Alopecia in rhesus macaques (Macaca mulatta): Association with pregnancy and chronic stress

Effects of Seasonality and Pregnancy on Hair Loss and Regrowth in Rhesus Macaques

Several studies have examined the etiology of alopecia, or hair loss, in rhesus macaques. While outcomes differ across studies, some commonalities have emerged. Females, particularly pregnant females, show more alopecia than males, and alopecia follows a seasonal pattern. Much research has explored causes of hair loss; however, alopecia can result from lack of hair growth in addition to hair loss. To better understand how sex, reproductive state, and season affect alopecia, we followed 241 rhesus macaques (Macaca mulatta) in outdoor breeding groups over one year, recording both alopecia severity and presence of hair regrowth. We found that both alopecia and hair regrowth followed a seasonal pattern; alopecia was highest in spring and lowest in late summer, while regrowth started in spring and peaked in late summer. Reproductive state also correlated with both alopecia and hair growth. Females in their third trimester had the highest average level of alopecia and the lowest amount of hair regrowth. Regrowth resumed postpartum, regardless of whether females were rearing an infant. Results indicate that the seasonal pattern of alopecia is due in part to the seasonal limitations on hair regrowth, and that breeding, which also occurs seasonally in rhesus macaques, may further suppress hair regrowth.

Clinical and histopathological investigation of symmetrical alopecia with associated chronic pruritus in tufted capuchin monkeys (Sapajus apella apella)

BACKGROUND

Symmetrical alopecia is a common symptom of endocrine and autoimmune diseases, which are rarely manifested with pruritus. Increased levels of stress in primates have been presented with increased levels of pruritus and alopecia appearance.

METHODS

A pruritic and alopecic disease was investigated in a group of tufted capuchin monkeys (N = 12), but due to ethical reasons, four random animals were further investigated by numerous diagnostic methods. The impact of food and enclosure enrichment was assessed and observed over a 2-year period.

RESULTS

Histopathology of four random tufted capuchin monkeys revealed lymphocytic perifolliculitis, with an appearance of a "swarm of bees" which was suggestive of alopecia areata. Etiological classification of pruritus excluded dermatological, systemic, and neurological causes, making it behavioral. Enclosure and food enrichment had a beneficial impact on pruritus (12/12) and alopecia (10/12).

CONCLUSION

The findings were suggestive of alopecia areata, while the pruritus was considered behavioral in origin. Alopecia and pruritus improved upon enclosure and food enrichment.

Whole blood transcriptome profiling identifies candidate genes associated with alopecia in male giant pandas (Ailuropoda melanoleuca)

Background

The giant panda (Ailuropoda melanoleuca) is a threatened species endemic to China. Alopecia, characterized by thinning and broken hair, mostly occurs in breeding males. Alopecia significantly affects the health and public image of the giant panda and the cause of alopecia is unclear.

Results

Here, we researched gene expression profiles of four alopecia giant pandas and seven healthy giant pandas. All pandas were approximately ten years old and their blood samples collected during the breeding season. A total of 458 up-regulated DEGs and 211 down-regulated DEGs were identified. KEGG pathway enrichment identified that upregulated genes were enriched in the Notch signaling pathway and downregulated genes were enriched in ribosome, oxidative phosphorylation, and thermogenesis pathways. We obtained 28 hair growth-related DEGs, and identified three hub genes NOTCH1, SMAD3, and TGFB1 in PPI analysis. Five hair growth-related signaling pathways were identified with abnormal expression, these were Notch, Wnt, TGF-β, Mapk, and PI3K-Akt. The overexpression of NOTCH1 delays inner root sheath differentiation and results in hair shaft abnormalities. The delayed hair regression was associated with a significant decrease in the expression levels of TGFB1.

Conclusions

Our data confirmed the abnormal expression of several hair-related genes and pathways and identified alopecia candidate genes in the giant panda. Results of this study provide theoretical basis for the establishment of prevention and treatment strategies for giant pandas with alopecia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08501-z.

Association between stress and bilateral symmetrical alopecia in free-ranging Formosan macaques in Mt. Longevity, Taiwan

Since 2013, a high incidence of bilateral symmetrical alopecia has been observed in free-ranging Formosan macaques (Macaca cyclopis) in Mt. Longevity, Taiwan. We hypothesized that stress induces alopecia in this population. To verify our hypothesis, we evaluated the histopathological characteristics of skin biopsy and used a validated enzyme immunoassay (EIA) for fecal glucocorticoid metabolite (FGM) analysis, which act as an indicator of stress experienced by the individual. Follicular densities were lower (2.1-3.0 mm²) in individuals with symmetrical alopecia than in those with normal hair conditions (4.7 mm²). Furthermore, anagen to catagen/telogen ratios were lower in individuals with alopecia (0-1.4) than in those with normal hair (4.0). The histopathological characteristics of alopecia were similar to those of telogen effluvium, which indicates that stress is one of the possible etiologies. On the basis of the analytical and biological validation of EIAs for FGM analysis, 11β-hydroxyetiocholanolone was considered suitable for monitoring adrenocortical activity in both sexes of Formosan macaques. The mean concentrations (standard error; sample size) of 11β-hydroxyetiocholanolone were 2.02 (0.17; n = 10) and 1.41 (0.10; n = 31) μg/g for individuals with and without alopecia, respectively. Furthermore, the results of logistic regression analysis show that 11β-hydroxyetiocholanolone (p = 0.012) concentration was positively associated with alopecia. Thus, stress was the most likely to trigger symmetrical alopecia in Formosan macaques in Mt. Longevity. Although stress can decrease the fitness of an individual, considering the population status of Formosan macaques in Taiwan is stable and alopecia was only observed in our study area, which is isolated from other populations, the impact on the total population of Formosan macaque in Taiwan is limited. Nonetheless, stress-induced immunosuppression and alopecia might affect the local abundance and increase zoonosis risk due to frequent human-macaque contact in Mt. Longevity. Future studies are suggested to focus on the causative factor of stress and the effects of stress and alopecia on the health and welfare in the Formosan macaques.

Hair cortisol in captive corral-housed baboons

Hair cortisol concentrations (HCCs) are measures of long-term hypothalamic-pituitary-adrenocortical (HPA) activity and can be used as indicators of chronic stress. However, intrinsic factors such as an animal's age and sex can also have an impact on resulting HCCs. Although baboons are commonly studied in captivity, little is known about baseline HCC in this population. Here we measured HCC in two same-sex groups of captive olive (Papio hamadryas anubis) baboons and olive/yellow baboon (Papio hamadryas cynocephalus) crosses housed in large outdoor corrals, and we assessed the impact of age and sex on HCC as major variables of interest. Hair was gently shaved from the back of the neck when the animals were sedated for routine physicals. Subjects were divided into three age categories: juvenile (2-4 years), adult (9-12 years), and senior (13-19 years). The "senior" category contained only males. Results confirm an effect of sex and age on HCCs. Females had higher levels of hair cortisol than males, and juveniles had higher levels than adults. There was also a significant sex × age interaction. There were no sex differences in HCCs in juveniles, but there was a greater decline in HCCs in adult males than in adult females. Within males, there was a significant difference in levels of hair cortisol across the three age categories. Juveniles had higher levels than did adults and seniors, but adults and seniors were not significantly different from one another. These results provide baseline measures of hair cortisol in captive baboons and demonstrate effects of sex and age on HCCs.