Adipose Tissue-Derived Stem Cells Retain Their Adipocyte Differentiation Potential in Three-Dimensional Hydrogels and Bioreactors †

Latest developments of microphysiological systems (MPS) in aging-related and geriatric diseases research: A review

Aging is a gradual and irreversible process accompanied by the decline in tissue function and a significantly increased risk of various aging-related and geriatric diseases. Especially in the paradoxical context of accelerated global aging and the widespread emergence of pandemics, aging-related and geriatric diseases have become leading causes of individual mortality and disability, drawing increasing attention from researchers and investors alike. Despite the utility of current in vitro systems and in vivo animal models for studying aging, these approaches are limited by insurmountable inherent constraints. In response, microphysiological systems (MPS), leveraging advances in tissue engineering and microfluidics, have emerged as highly promising platforms. MPS are capable of replicating key features of the tissue microenvironment within microfabricated devices, offering biomimetic tissue culture conditions that enhance the in vitro simulation of intact or precise human body structure and function. This capability improves the predictability of clinical trial outcomes while reducing time and cost. In this review, we focus on recent advancements in MPS used to study age-related and geriatric diseases, with particular emphasis on the application of organoids and organ-on-a-chip technologies in understanding cardiovascular diseases, cerebrovascular diseases, neurodegenerative diseases, fibrotic diseases, locomotor and sensory degenerative disorders, and rare diseases. And we aim to provide readers with critical guidelines and an overview of examples for modeling age-related and geriatric diseases using MPS, exploring mechanisms, treatments, drug screening, and other subsequent applications, from a physiopathological perspective, emphasizing the characteristic of age-related and geriatric diseases and their established correlations with the aging process. We also discuss the limitations of current models and propose future directions for MPS in aging research, highlighting the potential of interdisciplinary approaches to address unresolved challenges in the field.

ECM-mimicking hydrogel models of human adipose tissue identify deregulated lipid metabolism in the prostate cancer-adipocyte crosstalk under antiandrogen therapy

Antiandrogen therapies are effectively used to treat advanced prostate cancer, but eventually cancer adaptation drives unresolved metastatic castration-resistant prostate cancer (mCRPC). Adipose tissue influences metabolic reprogramming in cancer and was proposed as a contributor to therapy resistance. Using extracellular matrix (ECM)-mimicking hydrogel coculture models of human adipocytes and prostate cancer cells, we show that adipocytes from subcutaneous or bone marrow fat have dissimilar responses under the antiandrogen Enzalutamide. We demonstrate that androgen receptor (AR)-dependent cancer cells (LNCaP) are more influenced by human adipocytes than AR-independent cells (C4-2B), with altered lipid metabolism and adipokine secretion. This response changes under Enzalutamide, with increased AR expression and adipogenic and lipogenic genes in cancer cells and decreased lipid content and gene dysregulation associated with insulin resistance in adipocytes. This is in line with the metabolic syndrome that men with mCRPC under Enzalutamide experience. The all-human, all-3D, models presented here provide a significant advance to dissect the role of fat in therapy response for mCRPC.

Metabolic Functions of the Infrapatellar Fat Pad: Implications for Knee Health and Pathology

» Despite being historically viewed as a vestigial structure, the infrapatellar fat pad (IPFP) is now recognized as a metabolically active structure, influencing knee health through cytokine production and metabolic pathways.» With distinct anatomical regions, the IPFP contains diverse cell types including adipocytes, fibroblasts, and immune cells, influencing its functional roles, pathology, and contributions to knee disorders.» The IPFP acts as an endocrine organ by releasing adipokines such as adiponectin, leptin, and tumor necrosis factor α, regulating energy balance, immune responses, and tissue remodelling, with implications for knee joint health.» The IPFP's metabolic interactions with neighboring tissues influence joint health, clinical conditions such as knee pain, osteoarthritis, postoperative complications, and ganglion cysts, highlighting its therapeutic potential and clinical relevance.» Understanding the multifaceted metabolic role of the IPFP opens avenues for collaborative approaches that integrate orthopaedics, endocrinology, and immunology to develop innovative therapeutic strategies targeting the intricate connections between adipokines, joint health, and immune responses.

The biphasic role of the infrapatellar fat pad in osteoarthritis

Osteoarthritis (OA) is a progressive degenerative disease resulting in joint deterioration. It is a whole organ disease characterized by cartilage degeneration and varying degrees of synovitis, involving pathological changes in all joint tissues, such as cartilage, subchondral bone, ligaments, meniscus, synovium, and infrapatellar fat pad (IPFP). IPFP is the largest adipose tissue structure in the knee joint and is composed of fat cells, immune cells and blood vessels. Moreover, IPFP is located close to the cartilage and bone surface so that it may reduce the impact of loading and absorb forces generated through the knee joint, and may have a protective role in joint health. IPFP has been shown to release various cytokines and adipokines that play pro-inflammatory and pro-catabolic roles in cartilage, promoting OA progression. Intra-articular injections of IPFP-derived mesenchymal stem cells and exosomes have been shown to reduce pain and prevent OA progression in patients with knee OA. Previous studies have shown that IPFP has a biphasic effect on OA progression. This article reviews the latest research progress of IPFP, discusses the role and mechanism of IPFP in OA, provide new intervention strategies for the treatment of OA. This article will also discuss the handling of IPFP during the procedure of total knee arthroplasty.

Lesson on obesity and anatomy of adipose tissue: new models of study in the era of clinical and translational research

Obesity is a serious global illness that is frequently associated with metabolic syndrome. Adipocytes are the typical cells of adipose organ, which is composed of at least two different tissues, white and brown adipose tissue. They functionally cooperate, interconverting each other under physiological conditions, but differ in their anatomy, physiology, and endocrine functions. Different cellular models have been proposed to study adipose tissue in vitro. They are also useful for elucidating the mechanisms that are responsible for a pathological condition, such as obesity, and for testing therapeutic strategies. Each cell model has its own characteristics, culture conditions, advantages and disadvantages. The choice of one model rather than another depends on the specific study the researcher is conducting. In recent decades, three-dimensional cultures, such as adipose spheroids, have become very attractive because they more closely resemble the phenotype of freshly isolated cells. The use of such models has developed in parallel with the evolution of translational research, an interdisciplinary branch of the biomedical field, which aims to learn a scientific translational approach to improve human health and longevity. The focus of the present review is on the growing body of data linking the use of new cell models and the spread of translational research. Also, we discuss the possibility, for the future, to employ new three-dimensional adipose tissue cell models to promote the transition from benchside to bedsite and vice versa, allowing translational research to become routine, with the final goal of obtaining clinical benefits in the prevention and treatment of obesity and related disorders.

Engineering Innervated Musculoskeletal Tissues for Regenerative Orthopedics and Disease Modeling

Musculoskeletal (MSK) disorders significantly burden patients and society, resulting in high healthcare costs and productivity loss. These disorders are the leading cause of physical disability, and their prevalence is expected to increase as sedentary lifestyles become common and the global population of the elderly increases. Proper innervation is critical to maintaining MSK function, and nerve damage or dysfunction underlies various MSK disorders, underscoring the potential of restoring nerve function in MSK disorder treatment. However, most MSK tissue engineering strategies have overlooked the significance of innervation. This review first expounds upon innervation in the MSK system and its importance in maintaining MSK homeostasis and functions. This will be followed by strategies for engineering MSK tissues that induce post-implantation in situ innervation or are pre-innervated. Subsequently, research progress in modeling MSK disorders using innervated MSK organoids and organs-on-chips (OoCs) is analyzed. Finally, the future development of engineering innervated MSK tissues to treat MSK disorders and recapitulate disease mechanisms is discussed. This review provides valuable insights into the underlying principles, engineering methods, and applications of innervated MSK tissues, paving the way for the development of targeted, efficacious therapies for various MSK conditions.

Unleashing the potential of adipose organoids: A revolutionary approach to combat obesity-related metabolic diseases

Obesity-related metabolic diseases, including obesity, diabetes, hyperlipidemia, and non-alcoholic fatty liver diseases pose a significant threat to health. However, comprehensive pathogenesis exploration and effective therapy development are impeded by the limited availability of human models. Notably, advances in organoid technology enable the generation of adipose organoids that recapitulate structures and functions of native human adipose tissues to investigate mechanisms and develop corresponding treatments for obesity-related metabolic diseases. Here, we review the general principles, sources, and three-dimensional techniques for engineering adipose organoids, along with strategies to promote maturation. We also outline the application of white adipose organoids, primarily for disease modeling and drug screening, and highlight the therapeutic potential of thermogenic beige and brown adipose organoids in promoting weight loss and glucose and lipid metabolic homeostasis. We also discuss the challenges and prospects in the establishment and bench-to-bedside of adipose organoids, as well as their potential applications.

Methacrylated Gelatin as a Scaffold for Mechanically Isolated Stromal Vascular Fraction for Cutaneous Wound Repair

Mechanically processed stromal vascular fraction (mSVF) is a highly interesting cell source for regenerative purposes, including wound healing, and a practical alternative to enzymatically isolated SVF. In the clinical context, SVF benefits from scaffolds that facilitate viability and other cellular properties. In the present work, the feasibility of methacrylated gelatin (GelMA), a stiffness-tunable, light-inducible hydrogel with high biocompatibility is investigated as a scaffold for SVF in an in vitro setting. Lipoaspirates from elective surgical procedures were collected and processed to mSVF and mixed with GelMA precursor solutions. Non-encapsulated mSVF served as a control. Viability was measured over 21 days. Secreted basic fibroblast growth factor (bFGF) levels were measured on days 1, 7 and 21 by ELISA. IHC was performed to detect VEGF-A, perilipin-2, and CD73 expression on days 7 and 21. The impact of GelMA-mSVF on human dermal fibroblasts was measured in a co-culture assay by the same viability assay. The viability of cultured GelMA-mSVF was significantly higher after 21 days (p < 0.01) when compared to mSVF alone. Also, GelMA-mSVF secreted stable levels of bFGF over 21 days. While VEGF-A was primarily expressed on day 21, perilipin-2 and CD73-positive cells were observed on days 7 and 21. Finally, GelMA-mSVF significantly improved fibroblast viability as compared with GelMA alone (p < 0.01). GelMA may be a promising scaffold for mSVF as it maintains cell viability and proliferation with the release of growth factors while facilitating adipogenic differentiation, stromal cell marker expression and fibroblast proliferation.

Enhanced Angiogenesis in HUVECs Preconditioned with Media from Adipocytes Differentiated from Lipedema Adipose Stem Cells In Vitro

Lipedema is a connective tissue disorder characterized by increased dilated blood vessels (angiogenesis), inflammation, and fibrosis of the subcutaneous adipose tissue. This project aims to gain insights into the angiogenic processes in lipedema using human umbilical vein endothelial cells (HUVECs) as an in vitro model. HUVECs were cultured in conditioned media (CM) collected from healthy (non-lipedema, AQH) and lipedema adipocytes (AQL). The impacts on the expression levels of multiple endothelial and angiogenic markers [CD31, von Willebrand Factor (vWF), angiopoietin 2 (ANG2), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), matrix metalloproteinase (MMPs), NOTCH and its ligands] in HUVECs were investigated. The data demonstrate an increased expression of CD31 and ANG2 at both the gene and protein levels in HUVECs treated with AQL CM in 2D monolayer and 3D cultures compared to untreated cells. Furthermore, the expression of the vWF, NOTCH 4, and DELTA-4 genes decreased. In contrast, increased VEGF, MMP9, and HGF gene expression was detected in HUVECs treated with AQL CM cultured in a 2D monolayer. In addition, the results of a tube formation assay indicate that the number of formed tubes increased in lipedema-treated HUVECs cultured in a 2D monolayer. Together, the data indicate that lipedema adipocyte-CM promotes angiogenesis through paracrine-driven mechanisms.

GelMA and Biomimetic Culture Allow the Engineering of Mineralized, Adipose, and Tumor Tissue Human Microenvironments for the Study of Advanced Prostate Cancer In Vitro and In Vivo

Increasing evidence shows bone marrow (BM)-adipocytes as a potentially important contributor in prostate cancer (PCa) bone metastases. However, a lack of relevant models has prevented the full understanding of the effects of human BM-adipocytes in this microenvironment. It is hypothesized that the combination of tunable gelatin methacrylamide (GelMA)-based hydrogels with the biomimetic culture of human cells would offer a versatile 3D platform to engineer human bone tumor microenvironments containing BM-adipocytes. Human osteoprogenitors, adipocytes, and PCa cells are individually cultured in vitro in GelMA hydrogels, leading to mineralized, adipose, and PCa tumor 3D microtissues, respectively. Osteoblast mineralization and tumor spheroid formation are tailored by hydrogel stiffness with lower stiffnesses correlating with increased mineralization and tumor spheroid size. Upon coculture with tumor cells, BM-adipocytes undergo morphological changes and delipidation, suggesting reciprocal interactions between the cell types. When brought in vivo, the mineralized and adipose microtissues successfully form a humanized fatty bone microenvironment, presenting, for the first time, with human adipocytes. Using this model, an increase in tumor burden is observed when human adipocytes are present, suggesting that adipocytes support early bone tumor growth. The advanced platform presented here combines natural aspects of the microenvironment with tunable properties useful for bone tumor research.

One-Pot Synthesis of Double-Network PEG/Collagen Hydrogel for Enhanced Adipogenic Differentiation and Retrieval of Adipose-Derived Stem Cells

Hydrogels are widely used in stem cell therapy due to their extensive tunability and resemblance to the extracellular matrix (ECM), which has a three-dimensional (3D) structure. These features enable various applications that enhance stem cell maintenance and function. However, fast and simple hydrogel fabrication methods are desirable for stem cells for efficient encapsulation and to reduce adverse effects on the cells. In this study, we present a one-pot double-crosslinked hydrogel consisting of polyethylene glycol (PEG) and collagen, which can be prepared without the multi-step sequential synthesis of each network, by using bio-orthogonal chemistry. To enhance the adipogenic differentiation efficiency of adipose-derived stem cells (ADSCs), we added degradable components within the hydrogel to regulate matrix stiffness through cell-mediated degradation. Bio-orthogonal reactions used for hydrogel gelation allow rapid gel formation for efficient cell encapsulation without toxic by-products. Furthermore, the hybrid network of synthetic (PEG) and natural (collagen) components demonstrated adequate mechanical strength and higher cell adhesiveness. Therefore, ADSCs grown within this hybrid hydrogel proliferated and functioned better than those grown in the single-crosslinked hydrogel. The degradable elements further improved adipogenesis in ADSCs with dynamic changes in modulus during culture and enabled the retrieval of differentiated cells for potential future applications.

Synovial joint-on-a-chip for modeling arthritis: progress, pitfalls, and potential

Disorders of the synovial joint, such as osteoarthritis (OA) and rheumatoid arthritis (RA), afflict a substantial proportion of the global population. However, current clinical management has not been focused on fully restoring the native function of joints. Organ-on-chip (OoC), also called a microphysiological system, which typically accommodates multiple human cell-derived tissues/organs under physiological culture conditions, is an emerging platform that potentially overcomes the limitations of current models in developing therapeutics. Herein, we review major steps in the generation of OoCs for studying arthritis, discuss the challenges faced when these novel platforms enter the next phase of development and application, and present the potential for OoC technology to investigate the pathogenesis of joint diseases and the development of efficacious therapies.

Prussian Blue Nanoparticle-Entrapped GelMA Gels Laden with Mesenchymal Stem Cells as Prospective Biomaterials for Pelvic Floor Tissue Repair

Pelvic organ prolapse (POP) seriously affects elderly patients' quality of life, and new repair materials are urgently needed. To solve this problem, we synthesized methacrylated gelatin (GelMA) hydrogels and incorporated photothermally active Prussian blue nanoparticles (PBNPs) to synthesize PBNP@GelMA. Then, MSCs were encapsulated in the PBNP@GelMA and exposed to a 1.0 W/cm² of 808 nm laser for 10 min to perform heat shock pretreatment for the implantation of mesenchymal stem cells (MSCs). Next, we tested the repair efficacy of scaffold-cell complexes both in vitro and in vivo. Our results reveal that the heat shock treatment induced by PBNP@GelMA improved the viability of MSCs, and the underlying mechanism may be related to HSP70. Furthermore, 2 weeks after implantation in the SD rat model, the collagen content increased in the MSC implantation group and PBNP@GelMA implantation group. However, the muscle regeneration at the implanting position was mostly enhanced after the implantation of the heat-shock-pretreated MSCs, which illustrates that heat shock treatment can further promote the MSC-mediated muscle regeneration. Therefore, manipulating the cell environment and providing proper heat stimulus by using PBNP@GelMA with NIR is a novel strategy to enhance the regenerative potential of MSCs and to promote pelvic tissue repair.

Alternative Methods as Tools for Obesity Research: In Vitro and In Silico Approaches

The study of adipogenesis is essential for understanding and treating obesity, a multifactorial problem related to body fat accumulation that leads to several life-threatening diseases, becoming one of the most critical public health problems worldwide. In this review, we propose to provide the highlights of the adipogenesis study based on in vitro differentiation of human mesenchymal stem cells (hMSCs). We list in silico methods, such as molecular docking for identification of molecular targets, and in vitro approaches, from 2D, more straightforward and applied for screening large libraries of substances, to more representative physiological models, such as 3D and bioprinting models. We also describe the development of physiological models based on microfluidic systems applied to investigate adipogenesis in vitro. We intend to identify the main alternative models for adipogenesis evaluation, contributing to the direction of preclinical research in obesity. Future directions indicate the association of in silico and in vitro techniques to bring a clear picture of alternative methods based on adipogenesis as a tool for obesity research.

Umbilical cord derived mesenchymal stem cell-GelMA microspheres for accelerated wound healing

Mesenchymal stem cells (MSCs) are an ideal seed cell for tissue engineering and stem cell transplantation. MSCs combined with biological scaffolds play an important role in promoting the repair of cutaneous wound. However, direct administration of MSCs is challenging for MSCs survival and integration into tissues. Providing MSCs with a biocompatible scaffold can improve MSCs survival, but the effect of gelatin methacrylate (GelMA) loaded MSCs from umbilical cord MSCs (UC-MSCs) in wound healing remains unknown. Here, we investigated the ability of GelMA with UC-MSCs complexes to promote migration and proliferation and the effect on wound healing in mouse models. We discovered that UC-MSCs attached to GelMA and promoted the proliferation and migration of fibroblasts. Both UC-MSCs and UC-MSCs-derived extracellular vesicles accelerated wound healing. MSC + Gelatin methacrylate microspheres (GMs) application decreased expression of transforming growth factor-β(TGF-β) and Type III collagen (Col3)in vivo, leading to new collagen deposition and angiogenesis, and accelerate wound healing and skin tissue regeneration. Taken together, these findings indicate MSC + GMs can promote wound healing by regulating wound healing-related factors in the paracrine. Therefore, our research proves that GelMA is an ideal scaffold for the top management of UC-MSCs in wound healing medical practice.

Harvestable tumour spheroids initiated in a gelatin-carboxymethyl cellulose hydrogel for cancer targeting and imaging with fluorescent gold nanoclusters

Cancer cell spheroids are the simplest 3D in vitro cancer models and have been extensively used for cancer research. More recently, models have been becoming complex, with the introduction of a matrix and non-cancer cell types to mimic specific tumour aspects. However, applying drugs or agents in matrix-embedded cancer spheroids can be problematic. Most matrices can impede and also bind drugs or visualizing agents non-specifically, in the vicinity of the embedded spheroids. This may interfere with imaging or further analysis without breaking apart the 3D model into its constituents. Here, we developed a combined gelatin-carboxymethyl cellulose (G-CMC) hydrogel for initiating cancer spheroids that enabled intact harvesting pre/post treatment for further investigation, such as targeting and imaging. We combined CMC (1.25%) and gelatin (2.5%) at 25 °C and initiated polymerisation after autoclaving (121 °C) to obtain a mechanical strength (sheer stress) of 38 Pas versus 1.28 Pas for CMC alone. These matrix conditions facilitated separation of the spheroids from the G-CMC, using low centrifugation (100 g). We described growth of colorectal and breast cancer spheroids within the G-CMC matrix (with average diameters of 220 mm and 180 μm for representative cell lines HT29 and MCF7 at 10 days, respectively). As the cancer cells express the surface biomarker calreticulin (CRT), we manufactured anti-calreticulin IgG (anti-CRT) conjugated to fluorescent gold nanoclusters (anti-CRT-AuNC) as a probe. We harvested cancer spheroids and incubated live with the nanoclusters. Imaging demonstrated strong binding of CRT-targeted AuNCs compared to control AuNCs. This novel model preserves cancer spheroid integrity upon isolation and is well suited for targeted imaging and drug delivery of cancer in 3D.

Bioprinting of 3D Adipose Tissue Models Using a GelMA-Bioink with Human Mature Adipocytes or Human Adipose-Derived Stem Cells

Adipose tissue is related to the development and manifestation of multiple diseases, demonstrating the importance of suitable in vitro models for research purposes. In this study, adipose tissue lobuli were explanted, cultured, and used as an adipose tissue control to evaluate in vitro generated adipose tissue models. During culture, lobule exhibited a stable weight, lactate dehydrogenase, and glycerol release over 15 days. For building up in vitro adipose tissue models, we adapted the biomaterial gelatin methacryloyl (GelMA) composition and handling to homogeneously mix and bioprint human primary mature adipocytes (MA) and adipose-derived stem cells (ASCs), respectively. Accelerated cooling of the bioink turned out to be essential for the homogeneous distribution of lipid-filled MAs in the hydrogel. Last, we compared manual and bioprinted GelMA hydrogels with MA or ASCs and the explanted lobules to evaluate the impact of the printing process and rate the models concerning the physiological reference. The viability analyses demonstrated no significant difference between the groups due to additive manufacturing. The staining of intracellular lipids and perilipin A suggest that GelMA is well suited for ASCs and MA. Therefore, we successfully constructed physiological in vitro models by bioprinting MA-containing GelMA bioinks.

Reassessment of adipocyte technology for cellular agriculture of alternative fat

Alternative proteins, such as cultivated meat, have recently attracted significant attention as novel and sustainable food. Fat tissue/cell is an important component of meat that makes organoleptic and nutritional contributions. Although adipocyte biology is relatively well investigated, there is limited focus on the specific techniques and strategies to produce cultivated fat from agricultural animals. In the assumed standard workflow, stem/progenitor cell lines are derived from tissues of animals, cultured for expansion, and differentiated into mature adipocytes. Here, we compile information from literature related to cell isolation, growth, differentiation, and analysis from bovine, porcine, chicken, other livestock, and seafood species. A diverse range of tissue sources, cell isolation methods, cell types, growth media, differentiation cocktails, and analytical methods for measuring adipogenic levels were used across species. Based on our analysis, we identify opportunities and challenges in advancing new technology era toward producing "alternative fat" that is suitable for human consumption.

Aberrant Expression of COX-2 and FOXG1 in Infrapatellar Fat Pad-Derived ASCs from Pre-Diabetic Donors

Osteoarthritis (OA) is a degenerative joint disease resulting in limited mobility and severe disability. Type II diabetes mellitus (T2D) is a weight-independent risk factor for OA, but a link between the two diseases has not been elucidated. Adipose stem cells (ASCs) isolated from the infrapatellar fat pad (IPFP) may be a viable regenerative cell for OA treatment. This study analyzed the expression profiles of inflammatory and adipokine-related genes in IPFP-ASCs of non-diabetic (Non-T2D), pre-diabetic (Pre-T2D), and T2D donors. Pre-T2D ASCs exhibited a substantial decrease in levels of mesenchymal markers CD90 and CD105 with no change in adipogenic differentiation compared to Non-T2D and T2D IPFP-ASCs. In addition, Cyclooxygenase-2 (COX-2), Forkhead box G1 (FOXG1) expression and prostaglandin E2 (PGE2) secretion were significantly increased in Pre-T2D IPFP-ASCs upon stimulation by interleukin-1 beta (IL-1β). Interestingly, M1 macrophages exhibited a significant reduction in expression of pro-inflammatory markers TNFα and IL-6 when co-cultured with Pre-T2D IPFP-ASCs. These data suggest that the heightened systemic inflammation associated with untreated T2D may prime the IPFP-ASCs to exhibit enhanced anti-inflammatory characteristics via suppressing the IL-6/COX-2 signaling pathway. In addition, the elevated production of PGE2 by the Pre-T2D IPFP-ASCs may also suggest the contribution of pre-diabetic conditions to the onset and progression of OA.

Using Vertebrate Stem and Progenitor Cells for Cellular Agriculture, State-of-the-Art, Challenges, and Future Perspectives

Global food systems are under significant pressure to provide enough food, particularly protein-rich foods whose demand is on the rise in times of crisis and inflation, as presently existing due to post-COVID-19 pandemic effects and ongoing conflict in Ukraine and resulting in looming food insecurity, according to FAO. Cultivated meat (CM) and cultivated seafood (CS) are protein-rich alternatives for traditional meat and fish that are obtained via cellular agriculture (CA) i.e., tissue engineering for food applications. Stem and progenitor cells are the building blocks and starting point for any CA bioprocess. This review presents CA-relevant vertebrate cell types and procedures needed for their myogenic and adipogenic differentiation since muscle and fat tissue are the primary target tissues for CM/CS production. The review also describes existing challenges, such as a need for immortalized cell lines, or physical and biochemical parameters needed for enhanced meat/fat culture efficiency and ways to address them.

A Comparative Study on the Adipogenic Differentiation of Mesenchymal Stem/Stromal Cells in 2D and 3D Culture

Mesenchymal stem/stromal cells (MSC) are capable of renewing the progenitor cell fraction or differentiating in a tissue-specific manner. Adipogenic differentiation of adipose-tissue-derived MSC (adMSC) is important in various pathological processes. Adipocytes and their progenitors are metabolically active and secrete molecules (adipokines) that have both pro- and anti-inflammatory properties. Cell culturing in 2D is commonly used to study cellular responses, but the 2D environment does not reflect the structural situation for most cell types. Therefore, 3D culture systems have been developed to create an environment considered more physiological. Since knowledge about the effects of 3D cultivation on adipogenic differentiation is limited, we investigated its effects on adipogenic differentiation and adipokine release of adMSC (up to 28 days) and compared these with the effects in 2D. We demonstrated that cultivation conditions are crucial for cell behavior: in both 2D and 3D culture, adipogenic differentiation occurred only after specific stimulation. While the size and structure of adipogenically stimulated 3D spheroids remained stable during the experiment, the unstimulated spheroids showed signs of disintegration. Adipokine release was dependent on culture dimensionality; we found upregulated adiponectin and downregulated pro-inflammatory factors. Our findings are relevant for cell therapeutic applications of adMSC in complex, three-dimensionally arranged tissues.

VIABILITY OF 3T3-L1 PREADIPOCYTES IS MODULATED BY THE APPLIED FREQUENCY BUT NOT THE EXPOSURE DURATION OF LOW INTENSITY VIBRATORY STIMULATION

Mechanical forces are the integral determinants in cell and tissue homeostasis and regeneration, and they can affect numerous biological process from proliferation to fate determination. Mechanical forces that possess low magnitude and high frequency characteristics are also known as low intensity vibrations (LIVs). These signals were studied widely on many cell types for regenerative purposes, however most of these studies select components of LIV signals (e.g., magnitude, frequency, duration, etc.) arbitrarily. Here, we addressed the effect of LIV applied frequency, LIV daily exposure time and fate induction on the viability of preadipocyte 3T3-L1 cells. For this, we performed a frequency sweep that was ranging from 30[Formula: see text]Hz to 120[Formula: see text]Hz with 15[Formula: see text]Hz increments applied for 5, 10 or 20[Formula: see text]min during quiescent growth or adipogenesis for up to 10 days. Results suggest that the applied frequency and fate induction was an important determinant of cell viability while daily exposure time had no effect. These findings contribute to the effort of optimizing a relevant mechanical stimulus that can inhibit adipogenesis.

Additive-Free Gelatine-Based Devices for Chondral Tissue Regeneration: Shaping Process Comparison among Mould Casting and Three-Dimensional Printing

Gelatine is a well-known and extensively studied biopolymer, widely used in recent decades to create biomaterials in many different ways, exploiting its molecular resemblance with collagen, the main constituent of the extra-cellular matrix, from which it is derived. Many have employed this biopolymer in tissue engineering and chemically modified (e.g., gelatin methacryloyl) or blended it with other polymers (e.g., alginate) to modulate or increase its performances and printability. Nevertheless, little is reported about its use as a stand-alone material. Moreover, despite the fact that multiple works have been reported on the realization of mould-casted and three-dimensional printed scaffolds in tissue engineering, a clear comparison among these two shaping processes, towards a comparable workflow starting from the same material, has never been published. Herein, we report the use of gelatine as stand-alone material, not modified, blended, or admixed to be processed or crosslinked, for the realization of suitable scaffolds for tissue engineering, towards the two previously mentioned shaping processes. To make the comparison reliable, the same pre-process (e.g., the gelatin solution preparation) and post-process (e.g., freeze-drying and crosslinking) steps were applied. In this study, gelatine solution was firstly rheologically characterized to find a formulation suitable for being processed with both the shaping processes selected. The realized scaffolds were then morphologically, phisico-chemically, mechanically, and biologically characterized to determine and compare their performances. Despite the fact that the same starting material was employed, as well as the same pre- and post-process steps, the two groups resulted, for most aspects, in diametrically opposed characteristics. The mould-casted scaffolds that resulted were characterized by small, little-interconnected, and random porosity, high resistance to compression and slow cell colonization, while the three-dimensional printed scaffolds displayed big, well-interconnected, and geometrically defined porosity, high elasticity and recover ability after compression, as well as fast and deep cell colonization.

Adipose Stem Cells in Regenerative Medicine: Looking Forward

Over the last decade, stem cell-based regenerative medicine has progressed to clinical testing and therapeutic applications. The applications range from infusions of autologous and allogeneic stem cells to stem cell-derived products. Adult stem cells from adipose tissue (ASCs) show significant promise in treating autoimmune and neurodegenerative diseases, vascular and metabolic diseases, bone and cartilage regeneration and wound defects. The regenerative capabilities of ASCs in vivo are primarily orchestrated by their secretome of paracrine factors and cell-matrix interactions. More recent developments are focused on creating more complex structures such as 3D organoids, tissue elements and eventually fully functional tissues and organs to replace or repair diseased or damaged tissues. The current and future applications for ASCs in regenerative medicine are discussed here.

Caveolin-1 mediates soft scaffold-enhanced adipogenesis of human mesenchymal stem cells

BACKGROUND

Human bone marrow-derived mesenchymal stem cells (hBMSCs) can differentiate into adipocytes upon stimulation and are considered an appropriate cell source for adipose tissue engineering. In addition to biochemical cues, the stiffness of a substrate that cells attach to has also been shown to affect hBMSC differentiation potential. Of note, most current studies are conducted on monolayer cultures which do not directly inform adipose tissue engineering, where 3-dimensional (3D) scaffolds are often used to create proper tissue architecture. In this study, we aim to examine the adipogenic differentiation of hBMSCs within soft or stiff scaffolds and investigate the molecular mechanism mediating the response of hBMSCs to substrate stiffness in 3D culture, specifically the involvement of the integral membrane protein, caveolin-1 (CAV1), known to regulate signaling in MSCs via compartmentalizing and concentrating signaling molecules.

METHODS

By adjusting the photo-illumination time, photocrosslinkable gelatin scaffolds with the same polymer concentration but different stiffnesses were created. hBMSCs were seeded within soft and stiff scaffolds, and their response to adipogenic induction under different substrate mechanical conditions was characterized. The functional involvement of CAV1 was assessed by suppressing its expression level using CAV1-specific siRNA.

RESULTS

The soft and stiff scaffolds used in this study had a compressive modulus of ~0.5 kPa and ~23.5 kPa, respectively. hBMSCs showed high viability in both scaffold types, but only spread out in the soft scaffolds. hBMSCs cultured in soft scaffolds displayed significantly higher adipogenesis, as revealed by histology, qRT-PCR, and immunostaining. Interestingly, a lower CAV1 level was observed in hBMSCs in the soft scaffolds, concomitantly accompanied by increased levels of Yes-associated protein (YAP) and decreased YAP phosphorylation, when compared to cells seeded in the stiff scaffolds. Interestingly, reducing CAV1 expression with siRNA was shown to further enhance hBMSC adipogenesis, which may function through activation of the YAP signaling pathway.

CONCLUSIONS

Soft biomaterials support superior adipogenesis of encapsulated hBMSCs in 3D culture, which is partially mediated by the CAV1-YAP axis. Suppressing CAV1 expression levels represents a robust method in the promotion of hBMSC adipogenesis.

Human Adipose-Derived Stromal/Stem Cell Culture and Analysis Methods for Adipose Tissue Modeling In Vitro: A Systematic Review

Human adipose-derived stromal/stem cells (hASC) are widely used for in vitro modeling of physiologically relevant human adipose tissue. These models are useful for the development of tissue constructs for soft tissue regeneration and 3-dimensional (3D) microphysiological systems (MPS) for drug discovery. In this systematic review, we report on the current state of hASC culture and assessment methods for adipose tissue engineering using 3D MPS. Our search efforts resulted in the identification of 184 independent records, of which 27 were determined to be most relevant to the goals of the present review. Our results demonstrate a lack of consensus on methods for hASC culture and assessment for the production of physiologically relevant in vitro models of human adipose tissue. Few studies have assessed the impact of different 3D culture conditions on hASC adipogenesis. Additionally, there has been a limited use of assays for characterizing the functionality of adipose tissue in vitro. Results from this study suggest the need for more standardized culture methods and further analysis on in vitro tissue functionality. These will be necessary to validate the utility of 3D MPS as an in vitro model to reduce, refine, and replace in vivo experiments in the drug discovery regulatory process.

Breast Cancer Reconstruction: Design Criteria for a Humanized Microphysiological System

International regulatory agencies such as the Food and Drug Administration have mandated that the scientific community develop humanized microphysiological systems (MPS) as an in vitro alternative to animal models in the near future. While the breast cancer research community has long appreciated the importance of three-dimensional growth dynamics in their experimental models, there are remaining obstacles preventing a full conversion to humanized MPS for drug discovery and pathophysiological studies. This perspective evaluates the current status of human tissue-derived cells and scaffolds as building blocks for an "idealized" breast cancer MPS based on bioengineering design principles. It considers the utility of adipose tissue as a potential source of endothelial, lymphohematopoietic, and stromal cells for the support of breast cancer epithelial cells. The relative merits of potential MPS scaffolds derived from adipose tissue, blood components, and synthetic biomaterials is evaluated relative to the current "gold standard" material, Matrigel, a murine chondrosarcoma-derived basement membrane-enriched hydrogel. The advantages and limitations of a humanized breast cancer MPS are discussed in the context of in-process and destructive read-out assays. Impact statement Regulatory authorities have highlighted microphysiological systems as an emerging tool in breast cancer research. This has been led by calls for more predictive human models and reduced animal experimentation. This perspective describes how human-derived cells, extracellular matrices, and hydrogels will provide the building blocks to create breast cancer models that accurately reflect diversity at multiple levels, that is, patient ethnicity, pathophysiology, and metabolic status.

3D Spheroids Derived from Human Lipedema ASCs Demonstrated Similar Adipogenic Differentiation Potential and ECM Remodeling to Non-Lipedema ASCs In Vitro

The growth and differentiation of adipose tissue-derived stem cells (ASCs) is stimulated and regulated by the adipose tissue (AT) microenvironment. In lipedema, both inflammation and hypoxia influence the expansion and differentiation of ASCs, resulting in hypertrophic adipocytes and deposition of collagen, a primary component of the extracellular matrix (ECM). The goal of this study was to characterize the adipogenic differentiation potential and assess the levels of expression of ECM-remodeling markers in 3D spheroids derived from ASCs isolated from both lipedema and healthy individuals. The data showed an increase in the expression of the adipogenic genes (ADIPOQ, LPL, PPAR-γ and Glut4), a decrease in matrix metalloproteinases (MMP2, 9 and 11), with no significant changes in the expression of ECM markers (collagen and fibronectin), or integrin A5 in 3D differentiated lipedema spheroids as compared to healthy spheroids. In addition, no statistically significant changes in the levels of expression of inflammatory genes were detected in any of the samples. However, immunofluorescence staining showed a decrease in fibronectin and increase in laminin and Collagen VI expression in the 3D differentiated spheroids in both groups. The use of 3D ASC spheroids provide a functional model to study the cellular and molecular characteristics of lipedema AT.