Practical pathology of aging mice

Pettan-Brewer, Christina; Treuting, Piper M.

Dysplastic and degenerative dental and joint lesions are presented in Fig. 7 as examples of subclinical histologic disease, which likely contributes significantly to the decline in functional health of the affected mouse and may be under diagnosed. We and others (54) have noted dysplastic intrapulpal denticles in the incisors of older mice (Fig. 7A,B) . These lesions may result in abnormal wear and or breakage of the incisors that contribute to periodontitis and decreased ability to effectively gnaw rodent chow. We have noted, in two of three cases of intrapulpal denticles, an association with moderate to severe temporomandibular osteoarthritis (Fig. 7C,D) . The precise relationship between the development of these two lesions is unknown Á whether the abnormal tooth development aggravated the joint disease or vice versa. It is plausible that the combination of the lesions results in painful and ineffective mastication. Osteoarthritis of the knee, hip, elbow, and vertebra would result in abnormal gaits and, if severe, clinically recognizable joint swelling due ossification of the joint capsule and periarticular fibrosis (55) . Preliminary necropsy results from the current health span study in CB6F1 suggest the incidence of clinical osteoarthritis may be relatively high (personal observation CPB). Other preliminary observations from necropsies in the on-going health span study include high incidence of skin, male reproductive tract, renal lesions, and hepatosplenomegaly that likely is due to hematopoietic neoplasia.