Anti-Müllerian hormone (AMH) is widely used in the clinic as a biomarker for ovarian reserve and to predict ovarian response to gonadotropin stimulation. Patients with higher AMH levels tend to yield more oocytes and have better outcomes from assisted reproductive technology procedures. The goal of this study is to determine if AMH can be used to predict the outcome of controlled ovarian stimulation in rhesus macaques, which are commonly used in biomedical research, to refine animal use while maximizing oocyte yield. We hypothesized that pre-stimulation AMH values can be used to predict oocyte yield and quality. Regularly cycling adult macaques underwent controlled ovarian stimulation and baseline (pre-stimulation) plasma AMH levels were determined using an AMH-specific enzyme-linked immunoassay. Oocytes were collected by laparoscopic or ultrasound-guided aspiration, then counted and evaluated for quality and stage of meiosis. Sperm from established fertile males were used to inseminate the oocytes in vitro with fertilization success checked 14-16 h later. Females were grouped by oocyte yield: low ≤17; mid = 18-41; high ≥42. We found that high and mid yielders had significantly higher AMH than low yielders (p < 0.0001) and the percent of mature oocytes was greater in the high and mid yielders. There were no significant differences in oocyte quality or ova fertilization rate. These data suggest that AMH is a useful measure for controlled ovarian stimulation success in rhesus macaques and can be used to identify suitable animals for oocyte donation before entering them into a stimulation protocol.

There are more than 200 species and subspecies of Neotropical Primates of which more than 40

Obtaining quality oocytes is a prerequisite for ART-based studies. Here we describe a method for transabdominal ultrasound-guided (US) oocyte retrieval in rhesus macaques (Macaca mullata) and compare it to the standard surgical approach using laparoscopy (LAP). We analyzed oocyte yield from six continuous reproductive seasons (2017-2023) that included n = 177 US-guided and n = 136 laparoscopic oocyte retrievals. While the ultrasound-guided technique retrieved significantly fewer oocytes on average (LAP: 40 ± 2 vs. US: 27 ± 1), there was no difference in the number of mature metaphase II oocytes (MII) between the two techniques (LAP: 17 ± 1 vs. US: 15 ± 1). We show that oocytes retrieved by the ultrasound-guided approach fertilize at the same rates as those obtained via the laparoscopic procedure (LAP Fert Rate: 84% ± 2% vs. US Fert Rate: 83% ± 2%). In conclusion, minimally invasive ultrasound-guided oocyte retrieval improves animal welfare while delivering equivalent numbers of mature oocytes, which are ideal for ART. Furthermore, we show that oocyte competency, as represented by fertilization rate, is not affected by retrieval technique. Therefore, the Oregon National Primate Research Center (ONPRC) has adopted the ultrasound-guided approach as the standard technique for oocyte retrieval.

The Sperm Chromatin Structure Assay (SCSA) is a robust test with high repeatability and precision. It is a clinically accepted assay that defines risk for infertility in men by measuring the degree of DNA fragmentation (% DFI) in sperm. The objective of this study was to adapt and validate the SCSA for rhesus macaques ( Macaca mulatta ) and establish a range for % DFI in fertile males. Sperm samples from two different males were used to produce a % DFI validation curve before establishing a range using additional samples from n = 11 males. Sperm labeled with acridine orange were analyzed by flow cytometry to measure green fluorescence (native or intact DNA) and red fluorescence (fragmented DNA). Data were exported to FlowJo software to determine the % DFI for each sample. DNA fragmentation ranged from 0.1 to 2.4% DFI, with a mean ± SD = 1.1 ± 0.7% DFI (validation curve optimized to R 2 > 0.95). In conclusion, we were able to successfully validate the SCSA in our institution and establish the first normal range for sperm DNA fragmentation in rhesus macaques. Our study provides a quantitative baseline for future evaluations to assess macaque fertility through the SCSA test.

Objective: To determine whether discontinuation of delta-9-tetrahydrocannabinol (THC) use mitigates THC-associated changes in male reproductive health using a rhesus macaque model of daily THC edible consumption. Design: Research animal study. Setting: Research institute environment. Patient(s): Adult male rhesus macaques (age, 8-10 years; n 1/4 6).Intervention(s): Chronic daily THC edible administration at medically and recreationally relevant contemporary doses followed by cessation of THC use. Main Outcome Measure(s): Testicular volume, serum male hormones, semen parameters, sperm deoxyribonucleic acid (DNA) frag-mentation, seminal fluid proteomics, and whole genome bisulfite sequencing of sperm DNA. Result(s): Chronic THC use resulted in significant testicular atrophy, increased gonadotropin levels, decreased serum sex steroid levels, changes in seminal fluid proteome, and increased DNA fragmentation with partial recovery after discontinuation of THC use. For every increase of 1 mg/7 kg/day in THC dosing, there was a significant decrease in the total testicular volume bilaterally by 12.6 cm(3) (95% confidence interval [CI], 10.6-14.5), resulting in a 59% decrease in volume. With THC abstinence, the total testicular volume increased to 73% of its original volume. Similarly, with THC exposure, there were significant decreases in the mean total testosterone and estradiol levels and a significant increase in the follicle-stimulating hormone level. With increasing THC dose, there was a significant decrease in the liquid semen ejaculate volume and weight of coagulum; however, no other significant changes in the other semen parameters were noted. After discontinuing THC use, there was a significant increase in the total serum testosterone level by 1.3 ng/mL (95% CI, 0.1-2.4) and estradiol level by 2.9 pg/mL (95% CI, 0.4-5.4), and the follicle-stimulating hormone level significantly decreased by 0.06 ng/mL (95% CI, 0.01-0.11). Seminal fluid proteome analysis revealed differential expression of proteins enriched for processes related to cellular secretion, immune response, and fibrinolysis. Whole genome bisulfite sequencing identified 23,558 CpGs differentially methylated in heavy-THC vs. pre-THC sperm, with partial restoration of methylation after discontinuation of THC use. Genes associated with altered differentially methylated regions were enriched for those involved in the development and function of the nervous system. Conclusion(s): This is the first study demonstrating that discontinuation of chronic THC use in rhesus macaques partially restores adverse impacts to male reproductive health, THC-associated sperm differentially methylated regions in genes important for development, and expression of proteins important for male fertility. (Fertil Sterile 2023;120:163-74. (c) 2023 by American Society for Reproductive Medicine.)

Objective: To determine the dose-dependent effect of delta-9-tetrahydrocannabinol (THC) exposure on male testes and reproductive health in a nonhuman primate model. Design: Research animal study. Setting: Research institute. Animal(s): Adult male rhesus macaques 8-10 years of age (n = 6). Intervention(s): Daily edible THC at medically and recreationally relevant doses. Main Outcome Measure(s): Testicular volume and epididymal head width, serum levels of inhibin B, albumin, total testosterone, prolactin, follicle-stimulating hormone, estradiol, and luteinizing hormone; semen volume; and sperm motility, morphology, and concentration. Result(s): For each 1 mg/7 kg/day increase in THC dosing, there was a marked loss in total bilateral testicular volume of 11.8 cm(3) (95% confidence interval [CI]: 8.3-15.4). In total, average bilateral testicular volume decreased by 58%. Significant dose-response decreases in mean total testosterone level by 1.49 ng/mL (95% CI: 0.83-2.15) and in estradiol level by 3.8 pg/mL (95% CI: 2.2-5.4) were observed, but significant increases in the levels of follicle-stimulating hormone by 0.06 ng/mL (95% CI: 0.02-0.10), luteinizing hormone by 0.16 ng/mL (95% CI: 0.08-0.25), and prolactin by 7.4 ng/mL (95% CI: 3.4-11.3) were observed. There were no statistically significant changes in semen parameters. Conclusion(s): In rhesus macaques, chronic exposure to THC resulted in significant dose-response testicular atrophy, increased serum gonadotropin levels, and decreased serum sex steroids, suggestive of primary testicular failure. Further studies are needed to determine if reversal of these observed adverse effects would occur if THC was discontinued and for validation of thefindings in a human cohort. ((C) 2021 by American Society for Reproductive Medicine.) El resumen esta disponible en Espanol al final del articulo.

Mutations in the MYO7A gene lead to Usher syndrome type 1B (USH1B), a disease characterized by congenital deafness, vision loss, and balance impairment. To create a nonhuman primate (NHP) USH1B model, CRISPR/Cas9 was used to disrupt MYO7A in rhesus macaque zygotes. The targeting efficiency of Cas9 mRNA and hybridized crRNA-tracrRNA (hyb-gRNA) was compared to Cas9 nuclease (Nuc) protein and synthetic single guide (sg)RNAs. Nuc/sgRNA injection led to higher editing efficiencies relative to mRNA/hyb-gRNAs. Mutations were assessed by preimplantation genetic testing (PGT) and those with the desired mutations were transferred into surrogates. A pregnancy was established from an embryo where 92.1% of the PGT sequencing reads possessed a single G insertion that leads to a premature stop codon. Analysis of single peripheral blood leukocytes from the infant revealed that half the cells possessed the homozygous single base insertion and the remaining cells had the wild-type MYO7A sequence. The infant showed sensitive auditory thresholds beginning at 3 months. Although further optimization is needed, our studies demonstrate that it is feasible to use CRISPR technologies for creating NHP models of human diseases.

Direct injection of CRISPR/Cas9 into zygotes enables the production of genetically modified nonhuman primates (NHPs) essential for modeling specific human diseases, such as Usher syndrome, and for developing novel therapeutic strategies. Usher syndrome is a rare genetic disease that causes loss of hearing, retinal degeneration, and problems with balance, and is attributed to a mutation in MYO7A, a gene that encodes an uncommon myosin motor protein expressed in the inner ear and retinal photoreceptors. To produce an Usher syndrome type 1B (USH1B) rhesus macaque model, we disrupted the MYO7A gene in developing zygotes. Identification of appropriately edited MYO7A embryos for knockout embryo transfer requires sequence analysis of material recovered from a trophectoderm (TE) cell biopsy. However, the TE biopsy procedure is labor intensive and could adversely impact embryo development. Recent studies have reported using cell-free DNA (cfDNA) from embryo culture media to detect aneuploid embryos in human in vitro fertilization (IVF) clinics. The cfDNA is released from the embryo during cell division or cell death, suggesting that cfDNA may be a viable resource for sequence analysis. Moreover, cfDNA collection is not invasive to the embryo and does not require special tools or expertise. We hypothesized that selection of appropriate edited embryos could be performed by analyzing cfDNA for MYO7A editing in embryo culture medium, and that this method would be advantageous for the subsequent generation of genetically modified NHPs. The purpose of this experiment is to determine whether cfDNA can be used to identify the target gene mutation of CRISPR/Cas9 injected embryos. In this study, we were able to obtain and utilize cfDNA to confirm the mutagenesis of MYO7A, but the method will require further optimization to obtain better accuracy before it can replace the TE biopsy approach.