Bone Abstracts

While the importance of interactions between bone and tumors is well-established, the mechanism by which the physical bone microenvironment regulates disease progression is limited by the lack of suitable in vitro models. We have designed 3D Tissue Engineered Constructs (TECs) using microCT imaging in tandem with inkjet 3D printing technology that recapitulate the mechanical and morphometric properties of trabecular bone. 3D-printed TECs exhibited no significant differences in bone morphometric parameters compared to the human femoral head, tibial plateau, and lumbar spine templates from which they were prepared (P<0.05). The substrate modulus of the TECs was 266 MPa, which is within the reported range for trabecular bone (93–266 MPa). Culture of rat MSCs on the bone-like TECs exhibited a significant (P<0.05) 1.7-fold increase in mineralization compared to collagen-like TECs. Culture of bone-metastatic MDA-MB-231 breast cancer cells on bone-like TECs in a perfusion bioreactor showed a significant (P<0.05) >5-fold increase in expression of integrin beta 3, Gli2, and PTHrP compared to collagen-like TECs. Importantly, drug response differed remarkably when tumors were cultured on bone-like 3D TECs compared to tissue culture well plates. When MDA-MB-231 cells were treated with the integrin inhibitor Cilengitide or the TGF-beta receptor kinase inhibitor SD208 in 2D culture, expression of Gli2 and PTHrP significantly decreased two to three fold (P<0.01). However, treatment with these drugs did not significantly reduce Gli2 or PTHrP expression on 3D bone-like TECs. In contrast, treatment with the Gli2 inhibitor GANT58 significantly reduced both Gli2 and PTHrP expression >3-fold (P<0.01) in both 3D and 2D. These findings suggest that targeting factors downstream of cell receptors may be an effective approach to blocking establishment of tumors in bone. The TEC approach highlights the important contribution of the physical bone microenvironment for studying tumor and bone interactions and testing inhibitors of tumor-induced bone disease.