Yonsei Med J.  2012 May;53(3):625-633. 10.3349/ymj.2012.53.3.625.

Altered Cellular Kinetics in the Growth Plate of the Femoral Head of Spontaneously Hypertensive Rats

• Park H
• Kong SY
• Kim HW

• KMID: 1777000
• DOI: http://doi.org/10.3349/ymj.2012.53.3.625

Abstract

PURPOSE
Pathologic changes in the growth plate remain unknown in Legg-Calve-Perthes (LCP) disease. Spontaneously hypertensive rats have proven to be a good model for studying LCP disease. This study investigated the histopathologic changes and the expression of vascular endothelial growth factor in the growth plate of spontaneously hypertensive rats (SHR).
MATERIALS AND METHODS
Sixty SHR rats were divided into two groups: those showing osteonecrosis (SHR+n group: 32), and those showing normal ossification (SHR-n group: 28). Thirty Wister Kyoto rats served as a control. For histomorphological measurement, the length of each zone of the growth plate was measured. Cell kinetics was measured by 5-bromo-2'-deoxyuridin (BrdU) immunohistochemistry and transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) assays. Vascular endothelial growth factor (VEGF) immunohistochemistry was used to identify of expression of VEGF.
RESULTS
The lengths of growth plates of the SHR+n group were significantly shorter in the initial growth period than those of the other groups. The lowest proliferative rate and the highest apoptosis rate were observed in the SHR+n group at the initial growth period. The expression of VEGF in the growth plate of the SHR group was lower than the control group, and it was lower in the SHR+n group than in the SHR-n group.
CONCLUSION
The growth plate of the SHR+n group was found to be affected by disease process of ischemic necrosis of the femoral head, and this might explain the relative overgrowth of the greater trochanter in the later stages of LCP disease.

Keyword

Spontaneous hypertensive rats; growth plate; avascular necrosis; apoptosis; vascular endothelial growth factor

MeSH Terms

Animals
Apoptosis
Femur Head/metabolism/*pathology
Femur Head Necrosis/metabolism/pathology
Growth Plate/*cytology/metabolism
Osteogenesis/physiology
Rats
Rats, Inbred SHR
Rats, Sprague-Dawley
Vascular Endothelial Growth Factor A/metabolism

Figure

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  Fig. 1 Measurement of the length of the growth plate using an image analyzer (×100). L1, L5, L9, L13: total length; L2, L6, L10, L14: resting zone; L3, L7, L9, L15: proliferation zone; L4, L8, L12, L16: hypertrophic zone.

• 

  Fig. 2 Measurement of the length of the growth plate according to age (*p<0.01). WKY, Wister-Kyoto rat; SHR-n, SHR without evidence of ischemic necrosis of the epiphysis; SHR+n, SHR with evidence of ischemic necrosis of the epiphysis.

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  Fig. 3 Findings of BrdU immunohistochemistry (×100). (A) 9 weeks WKY, (B) 9 weeks SHR-n, (C) 9 weeks SHR+n.

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  Fig. 4 Comparison of apoptosis between groups (*p<0.01). WKY, Wister-Kyoto rat; SHR-n, SHR without evidence of ischemic necrosis of the epiphysis; SHR+n: SHR, with evidence of ischemic necrosis of the epiphysis.

• 

  Fig. 5 Findings of apoptosis (×100, TUNEL assay). (A) 9 weeks WKY, (B) 9 weeks SHR-n, (C) 9 weeks SHR+n.

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  Fig. 6 Comparison of VEGF expression between groups (*p<0.01). WKY, Wister-Kyoto rat; SHR-n, SHR without evidence of ischemic necrosis of the epiphysis; SHR+n, SHR with evidence of ischemic necrosis of the epiphysis; VEGF, vascular endothelial growth factor.

• 

  Fig. 7 Findings of VEGF expression in the growth plate of the WKY group (×200). (A) 9 weeks, (B) 12 weeks, (C) 15 weeks. VEGF, vascular endothelial growth factor.

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