Short-term post-implantation dynamics of in vitro engineered human microvascularized adipose tissues

Heparan Sulfate: A Regulator of White Adipocyte Differentiation and of Vascular/Adipocyte Interactions

White adipose tissues are major endocrine organs that release factors, termed adipokines, which affect other major organ systems. The development and functions of adipose tissues depend largely upon the glycosaminoglycan heparan sulfate. Heparan sulfate proteoglycans (HSPGs) surround both adipocytes and vascular structures and facilitate the communication between these two components. This communication mediates the continued export of adipokines from adipose tissues. Heparan sulfates regulate cellular physiology and communication through a sulfation code that ionically interacts with heparan-binding regions on a select set of proteins. Many of these proteins are growth factors and chemokines that regulate tissue function and inflammation. Cells regulate heparan sulfate sulfation through the release of heparanases and sulfatases. It is now possible to tissue engineer vascularized adipose tissues that express heparan sulfate proteoglycans. This makes it possible to use these tissue constructs to study the role of heparan sulfates in the regulation of adipokine production and release. It is possible to regulate the production of heparanases and sulfatases in order to fine-tune experimental studies.

Genitourinary Tissue Engineering: Reconstruction and Research Models

Tissue engineering is an emerging field of research that initially aimed to produce 3D tissues to bypass the lack of adequate tissues for the repair or replacement of deficient organs. The basis of tissue engineering protocols is to create scaffolds, which can have a synthetic or natural origin, seeded or not with cells. At the same time, more and more studies have indicated the low clinic translation rate of research realised using standard cell culture conditions, i.e., cells on plastic surfaces or using animal models that are too different from humans. New models are needed to mimic the 3D organisation of tissue and the cells themselves and the interaction between cells and the extracellular matrix. In this regard, urology and gynaecology fields are of particular interest. The urethra and vagina can be sites suffering from many pathologies without currently adequate treatment options. Due to the specific organisation of the human urethral/bladder and vaginal epithelium, current research models remain poorly representative. In this review, the anatomy, the current pathologies, and the treatments will be described before focusing on producing tissues and research models using tissue engineering. An emphasis is made on the self-assembly approach, which allows tissue production without the need for biomaterials.

Human Organ-Specific 3D Cancer Models Produced by the Stromal Self-Assembly Method of Tissue Engineering for the Study of Solid Tumors

Cancer research has considerably progressed with the improvement of in vitro study models, helping to understand the key role of the tumor microenvironment in cancer development and progression. Over the last few years, complex 3D human cell culture systems have gained much popularity over in vivo models, as they accurately mimic the tumor microenvironment and allow high-throughput drug screening. Of particular interest, in vitrohuman 3D tissue constructs, produced by the self-assembly method of tissue engineering, have been successfully used to model the tumor microenvironment and now represent a very promising approach to further develop diverse cancer models. In this review, we describe the importance of the tumor microenvironment and present the existing in vitro cancer models generated through the self-assembly method of tissue engineering. Lastly, we highlight the relevance of this approach to mimic various and complex tumors, including basal cell carcinoma, cutaneous neurofibroma, skin melanoma, bladder cancer, and uveal melanoma.

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.

In vitro tissue-engineered adipose constructs for modeling disease

BACKGROUND

Adipose tissue is a vital tissue in mammals that functions to insulate our bodies, regulate our internal thermostat, protect our organs, store energy (and burn energy, in the case of beige and brown fat), and provide endocrine signals to other organs in the body. Tissue engineering of adipose and other soft tissues may prove essential for people who have lost this tissue from trauma or disease.

MAIN TEXT

In this review, we discuss the applications of tissue-engineered adipose tissue specifically for disease modeling applications. We provide a basic background to adipose depots and describe three-dimensional (3D) in vitro adipose models for obesity, diabetes, and cancer research applications.

CONCLUSIONS

The approaches to engineering 3D adipose models are diverse in terms of scaffold type (hydrogel-based, silk-based and scaffold-free), species of origin (H. sapiens and M. musculus) and cell types used, which allows researchers to choose a model that best fits their application, whether it is optimization of adipocyte differentiation or studying the interaction of adipocytes and other cell types like endothelial cells. In vitro 3D adipose tissue models support discoveries into the mechanisms of adipose-related diseases and thus support the development of novel anti-cancer or anti-obesity/diabetes therapies.