Deciphering Stem Cell from Apical Papilla - Macrophage Choreography using a Novel 3D Organoid System

Organoids in the oral and maxillofacial region: present and future

The oral and maxillofacial region comprises a variety of organs made up of multiple soft and hard tissue, which are anatomically vulnerable to the pathogenic factors of trauma, inflammation, and cancer. The studies of this intricate entity have been long-termly challenged by a lack of versatile preclinical models. Recently, the advancements in the organoid industry have provided novel strategies to break through this dilemma. Here, we summarize the existing biological and engineering approaches that were employed to generate oral and maxillofacial organoids. Then, we detail the use of modified co-culture methods, such as cell cluster co-inoculation and air-liquid interface culture technology to reconstitute the vascular network and immune microenvironment in assembled organoids. We further retrospect the existing oral and maxillofacial assembled organoids and their potential to recapitulate the homeostasis in parental tissues such as tooth, salivary gland, and mucosa. Finally, we discuss how the next-generation organoids may benefit to regenerative and precision medicine for treatment of oral-maxillofacial illness.

The use of organoids in creating immune microenvironments and treating gynecological tumors

Owing to patient-derived tumor tissues and cells, significant advances have been made in personalized cancer treatment and precision medicine, with cancer stem cell-derived three-dimensional tumor organoids serving as crucial in vitro models that accurately replicate the structural, phenotypic, and genetic characteristics of tumors. However, despite their extensive use in drug testing, genome editing, and transplantation for facilitating personalized treatment approaches in clinical practice, the inadequate capacity of these organoids to effectively model immune cells and stromal components within the tumor microenvironment limits their potential. Additionally, effective clinical immunotherapy has led the tumor immune microenvironment to garner considerable attention, increasing the demand for simulating patient-specific tumor-immune interactions. Consequently, co-culture techniques integrating tumor organoids with immune cells and tumor microenvironment constituents have been developed to expand the possibilities for personalized drug response investigations, with recent advancements enhancing the understanding of the strengths, limitations, and applicability of the co-culture approach. Herein, the recent advancements in the field of tumor organoids have been comprehensively reviewed, specifically highlighting the tumor organoid co-culture-related developments with various immune cell models and their implications for clinical research. Furthermore, this review delineates the current state of research and application of organoid models regarding the therapeutic approaches and related challenges for gynecological tumors. This study may provide a theoretical basis for further research on the use of patient-derived organoids in tumor immunity, drug development, and precision medicine.

Regenerative application of oral and maxillofacial 3D organoids based on dental pulp stem cell

Dental pulp stem cells (DPSCs) originate from the neural crest and the present mesenchymal phenotype showed self-renewal capabilities and can differentiate into at least three lineages. DPSCs are easily isolated with minimal harm, no notable ethical constraints, and without general anesthesia to the donor individuals. Furthermore, cryopreservation of DPSCs provides this opportunity for autologous transplantation in future studies without fundamental changes in stemness, viability, proliferation, and differentiating features. Current approaches for pulp tissue regeneration include pulp revascularization, cell-homing-based regenerative endodontic treatment (RET), cell-transplantation-based regenerative endodontic treatment, and allogeneic transplantation. In recent years, a novel technology, organoid, provides a mimic physiological condition and tissue construct that can be applied for tissue engineering, genetic manipulation, disease modeling, single-cell high throughput analysis, living biobank, cryopreserving and maintaining cells, and therapeutic approaches based on personalized medicine. The organoids can be a reliable preclinical prediction model for evaluating cell behavior, monitoring drug response or resistance, and comparing healthy and pathological conditions for therapeutic and prognostic approaches. In the current review, we focused on the promising application of 3D organoid technology based on DPSCs in oral and maxillofacial tissue regeneration. We discussed encountering challenges and limitations, and found promising solutions to overcome obstacles.

3D Organoids for Regenerative Endodontics

Apical periodontitis is the inflammation and destruction of periradicular tissues, mediated by microbial factors originating from the infected pulp space. This bacteria-mediated inflammatory disease is known to interfere with root development in immature permanent teeth. Current research on interventions in immature teeth has been dedicated to facilitating the continuation of root development as well as regenerating the dentin-pulp complex, but the fundamental knowledge on the cellular interactions and the role of periapical mediators in apical periodontitis in immature roots that govern the disease process and post-treatment healing is limited. The limitations in 2D monolayer cell culture have a substantial role in the existing limitations of understanding cell-to-cell interactions in the pulpal and periapical tissues. Three-dimensional (3D) tissue constructs with two or more different cell populations are a better physiological representation of in vivo environment. These systems allow the high-throughput testing of multi-cell interactions and can be applied to study the interactions between stem cells and immune cells, including the role of mediators/cytokines in simulated environments. Well-designed 3D models are critical for understanding cellular functions and interactions in disease and healing processes for future therapeutic optimization in regenerative endodontics. This narrative review covers the fundamentals of (1) the disease process of apical periodontitis; (2) the influence and challenges of regeneration in immature roots; (3) the introduction of and crosstalk between mesenchymal stem cells and macrophages; (4) 3D cell culture techniques and their applications for studying cellular interactions in the pulpal and periapical tissues; (5) current investigations on cellular interactions in regenerative endodontics; and, lastly, (6) the dental-pulp organoid developed for regenerative endodontics.

Differential Effects of Escherichia coli- Versus Porphyromonas gingivalis-derived Lipopolysaccharides on Dental Pulp Stem Cell Differentiation in Scaffold-free Engineered Tissues

INTRODUCTION

To leverage the therapeutic capabilities of dental pulp stem cells (DPSCs) for regenerative endodontic applications, a better understanding of their innate defense and reparative processes is needed. Lipopolysaccharide (LPS) is a major virulent factor of gram-negative bacteria and contributor to endodontic infections. We have developed 3-dimensional scaffold-free DPSC tissues that self-organize into dentin-pulp organoids comprising a mineralized dentin-like tissue on the periphery and an unmineralized pulp-like core. In this study, scaffold-free DPSC constructs were used as controllable experimental models to study the DPSC response to bacterial challenge.

METHODS

Scaffold-free constructs were engineered using DPSCs isolated from human third molars. To simulate bacterial exposure, DPSC constructs were exposed to either Porphyromonas gingivalis-derived LPS or Escherichia coli-derived LPS. The effects of LPS on DPSC differentiation, proliferation, and apoptosis were evaluated.

RESULTS

Engineered tissues lacking LPS treatment self-organized into dentin-pulp organoids. LPS treatment did not negatively affect DPSC proliferation or apoptosis in the engineered tissues. Both E. coli LPS and P. gingivalis LPS inhibited the up-regulation of RUNX2 messenger RNA expression and reduced the expression of the odontoblast-associated proteins (P < .05), suggesting that LPS is inhibiting odontoblastic differentiation. However, only E. coli LPS treatment significantly reduced mineral deposition in the DPSC (P < .05) constructs, indicating that E. coli LPS but not P. gingivalis LPS reduced functional differentiation of DPSCs and prevented DPSCs from self-organizing into a dentin-pulp complex-like structure.

CONCLUSIONS

This study establishes scaffold-free DPSC constructs as models of oral disease. Furthermore, it emphasizes the diversity of LPS derived from different bacterial species and highlights the necessity of using LPS derived from clinically relevant bacteria in basic science investigations.