Kim Harry K W, Bian Haikuo, Randall Timothy, Garces Amanda, Gerstenfeld Louis C, Einhorn Thomas A
Center for Research in Skeletal Development and Pediatric Orthopaedics, Shriners Hospitals for Children, 12502 Pine Drive, Tampa, FL 33612, USA.
J Bone Miner Res. 2004 Dec;19(12):2041-8. doi: 10.1359/JBMR.040911. Epub 2004 Sep 20.
Ischemic injury to the immature femoral head produces epiphyseal cartilage damage and cessation of endochondral ossification. This study suggests that VEGF facilitates the repair of the necrotic epiphyseal cartilage, which is essential for restoration of endochondral ossification and re-establishment of the growth of the immature femoral head after ischemic necrosis.
Legg-Calve-Perthes disease (LCPD) is a childhood form of osteonecrosis that produces growth arrest of the secondary center of ossification. The cessation of growth is caused by ischemic damage to the hypertrophic zone of the epiphyseal cartilage where endochondral ossification normally occurs. The role of vascular endothelial growth factor (VEGF) in restoring endochondral ossification in the epiphyseal cartilage after ischemic necrosis was investigated in a piglet model of LCPD because the resumption of normal growth is important for maintaining the spherical shape of the femoral head.
Piglet femoral heads were assessed 24 h to 8 weeks after the surgical induction of ischemia. Western blot analysis, ribonuclease protection assay (RPA), immunohistochemistry, and in situ hybridization were performed.
Western blot analysis and RPA showed increased VEGF protein and mRNA expression, respectively, in the epiphyseal cartilage of the infarcted heads compared with the contralateral normal heads. In the normal femoral heads, VEGF-immunoreactivity (VEGF-IR) and transcripts were observed in the hypertrophic zone of the epiphyseal cartilage. In the infarcted heads, VEGF-IR and transcripts were no longer observed in the hypertrophic zone because of diffuse cell death in that zone from ischemia. However, VEGF-IR and transcripts were observed in the proliferative zone above the necrotic hypertrophic zone. At 8 weeks, vascular granulation tissue invasion of the necrotic hypertrophic zone was observed with active resorption of the necrotic cartilage. In some areas where the necrotic cartilage was completely resorbed, restoration of endochondral ossification was observed. In these areas, VEGF transcripts were observed in the newly formed hypertrophic zone.
VEGF expression was increased, and its spatial expression was altered in the epiphyseal cartilage after ischemic necrosis of the immature femoral head. VEGF upregulation in the proliferative zone after ischemic damage may play a role in stimulating vascular invasion and granulation tissue formation in the necrotic hypertrophic zone of the epiphyseal cartilage. This may be an important step toward facilitating the resorption of the necrotic cartilage and restoration of endochondral ossification leading to further growth and development of the femoral head.
未成熟股骨头的缺血性损伤会导致骨骺软骨损伤和软骨内成骨停止。本研究表明，血管内皮生长因子（VEGF）促进坏死骨骺软骨的修复，这对于软骨内成骨的恢复以及缺血性坏死后未成熟股骨头生长的重新建立至关重要。
Legg-Calve-Perthes病（LCPD）是儿童期的一种骨坏死形式，会导致继发骨化中心生长停滞。生长停止是由骨骺软骨肥大区的缺血性损伤引起的，而软骨内成骨通常在此处发生。在LCPD仔猪模型中研究了血管内皮生长因子（VEGF）在缺血性坏死后恢复骨骺软骨内软骨内成骨中的作用，因为恢复正常生长对于维持股骨头的球形形状很重要。
在手术诱导缺血后24小时至8周对仔猪股骨头进行评估。进行了蛋白质免疫印迹分析、核糖核酸酶保护分析（RPA）、免疫组织化学和原位杂交。
蛋白质免疫印迹分析和RPA显示，与对侧正常股骨头相比，梗死股骨头的骨骺软骨中VEGF蛋白和mRNA表达分别增加。在正常股骨头中，在骨骺软骨的肥大区观察到VEGF免疫反应性（VEGF-IR）和转录本。在梗死股骨头中，由于该区域因缺血而弥漫性细胞死亡，在肥大区不再观察到VEGF-IR和转录本。然而，在坏死肥大区上方的增殖区观察到VEGF-IR和转录本。在8周时，观察到血管肉芽组织侵入坏死肥大区，坏死软骨有活跃吸收。在坏死软骨完全吸收的一些区域，观察到软骨内成骨的恢复。在这些区域，在新形成的肥大区观察到VEGF转录本。
未成熟股骨头缺血性坏死后，骨骺软骨中VEGF表达增加，其空间表达发生改变。缺血损伤后增殖区VEGF上调可能在刺激骨骺软骨坏死肥大区的血管侵入和肉芽组织形成中起作用。这可能是促进坏死软骨吸收和软骨内成骨恢复从而导致股骨头进一步生长发育的重要一步。
