Mass spectrometry-based proteomics of 3D cell culture: A useful tool to validate culture of spheroids and organoids

Musculoskeletal organoids: An emerging toolkit for establishing personalized models of musculoskeletal disorders and developing regenerative therapies

Musculoskeletal (MSK) conditions are the primary cause of physical disability globally. These disorders are physically and mentally debilitating and severely impact the patients' quality of life. As the median age of the world's population increases, there has been an intensifying urgency of developing efficacious therapies for various orthopaedic conditions. Furthermore, the highly heterogeneous nature of MSK conditions calls for a personalized approach to studying disease mechanisms and developing regenerative treatments. Organoids have emerged as an advanced approach to generating functional tissue/organ mimics in vitro, which hold promise in MSK regeneration, disease modeling, and therapeutic development. Herein, we review the preparation, characterization, and application of various MSK organoids. We highlight the potential of patient-specific organoids in the development of personalized medicine and discuss the challenges and opportunities in the future development of MSK organoids. STATEMENT OF SIGNIFICANCE: Despite decades of research, translation of MSK research into clinical applications remains limited, partially attributed to our inadequate understanding of disease mechanisms. To advance therapeutic development, there are critical needs for MSK disease models with higher clinical relevance and predictive power. Additionally, engineered constructs that closely mimic the structural and functional features of native MSK tissues are highly desirable. MSK organoids have emerged as a promising approach to meet the above requirements. To unleash the full potential of MSK organoids necessitates a comprehensive understanding of their categories, construction, development, functions, applications, and challenges. This review aims to fulfill this crucial need, aiming to accelerate the clinical translation of MSK organoid platforms to benefit millions of patients afflicted with MSK conditions.

Proximity labeling and SILAC based proteomic approach identifies proteins at the interface of homotypic and heterotypic cancer cell interactions

Cell-cell interactions are critical for the growth of organisms and maintaining homeostasis. In the tumor microenvironment, these interactions promote cancer progression. Given their importance in healthy and diseased conditions, we have developed a method to analyze the cell-to-cell interactome. Our approach uses enzyme-catalyzed proximity labeling and SILAC-based proteomics to identify the proteins involved in cancer cell interactions. By targeting HRP to the outer leaflet of the plasma membrane in bait cells, we were able to label the neighboring prey cells and distinguish between the proteomes of bait and prey cells using SILAC labeling in a co-culture system. We mapped both the homotypic and heterotypic interactomes of epithelial and mesenchymal breast cancer cells. The enrichment of cell surface and extracellular proteins confirms the specificity of our methodology. We further verified selected hits from different cell-cell interactomes in co-cultures using microscopy. This method revealed prominent signaling pathways orchestrating homotypic and heterotypic interactions of epithelial and mesenchymal cells. It also highlights the importance of exosomes in these interactions. Our methodology can be applied to any type of cell-cell interaction in 2D co-culture or 3D tumor models.

Mass Spectrometry Imaging of Organoids to Improve Preclinical Research

Preclinical models are essential research tools before novel therapeutic or diagnostic methods can be applied to humans. These range from in vitro cell monocultures to vastly more complex animal models, but clinical translation to humans often fails to deliver significant results. Three-dimensional (3D) organoid systems are being increasingly studied to establish physiologically relevant in vitro platforms in a trade-off between the complexity of the research question and the complexity of practical experimental setups. The sensitivity and precision of analytical tools are yet another limiting factors in what can be investigated, and mass spectrometry (MS) is one of the most powerful analytical techniques available to the scientific community. Its innovative use to spatially resolve biological samples has opened many research avenues in the field of MS imaging (MSI). Here, this work aims to explore the current scientific landscape in the application of MSI on organoids, with an emphasis on their combined potential to facilitate and improve preclinical studies.

Mini-bones: miniaturized bone in vitro models

In bone tissue engineering (TE) and regeneration, miniaturized, (sub)millimeter-sized bone models have become a popular trend since they bring about physiological biomimicry, precise orchestration of concurrent stimuli, and compatibility with high-throughput setups and high-content imaging. They also allow efficient use of cells, reagents, materials, and energy. In this review, we describe the state of the art of miniaturized in vitro bone models, or 'mini-bones', describing these models based on their characteristics of (multi)cellularity and engineered extracellular matrix (ECM), and elaborating on miniaturization approaches and fabrication techniques. We analyze the performance of 'mini-bone' models according to their applications for studying basic bone biology or as regeneration models, disease models, and screening platforms, and provide an outlook on future trends, challenges, and opportunities.

Improving obesity research: Unveiling metabolic pathways through a 3D In vitro model of adipocytes using 3T3-L1 cells

Obesity, a burgeoning global health crisis, has tripled in prevalence over the past 45 years, necessitating innovative research methodologies. Adipocytes, which are responsible for energy storage, play a central role in obesity. However, most studies in this field rely on animal models or adipocyte monolayer cell cultures, which are limited in their ability to fully mimic the complex physiology of a living organism, or pose challenges in terms of cost, time consumption, and ethical considerations. These limitations prompt a shift towards alternative methodologies. In response, here we show a 3D in vitro model utilizing the 3T3-L1 cell line, aimed at faithfully replicating the metabolic intricacies of adipocytes in vivo. Using a workable cell line (3T3-L1), we produced adipocyte spheroids and differentiated them in presence and absence of TNF-α. Through a meticulous proteomic analysis, we compared the molecular profile of our adipose spheroids with that of adipose tissue from lean and obese C57BL/6J mice. This comparison demonstrated the model's efficacy in studying metabolic conditions, with TNF-α treated spheroids displaying a notable resemblance to obese white adipose tissue. Our findings underscore the model's simplicity, reproducibility, and cost-effectiveness, positioning it as a robust tool for authentically mimicking in vitro metabolic features of real adipose tissue. Notably, our model encapsulates key aspects of obesity, including insulin resistance and an obesity profile. This innovative approach has the potential to significantly impact the discovery of novel therapeutic interventions for metabolic syndrome and obesity. By providing a nuanced understanding of metabolic conditions, our 3D model stands as a transformative contribution to in vitro research, offering a pathway for the development of small molecules and biologics targeting these pervasive health issues in humans.

Photon and Proton irradiation in Patient-derived, Three-Dimensional Soft Tissue Sarcoma Models

BACKGROUND

Despite their heterogeneity, the current standard preoperative radiotherapy regimen for localized high-grade soft tissue sarcoma (STS) follows a one fits all approach for all STS subtypes. Sarcoma patient-derived three-dimensional cell culture models represent an innovative tool to overcome challenges in clinical research enabling reproducible subtype-specific research on STS. In this pilot study, we present our methodology and preliminary results using STS patient-derived 3D cell cultures that were exposed to different doses of photon and proton radiation. Our aim was: (i) to establish a reproducible method for irradiation of STS patient-derived 3D cell cultures and (ii) to explore the differences in tumor cell viability of two different STS subtypes exposed to increasing doses of photon and proton radiation at different time points.

METHODS

Two patient-derived cell cultures of untreated localized high-grade STS (an undifferentiated pleomorphic sarcoma (UPS) and a pleomorphic liposarcoma (PLS)) were exposed to a single fraction of photon or proton irradiation using doses of 0 Gy (sham irradiation), 2 Gy, 4 Gy, 8 Gy and 16 Gy. Cell viability was measured and compared to sham irradiation at two different time points (four and eight days after irradiation).

RESULTS

The proportion of viable tumor cells four days after photon irradiation for UPS vs. PLS were significantly different with 85% vs. 65% (4 Gy), 80% vs. 50% (8 Gy) and 70% vs. 35% (16 Gy). Proton irradiation led to similar diverging viability curves between UPS vs. PLS four days after irradiation with 90% vs. 75% (4 Gy), 85% vs. 45% (8 Gy) and 80% vs. 35% (16 Gy). Photon and proton radiation displayed only minor differences in cell-killing properties within each cell culture (UPS and PLS). The cell-killing effect of radiation sustained at eight days after irradiation in both cell cultures.

CONCLUSIONS

Pronounced differences in radiosensitivity are evident among UPS and PLS 3D patient-derived sarcoma cell cultures which may reflect the clinical heterogeneity. Photon and proton radiation showed similar dose-dependent cell-killing effectiveness in both 3D cell cultures. Patient-derived 3D STS cell cultures may represent a valuable tool to enable translational studies towards individualized subtype-specific radiotherapy in patients with STS.

Unraveling White Adipose Tissue Heterogeneity and Obesity by Adipose Stem/Stromal Cell Biology and 3D Culture Models

The immune and endocrine dysfunctions of white adipose tissue are a hallmark of metabolic disorders such as obesity and type 2 diabetes. In humans, white adipose tissue comprises distinct depots broadly distributed under the skin (hypodermis) and as internal depots (visceral). Depot-specific ASCs could account for visceral and subcutaneous adipose tissue properties, by regulating adipogenesis and immunomodulation. More importantly, visceral and subcutaneous depots account for distinct contributions to obesity and its metabolic comorbidities. Recently, distinct ASCs subpopulations were also described in subcutaneous adipose tissue. Interestingly, the superficial layer closer to the dermis shows hyperplastic and angiogenic capacities, whereas the deep layer is considered as having inflammatory properties similar to visceral. The aim of this focus review is to bring the light of recent discoveries into white adipose tissue heterogeneity together with the biology of distinct ASCs subpopulations and to explore adipose tissue 3D models revealing their advantages, disadvantages, and contributions to elucidate the role of ASCs in obesity development. Recent advances in adipose tissue organoids opened an avenue of possibilities to recreate the main cellular and molecular events of obesity leading to a deep understanding of this inflammatory disease besides contributing to drug discovery. Furthermore, 3D organ-on-a-chip will add reproducibility to these adipose tissue models contributing to their translation to the pharmaceutical industry.

Towards better models for studying human adipocytes in vitro

With obesity and its comorbidities continuing to rise, we urgently need to improve our understanding of what mechanisms trigger the white adipose tissue to become dysfunctional in response to over-feeding. The recent invent of 3D culturing models has produced several noteworthy protocols for differentiating unilocular adipocytes in vitro, promising to revolutionize the obesity research field by providing more representative adipose tissue models for such mechanistic studies. In parallel, these 3D models provide important insights to how profoundly the microenvironment influences adipocyte differentiation and morphology. This commentary highlights some of the most recent 3D models, including human unilocular vascularized adipocyte spheroids (HUVASs), developed by our lab. We discuss recent developments in the field, provide further insights to the importance of the microvasculature for adipocyte maturation, and summarize what challenges remain to be solved before we can achieve a culture model that fully recapitulates all aspects of human white adipocyte biology in vitro. Taken together, the commentary highlights important recent advances regarding 3D adipocyte culturing and underlines the many advantages these models provide over traditional 2D cultures, with the aim of convincing more laboratories to switch to 3D models.