Pilot investigation on the dose-dependent impact of irradiation on primary human alveolar osteoblasts in vitro.

Radiotherapy of head and neck squamous cell carcinoma can lead to long-term complications like osteoradionecrosis, resulting in severe impairment of the jawbone. Current standard procedures require a 6-month wait after irradiation before dental reconstruction can begin. A comprehensive characterization of the irradiation-induced molecular and functional changes in bone cells could allow the development of novel strategies for an earlier successful dental reconstruction in patients treated by radiotherapy. The impact of ionizing radiation on the bone-forming alveolar osteoblasts remains however elusive, as previous studies have relied on animal-based models and fetal or animal-derived cell lines. This study presents the first in vitro data obtained from primary human alveolar osteoblasts. Primary human alveolar osteoblasts were isolated from healthy donors and expanded. After X-ray irradiation with 2, 6 and 10 Gy, cells were cultivated under osteogenic conditions and analyzed regarding their proliferation, mineralization, and expression of marker genes and proteins. Proliferation of osteoblasts decreased in a dose-dependent manner. While cells recovered from irradiation with 2 Gy, application of 6 and 10 Gy doses not only led to a permanent impairment of proliferation, but also resulted in altered cell morphology and a disturbed structure of the extracellular matrix as demonstrated by immunostaining of collagen I and fibronectin. Following irradiation with any of the examined doses, a decrease of marker gene expression levels was observed for most of the investigated genes, revealing interindividual differences. Primary human alveolar osteoblasts presented a considerably changed phenotype after irradiation, depending on the dose administered. Mechanisms for these findings need to be further investigated. This could facilitate improved patient care by re-evaluating current standard procedures and investigating faster and safer reconstruction concepts, thus improving quality of life and social integrity.

Comparison of the Translational Potential of Human Mesenchymal Progenitor Cells from Different Bone Entities for Autologous 3D Bioprinted Bone Grafts.

Reconstruction of segmental bone defects by autologous bone grafting is still the standard of care but presents challenges including anatomical availability and potential donor site morbidity. The process of 3D bioprinting, the application of 3D printing for direct fabrication of living tissue, opens new possibilities for highly personalized tissue implants, making it an appealing alternative to autologous bone grafts. One of the most crucial hurdles for the clinical application of 3D bioprinting is the choice of a suitable cell source, which should be minimally invasive, with high osteogenic potential, with fast, easy expansion. In this study, mesenchymal progenitor cells were isolated from clinically relevant human bone biopsy sites (explant cultures from alveolar bone, iliac crest and fibula; bone marrow aspirates; and periosteal bone shaving from the mastoid) and 3D bioprinted using projection-based stereolithography. Printed constructs were cultivated for 28 days and analyzed regarding their osteogenic potential by assessing viability, mineralization, and gene expression. While viability levels of all cell sources were comparable over the course of the cultivation, cells obtained by periosteal bone shaving showed higher mineralization of the print matrix, with gene expression data suggesting advanced osteogenic differentiation. These results indicate that periosteum-derived cells represent a highly promising cell source for translational bioprinting of bone tissue given their superior osteogenic potential as well as their minimally invasive obtainability.