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Orthotopic Ovarian Transplantation Procedures to Investigate the Life- and Health-span Influence of Ovarian Senescence in Female Mice

Ovarian transplantation was first conducted at Utah State University in 1963. In more recent work, heterochronic transplantation of mammalian ovaries is ...

Utah State University

Previously, transplantation of ovaries from young, cycling mice into old, postreproductive-age mice increased life span and decreased cardiomyopathy at death. We anticipated that the same factors that increased life span and decreased cardiomyopathy could also influence the progression of orthopedic disease. At 11 months of age, prepubertally ovariectomized and ovary-intact mice (including reproductively cycling and acyclic mice) received new 60-day-old ovaries. At death, epiphyseal bone in the proximal tibia and the distal femur and mid-shaft tibial and femoral diaphyseal bone was analyzed with micro-computed tomography. For qualitative analysis of osteophytosis, we also included mineralized connective tissue within the stifle joint. Prepubertal ovariectomy had the greatest influence on bone volume, ovarian transplantation had the greatest influence on bone architecture and both treatments influenced bone density. Ovarian transplantation increased cortical, but not trabecular bone density and tended to increase osteophytosis and heterotopic mineralization, except in acyclic recipients. These effects may have been dictated by the timing of the treatments, with ovariectomy appearing to influence early development and ovarian transplantation limited to influencing only the postreproductive period. However, major differences observed between cycling, acyclic and ovariectomized recipients of new ovaries may have been, in part due to differences in the levels of hormone receptors present and the responsiveness of specific bone processes to hormone signaling. Changes that resulted from these treatments may represent a compensatory response to normal age-associated, negative, orthopedic changes. Alternatively, differences between treatments may simply be the 'preservation' of unblemished orthopedic conditions, prior to the influence of negative, age-associated effects. These findings may suggest that in women, tailoring hormone replacement therapy to the patient's current reproductive status may improve therapy effectiveness and that beginning therapy earlier may help preserve trabecular bone mineral density that would otherwise be lost during perimenopause.

Manipulation of Ovarian Function Significantly Influenced Trabecular and Cortical Bone Volume, Architecture and Density in Mice at Death.

Previously, transplantation of ovaries from young cycling mice into old postreproductive-age mice increased life span. We anticipated that the same factors that increased life span could also influence health span. Female CBA/J mice received new (60 d) ovaries at 12 and 17 months of age and were evaluated at 16 and 25 months of age, respectively. There were no significant differences in body weight among any age or treatment group. The percentage of fat mass was significantly increased at 13 and 16 months of age but was reduced by ovarian transplantation in 16-month-old mice. The percentages of lean body mass and total body water were significantly reduced in 13-month-old control mice but were restored in 16- and 25-month-old recipient mice by ovarian transplantation to the levels found in six-month-old control mice. In summary, we have shown that skeletal muscle mass, which is negatively influenced by aging, can be positively influenced or restored by reestablishment of active ovarian function in aged female mice. These findings provide strong incentive for further investigation of the positive influence of young ovaries on restoration of health in postreproductive females.

Manipulation of Ovarian Function Significantly Influenced Sarcopenia in Postreproductive-Age Mice.

Our goals in the current experiments were to determine if (a) upregulation of Wnt signaling would induce osteoarthritis changes in stable stifle joints and (b) if downregulation of Wnt signaling in destabilized joints would influence the progression of OA.

Wnt10b and Dkk-1 gene therapy differentially influenced trabecular bone architecture, soft tissue integrity, and osteophytosis in a skeletally mature rat model of osteoarthritis.

Proper immune functioning is necessary to maximize reproductive success. In addition, age-associated uremia in women is often associated with hypothalamic--pituitary-gonadal dysfunction. In the present experiments, we tested immune and renal function to determine if exposure of postreproductive mice to young, reproductively cycling ovaries would influence non-reproductive physiological functions. Control female CBA/J mice were evaluated at 6, 13 and 16 months of age. Additional mice received new (60-day-old) ovaries at 12 months of age and were evaluated at 16 months of age. Consequently, 6-month-old control mice and 16-month-old recipient mice both possessed 6-month-old ovaries and were reproductively cycling. A significant age-related decline in immune function (T-cell subset analysis) was found in 16-month-old mice, but was improved 64% by ovarian transplantation. Renal function (blood urea nitrogen:creatinine ratio) was also decreased with aging, but ovarian transplantation restored function to levels found in 6-month-old mice. In summary, we have shown that immune and renal function, which are negatively influenced by aging, can be positively influenced or restored by re-establishment of active ovarian function in aged female mice. These findings provide a strong incentive for further investigation of the positive influence of young ovaries on restoration of health in postreproductive females.

Restoration of immune and renal function in aged females by re-establishment of active ovarian function.

In mammals, the relationship between reproductive function and health has been particularly difficult to define. Previously, in old, postreproductive-aged mice, replacement of senescent ovaries with new ovaries from young, actively cycling mice increased life span. We hypothesized that the same factors that increased life span would also influence health span. In the current experiments, we tested two of the seven domains of function/health, sensory function and cognition to determine if exposure of postreproductive female mice to young transplanted ovaries influenced health span. We evaluated control female CBA/J mice at six, 13 and 16months of age. Additional mice received new (60d) ovaries at 12 or 17months of age and were subsequently evaluated at 16 or 25months of age, respectively. Evaluation of sensory function included two measures of olfactory perception; olfactory identification (buried pellet test) and olfactory discrimination (novel recognition block test). We found a significant age-related decline in olfactory identification in 16-month old mice. This decline was avoided by ovarian transplantation at 12months of age. The olfactory discrimination block test revealed an age-associated increase in time spent on both the novel and familiar blocks. This trend was reversed in 16-month old new-ovary recipients. We evaluated cognitive behavior with a burrowing behavior test. We detected a significant age-related decrease in burrowing behavior at 16months of age. This age-related decrease in burrowing behavior was prevented by ovarian transplantation at 12months of age. In summary, we have shown that cognitive behavior and sensory function, which are negatively influenced by aging, can be positively influenced or restored by re-establishment of active ovarian function in aged female mice. These findings provide strong incentive for further investigation of the positive influence of young ovaries on restoration of health in postreproductive females.

Cognitive behavior and sensory function were significantly influenced by restoration of active ovarian function in postreproductive mice.

Large animal models of osteoarthritis are a necessary testing ground for FDA approval of human medicine applications. Sheep models have advantages over other available large animals, but development and progression of osteoarthritis in sheep is exceedingly slow, which handicaps progress in development of potential treatments. We combined oblique angle forced exercise to increase stress on the stifle, with surgical destabilization to hasten the development of osteoarthritis in ewes. Methods for early detection of clinical signs included radiography, urine, and serum biomarker assays and gait analysis and ex vivo we used microcomputed tomography and macroscopic joint analysis. Our model was able to produce clinically detectable signs of osteoarthritis in a relatively short period (14 weeks). Changes in bone were highly correlated between microcomputed tomography and radiographic analysis and changes in cartilage correlated well between urinary glycosaminoglycan levels and serum aggrecanase analyses. Exercise improved the negative effects of destabilization in bone but exacerbated the negative effects of destabilization in cartilage. These observations suggest that we may need to consider treatments for bone and cartilage separately. These results represent an improved large animal model of osteoarthritis with rapid onset of disease and superior detection of bone and soft tissue changes.

The Influence of Oblique Angle Forced Exercise in Surgically Destabilized Stifle Joints Is Synergistic with Bone, but Antagonistic with Cartilage in an Ovine Model of Osteoarthritis.

Jeffrey B. Mason

Department of Animal,
Dairy and Veterinary Sciences,
Center for Integrated BioSystems,
School of Veterinary Medicine,
Department of Animal, Dairy and Veterinary Sciences, Center for Integrated BioSystems, School of Veterinary Medicine

Utah State University

Orthotopic Ovarian Transplantation Procedures to Investigate the Life- and Health-span Influence of Ovarian Senescence in Female Mice