Levich Institute Seminar Announcement, 12/02/2008

Tuesday, 12/02/2008 2:00 PM Steinman Hall, Room #312 (Chemical Engineering Conference Room) Professor Mitchell Schaffler City College of CUNY Biomedical Engineering Department "Mechanical Factors and Remodeling in Bone: Life at the Extremes"

ABSTRACT

Healthy bone maintains a balance between wear and tear damage (i.e., fatigue) and intrinsic, matrix-level repair. Imbalance in this damage-repair homeostasis, either because of excessively rapid damage accumulation or because of ineffective, inadequate or inappropriate biological responses leads to pathology and ultimately mechanical failure of skeletal elements. In bone, remodeling serves to remove and replace focal regions of tissue that have reached the end of their life span. How bone remodeling units "target" such effete microscopic areas of bone for replacement remains unclear. This talk will focus on our efforts to understand the cellular controls of targeting remodeling by exploring the remodeling responses that occur in responses to fatigue microdamage in vivo. We have found that fatigue damage leads to osteocyte apoptosis, or programmed cell death, in the immediate regions surrounding bone microcracks. These areas of apoptosis precede and co-localize with the area of subsequent osteoclastic resorption in fatigue bone. This has led to the hypothesis that osteocyte apoptosis may provide the activating or targeting signal for this remodeling. We confirmed this in recent pharmacological studies, which demonstrate that there is a causal relationship between osteocyte apoptosis at microdamage sites and the subsequent activation of bone remodeling. Implications of osteocyte apoptosis for bone remodeling activation in response to other challenges (e.g., estrogen loss, immobilization) will also be discussed.

BRIEF ACADEMIC/EMPLOYMENT BACKGROUND:

Mitchell B. Schaffler, PhD is the Wallace Coulter and Presidential Professor of Biomedical Engineering at the City College of New York (CUNY). He is Director of the New York Center for Biomedical Engineering. Dr. Schaffler comes to the City College from the Mount Sinai School of Medicine, where he was the Director of the Orthopaedic Research Laboratories from 1998-2008. He was previously on faculty at the University of California, San Diego and the University of Michigan. Dr.Schaffler's research focuses on understanding the cellular and tissue processes underlying adaptations of skeletal tissues to mechanical usage, and understanding the mechanisms by which failures of those adaptive processes lead to skeletal disease and fragility.

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