In vitro effects of elastase on periosteum of long bones: an histochemical, immunohistochemical and morphometric study.

The aim of the study was to determine the in vitro effects of porcine pancreatic elastase on the periosteum of long bones and to what extent the effects are selective for the elastic fibres of the tissue. Twenty-eight new-born chicks' tibiae were incubated for 1 or 3 hours in different experimental conditions (PBS, 30 or 60 units (U)/ml of porcine pancreatic elastase) or immediately formalin fixed. The tibiae were then processed for histo-chemical (Verhoeff and van Gieson stain), immunohistochemical (anti-elastin antibody) and histomorphometric analysis. A decrease of periosteal elastic fibres in all the specimens incubated with elastase in comparison with non incubated specimens was evident. The effect of elastase was easily detectable even at the lower concentration (30 U/ml) and at the shorter time of incubation (1 h). The amount of elastic fibres decreased in accordance with the rise of enzyme levels and incubation time, while periosteal collagen fibre content was not substantially modified by elastase activity. Present data are a prerequisite to evaluate the in vitro and in vivo effects of experimental destruction of periosteal elastic fibres by elastase and to assess the role of these fibres in the growth process of long bones.