STUDY QUESTION How is the localisation of ovarian follicles affected by ageing and chronic diseases? SUMMARY ANSWER Ovarian follicles shift deeper towards the medulla, due to thickening of the tunica albuginea (TA), with ageing and some major common chronic diseases. WHAT IS KNOWN ALREADY The ovary undergoes morphological and functional changes with ageing. The follicular pool follows these changes with alterations in the amount and distribution of residual follicles. Diseases causing a chronic inflammatory process are associated with morphological changes and impaired ovarian function. STUDY DESIGN, SIZE, DURATION We conducted a cross-sectional study, examining 90 ovaries from 90 female monkeys. The samples were collected from April 2018 to March 2019 at Tsukuba Primate Research Center in National Institutes of Biomedical Innovation, Health and Nutrition, Japan. PARTICIPANTS/MATERIALS, SETTING, METHODS Ovarian samples were obtained from cynomolgus monkeys that died from natural causes or were euthanised. Ovarian sections were stained with haematoxylin and eosin (H&E) for histological analyses. In ovarian sections from 64 female macaques aged 0–25 years, a total of 13 743 follicles at different developmental stages (primordial, intermediary, primary, early secondary and late secondary) were assessed to determine the depth of each follicle from the outer surface of the ovarian cortex to the far end of the follicle, by using a digital imaging software. TA thickness was measured as sum of basal membrane and tunica collagen layer for each ovary under H&E staining. To explore the possibility of age-related trends in ovarian morphometric characteristics, samples were divided into four different age groups (0–3 years (pre-menarche), 4–9 years, 10–14 years and 15–20 years). To evaluate the effect of common chronic diseases on ovarian morphometric characteristics, macaques with diabetes mellitus (DM) (n = 10), endometriosis (n = 8) or inflammatory bowel disease (IBD) (n = 8) were compared to age-matched controls without chronic diseases. MAIN RESULTS AND THE ROLE OF CHANCE Ovarian morphometric analysis revealed that the relative location of follicles became deeper in all age groups according to development of follicles (P < 0.05). Total follicle distance from the ovarian surface was increased with ageing (P < 0.05). In a sub-analysis according to developmental stage, only primordial and intermediary follicles were localised deeper with increasing age (P < 0.05). TA thickness was also increased with ageing (P < 0.05). The localisation of the total number of follicles became deeper in ovaries from monkeys with DM, endometriosis or IBD as compared to the control group (P < 0.05). With DM, analysis of follicles distance at almost each developmental stage was significantly deeper compared to controls (P < 0.05) with the exception of early secondary follicles. With endometriosis, follicles at primary and early and late secondary stages were significantly deeper compared to controls (P < 0.05). Also with IBD, follicles at primary and early and late secondary follicles were significantly deeper compared to controls (P < 0.001). The TA was thicker with DM and endometriosis compared to controls (P < 0.05), but not with IBD (P = 0.16). LARGE SCALE DATA NA. LIMITATIONS, REASONS FOR CAUTION Two-dimensional histology was used to assess follicle localisation. The possibility of minimal variations between the measured distance to the actual distance in a spherical structure cannot be excluded. Additionally, the severity of disease was not assessed. WIDER IMPLICATIONS OF THE FINDINGS This study is the first step towards enhancing our understanding of how ageing and chronic diseases affect the relative localisation of dormant and developing follicles. These observations, combined with possible future human studies, may have managerial implications in the field of fertility preservation and other conditions involving ovarian tissue cryopreservation. STUDY FUNDING/COMPETING INTEREST(S) The present work was supported by the Grant-in-Aid for Scientific Research B (19H03801) (to K.K.), Challenging Exploratory Research (18K19624), Japan Agency for Medical Research and Development, Mochida Memorial Foundation for Medical and Pharmaceutical Research, Takeda Science Foundation and Naito Foundation (to K.K.). All authors have no conflicts of interest directly relevant to the content of this article.

中文翻译：

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食蟹猴（Macaca fascicularis）卵巢卵泡形态特征的衰老和慢性疾病相关变化

研究问题 卵巢卵泡的定位如何受衰老和慢性疾病的影响？摘要 答案 由于白膜 (TA) 增厚，随着年龄的增长和一些主要的常见慢性疾病，卵巢卵泡向髓质移动更深。已知情况 随着年龄的增长，卵巢会发生形态和功能变化。卵泡池随着这些变化而改变残余卵泡的数量和分布。引起慢性炎症过程的疾病与形态变化和卵巢功能受损有关。研究设计、大小、持续时间 我们进行了一项横断面研究，检查了 90 只雌性猴子的 90 个卵巢。样本于 2018 年 4 月至 2019 年 3 月在国立生物医学创新研究院筑波灵长类动物研究中心采集，健康与营养，日本。参与者/材料、设置、方法卵巢样品从因自然原因死亡或被安乐死的食蟹猴获得。卵巢切片用苏木精和伊红 (H&E) 染色用于组织学分析。在 64 只 0-25 岁雌性猕猴的卵巢切片中，评估了 13 743 个处于不同发育阶段（原始、中间、初级、早期次级和晚期次级）的卵泡，以确定每个卵泡距卵巢外表面的深度。通过使用数字成像软件，将卵巢皮质连接到卵泡的远端。TA 厚度测量为在 H&E 染色下每个卵巢的基底膜和被膜胶原层的总和。探讨卵巢形态特征的年龄相关趋势的可能性，样本分为四个不同的年龄组（0-3 岁（初潮前）、4-9 岁、10-14 岁和 15-20 岁）。为了评估常见慢性疾病对卵巢形态特征的影响，将患有糖尿病 (DM) (n = 10)、子宫内膜异位症 (n = 8) 或炎症性肠病 (IBD) (n = 8) 的猕猴与年龄匹配的猕猴进行比较控制无慢性病。主要结果及机会的作用 卵巢形态计量学分析显示，随着卵泡的发育，各个年龄组的卵泡的相对位置都变得更深（P < 0.05）。卵泡与卵巢表面的总距离随着年龄的增长而增加（P < 0.05）。在根据发育阶段的亚分析中，只有原始和中间卵泡随着年龄的增长而定位更深（P <0.05）。TA厚度也随着老化而增加（P＜0.05）。与对照组相比，患有糖尿病、子宫内膜异位症或IBD的猴子卵巢中卵泡总数的定位变得更深（P＜0.05）。对于 DM，除了早期的次级卵泡外，几乎每个发育阶段的卵泡距离分析都比对照组更深 (P < 0.05)。对于子宫内膜异位症，与对照组相比，初级和次级早期和晚期的卵泡明显更深（P <0.05）。同样对于 IBD，与对照组相比，初级和早期和晚期次级卵泡的卵泡明显更深（P < 0.001）。与对照组相比，DM 和子宫内膜异位症的 TA 更厚（P < 0.05），但 IBD 没有（P = 0.16）。大规模数据不适用。限制，小心的原因 二维组织学用于评估毛囊定位。不能排除在球形结构中测量距离与实际距离之间存在最小变化的可能性。此外，未评估疾病的严重程度。研究结果的更广泛意义 这项研究是加强我们对衰老和慢性疾病如何影响休眠和发育卵泡的相对定位的理解的第一步。这些观察结果与未来可能的人体研究相结合，可能对生育力保存和涉及卵巢组织冷冻保存的其他条件具有管理意义。研究资金/竞争利益 目前的工作得到了科学研究资助 B (19H03801) (给 KK) 的支持，具有挑战性的探索性研究 (18K19624)、日本医学研究与开发机构、持田医学和药物研究纪念基金会、武田科学基金会和内藤基金会（至 KK）。所有作者都没有与本文内容直接相关的利益冲突。