Elevated molecular stress in women is known to have negative impacts on the reproductive development of oocytes and the embryos prior to implantation. In recent years, the prevalence of cannabis use among women of reproductive age has risen due to its ability to relieve psychological stress and nausea, which are mediated by its psychoactive component, ∆-9-tetrahydrocannabinol (THC). Although cannabis is the most popular recreational drug of the 21st century, much is unknown about its influence on molecular stress in reproductive tissues. The current literature has demonstrated that THC causes dose- and time-dependent alterations in glucocorticoid signaling, which have the potential to compromise morphology, development, and quality of oocytes and embryos. However, there are inconsistencies across studies regarding the mechanisms for THC-dependent changes in stress hormones and how either compounds may drive or arrest development. Factors such as variability between animal models, physiologically relevant doses, and undiscovered downstream gene targets of both glucocorticoids and THC could account for such inconsistencies. This review evaluates the results of studies which have investigated the effects of glucocorticoids on reproductive development and how THC may alter stress signaling in relevant tissues.

Induced pluripotent stem cells (iPSCs) are produced by resetting the epigenetic and transcriptional landscapes of somatic cells to express the endogenous pluripotency network and revert them back to an undifferentiated state. The reduced ethical concerns associated with iPSCs and their capacity for extensive self-renewal and differentiation make them an unparalleled resource for drug discovery, disease modeling, and novel therapies. Canines (c) share many human diseases and environmental exposures, making them a superior translational model for drug screening and investigating human pathologies compared to other mammals. However, well-defined protocols for legitimate ciPSC production are lacking. Problems during canine somatic cell reprogramming (SCR) yield putative ciPSCs with incomplete pluripotency, at very low efficiencies. Despite the value of ciPSCs, the molecular mechanisms underlying their unsuccessful production and how these may be addressed have not been fully elucidated. Factors, including cost, safety, and feasibility, may also limit the widespread clinical adoption of ciPSCs for treating canine disease. The purpose of this narrative review is to identify barriers to canine SCR on molecular and cellular levels, using comparative research to inform potential solutions to their use in both research and clinical contexts. Current research is opening new doors for the application of ciPSCs in regenerative medicine for the mutual benefit of veterinary and human medicine.

Study question Does THC alter sperm function and early embryo development following in vitro fertilization with THC-exposed sperm? Summary answer THC reduces sperm mitochondrial membrane potential (MMP), mainly through cannabinoid receptor agonism, but does not alter the acrosome reaction or rates of embryo development. What is known already Cannabis is the most commonly used recreational drug among males of reproductive age. THC is the main psychoactive component of cannabis and can cross the blood-testis barrier, disrupting the endocannabinoid system (ECS) in sperm. However, the mechanisms by which THC affect sperm function and early embryo development are unclear. In sperm, endogenous cannabinoids influence the acrosome reaction and MMP, which are critical for motility, viability and, ultimately, fertilization. To date, no studies have investigated how sperm exposed to physiologically relevant doses of THC may impact in-vitro early embryo development, and cannabis use recommendations remain unclear for patients undergoing IVF procedures. Study design, size, duration Bovine sperm and cumulus oocyte complexes (COCs) were used as a translational model for humans. Cryo-thawed sperm was separated using a Percoll gradient and incubated for 6-hours in one of five treatment groups: control, vehicle (0.01% ethanol), low-THC (0.032µM), mid-THC (0.32µM), and high-THC (4.8µM) – concentrations equivalent to THC plasma levels following therapeutic and mid-high recreational use, respectively (Whan et al., 2006). A minimum of 30,000 sperm and 60 COCs were analyzed per group. Participants/materials, setting, methods Sperm were treated for 6-hours prior to all experiments. Flow cytometry using sperm (1-2x106) stained with propidium iodide (PI) and FITC-conjugated peanut agglutinin (FITC-PNA) or JC-1 was used to measure either the acrosomal reaction or MMP, respectively. COCs were aspirated from slaughterhouse ovaries and matured in-vitro for 24-hours. IVF was performed with THC-treated sperm (1x106/mL/drop) for 10-hours. Presumptive zygotes were cultured in-vitro for 8-days. Cleavage and blastocyst rates were measured 48-hours and 8-days post-fertilization, respectively. Main results and the role of chance Measuring PI and FITC-PNA fluorescence showed the percent of sperm that were acrosome-reacted and either alive or necrotic. There were no significant differences in acrosome-reacted sperm among groups (n = 9). Measuring JC-1 fluorescence showed the percentage of sperm with high MMP. Results indicate a significant reduction in sperm with high MMP (37%) following high THC (4.8µM) exposure (p = 0.002418, n = 4). No significant differences in MMP were observed among other groups. To elicit the mechanism by which THC was reducing sperm MMP, we repeated experiments using only JC-1-stained sperm exposed to high THC treated with SR141716 and SR144528, which are CB-1 and -2 antagonists, respectively. Additional groups included: SR141716 (4.8.µM), SR144528 (4.8µM), THC + SR141716 and THC + SR144528. Results indicate a significant reduction in sperm with high MMP (38%) in the THC group (4.8µM) compared to control (51%) (p = 0.0417, n = 6), vehicle (54%) (p = 0.0069, n = 6), and SR141716 (65%) (p < 0.0001, n = 6). There were no significant differences in sperm with high MMP in THC + SR141716 or THC + SR144528 groups, indicating that THC is acting agonistically, primarily at CB1 receptors. Following IVF with THC-treated sperm, there were no significant differences in cleavage or blastocyst rates among treatment groups. Limitations, reasons for caution The use of bovine instead of human cells could be considered a limitation. However, as studying effects of THC-treated sperm on IVF outcomes would not be possible using human samples, it is actually an advantage. The similarity between bovine and human gametes makes bovine an ideal translational model for humans Wider implications of the findings As cannabis use and THC concentrations increase, this research addresses the growing concern of how cannabis impacts fertility and, ultimately, pregnancy outcome. Understanding how THC affects sperm function and embryo development will provide physicians with science-based recommendations concerning cannabis use for patients trying to conceive, pregnant, or undergoing fertility treatments. Trial registration number not applicable

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