Costal cartilage overgrowth does not induce pectus-like deformation in the chest wall of a rat model

Overgrowth of the costal cartilages has been frequently reported to be an etiological factor of chest wall deformities in children. The present study aimed to investigate if induced overgrowth of the costal cartilages could lead to deformation of the chest wall in a rat model. An insulin-like growth factor 1 (IGF1) solution was directly injected under the perichondrium of the last three costal cartilages of 2-week-old rat pups. Two different concentrations, 50 mu g/ml (E50) and 100 mu g/ml (E100), were applied. This procedure was repeated once per week for 5 consecutive weeks. Subsequently, 14 days after the last injection, all animals were euthanized before the shape of the thoracic cage was assessed, and the diameter was measured. In addition, the last three costal cartilages were dissected before the samples were prepared and examined by light microscopy. Rats that received E100 exhibited larger sagittal and coronal rib cage diameters compared with those in the E50 and control groups. However, no deformation could be observed in the chest wall. Microscopic examinations revealed an anabolic pattern in the E100 group. The present findings suggested that locally administered IGF1 stimulated cell proliferation and tissue growth in coastal cartilages in a dose-dependent manner in vivo. However, this induced overgrowth of the costal cartilages did not result in the deformation of the chest wall.