Turbinate osteoporosis in pigs following intranasal inoculation of purified Pasteurella toxin: histomorphometric and ultrastructural studies

Abstract

Turbinate osteoporosis, induced by intranasal inoculation of purified toxin isolated from serotype D Pasteurella multocida, was investigated in 3- to 5-week-old, caesarean-derived, colostrum-deprived, isolation-reared pigs. Marked bilateral reduction in relative volume of trabecular bone occurred in osseous cores of turbinates of toxin-treated pigs relative to control pigs on post-inoculation day (p.i.d.) 3, 6, 9, 12, and 15. The fractional resorptive surface along turbinate bone was greater in toxin-treated pigs when compared to controls on p.i.d. 3 and 6. A significant decrease in resorptive surface occurred over time in toxin-treated pigs, whereas the fractional resorptive surface was constant over time in control pigs. Osteoclasts in medullary spaces separating bony trabeculae of turbinates were abundant in toxin-treated pigs and scant in controls on p.i.d. 3, 6, and 9. Degeneration and necrosis of bone forming cells, principally osteoblasts, were progressively more extensive with time and were associated with decreased mineralization and reduced thickness of osteoid and woven bone matrix. Osteoclasts along resorptive surfaces of turbinate bone in toxin-treated pigs had more abundant, more highly vacuolated cytoplasm, a more prominent microvillous border, and a greater number of nuclei per cell than osteoclasts from control pigs on p.i.d. 3 and 6. We conclude that this Pasteurella toxin stimulates osteoclastic osteolysis and inhibits osteogenesis in turbinates by causing degeneration and death of osteoblasts.