Andre J. van Wijnen

Osteoporosis and osteoarthritis

Osteocytes are thought to be the mechanosensors of bone by sensing mechanical loads imposed upon the bone and transmitting these signals to the other bone cells to initiate bone modeling and remodeling. The location of osteocytes deep within bone is ideal for their function. However, this location makes the study of osteocytes in vivo technically diffi cult. There are several methods for obtaining and culturing primary osteocytes for in vitro experiments and ex vivo observation. In this chapter, several proven methods are discussed including the isolation of avian osteocytes from chicks and osteocytes from calvaria and long bones of young mice. A detailed protocol for the isolation of osteocytes from hypermineralized bone of mature and aged animals is provided.

Cell Cycle Control of Transcription at the G1/S Phase Transition

Competency for proliferation and cell cycle progression are functionally linked to the activities of regulatory factors that modulate the cell division cycle in response to the multi-directional signals of cell type specific signaling cascades. The parameters that mediate growth control are complex and interdependent, and whether cells grow or cease division reflects the integration of a broad spectrum of positive and negative growth regulatory signals that operate within distinct biological contexts. Equally important from a clinical perspective, fidelity of cell cycle regulatory mechanisms is compromised in transformed and tumor cells and in nonmalignant disorders, and reflects deregulation of cell growth or abrogation of cell death.