Age- and sex-related changes in body weights and clinical pathology analytes in cynomolgus monkeys (Macaca Fascicularis) of Mauritius origin

Age-related changes in hematological biomarkers in common marmosets

Researchers and veterinarians often use hematology and clinical chemistry to evaluate animal health. These biomarkers are relatively easy to obtain, and understanding how they change across healthy aging is critical to clinical care and diagnostics for these animals. We aimed to evaluate how clinical biomarkers from a chemistry profile and complete blood count (CBC) change with age in common marmosets (Callithrix jacchus). We assessed blood samples collected during routine physical exams at the Southwest National Primate Research Center and the University of Texas Health San Antonio marmoset colonies from November 2020-November 2021. We found that chemistry and CBC profiles varied based on facility, sex, and age. Significant changes in albumin, phosphorus/creatinine ratio, albumin/globulin ratio, amylase, creatinine, lymphocyte percent, hematocrit, granulocytes percent, lymphocytes, hemoglobin, red cell distribution width, and platelet distribution width were all reported with advancing age. Aged individuals also demonstrated evidence for changes in liver, kidney, and immune system function compared with younger individuals. Our results suggest there may be regular changes associated with healthy aging in marmosets that are outside of the range typically considered as normal values for healthy young individuals, indicating the potential need for redefined healthy ranges for clinical biomarkers in aged animals. Identifying animals that exhibit values outside of this defined healthy aging reference will allow more accurate diagnostics and treatments for aging colonies.

Reduced Fasting Duration in Cynomolgus Monkeys Enhances Animal Welfare During Toxicology Studies

During toxicology studies, fasting animals prior to clinical pathology blood collection is believed to reduce variability in some clinical chemistry analytes. However, fasting adds stress to animals that are already stressed from the administration of potentially toxic doses of the test article. The purpose of this study was to assess the impacts of different fasting durations on cynomolgus monkeys' welfare during toxicology studies. To this end, we assessed the cynomolgus monkeys traditional and ancillary clinical pathology endpoints at different fasting times. We showed that most clinical pathology endpoints were largely comparable between different fasting times suggesting that cynomolgus monkeys could be fasted for as little as 4 hours for toxicology studies, as longer fasting times (up to 20 hours) resulted in stress, dehydration, and significant decreases in blood glucose- changes that impacts animal welfare. Shorter fasting times were associated with higher triglycerides variability among individual animals. Therefore, we propose that shorter fasting time (i.e., 4 hours) should be adequate for most toxicology studies except when: (1) parameters that could be affected by non-fasting conditions are important for safety and pharmacodynamic assessments (i.e., glucose and lipids) and (2) fasting would be needed for the bioavailability of an orally administered test article.

Biology and postnatal development of organ systems of cynomolgus monkeys (Macaca fascicularis)

BACKGROUND

The cynomolgus macaque has become the most used non-human primate species in nonclinical safety assessment during the past decades.

METHODS

This review summarizes the biological data and organ system development milestones of the cynomolgus macaque available in the literature.

RESULTS

The cynomolgus macaque is born precocious relative to humans in some organ systems (e.g., nervous, skeletal, respiratory, and gastrointestinal). Organ systems develop, refine, and expand at different rates after birth. In general, the respiratory, gastrointestinal, renal, and hematopoietic systems mature at approximately 3 years of age. The female reproductive, cardiovascular and hepatobiliary systems mature at approximately 4 years of age. The central nervous, skeletal, immune, male reproductive, and endocrine systems complete their development at approximately 5 to 9 years of age.

CONCLUSIONS

The cynomolgus macaque has no meaningful developmental differences in critical organ systems between 2 and 3 years of age for use in nonclinical safety assessment.