Inflammatory and developmental
cysts of the jaws are relatively common bone destructive lesions in the human maxillofacial skeleton but their pathogenesis is still poorly understood. In this study the role of mast cells (MC), and
mast cell tryptase in particular, was evaluated in the pathophysiology of
bone resorption and
jaw cyst formation in different types of
cysts. The distribution of MC and the amount of
tryptase in histological tissue sections were determined by immunohistochemistry using monoclonal antihuman
tryptase antibodies and the results were quantitated by using an image analyzing system. The amount of
tryptase was further studied by Western-blotting and measurement of
trypsin-like activity from the neutral
salt extracts obtained from different types of
jaw cysts. In contrast to control tissue, high
trypsin-like activities and abundant immunoreactive
tryptase were observed in the extracts of all types of
cysts studied (radicular, dentigerous and
keratocyst). In tissue sections the highest amount of
tryptase-positive staining was observed in
radicular cysts (mean 6.2% of reference area) and the lowest amount in
keratocysts (mean 2.1% of reference area, P < 0.01). MC were found to be located in inflammatory cell-rich tissue areas and just beneath the
cyst epithelium. Importantly, MC located at the border of bone were observed to be degranulated, indicating high activity of MC and release of
tryptase at the regions of early bone destruction. Based on previous findings addressing the role of
mast cell tryptase in proteolytic cascades, and the known association of MC with
osteoporosis, we suggest that mast cells and
mast cell tryptase may contribute significantly to
jaw cyst tissue remodelling during growth of a
cyst, and to the destruction of the surrounding bone, resulting in
jaw cyst expansion.