Kyoto University successfully creates jawbone-like organoids from human iPS cells

A research group comprising Assistant Professor Souta Motoike, Professor Makoto Ikeya, Technical Staff Yoshiko Inada, and Program-Specific Research Center Professor Junya Toguchida of the Center for iPS Cell Research and Application (CiRA), Kyoto University, along with Professor Mikihito Kajiya of the Center for Oral Clinical Examination, Hiroshima University Hospital, announced the successful generation of jawbone organoids from human iPS cells by recapitulating the developmental process. The research group confirmed that transplanting these organoids into mice resulted in vascular neogenesis and the formation of mature bone tissue. They also verified that disease phenotypes could be recapitulated using iPS cells derived from patients with osteogenesis imperfecta, a rare disease. This is expected to lead to the development of therapies for diseases causing abnormalities in the jawbone. The results were published in the July 2 issue of Nature Biomedical Engineering.

The jawbone consists of the maxillary and mandibular bones. Once extensively damaged by bacteria, overload, tumors, or other factors, healing and functional recovery are difficult, and many intractable diseases with unknown pathophysiology remain.

While most bones throughout the body derive from mesoderm, the jawbone originates from neural crest cells (NCCs) and is formed through differentiation into the first pharyngeal arch ectomesenchyme (PA1-EM) after migration to the first pharyngeal arch. Furthermore, while major bones are formed through endochondral ossification, where cartilage templates are gradually replaced by bone, the jawbone is formed through intramembranous ossification, where aggregated cells directly form bone without cartilage formation. However, recapitulation of the three-dimensional network structure of osteocytes, which is important for functional performance in the jawbone and other locations, had not been achieved, and methods for inducing PA1-EM had not been established.

Therefore, the research group investigated the induction of jawbone organoids with three-dimensional network structures from iPS cells. They also aimed to develop methods enabling induction under xeno-free conditions without animal-derived components or serum, considering future clinical applications.

It was known that during development, the region to which NCCs migrate is determined by HOX gene expression patterns and that NCCs migrating to the first pharyngeal arch do not express HOX genes. The first pharyngeal arch divides into the maxillary prominence, which becomes the future maxilla, and the mandibular prominence, which becomes the mandible. NCCs in the mandibular prominence differentiate into ectomesenchyme (mdEM) in layers expressing DLX2, DLX2 and DLX5, and DLX2 and DLX5 and HAND2.

Therefore, the research group developed a method to induce HOX-negative NCCs by culturing human iPS cells in three dimensions. When they examined gene expression in cell aggregates approximately 500 µm in diameter obtained on day 5 of induction from iPS cells, they found that most were composed of NCCs and did not express HOX genes. Furthermore, these cell aggregates reproduced the expression pattern with DLX2 in the center, DLX2 and DLX5 in the surrounding area, and DLX2 and DLX5 and HAND2 in the outer periphery.

When these cell aggregates underwent osteogenic induction, the research group successfully obtained mandibular bone organoids approximately 1.5 mm in size (rice grain-shaped) and rich in bone-related proteins on day 38 of induction from iPS cells. They confirmed that the obtained mandibular bone organoids were highly mineralized, contained osteoblasts, and reproduced the three-dimensional network of osteocytes.

To verify the function of these mandibular bone organoids, they created 2 mm diameter defects in the mandibles of immunodeficient mice and transplanted three of the obtained mandibular bone organoids. They compared this with the bone graft group and the non-grafted group.

Micro-CT imaging performed 4 weeks after transplantation showed that defects transplanted with jawbone organoids closed to the same extent as the bone graft group, and histological examination confirmed regeneration with vascular neogenesis inside the defect sites. In contrast, defects remained unhealed in the non-grafted group.

Finally, the research group verified whether disease recapitulation was possible with jawbone organoids. They induced jawbone organoids using iPS cells derived from patients with severe osteogenesis imperfecta and patient-derived iPS cells with the disease-causing mutation corrected.

As a result, the matrices of patient-derived jawbone organoids were found to contain abundant misfolded collagen and recapitulated pathological features with disrupted osteocyte networks. In contrast, these pathological features were not observed in organoids derived from patients with corrected mutations.

The research is still basic, and further improvements will be made in the future. Motoike commented: "The jawbone organoids we created have become considerably harder compared to typical cells, but their maturity is still low, and I believe improving this maturity will be a future challenge."

Journal Information
Publication: Nature Biomedical Engineering
Title: Jawbone-like organoids generated from human pluripotent stem cells
DOI: 10.1038/s41551-025-01419-3