Additionally, co-culture cells, such as primary human osteoblasts (HOBs) [6] or human bone marrow-derived mesenchymal stem cells (hBM–MSCs) and human umbilical vein endothelial cells (HUVECs) [68], human adipose-derived stem cells (ADSCs) [69] or metastatic breast cancer (BrCa) cells [70], and joining specific growth factors such as BMP-2 could be employed to better mimic bone microenvironment [68] in either physiological or pathological conditions. The gene discussed is BMP2; the disease is breast carcinoma.