MSCs released high levels of MCP-1 upon stimulation with TNF-α and IL-1β.

SIGNIFICANCE

The data indicate that both cannabinoid receptors regulate inflammation, and this study emphasizes the important role of CB1 in wound repair. Furthermore, our findings suggest that the secretome of CB1-deficient MSCs may contribute to the wound healing delay, in vivo.

Adipose-Derived Stem/Stromal Cells in Kidney Transplantation: Status Quo and Future Perspectives

Kidney transplantation (KT) is the gold standard treatment of end-stage renal disease. Despite progressive advances in organ preservation, surgical technique, intensive care, and immunosuppression, long-term allograft survival has not significantly improved. Among the many peri-operative complications that can jeopardize transplant outcomes, ischemia–reperfusion injury (IRI) deserves special consideration as it is associated with delayed graft function, acute rejection, and premature transplant loss. Over the years, several strategies have been proposed to mitigate the impact of IRI and favor tolerance, with rather disappointing results. There is mounting evidence that adipose stem/stromal cells (ASCs) possess specific characteristics that could help prevent, reduce, or reverse IRI. Immunomodulating and tolerogenic properties have also been suggested, thus leading to the development of ASC-based prophylactic and therapeutic strategies in pre-clinical and clinical models of renal IRI and allograft rejection. ASCs are copious, easy to harvest, and readily expandable in culture. Furthermore, ASCs can secrete extracellular vesicles (EV) which may act as powerful mediators of tissue repair and tolerance. In the present review, we discuss the current knowledge on the mechanisms of action and therapeutic opportunities offered by ASCs and ASC-derived EVs in the KT setting. Most relevant pre-clinical and clinical studies as well as actual limitations and future perspective are highlighted.

Mesenchymal Stem Cells in Adipose Tissue and Extracellular Vesicles in Ovarian Cancer Patients: A Bridge toward Metastatic Diffusion or a New Therapeutic Opportunity?

Ovarian cancer is one of the deadliest malignancies among women. Approximately 75% of the patients with ovarian cancer are diagnosed with advanced disease that already has metastasis, particularly to the omentum. The omentum constitutes the ideal soil for ovarian cancer metastasis due to a complex intraperitoneal milieu that favors and supports the whole metastatic process. Adipose-derived stem/stromal cells (ADSCs) are part of this microenvironment and foster tumor progression via sustained paracrine secretion, including extracellular vesicles (EVs). Nonetheless, the preferential relationship between ADSCs, ADSC-derived EVs, and ovarian cancer cells could be exploited to use ADSCs and EVs as a vehicle for anti-cancer therapies. This review will analyze the strict relations between tumor progression, metastatic disease, and adipose tissue with its staminal components. In addition, we will describe the crosstalk and biologic relationship between ADSCs and tumor cells, the role of EVs in intercellular communication, the establishment of drug resistance, metastatic capacity, and ovarian cancer progression. We will analyze the new therapeutic opportunities in treating ovarian cancer offered by ADSCs and EVs as a vehicle for therapeutic molecules to target precisely tumor cells and limit the systemic adverse effects. Finally, we will discuss the limitations of these therapeutic approaches.

'Fat chance': a review of adipose tissue engineering and its role in plastic and reconstructive surgery

Soft tissue reconstruction remains a continuing challenge for plastic and reconstructive surgeons. Standard methods of reconstruction such as local tissue transfer and free autologous tissue transfer are successful in addressing soft tissue cover, yet they do not come without the additional morbidity of donor sites. Autologous fat transfer has been used in reconstruction of soft tissue defects in different branches of plastic surgery, specifically breast and facial defect reconstruction, while further maintaining a role in body contouring procedures. Current autologous fat transfer techniques come with the drawbacks of donor-site morbidity and, more significantly, resorption of large amounts of fat. Advancement in tissue engineering has led to the use of engineered adipose tissue structures based on adipose-derived stem cells. This enables a mechanically similar reconstruct that is abundantly available. Cosmetic and mechanical similarity with native tissue is the main clinical goal for engineered adipose tissue. Development of novel techniques in the availability of natural tissue is an exciting prospect; however, it is important to investigate the potential of cell sources and culture strategies for clinical applications. We review these techniques and their applications in plastic surgery.

Endocannabinoids increase human adipose stem cell differentiation and growth factor secretion in vitro

Adipose stem cells (ASCs) possess the capacity to proliferate, to differentiate into various cells types, and they are able to secrete growth factors. These characteristics are supposed to contribute to their potential for regenerative medicine approaches. In order to advance the therapeutic effects of ASCs, different modulatory procedures have been examined. In this context, the endocannabinoid system (ECS) represents an interesting possibility, since the increased availability of cannabinoids and the underlying molecular pathways of the ECS are of relevance for the development of new regenerative strategies. The effects of the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) were investigated on ASC metabolic activity, quantified by PrestoBlue conversion, and cell numbers, evaluated by crystal violet staining. enzyme-linked immunosorbent assay (ELISA) measures were performed to determine cytokine release, and differentiation was assessed by specific labeling techniques. AEA increased the metabolic activity, while 2-AG decreased it in a concentration dependent manner. AEA significantly enhanced OilRed O staining after adipogenic differentiation by over 100%, and both compounds significantly increased cresolphthalein staining after osteogenic differentiation. By contrast, they did not affect sphere diameter or safranin O staining after chondrogenic differentiation. Both substances significantly increased the release of insulin-like growth factor-1 and hepatocyte growth factor, while only AEA enhanced transforming growth factor-β secretion. The results demonstrated that stimulating the ECS exerted significant effects on the biology of ASCs. Exposure to endocannabinoids modulated viability, induced release of regenerative growth factors, and promoted adipogenic and osteogenic differentiation. Our findings could be of specific relevance in ASC based therapies for regenerative medicine.

The immunosuppressive effect of the endocannabinoid system on the inflammatory phenotypes of macrophages and mesenchymal stromal cells: a comparative study

BACKGROUND

The inflammatory sequence is the first phase of wound healing. Macrophages (MPhs) and mesenchymal stromal cells (MSCs) respond to an inflammatory microenvironment by adapting their functional activity, which polarizes them into the pro-inflammatory phenotypes M1 and MSC1. Prolongation of the inflammatory phase results in the formation of chronic wounds. The endocannabinoid system (ECS) possesses immunomodulatory properties that may impede this cellular phenotypic switch.

METHODS

We investigated the immunosuppressive influence of the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) on the M1 and MSC1 cytokine secretion. Lipopolysaccharides (LPS) were used as inflammagen to stimulate MPhs and MSCs. Both inflammatory phenotypes were co-exposed to AEA or 2-AG, the specific cannabinoid receptor CB2 agonist JWH-133 served as reference. The inflammatory responses were detected by CD80/163 immuno-labelling and by ELISA measures of secreted IL-6, IL-8, MIF, TNF-α, TGF-β, and VEGF.

RESULTS

M1 cells were found positive for CD80 expression and secreted less IL-6 and IL-8 than MSC1 cells, while both cell types produced similar amounts of MIF. TNF-α release was increased by M1, and growth factors were secreted by MSC1, only. Cannabinoid receptor ligands efficiently decreased the inflammatory response of M1, while their impact was less pronounced in MSC1.

CONCLUSIONS

The ECS down-regulated the inflammatory responses of MPhs and MSCs by decreasing the cytokine release upon LPS treatment, while CB2 appeared to be of particular importance. Hence, stimulating the ECS by manipulation of endo- or use of exogenous cannabinoids in vivo may constitute a potent therapeutic option against inflammatory disorders.

Warp-Knitted Spacer Fabrics: A Versatile Platform to Generate Fiber-Reinforced Hydrogels for 3D Tissue Engineering

Mesenchymal stem cells (MSCs) possess huge potential for regenerative medicine. For tissue engineering approaches, scaffolds and hydrogels are routinely used as extracellular matrix (ECM) carriers. The present study investigated the feasibility of using textile-reinforced hydrogels with adjustable porosity and elasticity as a versatile platform for soft tissue engineering. A warp-knitted poly (ethylene terephthalate) (PET) scaffold was developed and characterized with respect to morphology, porosity, and mechanics. The textile carrier was infiltrated with hydrogels and cells resulting in a fiber-reinforced matrix with adjustable biological as well as mechanical cues. Finally, the potential of this platform technology for regenerative medicine was tested on the example of fat tissue engineering. MSCs were seeded on the construct and exposed to adipogenic differentiation medium. Cell invasion was detected by two-photon microscopy, proliferation was measured by the PrestoBlue assay. Successful adipogenesis was demonstrated using Oil Red O staining as well as measurement of secreted adipokines. In conclusion, the given microenvironment featured optimal mechanical as well as biological properties for proliferation and differentiation of MSCs. Besides fat tissue, the textile-reinforced hydrogel system with adjustable mechanics could be a promising platform for future fabrication of versatile soft tissues, such as cartilage, tendon, or muscle.