Xiao Wenmei, Li Shuai, Pacios Sandra, Wang Yu, Graves Dana T
Front Oral Biol. 2016;18:17-27. doi: 10.1159/000351896. Epub 2015 Nov 24.
Bone is masterfully programmed to repair itself through the coupling of bone formation following bone resorption, a process referred to as coupling. In inflammatory or other conditions, the balance between bone resorption and bone formation shifts so that a net bone loss results. This review focuses on four pathologic conditions in which remodeling leads to net loss of bone, postmenopausal osteoporosis, arthritis, periodontal disease, and disuse bone loss, which is similar to bone loss associated with microgravity. In most of these there is an acceleration of the resorptive process due to increased formation of bone metabolic units. This initially leads to a net bone loss since the time period of resorption is much faster than the time needed for bone formation that follows. In addition, each of these processes is characterized by an uncoupling that leads to net bone loss. Mechanisms responsible for increased rates of bone resorption, i.e. the formation of more bone metabolic units, involve enhanced expression of inflammatory cytokines and increased expression of RANKL. Moreover, the reasons for uncoupling are discussed which range from a decrease in expression of growth factors and bone morphogenetic proteins to increased expression of factors that inhibit Wnt signaling.
骨骼具有精妙的程序，可通过骨吸收后骨形成的耦合来自我修复，这一过程称为耦合。在炎症或其他情况下，骨吸收与骨形成之间的平衡会发生变化，从而导致净骨丢失。本综述重点关注四种病理状况，即绝经后骨质疏松症、关节炎、牙周病和废用性骨丢失，其中重塑会导致骨净丢失，废用性骨丢失与微重力相关的骨丢失相似。在大多数这些情况中，由于骨代谢单位形成增加，吸收过程加速。这最初会导致骨净丢失，因为吸收的时间段比随后骨形成所需的时间快得多。此外，这些过程中的每一个都具有导致骨净丢失的解耦合特征。导致骨吸收速率增加的机制，即形成更多的骨代谢单位，涉及炎症细胞因子表达增强和RANKL表达增加。此外，还讨论了解耦合的原因，其范围从生长因子和骨形态发生蛋白表达的降低到抑制Wnt信号传导的因子表达的增加。
