Organoid vs In Vivo Mouse Model: Which is Better Research Tool to Understand the Biologic Mechanisms of Intestinal Epithelium?

Urine-derived stem cells display homing, incorporation, and regeneration in human organoid and mouse models of acute kidney injury

Urine-derived stem cells (USCs) are adult human stem cells that can be collected noninvasively from urine and cultured in vitro. Because of their renal origin and reported therapeutic effects, we hypothesized that USCs would home to the injured kidney in acute kidney injury (AKI) models. We used mouse models of glycerol-induced rhabdomyolysis or unilateral nephrectomy with clamping ischemia reperfusion injury to model AKI. To track USC homing by live animal imaging, we administered luciferase-expressing (Luc) USCs to mice by intraperitoneal injection. We observed USC localization to both the tubules and glomeruli of injured mice within 3 h by histology. We confirmed the presence of Luc-USCs in the kidney at 3 h, 24 h, and 48 h after the injection using biodistribution analysis of quantitative bioluminescence tomography imaging. We performed immunostaining for kidney injury molecule-1 (KIM-1/HAVCR1/TIM-1) for kidney injury and found reduced expression in USC-treated group at 24 h after injection. To evaluate the effects of the human USCs on injured human nephrons, we injured human kidney organoids with the nephrotoxin cisplatin (5 μM) followed by 5 × 104 USC treatment. USCs were incorporated and lowered expression of KIM-1 in the organoids. USCs home to injured nephrons and reduce measures of kidney injury.

Small extracellular vesicles derived from umbilical cord mesenchymal stem cells alleviate radiation-induced cardiac organoid injury

BACKGROUND

Radiation-induced heart disease (RIHD) is one of the most serious complications of radiation therapy (RT) for thoracic tumors, and new interventions are needed for its prevention and treatment. Small extracellular vesicles (sEVs) from stem cells have attracted much attention due to their ability to repair injury. However, the role of umbilical cord mesenchymal stem cell (UCMSC)-derived sEVs in protecting cardiac organoids from radiation-induced injury and the underlying mechanisms are largely unknown.

METHODS

A radiation-induced cardiac organoid injury model was established by using X-ray radiation, and the optimal radiation dose of 20 Gy was determined by live/dead staining. After radiation, the cardiac organoids were treated with sEVs derived from UCMSCs, and energy metabolism, calcium transient changes and the ultrastructure of the organoids were assessed through Seahorse analysis, optical mapping and transmission electron microscopy, respectively. Confocal microscopy was used to observe the changes in mitochondrial ROS and mitochondrial membrane potential (ΔΨm). Furthermore, real-time quantitative PCR was used to verify the RNA-seq results.

RESULTS

After X-ray radiation, the mortality of cardiac organoids significantly increased, energy metabolism decreased, and calcium transients changed. We also observed that the mitochondrial structure of cardiac organoids was disrupted and that ΔΨm was decreased. These effects could be inhibited by sEVs treatment. sEVs may protect against radiation-induced cardiac organoid injury by regulating oxidative phosphorylation and the p53 signaling pathway.

CONCLUSION

sEVs derived from UCMSCs can be used as a potential therapeutic strategy for radiation-induced heart disease.

Engineering next generation vascularized organoids

Organoids are self-organizing 3D cell culture models that are valuable for studying the mechanisms underlying both development and disease in multiple species, particularly, in humans. These 3D engineered tissues can mimic the structure and function of human organs in vitro. Methods to generate organoids have substantially improved to better resemble, in various ways, their in vivo counterpart. One of the major limitations in current organoid models is the lack of a functional vascular compartment. Here we discuss methodological approaches to generating perfusable blood vessel networks in organoid systems. Inclusion of perfused vascular compartments markedly enhances the physiological relevance of organoid systems and is a critical step in the establishment of next generation, higher-complexity in vitro systems for use in developmental, clinical, and drug-development settings.

Advancements in understanding bacterial enteritis pathogenesis through organoids

Bacterial enteritis has a substantial role in contributing to a large portion of the global disease burden and serves as a major cause of newborn mortality. Despite advancements gained from current animal and cell models in improving our understanding of pathogens, their widespread application is hindered by apparent drawbacks. Therefore, more precise models are imperatively required to develop more accurate studies on host-pathogen interactions and drug discovery. Since the emergence of intestinal organoids, massive studies utilizing organoids have been conducted to study the pathogenesis of bacterial enteritis, revealing new mechanisms and validating established ones. In this review, we focus on the advancements of several bacterial pathogenesis mechanisms observed in intestinal organoid/enteroid models, exploring the host response and bacterial effectors during the infection process. Finally, we address the features that warrant additional investigation or could be enhanced in existing organoid models in order to guide future research endeavors.

Organoids are not organs: Sources of variation and misinformation in organoid biology

In the past decade, the term organoid has moved from obscurity to common use to describe a 3D in vitro cellular model of a tissue that recapitulates structural and functional elements of the in vivo organ it models. The term organoid is now applied to structures formed as a result of two distinct processes: the capacity for adult epithelial stem cells to re-create a tissue niche in vitro and the ability to direct the differentiation of pluripotent stem cells to a 3D self-organizing multicellular model of organogenesis. While these two organoid fields rely upon different stem cell types and recapitulate different processes, both share common challenges around robustness, accuracy, and reproducibility. Critically, organoids are not organs. This commentary serves to discuss these challenges, how they impact genuine utility, and shine a light on the need to improve the standards applied to all organoid approaches.

Human enteroids as a tool to study conventional and ultra-high dose rate radiation

Radiation therapy, one of the most effective therapies to treat cancer, is highly toxic to healthy tissue. The delivery of radiation at ultra-high dose rates, FLASH radiation therapy (FLASH), has been shown to maintain therapeutic anti-tumor efficacy while sparing normal tissues compared to conventional dose rate irradiation (CONV). Though promising, these studies have been limited mainly to murine models. Here, we leveraged enteroids, three-dimensional cell clusters that mimic the intestine, to study human-specific tissue response to radiation. We observed enteroids have a greater colony growth potential following FLASH compared with CONV. In addition, the enteroids that reformed following FLASH more frequently exhibited proper intestinal polarity. While we did not observe differences in enteroid damage across groups, we did see distinct transcriptomic changes. Specifically, the FLASH enteroids upregulated the expression of genes associated with the WNT-family, cell-cell adhesion, and hypoxia response. These studies validate human enteroids as a model to investigate FLASH and provide further evidence supporting clinical study of this therapy. Insight Box Promising work has been done to demonstrate the potential of ultra-high dose rate radiation (FLASH) to ablate cancerous tissue, while preserving healthy tissue. While encouraging, these findings have been primarily observed using pre-clinical murine and traditional two-dimensional cell culture. This study validates the use of human enteroids as a tool to investigate human-specific tissue response to FLASH. Specifically, the work described demonstrates the ability of enteroids to recapitulate previous in vivo findings, while also providing a lens through which to probe cellular and molecular-level responses to FLASH. The human enteroids described herein offer a powerful model that can be used to probe the underlying mechanisms of FLASH in future studies.

Can Kidney Organoid Xenografts Accelerate Therapeutic Development for Genetic Kidney Disorders?

A number of genetic kidney diseases can now be replicated experimentally, using kidney organoids generated from human pluripotent stem cells. This methodology holds great potential for drug discovery. Under in vitro conditions, however, kidney organoids remain developmentally immature, develop scarce vasculature, and may contain undesired off-target cell types. Those critical deficiencies limit their potential as disease-modeling tools. Orthotopic transplantation under the kidney capsule improves the anatomic maturity and vascularization of kidney organoids, while reducing off-target cell content. The improvements can translate into more accurate representations of disease phenotypes and mechanisms in vivo . Recent studies using kidney organoid xenografts highlighted the unique potential of this novel methodology for elucidating molecular mechanisms driving monogenic kidney disorders and for the development ofnovel pharmacotherapies.

In Vivo Intestinal Research Using Organoid Transplantation

Our understanding of the biology of the intestinal epithelium has advanced since the establishment of an organoid culture system. Although organoids have enabled investigation of the mechanism of self-renewal of human intestinal stem cells in vitro, it remains difficult to clarify the behavior of human normal and diseased intestinal epithelium in vivo. Recently, we developed a xenotransplantation system in which human intestinal organoids are engrafted onto epithelium-depleted mouse colons. This xenograft recapitulated the original tissue structures. Upon xenotransplantation, normal colon organoids developed normal colon crypt structures without tumorigenesis, whereas tumor-derived organoids formed colonic tumors resembling the original tumors. The non-tumorigenicity of human intestinal organoids highlights the safety of organoid-based regenerative medicine. As an example of regenerative medicine for short bowel syndrome, we devised a unique organ-repurposing approach to convert colons into small intestines by organoid transplantation. In this approach, the transplanted rat small intestinal organoids not only engrafted onto the rat colons but also remodeled the colon subepithelial structures into a small intestine-like conformation. Luminal flow accelerated the maturation of villi in the small intestine, which promoted the formation of a lymphovascular network mimicking lacteals. In this review, we provide an overview of recent advances in gastrointestinal organoid transplantation and share our understanding of human disease biology and regenerative medicine derived from these studies.

Advances in Tumor Organoids for the Evaluation of Drugs: A Bibliographic Review

Tumor organoids are defined as self-organized three-dimensional assemblies of heterogeneous cell types derived from patient samples that mimic the key histopathological, genetic, and phenotypic characteristics of the original tumor. This technology is proposed as an ideal candidate for the evaluation of possible therapies against cancer, presenting advantages over other models which are currently used. However, there are no reports in the literature that relate the techniques and material development of tumor organoids or that emphasize in the physicochemical and biological properties of materials that intent to biomimicry the tumor extracellular matrix. There is also little information regarding the tools to identify the correspondence of native tumors and tumoral organoids (tumoroids). Moreover, this paper relates the advantages of organoids compared to other models for drug evaluation. A growing interest in tumoral organoids has arisen from 2009 to the present, aimed at standardizing the process of obtaining organoids, which more accurately resemble patient-derived tumor tissue. Likewise, it was found that the characteristics to consider for the development of organoids, and therapeutic responses of them, are cell morphology, physiology, the interaction between cells, the composition of the cellular matrix, and the genetic, phenotypic, and epigenetic characteristics. Currently, organoids have been used for the evaluation of drugs for brain, lung, and colon tumors, among others. In the future, tumor organoids will become closer to being considered a better model for studying cancer in clinical practice, as they can accurately mimic the characteristics of tumors, in turn ensuring that the therapeutic response aligns with the clinical response of patients.

Stand by me: Fibroblasts regulation of the intestinal epithelium during development and homeostasis

The epithelium of the small intestine is composed of a single layer of cells that line two functionally distinct compartments, the villi that project into the lumen of the gut and the crypts that descend into the underlying connective tissue. Stem cells are located in crypts, where they divide and give rise to transit-amplifying cells that differentiate into secretory and absorptive epithelial cells. Most differentiated cells travel upwards from the crypt towards the villus tip, where they shed into the lumen. While some of these cell behaviors are an intrinsic property of the epithelium, it is becoming evident that tight coordination between the epithelium and the underlying fibroblasts plays a critical role in tissue morphogenesis, stem-cell niche maintenance and regionalized gene expression along the crypt-villus axis. Here, we will review the current literature describing the interaction between epithelium and fibroblasts during crypt-villus axis development and intestinal epithelium renewal during homeostasis.

Csf1r mediates enhancement of intestinal tumorigenesis caused by inactivation of Mir34a

The CSF1 receptor (CSF1R) encoding mRNA represents a direct target of miR-34a. However, the in vivo relevance of the suppression of CSF1R by miR-34a for intestinal tumor suppression mediated by the p53/miR-34a pathway has remained unknown. Here, Apc^Min/+ mice with intestinal-epithelial cell (IEC)-specific deletions of Mir34a showed increased formation of adenomas and decreased survival, whereas deletion of Csf1r decreased adenoma formation and increased survival. In adenomas deletion of Mir34a enhanced proliferation, STAT3 signaling, infiltration with fibroblasts, immune cells and microbes, and tumor stem cell abundance and decreased apoptosis. Deletion of Csf1r had the opposite effects. In addition, homeostasis of intestinal secretory and stem cells, and tumoroid formation were affected in opposite directions by deletion of Mir34a and CSF1R. Concomitant deletion of Csf1r and Mir34a neutralized the effects of the single deletions. mRNAs containing Mir34a seed-matching sites, which encode proteins related to EMT (epithelial-mesenchymal transition), stemness and Wnt signaling, were enriched after Mir34a inactivation in adenomas and derived tumoroids. Netrin-1/Ntn1 and Transgelin/Tagln were characterized as direct targets of Mir34a and Csf1r signaling. Mir34a-inactivation related expression signatures were associated with CMS4/CRISB+D, stage 4 CRCs and poor patient survival. In tumoroids the loss of Mir34a conferred resistance to 5-FU which was mediated by Csf1r. This study provides genetic evidence for a requirement of Mir34a-mediated Csf1r suppression for intestinal stem/secretory cell homeostasis and tumor suppression, and suggests that therapeutic targeting of CSF1R may be effective for the treatment of CRCs with defects in the p53/miR-34a pathway.

Everything You Always Wanted to Know About Organoid-Based Models (and Never Dared to Ask)

Homeostatic functions of a living tissue, such as the gastrointestinal tract, rely on highly sophisticated and finely tuned cell-to-cell interactions. These crosstalks evolve and continuously are refined as the tissue develops and give rise to specialized cells performing general and tissue-specific functions. To study these systems, stem cell-based in vitro models, often called organoids, and non-stem cell-based primary cell aggregates (called spheroids) appeared just over a decade ago. These models still are evolving and gaining complexity, making them the state-of-the-art models for studying cellular crosstalk in the gastrointestinal tract, and to investigate digestive pathologies, such as inflammatory bowel disease, colorectal cancer, and liver diseases. However, the use of organoid- or spheroid-based models to recapitulate in vitro the highly complex structure of in vivo tissue remains challenging, and mainly restricted to expert developmental cell biologists. Here, we condense the founding knowledge and key literature information that scientists adopting the organoid technology for the first time need to consider when using these models for novel biological questions. We also include information that current organoid/spheroid users could use to add to increase the complexity to their existing models. We highlight the current and prospective evolution of these models through bridging stem cell biology with biomaterial and scaffold engineering research areas. Linking these complementary fields will increase the in vitro mimicry of in vivo tissue, and potentially lead to more successful translational biomedical applications. Deepening our understanding of the nature and dynamic fine-tuning of intercellular crosstalks will enable identifying novel signaling targets for new or repurposed therapeutics used in many multifactorial diseases.

Human Intestinal Organoids: Promise and Challenge

The study of human intestinal biology in healthy and diseased conditions has always been challenging. Primary obstacles have included limited tissue accessibility, inadequate in vitro maintenance and ethical constrains. The development of three-dimensional organoid cultures has transformed this entirely. Intestinal organoids are self-organized three-dimensional structures that partially recapitulate the identity, cell heterogeneity and cell behaviour of the original tissue in vitro. This includes the capacity of stem cells to self-renew, as well as to differentiate towards major intestinal lineages. Therefore, over the past decade, the use of human organoid cultures has been instrumental to model human intestinal development, homeostasis, disease, and regeneration. Intestinal organoids can be derived from pluripotent stem cells (PSC) or from adult somatic intestinal stem cells (ISC). Both types of organoid sources harbour their respective strengths and weaknesses. In this mini review, we describe the applications of human intestinal organoids, discussing the differences, advantages, and disadvantages of PSC-derived and ISC-derived organoids.

Setting boundaries for tissue patterning

Engineers point the way toward more complex and homogeneous intestinal organoids.