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Down-regulation of osteoblastic cell differentiation by epidermal growth factor receptor
Abstract:
The role of epidermal growth factor receptors (EGF-R) in osteogenic cell differentiation was investigated using preosteoblastic MC3T3-E1 (MC3T3) cells and osteoblast-like ROS 17/2.8 (ROS) cells. When cultured in the presence of beta-glycerophosphate (GP) and ascorbic acid (AA), MC3T3 cells underwent spontaneous differentiation into osteoblasts which was confirmed as they expressed osteoblast markers such as alkaline phosphatase (ALP), bone sialoprotein (BSP) and osteocalcin (OC). Interestingly, the number of EGF-binding sites decreased during their differentiation into osteoblasts, and the osteogenic protein-1 (OP-1) treatment, which accelerated their differentiation, lowered the number of EGF-binding sites even further. On the other hand, ROS cells with high expression levels of osteoblast markers and no EGF-R, after being transfected with human EGF-R cDNA (EROS cells), expressed numerous EGF-binding sites as well as EGF-R mRNA and protein; in the process, they ceased to express osteoblast markers, indicating their dedifferentiation into osteoprogenitor cells. Both MC3T3 and EROS cells showed increased cell growth in response to EGF, whereas ROS cells did not. These results imply that the EGF/EGF-R system in osteogenic cells has a crucial function in osteoblast phenotype suppression and osteogenic cell proliferation.
Insights
The epidermal growth factor receptor (EGF-R) system suppresses osteoblast differentiation and promotes osteogenic cell proliferation. Blocking EGF-R signaling may enhance bone formation.
Area of Science:
- Cell Biology
- Biochemistry
- Bone Biology
Background:
- Epidermal growth factor receptors (EGF-R) are key regulators of cell growth and differentiation.
- The role of EGF-R in osteogenic cell differentiation remains incompletely understood.
Purpose of the Study:
- To investigate the function of the EGF/EGF-R system in osteogenic cell differentiation and proliferation.
Main Methods:
- Utilized MC3T3-E1 preosteoblastic cells and ROS 17/2.8 osteoblast-like cells.
- Investigated changes in EGF-binding sites and osteoblast markers during differentiation.
- Transfected ROS cells with human EGF-R cDNA to create EROS cells.
- Assessed cell proliferation in response to EGF.
Main Results:
- MC3T3 cell differentiation into osteoblasts correlated with decreased EGF-binding sites.
- Osteogenic protein-1 (OP-1) accelerated differentiation and further reduced EGF-binding sites.
- EROS cells, expressing EGF-R, dedifferentiated and showed increased proliferation with EGF, unlike ROS cells.
- EGF/EGF-R signaling suppressed osteoblast phenotype and promoted osteogenic cell proliferation.
Conclusions:
- The EGF/EGF-R system plays a critical role in suppressing osteoblast differentiation.
- EGF/EGF-R signaling promotes osteogenic cell proliferation, suggesting a dual role in bone biology.