Immunocytochemical expression of parathyroid hormone related protein (PTHrP) in odontogenic jaw cysts

Objective: To investigate the immunocytochemical expression of parathyroid-hormone-related protein (PTHrP) in odontogenic jaw cysts. Design: Retrospective study of archival tissue. Setting: University department, UK. Material: Odontogenic keratocysts (n=27), and dentigerous and radicular cysts (n=10 each). Intervention: Immunocytochemistry by biotin streptavidin technique. Main outcome measure: Intensity of staining of PTHrP determined by TV image analysis. Results: The epithelial linings of all the odontogenic keratocysts, 9/10 dentigerous, and 8/10 radicular cysts showed reactivity for PTHrP mainly localised to the basal and suprabasal layers. Odontogenic keratocyst linings expressed significantly higher levels of PTHrP than those of dentigerous and radicular cysts (P<0.003 in each case). There were no differences in epithelial expression of PTHrP between solitary, recurrent and naevoid basal cell carcinoma syndrome-associated odontogenic keratocysts. The fibrous tissue walls of all types of cyst reacted strongly for PTHrP with a trend towards decreasing intensity from odontogenic keratocysts, to dentigerous and then radicular cysts. Conclusion: It is possible that PTHrP modulates growth and bone resorption in odontogenic cysts. PTHrP may act synergistically with interleukin-1 to increase bone resorption or stimulate osteoblasts and inhibit osteoblasts (resulting in reduced resorption) via its transforming growth factor β-like activity.