Epiphyseal Fusion in the Human Growth Plate Does not Involve Classical Apoptosis

Abstract

By the end of puberty, growth ceases and epiphyseal fusion occurs through mechanisms not yet completely understood. Human growth plate tissues were collected in various pubertal stages including a unique late pubertal growth plate, which was about to fuse. Apoptosis was studied by TUNEL staining, immunolocalization of pro-and antiapoptotic proteins, and electron microscopy (EM). Morphologic analyses of the fusing growth plate revealed disorganized, large chondrocytes surrounded by a border of dense, corticallike bone. In the unfused growth plates, few chondrocytes were TUNEL positive. In contrast, the fusing growth plate contained no single TUNEL-positive cell. Antiapoptotic (Bcl-2 and Bcl-X L ) and proapoptotic (Bax, Bad, and cleaved caspase-3) proteins were detected in all growth plate zones without change in intensity during pubertal progression. Expression of antiapoptotic proteins was found in the fusing growth plate but of the proapoptotic proteins only Bad was detected. EM revealed no typical signs of apoptosis or autophagy in any of the growth plates. In contrast, morpohological signs of hypoxia and necrosis were observed. We conclude that classical apoptosis is not likely to be involved in the process of human growth plate fusion. (Pediatr Res 66: 654-659, 2009)

Osteonecrosis in children with acute lymphoblastic leukemia

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The skeleton: a multi-functional complex organ. The growth plate chondrocyte and endochondral ossification

“…Cells undergoing apoptosis show intense condensation of chromatin into geometric shapes, and fragmentation of the nucleus and cytoplasm into membrane-bound apoptotic bodies (Kerr et al 1972). A number of careful ultrastructural studies have failed to identify chondrocytes undergoing apoptosis in growth plates of several species (Roach & Clarke 1999, Colnot et al 2001, Roach et al 2004, Emons et al 2009). In fact, light and dark hypertrophic chondrocytes appear to die by cell type-specific (non-apoptotic) mechanisms (Ahmed et al 2007).…”

Autophagy Prior to Chondrocyte Cell Death During the Degeneration of Meckel's Cartilage

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