Related Experiment Videos
Bone morphogenetic protein (BMP) localization in developing human and rat growth plate, metaphysis, epiphysis, and
H C Anderson1, P T Hodges, X M Aguilera
1University of Kansas Medical Center, Department of Pathology and Laboratory Medicine, Kansas City, Kansas 06160, USA. handerso@kumc.edu
Insights
Bone morphogenetic proteins (BMPs) are expressed in developing cartilage and bone cells, including osteoclasts. This suggests BMPs play roles in chondrocyte differentiation and bone remodeling communication.
Area of Science:
- Skeletal Biology
- Developmental Biology
- Cell Biology
Background:
- Bone morphogenetic proteins (BMPs) are crucial signaling molecules in skeletal development and homeostasis.
- Understanding BMP distribution is key to elucidating mechanisms of bone and cartilage formation and remodeling.
Purpose of the Study:
- To investigate the localization and relative expression levels of BMPs-1-7 in the developing skeletal tissues of human fetuses and rats.
- To explore the potential roles of BMPs in chondrocyte differentiation, apoptosis, and intercellular communication during bone remodeling.
Main Methods:
- Immunohistochemistry was employed to detect BMP-1-7 distribution in tibial growth plates, epiphyses, metaphyses, and articular cartilage.
- Tissues from human fetuses (21-22 weeks) and Sprague-Dawley rats (10 weeks) were analyzed.
Main Results:
- BMPs were primarily localized in the cytoplasm of chondrocytes, osteoblasts, and osteoclasts, with minimal matrix staining.
- Highest BMP expression was observed in hypertrophic chondrocytes, osteoblasts, vascular cells, and notably, osteoclasts.
- Unexpectedly strong BMP staining (BMP-4, -5, -6) was found in osteoclasts, suggesting a role in bone remodeling.
Conclusions:
- BMP expression is associated with maturing chondrocytes in growth plate and articular cartilage, potentially influencing differentiation and apoptosis.
- BMPs are expressed by osteoclasts, indicating a possible role in intercellular signaling between osteoclasts and osteoprogenitor cells during bone remodeling.
Abstract:
We assessed the distribution and relative staining intensity of bone morphogenetic protein (BMP)-1-7 by immunohistochemistry in tibial growth plates, epiphyses, metaphyses, and articular cartilage in one 21-week and one 22-week human fetus and in five 10-week-old Sprague-Dawley rats. In the rats, articular cartilage was also examined. BMP proteins were mostly cytoplasmic, with negligible matrix staining. Highest BMP levels were seen in (a) hypertrophic and calcifying zone chondrocytes of growth plate (BMP-1-7), (b) osteoblasts and/or osteoprogenitor fibroblasts and vascular cells of the metaphyseal cortex and medulla (BMP-1-6), (c) osteoclasts of the metaphysis and epiphysis (BMP-1,-4,-5, and -6), and (d) mid to deep zone articular chondrocytes of weanling rats (BMP-1-7). BMP staining in osteoclasts, an unexpected finding, was consistently strong with BMP-4, -5, and -6 but was variable and dependent on osteoclast location with BMP-2,-3, and -7. BMP-1-7 were moderately to intensely stained in vascular canals of human fetal epiphyseal cartilage by endothelial cells and pericytes. BMP-1,-3,-5,-6, and -7 were localized in hypertrophic chondrocytes adjacent to cartilage canals. We conclude that BMP expression is associated with maturing chondrocytes of growth plate and articular cartilage, and may play a role in chondrocyte differentiation and/or apoptosis. BMP appears to be expressed by osteoclasts and might be involved in the intercellular "cross-talk" between osteoclasts and neighboring osteoprogenitor cells at sites of bone remodeling.