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Apoptosis is developmentally regulated in rat growth plate
Dionisios Chrysis1, Ola Nilsson, E Martin Ritzen
1Department of Woman and Child Health, Pediatric Endocrine Unit, Astrid Lindgren Children's Hospital, Karolinska Institute, Stockholm, Sweden. dionisios.chrysis@kbh.ki.se
Endocrine
|November 27, 2002
Summary
Apoptosis, programmed cell death, increases in rat growth plates with age, particularly in terminal hypertrophic chondrocytes. This developmental regulation impacts longitudinal bone growth.
Area of Science:
- Cell Biology
- Developmental Biology
- Orthopedics
Background:
- Apoptosis is crucial for normal and abnormal longitudinal bone growth.
- Understanding apoptosis in the growth plate is key to understanding skeletal development.
Purpose of the Study:
- To investigate the role and regulation of apoptosis during growth plate maturation in rats.
- To analyze the expression of apoptosis-related proteins during different developmental stages.
Main Methods:
- Terminal deoxynucleotidyl transferase (TdT)-mediated deoxy-UTP nick end-labeling (TUNEL) assay for apoptosis detection.
- Immunohistochemistry to detect p53, caspases-3 and -6, Bcl-2, Bcl-x, Bax, and Bad proteins.
- Analysis of rat tibial growth plates at 2, 4, 8, and 11 weeks of age.
Main Results:
- Apoptosis significantly increased in terminal hypertrophic chondrocytes (THPCs) with age.
- p53 expression increased in THPCs in older rats.
- Caspase-3 and -6 expression shifted to mature hypertrophic chondrocytes and THPCs in older animals.
- Expression of anti-apoptotic proteins Bcl-2 and Bcl-x decreased with age, while pro-apoptotic proteins Bax and Bad increased in mature chondrocytes.
Conclusions:
- Apoptosis is developmentally regulated in the rat growth plate.
- Increased apoptosis in THPCs correlates with decreased growth rate and growth plate height in older rats.