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Resorption of bone by mouse peritoneal macrophages
Abstract:
An experimental system is described in which mononuclear phagocytes are shown to cause contact-dependent resorption of bone powder in vitro. Endotoxin, which is known to stimulate macrophage functions, and which has also been shown to increase bone resorption in organ culture, increased bone dissolution by mononuclear phagocytes. On the other hand, parathyroid hormone and prostaglandin E2, hormones which increase th number and activity of osteoclasts, had no effect on resorption of bone powder by mononuclear phagocytes. This suggests that the osteoclast, which is probably derived from mononuclear phagocytes, is induced to respond to these hormones indirectly, following a primary hormonal effect on osteoblasts.
Insights
Mononuclear phagocytes dissolve bone powder directly. However, hormones that stimulate osteoclasts, like parathyroid hormone, do not directly affect this process, suggesting indirect hormonal influence on bone resorption.
Area of Science:
- Cell Biology
- Biochemistry
- Immunology
Background:
- Mononuclear phagocytes play a role in bone remodeling.
- Endotoxin is known to stimulate macrophage functions and bone resorption.
- Osteoclasts are the primary cells responsible for bone resorption.
Purpose of the Study:
- To investigate the direct effect of mononuclear phagocytes on bone resorption in vitro.
- To determine the influence of endotoxin, parathyroid hormone, and prostaglandin E2 on mononuclear phagocyte-mediated bone resorption.
Main Methods:
- Development of an experimental system to study bone powder resorption by mononuclear phagocytes in vitro.
- Treatment with endotoxin, parathyroid hormone, and prostaglandin E2.
Main Results:
- Mononuclear phagocytes directly mediated contact-dependent resorption of bone powder.
- Endotoxin enhanced bone dissolution by mononuclear phagocytes.
- Parathyroid hormone and prostaglandin E2 had no direct effect on mononuclear phagocyte-mediated bone resorption.
Conclusions:
- Mononuclear phagocytes are capable of direct bone resorption.
- The response of osteoclasts to hormones like parathyroid hormone and prostaglandin E2 is likely indirect, mediated through osteoblasts.
- This suggests a complex regulatory mechanism in bone remodeling involving interactions between different cell types.