Apoptotic cells of the human growth plate have not previously been demonstrated in situ. We have
investigated the distribution of apoptotic cells in costosternal growth plates and bone of premature infants
aged 4–11 d with a gestational age of ∼ 26 wk. In addition, we investigated the immunolocalisation of
apoptosis-related proteins within the growth plates and associated bone. A proportion of late hypertrophic
chondrocytes and osteocytes within newly formed primary spongiosa showed evidence of highly fragmented
DNA. The incidence of osteocyte apoptosis decreased as the distance from the chondroosseous junction
increased. Tissue transglutaminase (tTG) expression was associated with apoptosis of osteocytes and
hypertrophic chondrocytes. In contrast the presence of tTG was demonstrated in osteoblasts and bone lining
cells but it did not colocalise with evidence of apoptosis. The anti-apoptotic gene product Bcl-2 was absent
from the growth plate but was present in osteocytes. Visual assessment indicated a greater occurrence of the
protein in cells occupying regions of low apoptosis. P53 was not demonstrated in the growth plate or bone.
These findings would indicate that human growth plate chondrocytes appear to show little provision for
ensuring cell longevity. In contrast osteocyte apoptosis appears negatively correlated with the skeletal
distribution of Bcl-2 protein in the human infant, implying a potential selective vulnerability in individual
cells. Lack of Bcl-2 and the high incidence of osteocyte apoptosis in the more rapidly remodelling bone of
the human infant suggest a potential role of osteocyte apoptosis in the remodelling process.