Biomaterials and biosensors in intestinal organoid culture, a progress review

Probing organoid metabolism using fluorescence lifetime imaging microscopy (FLIM): The next frontier of drug discovery and disease understanding

Organoid models have been used to address important questions in developmental and cancer biology, tissue repair, advanced modelling of disease and therapies, among other bioengineering applications. Such 3D microenvironmental models can investigate the regulation of cell metabolism, and provide key insights into the mechanisms at the basis of cell growth, differentiation, communication, interactions with the environment and cell death. Their accessibility and complexity, based on 3D spatial and temporal heterogeneity, make organoids suitable for the application of novel, dynamic imaging microscopy methods, such as fluorescence lifetime imaging microscopy (FLIM) and related decay time-assessing readouts. Several biomarkers and assays have been proposed to study cell metabolism by FLIM in various organoid models. Herein, we present an expert-opinion discussion on the principles of FLIM and PLIM, instrumentation and data collection and analysis protocols, and general and emerging biosensor-based approaches, to highlight the pioneering work being performed in this field.

Biosensors integrated 3D organoid/organ-on-a-chip system: A real-time biomechanical, biophysical, and biochemical monitoring and characterization

As a full-fidelity simulation of human cells, tissues, organs, and even systems at the microscopic scale, Organ-on-a-Chip (OOC) has significant ethical advantages and development potential compared to animal experiments. The need for the design of new drug high-throughput screening platforms and the mechanistic study of human tissues/organs under pathological conditions, the evolving advances in 3D cell biology and engineering, etc., have promoted the updating of technologies in this field, such as the iteration of chip materials and 3D printing, which in turn facilitate the connection of complex multi-organs-on-chips for simulation and the further development of technology-composite new drug high-throughput screening platforms. As the most critical part of organ-on-a-chip design and practical application, verifying the success of organ model modeling, i.e., evaluating various biochemical and physical parameters in OOC devices, is crucial. Therefore, this paper provides a logical and comprehensive review and discussion of the advances in organ-on-a-chip detection and evaluation technologies from a broad perspective, covering the directions of tissue engineering scaffolds, microenvironment, single/multi-organ function, and stimulus-based evaluation, and provides a more comprehensive review of the progress in the significant organ-on-a-chip research areas in the physiological state.

NCOA4-mediated ferritinophagy is involved in ionizing radiation-induced ferroptosis of intestinal epithelial cells

Ferroptosis is a newly recognized form of regulated cell death that is characterized by severe lipid peroxidation initiated by iron overload and the generation of reactive oxygen species (ROS). However, the role of iron in ionizing radiation (IR)-induced intestinal injury has not been fully illustrated yet. In this study, we found that IR induced ferroptosis in intestinal epithelial cells, as indicated by the increase in intracellular iron levels and lipid peroxidation, upregulation of prostaglandin-endoperoxide synthase 2 (PTGS2) mRNA, reduced glutathione peroxidase 4 (GPX4) mRNA and glutathione (GSH) levels, and significant mitochondrial damage. In addition, the iron chelator deferoxamine (DFO) attenuated IR-induced ferroptosis and intestinal injury in vitro and in vivo. Intriguingly, pharmacological inhibition of autophagy with 3-methyladenine (3-MA) mitigated IR-induced ferritin downregulation, iron overload and ferroptosis. IR increased the levels of nuclear receptor coactivator 4 (NCOA4) mRNA and protein. NCOA4 knockdown significantly inhibited the reduction of ferritin, decreased the level of intracellular free iron, and mitigated ferroptosis induced by IR in HIEC cells, indicating that NCOA4-mediated autophagic degradation of ferritin (ferritinophagy) was required for IR-induced ferroptosis. Furthermore, cytoplasmic iron further activated mitoferrin2 (Mfrn2) on the mitochondrial membrane, which in turn increased iron transport into the mitochondria, resulting in increased ROS production and ferroptosis. In addition, mice fed with an iron-deficient diet for 3 weeks showed a significant reversal in the intestinal injury induced by abdominal IR exposure. Taken together, ferroptosis is a novel mechanism of IR-induced intestinal epithelial cytotoxicity, and is dependent on NCOA4-mediated ferritinophagy.

Structurally Dynamic Hydrogels for Biomedical Applications: Pursuing a Fine Balance between Macroscopic Stability and Microscopic Dynamics

Owing to their unique chemical and physical properties, hydrogels are attracting increasing attention in both basic and translational biomedical studies. Although the classical hydrogels with static networks have been widely reported for decades, a growing number of recent studies have shown that structurally dynamic hydrogels can better mimic the dynamics and functions of natural extracellular matrix (ECM) in soft tissues. These synthetic materials with defined compositions can recapitulate key chemical and biophysical properties of living tissues, providing an important means to understanding the mechanisms by which cells sense and remodel their surrounding microenvironments. This review begins with the overall expectation and design principles of dynamic hydrogels. We then highlight recent progress in the fabrication strategies of dynamic hydrogels including both degradation-dependent and degradation-independent approaches, followed by their unique properties and use in biomedical applications such as regenerative medicine, drug delivery, and 3D culture. Finally, challenges and emerging trends in the development and application of dynamic hydrogels are discussed.

Three-Dimensional Culture of Ameloblast-Originated HAT-7 Cells for Functional Modeling of Defective Tooth Enamel Formation

Background: Amelogenesis, the formation of dental enamel, is well understood at the histomorphological level but the underlying molecular mechanisms are poorly characterized. Ameloblasts secrete enamel matrix proteins and Ca²⁺, and also regulate extracellular pH as the formation of hydroxyapatite crystals generates large quantities of protons. Genetic or environmental impairment of transport and regulatory processes (e.g. dental fluorosis) leads to the development of enamel defects such as hypomineralization.

Aims: Our aims were to optimize the culture conditions for the three-dimensional growth of ameloblast-derived HAT-7 cells and to test the effects of fluoride exposure on HAT-7 spheroid formation.

Methods: To generate 3D HAT-7 structures, cells were dispersed and plated within a Matrigel extracellular matrix scaffold and incubated in three different culture media. Spheroid formation was then monitored over a two-week period. Ion transporter and tight-junction protein expression was investigated by RT-qPCR. Intracellular Ca²⁺ and pH changes were measured by microfluorometry using the fluorescent dyes fura-2 and BCECF.

Results: A combination of Hepato-STIM epithelial cell differentiation medium and Matrigel induced the expansion and formation of 3D HAT-7 spheroids. The cells retained their epithelial cell morphology and continued to express both ameloblast-specific and ion transport-specific marker genes. Furthermore, like two-dimensional HAT-7 monolayers, the HAT-7 spheroids were able to regulate their intracellular pH and to show intracellular calcium responses to extracellular stimulation. Finally, we demonstrated that HAT-7 spheroids may serve as a disease model for studying the effects of fluoride exposure during amelogenesis.

Conclusion: In conclusion, HAT-7 cells cultivated within a Matrigel extracellular matrix form three-dimensional, multi-cellular, spheroidal structures that retain their functional capacity for pH regulation and intracellular Ca²⁺ signaling. This new 3D model will allow us to gain a better understanding of the molecular mechanisms involved in amelogenesis, not only in health but also in disorders of enamel formation, such as those resulting from fluoride exposure.

Role of biomaterials in the diagnosis, prevention, treatment, and study of corona virus disease 2019 (COVID-19)

Recently emerged novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the resulting corona virus disease 2019 (COVID-19) led to urgent search for methods to prevent and treat COVID-19. Among important disciplines that were mobilized is the biomaterials science and engineering. Biomaterials offer a range of possibilities to develop disease models, protective, diagnostic, therapeutic, monitoring measures, and vaccines. Among the most important contributions made so far from this field are tissue engineering, organoids, and organ-on-a-chip systems, which have been the important frontiers in developing tissue models for viral infection studies. Also, due to low bioavailability and limited circulation time of conventional antiviral drugs, controlled and targeted drug delivery could be applied alternatively. Fortunately, at the time of writing this paper, we have two successful vaccines and new at-home detection platforms. In this paper, we aim to review recent advances of biomaterial-based platforms for protection, diagnosis, vaccination, therapeutics, and monitoring of SARS-CoV-2 and discuss challenges and possible future research directions in this field.

Non-matrigel scaffolds for organoid cultures

Organoids are three-dimensional cell cultures mostly from tissue-resident or embryonic stem cells (one or multiple) on hydrogels along with defined growth factors. Currently, matrigel is the most commonly employed matrix for 3D organoid cultures. However, certain undesirable attributes of matrigel have paved the way for several other natural and synthetic hydrogel scaffolds for organoid cultures. In this review, we discuss the constraints of matrigel and describe other alternative scaffolds that have been used for organoid cultures. Given the potential of organoids in a plethora of therapeutic and pharmaceutical applications, it is indeed imperative to develop defined and customized hydrogels other than the matrigel.

Three-dimensional scaffold-free microtissues engineered for cardiac repair

Cardiovascular diseases, including myocardial infarction (MI), persist as the leading cause of mortality and morbidity worldwide. The limited regenerative capacity of the myocardium presents significant challenges specifically for the treatment of MI and, subsequently, heart failure (HF). Traditional therapeutic approaches mainly rely on limiting the induced damage or the stress on the remaining viable myocardium through pharmacological regulation of remodeling mechanisms, rather than replacement or regeneration of the injured tissue. The emerging alternative regenerative medicine-based approaches have focused on restoring the damaged myocardial tissue with newly engineered functional and bioinspired tissue units. Cardiac regenerative medicine approaches can be broadly categorized into three groups: cell-based therapies, scaffold-based cardiac tissue engineering, and scaffold-free cardiac tissue engineering. Despite significant advancements, however, the clinical translation of these approaches has been critically hindered by two key obstacles for successful structural and functional replacement of the damaged myocardium, namely: poor engraftment of engineered tissue into the damaged cardiac muscle and weak electromechanical coupling of transplanted cells with the native tissue. To that end, the integration of micro- and nanoscale technologies along with recent advancements in stem cell technologies have opened new avenues for engineering of structurally mature and highly functional scaffold-based (SB-CMTs) and scaffold-free cardiac microtissues (SF-CMTs) with enhanced cellular organization and electromechanical coupling for the treatment of MI and HF. In this review article, we will present the state-of-the-art approaches and recent advancements in the engineering of SF-CMTs for myocardial repair.