Introduction

As a forefront innovation in modern medicine, organoid technology brings new insights into disease research and therapy. Organoids are 3D constructs developed from stem cells or progenitor cells in vitro, mirroring the shape, structure, and function of human organs with high fidelity. They provide an excellent simulation of organ physiological processes. The absence of a standardized preclinical model has been a persistent obstacle in oral disease research, but the development of oral organoids offers the potential to break this barrier, opening avenues for precise oral disease treatments.

Cultivation of Oral Organoids

The construction of oral organoids involves three key elements: cells, scaffolds, and construction strategies. Cells are the foundation of building oral organoids, with adult stem cells and pluripotent stem cells being the most studied, such as dental pulp stem cells, periodontal ligament stem cells, and induced pluripotent stem cells. Scaffolds play a crucial supportive and guiding role in organoid construction, with natural materials like Matrigel and collagen gel and synthetic materials like PLGA and PCL being extensively researched. The construction strategy depends on the interaction between cells and their microenvironment, which is the core of successful organoid construction. Different sources and functions of stem cells require different construction strategies. For example, in constructing salivary gland organoids, the focus is on restoring ductal structures and secretory functions, while the key to constructing tooth germ organoids lies in replicating the spatiotemporal interactions between dental epithelium and mesenchyme.

The cultivation of oral organoids requires strict control of various conditions such as temperature, humidity, oxygen concentration, and nutrient composition ratios. Appropriate growth factors and small molecules are crucial for inducing stem cell differentiation and organoid formation. Additionally, avoiding contamination and cell stress is essential to ensure the normal development of oral organoids.

Fig.1 Summary of the construction strategies of oral organoids. (Gao X., et al. 2021).

Research Progress on Oral Organoids

Tooth Organoids

Tooth organoids show significant potential in tooth regeneration research. Currently, tooth germ organoids can be derived from dental epithelium and mesenchymal cells or pluripotent stem cells. For instance, the mesenchymal-epithelial assembly model established by Hemeryck et al. demonstrated that dental pulp stem cells can trigger the differentiation of epithelial stem cells into ameloblasts. Ammar Alghadeer et al. achieved human ameloblast differentiation using iPSCs, with organoids expressing enamel proteins necessary for mineralization both in vitro and after in vivo transplantation. Although existing tooth germ organoids have yet to develop into perfect teeth in vitro, they can grow into functional teeth when transplanted into the jawbone, offering hope for dental regenerative medicine.

Salivary Gland Organoids

Salivary gland organoids provide new models and insights for treating salivary gland diseases. Researchers have successfully cultivated salivary gland organoids capable of secreting saliva using traditional cell culture techniques or advanced 3D bioprinting technology. When transplanted into damaged salivary glands, these organoids can significantly stimulate the regeneration and growth of epithelial and neuronal tissues in the affected glands. Adine, C. et al. utilized salivary gland organoids to study the mechanisms of stem cell response to radiation, simulating reduced saliva secretion due to radiation damage, offering new methods for treating xerostomia in patients undergoing radiotherapy for head and neck tumors.

Oral Mucosa Organoids

The construction of oral mucosa organoids holds promise for assisting in the treatment of viral infections and potentially malignant diseases, though their development is challenging. The oral mucosa is a unique moist, soft, and elastic tissue lining the inner surface of the mouth, with common diseases including oral ulcers, leukoplakia, lichen planus, and oral candidiasis. Currently, the development of oral mucosa organoids faces numerous difficulties, such as limited cell acquisition and complex culture system construction.

Oral Cancer Organoids

Oral cancer organoids play a crucial role in tumor research. Various tumor organoids, including those for oral cancer, have been established and used as personalized preclinical models for drug screening. Patient-derived organoids (PDOs) accurately reflect the physiological and pathological conditions of different patients, serving as an essential bridge between animal models and human clinical trials. The OSCC organoid culture model developed by Peking University School of Stomatology boasts a success rate of 86.2%, providing an excellent platform for preclinical research.

Conclusion

3D organoid technology provides a way to replicate the body's internal environment, enabling scientists to investigate cell behavior, drug reactions, and disease models outside the body. This technology paves the way for personalized healthcare, oral disease modeling, and tissue engineering, highlighting its extensive potential. Improved and consistent oral organoid culture methods are required to delve into oral disease mechanisms, identify effective drugs, and realize precision medicine.