Growth Plate Chondrocytes' Morphology and Intrauterine Hypervitaminosis A in Newborn Rats
Background: Longitudinal bone growth is dependent on the state of the chondrocytes and the extracellular matrix of the growth plate. Hypervitaminosis A is known to result in limb shortening in several models, this anomaly has been related to the early closure of the epiphyseal plate. The specific contribution of the different chondrocyte types and the growth plates are not fully understood. The time specific response of chondrocyte might further unlock the mystery surrounding the teratogenic effect of Hypervitaminosis A on longitudinal bone growth.
Objective: To evaluate the morphological response of the chondrocytes in the different zones of the growth plates following intrauterine hypervitaminosis A exposure at different periods of gestation.
Methods: 18 time m ated adult wistar rats were divided into 3 groups. Groups A and B were administered 100,000IU of vitamin A in the 1st and 3rd trimester of gestation, while Group C served as control. Rat pups were examined after delivery and the humerus was processed histologically. The proximal and distal growth plates were examined and findings were noted.
Result: In the proximal growth plate, the 1st trimester group showed smaller hypertrophic chondrocytes and a reduction in the height of the hypertrophic zone. Proliferating zone height was increased and columnar arrangement of chondrocyte was intact. In the 3rd trimester group, the height of the proliferating zone was reduced alongside disruption of the columnar arrangement of chondrocytes in the proliferating and hypertrophic zones. The distal growth plate revealed minimal differences between the chondrocytes of the different zones.
Conclusion: The limb shortening effect of intrauterine hypervitaminosis A involve the hypertrophic and proliferating chondrocytes of the proximal growth plate. A reduction in the size of the hypertrophic chondrocytes in the 1st trimester and disruption of the columnar arrangement of the chondrocyte in the 3rd trimester are the main contributors to the limb shortening effect of intrauterine hypervitaminosis A on the rat forelimb.
Keywords: Chondrocytes, Hypertrophic, Proliferating, Hypervitaminosis A, Growth plate.