Adipogenesis for soft tissue reconstruction

Comparative Analysis of Hydrogels From Porcine Extracellular Matrix for 3D Bioprinting of Adipose Tissue

The extracellular matrix (ECM) is the natural scaffold of all soft tissues in tissue engineering. Of special interest is the use of ECM as a hydrogel, which can be used to enclose cells and to be molded into any form by 3D bioprinting. Protocols for the preparation of ECM vary in the use of physical and chemical processing steps, the use of different detergents for decellularization, and the removal of DNA and RNA residues and show a different use of solvents and wash buffers. We have, therefore, compared seven different variations for the decellularization of a primary porcine isolate to manufacture decellularized adipose tissue (DAT) for their use in adipose tissue engineering and as a hydrogel in particular. Decellularization efficacy was assessed by DNA quantification while retention of ECM components was evaluated by measuring the content of hydroxyproline and glycosaminoglycan (GAGs). Depending on the decellularization protocol, the composition and DNA content of the resulting DAT were different. All DAT samples were processed into hydrogels to assess their mechanical properties as well as their influence on cellular metabolic activity and cell differentiation. The different compositions of the DAT and the resulting hydrogels had an effect on the stability and printability of the gels. Some DAT that were digested with hydrochloric acid (HCl) were more stable than those that were digested with acetic acid (AA). In addition, depending on the protocol, there was a clear effect on adipose-derived stem cells (ASC), endothelial cells and fibroblasts, cultured with the hydrogels. The differentiation of ASC to adipocytes could be achieved on most of the hydrogels. Human dermal microvascular endothelial cells (HDMEC) showed significantly better metabolic activity on hydrogels digested with HCl than digested with AA. HDMEC cultured on hydrogel #2 digested with HCl showed a 40% higher metabolic activity compared to collagen as a positive control, whereas culturing HDMEC on hydrogel #2 digested with AA resulted in a cellular metabolic activity loss of 60%. In a triculture of all three cell types, the formation of first tubular networks by HDMEC was achieved depending on the hydrogel used.

Macrophage-derived apoptotic vesicles regulate fate commitment of mesenchymal stem cells via miR155

BACKGROUND

In tissue engineering, mesenchymal stem cells (MSCs) are common seed cells because of abundant sources, strong proliferation ability and immunomodulatory function. Numerous researches have demonstrated that MSC-macrophage crosstalk played a key role in the tissue engineering. Macrophages could regulate the differentiation of MSCs via different molecular mechanisms, including extracellular vesicles. Apoptotic macrophages could generate large amounts of apoptotic vesicles (apoVs). ApoVs are rich in proteins, RNA (microRNAs, mRNAs, ncRNAs, etc.) and lipids, and are a key intercellular communication mediator that can exert different regulatory effects on recipient cells. MiRNAs account for about half of the total RNAs of extracellular vesicles, and play important roles in biological processes such as cell proliferation and differentiation, whereas the functions of macrophage-derived apoVs remain largely unknown. There was no research to clarify the role of macrophage-derived apoVs in MSC fate choices. In this study, we aimed to characterize macrophage-derived apoVs, and investigate the roles of macrophage-derived apoVs in the fate commitment of MSCs.

METHODS

We characterized macrophage-derived apoVs, and investigated their role in MSC osteogenesis and adipogenesis in vitro and in vivo. Furthermore, we performed microRNA loss- and gain-of-function experiments and western blot to determine the molecular mechanism.

RESULTS

Macrophages could produce a large number of apoVs after apoptosis. MSCs could uptake apoVs. Then, we found that macrophage-derived apoVs inhibited osteogenesis and promoted adipogenesis of MSCs in vitro and in vivo. In mechanism, apoVs were enriched for microRNA155 (miR155), and apoVs regulated osteogenesis and adipogenesis of MSCs by delivering miR155. Besides, miR155 regulated osteogenesis and adipogenesis of MSCs cultured with macrophage-derived apoVs via the SMAD2 signaling pathway.

CONCLUSIONS

Macrophage-derived apoVs could regulate the osteogenesis and adipogenesis of MSCs through delivering miR155, which provided novel insights for MSC-mediated tissue engineering.

Emerging Potential of Exosomes on Adipogenic Differentiation of Mesenchymal Stem Cells

The mesenchymal stem cells have multidirectional differentiation potential and can differentiate into adipocytes, osteoblasts, cartilage tissue, muscle cells and so on. The adipogenic differentiation of mesenchymal stem cells is of great significance for the construction of tissue-engineered fat and the treatment of soft tissue defects. Exosomes are nanoscale vesicles secreted by cells and widely exist in body fluids. They are mainly involved in cell communication processes and transferring cargo contents to recipient cells. In addition, exosomes can also promote tissue and organ regeneration. Recent studies have shown that various exosomes can influence the adipogenic differentiation of stem cells. In this review, the effects of exosomes on stem cell differentiation, especially on adipogenic differentiation, will be discussed, and the mechanisms and conclusions will be drawn. The main purpose of studying the role of these exosomes is to understand more comprehensively the influencing factors existing in the process of stem cell differentiation into adipocytes and provide a new idea in adipose tissue engineering research.

Modeling Adipogenesis: Current and Future Perspective

Adipose tissue is contemplated as a dynamic organ that plays key roles in the human body. Adipogenesis is the process by which adipocytes develop from adipose-derived stem cells to form the adipose tissue. Adipose-derived stem cells' differentiation serves well beyond the simple goal of producing new adipocytes. Indeed, with the current immense biotechnological advances, the most critical role of adipose-derived stem cells remains their tremendous potential in the field of regenerative medicine. This review focuses on examining the physiological importance of adipogenesis, the current approaches that are employed to model this tightly controlled phenomenon, and the crucial role of adipogenesis in elucidating the pathophysiology and potential treatment modalities of human diseases. The future of adipogenesis is centered around its crucial role in regenerative and personalized medicine.

A Straightforward Approach to Engineer Vascularized Adipose Tissue Using Microvascular Fragments

There is a need to overcome the donor-site morbidity and loss of volume over time that accompanies the current clinical approaches to treat soft tissue defects caused by disease and trauma. The development of bioactive constructs that can regenerate adipose tissue have made great progress toward addressing the limitations of current therapies, but their lack of vascularization and ability to meet the significant dimension requirements of tissue defects limit their clinical translatability. Microvascular fragments (MVFs) can form extensive vascular networks and contain resident cells that have the ability to differentiate into adipocytes. Therefore, the objective of this study was to determine if vascularized adipose tissue could be engineered using a fibrin-based hydrogel containing MVFs as the sole source of microvessels and adipocyte-forming cells. The potential for MVFs from different fat depots (epididymal, inguinal, and subcutaneous) to form microvascular networks and generate adipocytes when exposed to growth media (GM), adipogenic differentiation media (ADM), or when treated with GM before adipogenic induction (i.e., they were allowed to presprout before adipogenic induction) was evaluated. MVFs treated with adipogenic induction media, both with and without presprouting, contained lipid droplets, had an increase in expression levels of genes associated with adipogenesis (adiponectin and fatty acid synthase [FAS]), and had an increased rate of lipolysis. MVFs allowed to presprout before ADM treatment maintained their ability to form vascular networks while maintaining an elevated lipid content, adipogenic gene expression, and lipolysis rate. Collectively, these results support the contention that MVFs can serve as the sole source of biologic material for creating a vascularized adipose tissue scaffold. Impact statement Microvascular fragments have both the ability to form extensive vascular networks and function as a source of adipocytes. These phenomena were exploited as vascularized adipose tissue was generated by first allowing for a period of angiogenesis before the adipogenic induction. This strategy has the ability to provide a means of both improving soft tissue reconstruction while also serving as a model to better understand adipose tissue expansion.

Primary Cilia Mediate Wnt5a/β-catenin Signaling to Regulate Adipogenic Differentiation of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Following Calcium Induction

BACKGROUND

Regeneration of soft tissue defects is essential for adipose tissue pathologies and disease, trauma, or injury-induced damage. Here, we show that umbilical cord blood-derived mesenchymal stem cells could potentially be tailored and used for the reconstruction of specific damaged sites. Adipogenesis can be exploited in soft tissue reconstruction. Also, primary cilia play a role in the control of adipogenesis.

METHODS

The adipogenic differentiation capacity of mesenchymal stem cells (MSCs) was shown to influence ciliogenesis. MSCs transfected with intraflagellar transport 88 (IFT88) small interfering RNA (siRNA), which blocks the assembly and maintenance of cilia, were examined to confirm the relationship between adipogenesis and ciliogenesis. Also, 1,2-Bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) (BAPTA-AM), calcium chelator, inhibited the ciliogenesis of MSCs in adipogenic differentiation.

RESULTS

IFT88-knockdown led to decreased cilia formation and limitation of cilia elongation in adipogenesis. Additionally, intracellular calcium triggered cilia formation in MSCs adipogenesis. Interestingly, intracellular calcium cannot overcome the inhibition of adipogenesis caused by low numbers of cilia in MSCs.

CONCLUSION

Our data suggested that ciliogenesis was negatively regulated by Wnt5a/β-catenin signaling during adipogenesis. Thus, we suggest that calcium induction triggers adipogenesis and ciliogenesis.

Biological Features Implies Potential Use of Autologous Adipose-Derived Stem/Progenitor Cells in Wound Repair and Regenerations for the Patients with Lipodystrophy

A paradigm shift in plastic and reconstructive surgery is brought about the usage of cell-based therapies for wound healing and regeneration. Considering the imitations in the reconstructive surgeries in restoring tissue loss and deficiency, stem cell-based therapy, in particular, has been expected to pave the way for a new solution to the regenerative approaches. Limitations in the reconstructive surgeries in restoring tissue loss and deficiency have paved the way for new regenerative approaches. Among them, adipose-derived stem/progenitor cells (ADSCs)-based therapy could be the most promising clue, since ADSCs have pluripotent differentiation capabilities not only in adipocytes but also in a variety of cell types. Accumulating evidences have indicated that the unfavorable development of adipose-tissue damage, namely, lipodystrophy, is a systemic complication, which is closely related to metabolic abnormality. Considering ADSC-based regenerative medicine should be applied for the treatment of lipodystrophy, it is inevitable to ascertain whether the ADSCs obtained from the patients with lipodystrophy are capable of being used. It will be very promising and realistic if this concept is applied to lipoatrophy; one form of lipodystrophies that deteriorates the patients’ quality of life because of excessive loss of soft tissue in the exposed areas such as face and extremities. Since lipodystrophy is frequently observed in the human immunodeficiency virus (HIV)-infected patients receiving highly active antiretroviral therapy (HAART), the present study aims to examine the biological potentials of ADSCs isolated from the HIV-infected patients with lipodystrophy associated with the HAART treatment. Growth properties, adipogenic differentiation, and mitochondrial reactive oxygen species (ROS) production were examined in ADSCs from HIV-infected and HIV-uninfected patients. Our results clearly demonstrated that ADSCs from both patients showed indistinguishable growth properties and potentials for adipocyte differentiation in vitro. Thus, although the number of cases were limited, ADSCs isolated from the patients with lipodystrophy retain sufficient physiological and biological activity for the reconstitution of adipose-tissue, suggesting that ADSCs from the patients with lipodystrophy could be used for autologous ADSC-based regenerative therapy.

Biocompatibility in regenerative nanomedicine

Biocompatibility is a very common word that is used within biomaterial science and used for description of the interactions between the foreign material and the body. However, the meaning of biocompatibility as well as the mechanisms that collectively constitutes is still unclear. With the advance of nanotechnology, new concerns have been observed related to biocompatibility of these biomaterials. Due to their small size and variability of their physical and chemical properties, nanoparticles' (NP) distribution within the body and interactions with the target cells and tissues are highly variable. Here, we tried to provide an overview about NPs, the concept of biocompatibility and biocompatibility-related issues in nanomedicine and several different NPs.