A fully human In-vitro model for bone metastasis: potential of an electrospun scaffold as alternative to biological materials for osteoblast/osteoclast differentiation

The development of bone metastases poses a clinical challenge for patients with malignancies originating from diverse organs, including lungs, prostate, and breast. These metastatic events correlate with a poorer prognosis, and treatments are predominantly palliative. Furthermore, traditional in-vivo models for bone metastasis research have limitations, primarily due to species-specific differences. Therefore, we sought an alternative in-vitro model that is human cell based, robust and capable of a relatively quick establishment. Initially, we studied the potential of a decellularized porcine jejunum scaffold named Small Intestinal Submucosa with mucosa (SISmuc) and compared it to decellularized human bone and two synthetic scaffolds. We assessed various parameters related to osteoblast differentiation such as calcification, collagen I protein expression, and further differentiation to mature osteocytes indicated by sclerostin protein expression. The synthetic electrospun matrix demonstrated to be a good alternative to SISmuc, particularly when combined with bioactive glass 45S5, which enhanced calcification. We also incorporated osteoclasts into our model and demonstrated that monocytes could be more effectively differentiated into osteoclasts in a 3D environment compared to traditional 2D cultures. Within seven weeks, we successfully generate an in-vitro model incorporating osteoblasts, osteoclasts, and tumor cells. As a potential strategy for treating bone metastases, we found Chimeric Antigen Receptor T cells within lung and pancreatic bone metastasis models to be effective in reducing the number of tumor cells and inducing apoptosis. This innovative research establishes a foundation for more sophisticated 3D in-vitro models of bone metastasis, holding significant promise for advancing preclinical cancer research and therapeutic strategies.