Increased bone formation by prevention of osteoblast apoptosis with parathyroid hormone.
The mass of regenerating tissues, such as bone, is critically dependent on the number of executive cells, which in turn is determined by the rate of replication of progenitors and the life-span of mature cells, reflecting the timing of death by apoptosis. Bone mass can be increased by intermittent parathyroid hormone (PTH) administration, but the mechanism of this phenomenon has remained unknown. We report that daily PTH injections in mice with either normal bone mass or osteopenia due to defective osteoblastogenesis increased bone formation without affecting the generation of new osteoblasts. Instead, PTH increased the life-span of mature osteoblasts by preventing their apoptosis - the fate of the majority of these cells under normal conditions. The antiapoptotic effect of PTH was sufficient to account for the increase in bone mass, and was confirmed in vitro using rodent and human osteoblasts and osteocytes. This evidence provides proof of the basic principle that the work performed by a cell population can be increased by suppression of apoptosis. Moreover, it suggests novel pharmacotherapeutic strategies for osteoporosis and, perhaps, other pathologic conditions in which tissue mass diminution has compromised functional integrity.
Jilka
R L
RL
Division of Endocrinology and Metabolism, UAMS Center for Osteoporosis and Metabolic Bone Diseases, and Central Arkansas Veterans Health Care System, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA. rljilka@life.uams.edu
Weinstein
R S
RS
Bellido
T
T
Roberson
P
P
Parfitt
A M
AM
Manolagas
S C
SC
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015519:Bone Density / Q000187:drug effects; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D010006:Osteoblasts / Q000737:chemistry* / Q000187:drug effects*; D010011:Osteocytes / Q000166:cytology / Q000187:drug effects; D010012:Osteogenesis / Q000187:drug effects*; D019379:Teriparatide / Q000008:administration & dosage / Q000494:pharmacology*
D019379:Teriparatide