Abstract 12

INFLUENCE OF AGE ON BONE HEALING IN NORMAL AND IMMUNODEFICIENT MICE

Gan J., Yu Y., Chen J.B., Gillies R.M., Walsh W.R.

Orthopaedics Research Laboratories, Prince of Wales Hospital, University of New South Wales, Sydney, NSW, Australia

Aging is generally associated with the deterioration of bodily function, including bone healing. The influence of age, especially cell-mediated response on bone repair in immunodeficient animals is not well reported. Thirty young (3-month-old) and adult (5-month-old) nude and normal Balb/c mice were used following ethical approval. A round 1mm-diameter defect was drilled through the medio-lateral aspect of the distal femoral condyle. The animals were sacrificed at day 3, 7, 10, 14 and 21. New bone formation was analysed quantitatively from histology. Normal mice showed new bone formation at 7 days and progressed to complete healing by 3 weeks. There was a significant decrease in new bone in adult normal mice in the first 2 weeks (p < 0.05) compared to the young. Nude mice showed new bone formation at 7 days and up to 75% healing at 3 weeks. No significant difference in new bone formation was detected between young and adult nude mice. Assessment of both strains revealed a faster healing rate in young normal mice compared to their nude cousins. However, in the adult animals, normal mice showed delayed healing when compared to the nude. The result suggested that aging suppresses the initial phases of bone healing in normal animals. Absence or low levels of functional T-cells in athymic nude mice may have minimal effect during aging when compared to an intact immune system in normal mice. Despite this, both adult and young nude mice can be used as animal model for clinical research.

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