Male contraception: another Holy Grail

Reversible Contraception in Males: An Obtainable Target?

The last few decades have brought contraception to the forefront of research, with great strides made in effectively targeting and optimizing the physiology, pharmacology, and delivery processes that prevent pregnancy. However, these advances still predominantly target female contraceptives for the prevention of contraception, whereas targeting the male sex has lagged far behind. This has led to a marked deficiency in safe and effective male contraceptive agents, resulting in a heavy dependence on female contraceptives to prevent unwanted and unplanned pregnancies. Current research in the veterinary field and in rodents highlights several promising avenues whereby novel, safe, and effective male contraceptive alternatives are being developed-with an emphasis on reduced side effects and reversibility potential. This review aims to discuss current and novel male contraceptives (both human and veterinary formulations) while highlighting their efficacy, advantages, and disadvantages.

Advances in non-hormonal male contraception targeting sperm motility

BACKGROUND

The high rates of unintended pregnancy and the ever-growing world population impose health, economic, social, and environmental threats to countries. Expanding contraceptive options, including male methods, are urgently needed to tackle these global challenges. Male contraception is limited to condoms and vasectomy, which are unsuitable for many couples. Thus, novel male contraceptive methods may reduce unintended pregnancies, meet the contraceptive needs of couples, and foster gender equality in carrying the contraceptive burden. In this regard, the spermatozoon emerges as a source of druggable targets for on-demand, non-hormonal male contraception based on disrupting sperm motility or fertilization.

OBJECTIVE AND RATIONALE

A better understanding of the molecules governing sperm motility can lead to innovative approaches toward safe and effective male contraceptives. This review discusses cutting-edge knowledge on sperm-specific targets for male contraception, focusing on those with crucial roles in sperm motility. We also highlight challenges and opportunities in male contraceptive drug development targeting spermatozoa.

SEARCH METHODS

We conducted a literature search in the PubMed database using the following keywords: 'spermatozoa', 'sperm motility', 'male contraception', and 'drug targets' in combination with other related terms to the field. Publications until January 2023 written in English were considered.

OUTCOMES

Efforts for developing non-hormonal strategies for male contraception resulted in the identification of candidates specifically expressed or enriched in spermatozoa, including enzymes (PP1γ2, GAPDHS, and sAC), ion channels (CatSper and KSper), transmembrane transporters (sNHE, SLC26A8, and ATP1A4), and surface proteins (EPPIN). These targets are usually located in the sperm flagellum. Their indispensable roles in sperm motility and male fertility were confirmed by genetic or immunological approaches using animal models and gene mutations associated with male infertility due to sperm defects in humans. Their druggability was demonstrated by the identification of drug-like small organic ligands displaying spermiostatic activity in preclinical trials.

WIDER IMPLICATIONS

A wide range of sperm-associated proteins has arisen as key regulators of sperm motility, providing compelling druggable candidates for male contraception. Nevertheless, no pharmacological agent has reached clinical developmental stages. One reason is the slow progress in translating the preclinical and drug discovery findings into a drug-like candidate adequate for clinical development. Thus, intense collaboration among academia, private sectors, governments, and regulatory agencies will be crucial to combine expertise for the development of male contraceptives targeting sperm function by (i) improving target structural characterization and the design of highly selective ligands, (ii) conducting long-term preclinical safety, efficacy, and reversibility evaluation, and (iii) establishing rigorous guidelines and endpoints for clinical trials and regulatory evaluation, thus allowing their testing in humans.

A global grounded theory exploration of investigators' perspectives on male hormonal contraceptive development and acceptability

While best practices have been proposed on how to engage men in family planning (FP), the limited options of male hormonal contraceptives (MHC) are a barrier to reaching men as clients of FP programs. The lack of alternative MHC is preventing the global health community from providing holistic reproductive healthcare. A qualitative grounded theory study was conducted in 2020 to explore MHC experts' perceptions around the development and theoretical acceptability of MHCs. Individual in-depth interviews were conducted with 15 key informants. The informants cited evidence that there is a demand for MHC. The inability to access this data by the pharmaceutical industry was acknowledged. Many informants expressed concern of the possibility for MHC to increase male power in a predominantly patriarchal world. To most informants, at least for the initial introduction of MHC, fertility sharing is something that will largely happen among couples alone rather than individually. There is proven demand among women and men for MHC, however industries may still be reluctant to invest. Effort is needed by the sexual and reproductive health and rights community to include male engagement in FP and to advocate for the development and use of MHC as a tool for women's empowerment.

Recent progress in advanced biomaterials for long-acting reversible contraception

Unintended pregnancy is a global issue with serious ramifications for women, their families, and society, including abortion, infertility, and maternal death. Although existing contraceptive strategies have been widely used in people's lives, there have not been satisfactory feedbacks due to low contraceptive efficacy and related side effects (e.g., decreased sexuality, menstrual cycle disorder, and even lifelong infertility). In recent years, biomaterials-based long-acting reversible contraception has received increasing attention from the viewpoint of fundamental research and practical applications mainly owing to improved delivery routes and controlled drug delivery. This review summarizes recent progress in advanced biomaterials for long-acting reversible contraception via various delivery routes, including subcutaneous implant, transdermal patch, oral administration, vaginal ring, intrauterine device, fallopian tube occlusion, vas deferens contraception, and Intravenous administration. In addition, biomaterials, especially nanomaterials, still need to be improved and prospects for the future in contraception are mentioned.

Tetrahydroindazole inhibitors of CDK2/cyclin complexes

Over 50 tetrahydroindazoles were synthesized after 7-bromo-3,6,6-trimethyl-1-(pyridin-2-yl)-5,6,7,7a-tetrahydro-1H-indazol-4(3aH)-one (3) was identified as a hit compound in a high throughput screen for inhibition of CDK2 in complex with cyclin A. The activity of the most promising analogues was evaluated by inhibition of CDK2 enzyme complexes with various cyclins. Analogues 53 and 59 showed 3-fold better binding affinity for CDK2 and 2- to 10-fold improved inhibitory activity against CDK2/cyclin A1, E, and O compared to screening hit 3. The data from the enzyme and binding assays indicate that the binding of the analogues to a CDK2/cyclin complex is favored over binding to free CDK2. Computational analysis was used to predict a potential binding site at the CDK2/cyclin E1 interface.

Large-scale discovery of male reproductive tract-specific genes through analysis of RNA-seq datasets

Background

The development of a safe, effective, reversible, non-hormonal contraceptive method for men has been an ongoing effort for the past few decades. However, despite significant progress on elucidating the function of key proteins involved in reproduction, understanding male reproductive physiology is limited by incomplete information on the genes expressed in reproductive tissues, and no contraceptive targets have so far reached clinical trials. To advance product development, further identification of novel reproductive tract-specific genes leading to potentially druggable protein targets is imperative.

Results

In this study, we expand on previous single tissue, single species studies by integrating analysis of publicly available human and mouse RNA-seq datasets whose initial published purpose was not focused on identifying male reproductive tract-specific targets. We also incorporate analysis of additional newly acquired human and mouse testis and epididymis samples to increase the number of targets identified. We detected a combined total of 1178 genes for which no previous evidence of male reproductive tract-specific expression was annotated, many of which are potentially druggable targets. Through RT-PCR, we confirmed the reproductive tract-specific expression of 51 novel orthologous human and mouse genes without a reported mouse model. Of these, we ablated four epididymis-specific genes (Spint3, Spint4, Spint5, and Ces5a) and two testis-specific genes (Pp2d1 and Saxo1) in individual or double knockout mice generated through the CRISPR/Cas9 system. Our results validate a functional requirement for Spint4/5 and Ces5a in male mouse fertility, while demonstrating that Spint3, Pp2d1, and Saxo1 are each individually dispensable for male mouse fertility.

Conclusions

Our work provides a plethora of novel testis- and epididymis-specific genes and elucidates the functional requirement of several of these genes, which is essential towards understanding the etiology of male infertility and the development of male contraceptives.

Synthesis of 2-phenyl-5,6,7,8-tetrahydroquinoxaline derivatives and screening for P2X1-purinoceptor antagonist activity in isolated preparations of rat vas deferens, for translation into a male contraceptive†

Sympathetically mediated contractions of smooth muscle cells in the vasa deferentia are mediated by neuronally released adenosine 5′-triphosphate (ATP) and noradrenaline, which stimulate P2X1-purinoceptors and α_1A-adrenoceptors, respectively. This process is crucial for sperm transport, as demonstrated in knockout mouse studies where simultaneous genetic deletion of P2X1-purinoceptors and α_1A-adrenoceptors resulted in male infertility. We hypothesize that dual pharmacological antagonism of these two receptors could inhibit sperm transport sufficiently to provide a novel nonhormonal method of male contraception. To generate a suitable P2X1-purinoceptor antagonist, substituents were introduced on the phenyl moiety of 2-phenyl-5,6,7,8-tetrahydroquinoxaline to create a series of analogues that were tested for P2X1-purinoceptor antagonism in isolated preparations of rat vas deferens. Novel compounds were initially screened for their ability to attenuate contractile responses to electrical field stimulation (EFS: 60 V, 0.5 ms, 0.2 Hz). The addition of polar substituents to the meta, but not ortho, position markedly increased the inhibition of contractions, as did the addition of both polar and aliphatic substituents to the para position. Di-substituted compounds were also synthesized and tested, resulting in a compound 31 (2-hydroxy, 4-fluoro), which exhibited the greatest potency, with an IC₅₀ of 14 μM (95% confidence limits: 12–16 μM). Additionally, compound 31 noncompetitively antagonized contractions mediated by exogenously administered αß-methylene ATP (10 nM–30 μM) but had no inhibitory effect on contractions mediated by exogenously administered noradrenaline (30 nM–100 μM) or acetylcholine (30 nM–100 μM). These results have contributed to a structure–activity relationship profile for the P2X1-purinoceptor that will inform future designs of more potent antagonists.

Biomaterials and Contraception: Promises and Pitfalls

The present state of reproductive and sexual health around the world reveals disparities in contraceptive use and effectiveness. Unintended pregnancy and sexually transmitted infection transmission rates remain high even with current prevention methods. The 20th century saw a contraceptive revolution with biomedical innovation driving the success of new contraceptive technologies with central design concepts and materials. Current modalities can be broadly categorized according to their mode of function: reversible methods such as physical/chemical barriers or hormonal delivery devices via systemic (transdermal and subcutaneous) or localized (intrauterine and intravaginal) administration, and nonreversible sterilization procedures such as tubal ligation and vasectomy. Contraceptive biomaterials are at present dominated by well-characterized elastomers such as polydimethylsiloxane and ethylene vinyl acetate due to their favorable material properties and versatility. Contraceptives alter the normal function of cellular components in the reproductive systems to impair fertility. The purpose of this review is to highlight the bioengineering design of existing methods, explore novel adaptations, and address notable shortcomings in current contraceptive technologies.

BET proteins: Investigating BRDT as a potential target for male contraception

While many contraception options are available for women, birth control methods for men are limited to condoms and vasectomy. Past research into male contraceptives has focused on hormonal options but the associated side effects have thus far precluded this method from reaching the market. Non-hormonal male contraceptives and vas occlusion have also been explored, but to date no method has progressed past clinical testing. Recent interest in epigenetic research has unveiled a new potential non-hormonal male contraceptive target: the testis-specific bromodomain BRDT. Potent inhibitors for bromodomain-containing proteins are described in the literature, but a BRDT-specific compound has yet to be designed, prepared and tested. The high similarity between bromodomain proteins of the BET family makes development of selective and specific inhibitors both difficult and necessary. Selective inhibition of BRDT by a small molecule is an exciting new target in the search for a new non-hormonal male contraceptive.

Toward Development of the Male Pill: A Decade of Potential Non-hormonal Contraceptive Targets

With the continued steep rise of the global human population, and the paucity of safe and practical contraceptive options available to men, the need for development of effective and reversible non-hormonal methods of male fertility control is widely recognized. Currently there are several contraceptive options available to men, however, none of the non-hormonal alternatives have been clinically approved. To advance progress in the development of a safe and reversible contraceptive for men, further identification of novel reproductive tract-specific druggable protein targets is required. Here we provide an overview of genes/proteins identified in the last decade as specific or highly expressed in the male reproductive tract, with deletion phenotypes leading to complete male infertility in mice. These phenotypes include arrest of spermatogenesis and/or spermiogenesis, abnormal spermiation, abnormal spermatid morphology, abnormal sperm motility, azoospermia, globozoospermia, asthenozoospermia, and/or teratozoospermia, which are all desirable outcomes for a novel male contraceptive. We also consider other associated deletion phenotypes that could impact the desirability of a potential contraceptive. We further discuss novel contraceptive targets underscoring promising leads with the objective of presenting data for potential druggability and whether collateral effects may exist from paralogs with close sequence similarity.

Effects of pharmacologically induced Leydig cell testosterone production on intratesticular testosterone and spermatogenesis†

The Leydig cells of the mammalian testis produce testosterone (T) in response to luteinizing hormone (LH). In rats and men with reduced serum T levels, T replacement therapy (TRT) will raise T levels, but typically with suppressive effects on sperm formation. The rate-determining step in T formation is the translocation of cholesterol to the inner mitochondrial membrane, mediated by protein-protein interactions of cytosolic and outer mitochondrial membrane proteins. Among the involved proteins is cholesterol-binding translocator protein (TSPO) (18 kDa TSPO). We hypothesized that in contrast to TRT, the administration of the TSPO agonist N,N-dihexyl-2-(4-fluorophenyl)indole-3-acetamide (FGIN-1-27), by stimulating the ability of the Leydig cells to produce T, would result in the elevation of serum T levels while maintaining intratesticular T concentration and therefore without suppression of spermatogenesis. Age-related reductions in both serum and intratesticular T levels were seen in old Brown Norway rats. Both exogenous T and FGIN-1-27 increased serum T levels. With exogenous T, serum LH and Leydig cell T formation were suppressed, and intratesticular T was reduced to below the concentration required to maintain spermatogenesis quantitatively. In contrast, FGIN-1-27 stimulated Leydig cell T formation, resulting in increased serum T without reductions in intratesticular T concentrations or in testicular sperm numbers. FGIN-1-27 also significantly increased serum and intratesticular T levels in rats made LH-deficient by treatment with the gonadotropin-releasing hormone antagonist cetrorelix. These results point to a possible approach to increasing serum T without negative effects on spermatogenesis, based upon stimulating T production by the Leydig cells themselves rather than administering T exogenously.

N-Butyldeoxygalactonojirimycin Induces Reversible Infertility in Male CD Rats

This study shows for the first time that an iminosugar exerts anti-spermiogenic effect, inducing reversible infertility in a species that is not related to C57BL/6 male mice. In CD rats, N-butyldeoxygalactonojirimycin (NB-DGJ) caused reversible infertility at 150 mg/kg/day when administered daily as single oral dose. NB-DGJ inhibited CD rat-derived testicular β-glucosidase 2 (GBA2) activity at 10 µM but did not inhibit CD rat-derived testicular ceramide-specific glucosyltransferase (CGT) at doses up to 1000 µM. Pharmacokinetic studies revealed that sufficient plasma levels of NB-DGJ (50 µM) were achieved to inhibit the enzyme. Fertility was blocked after 35 days of treatment and reversed one week after termination of treatment. The rapid return of fertility indicates that the major effect of NB-DGJ may be epididymal rather than testicular. Collectively, our in vitro and in vivo studies in rats suggest that iminosugars should continue to be pursued as potential lead compounds for development of oral, non-hormonal male contraceptives. The study also adds evidence that GBA2, and not CGT, is the major target for the contraceptive effect of iminosugars.

The thermo-sensitive gene expression signatures of spermatogenesis

BACKGROUND

Spermatogenesis in most mammals (including human and rat) occurs at ~ 3 °C lower than body temperature in a scrotum and fails rapidly at 37 °C inside the abdomen. The present study investigates the heat-sensitive transcriptome and miRNAs in the most vulnerable germ cells (spermatocytes and round spermatids) that are primarily targeted at elevated temperature in a bid to identify novel targets for contraception and/or infertility treatment.

METHODS

Testes of adult male rats subjected to surgical cryptorchidism were obtained at 0, 24, 72 and 120 h post-surgery, followed by isolation of primary spermatocytes and round spermatids and purification to > 90% purity using a combination of trypsin digestion, centrifugal elutriation and density gradient centrifugation techniques. RNA isolated from these cells was sequenced by massive parallel sequencing technique to identify the most-heat sensitive mRNAs and miRNAs.

RESULTS

Heat stress altered the expression of a large number of genes by ≥2.0 fold, out of which 594 genes (286↑; 308↓) showed alterations in spermatocytes and 154 genes (105↑; 49↓) showed alterations in spermatids throughout the duration of experiment. 62 heat-sensitive genes were common to both cell types. Similarly, 66 and 60 heat-sensitive miRNAs in spermatocytes and spermatids, respectively, were affected by ≥1.5 fold, out of which 6 were common to both the cell types.

CONCLUSION

The study has identified Acly, selV, SLC16A7(MCT-2), Txnrd1 and Prkar2B as potential heat sensitive targets in germ cells, which may be tightly regulated by heat sensitive miRNAs rno-miR-22-3P, rno-miR-22-5P, rno-miR-129-5P, rno-miR-3560, rno-miR-3560 and rno-miR-466c-5P.

The future of male contraception: a fertile ground

The continued and rapid expansion of the Earth’s population mandates the need for safe and effective measures of contraception. While a plethora of options exist for women, methods of contraception for the male partner are limited to condoms and vasectomy. The sequela of this discrepancy has led to the family planning burden falling disproportionately on the female partner. For the past several decades, extensive research has been undertaken exploring the feasibility of hormonal male contraception. This proposed method of contraception has focused on suppressing spermatogenesis by exploiting the hypothalamic-pituitary-gonadal (HPG) axis. Beginning with proof of concept studies in the early nineties, administration of testosterone in healthy male subjects has been shown to be an efficacious method of inducing sterility. Owing to ethnic differences in spermatogenesis suppression and the comparatively low rate of azoospermia in Caucasian men with androgen-only regimens, investigators have explored the addition of progestins to further enhance the efficacy of hormonal contraception. Though studies have revealed promise with androgen-progestin regimens, the lack of long-term studies has precluded the development of a marketable product. Recently, more research has been directed towards identifying non-hormonal alternatives to male contraception. These non-hormonal options have ranged from the development of devices facilitating reversible occlusion of the vas deferens lumen to medications disrupting various pathways in the process of spermatogenesis. Underlying the development of hormonal and non-hormonal strategies is the shared enthusiasm men and women have towards these male directed methods. The willingness of couples to pursue these alternatives combined with the global need to reduce the psychological and socioeconomic implications of unintended pregnancy ensures that research will continue to bring this goal to fruition.

Contraction of Rat Cauda Epididymis Smooth Muscle to α1-Adrenoceptor Activation Is Mediated by α1A-Adrenoceptors

The cauda epididymis (CE), the site of sperm storage until the ejaculation, is densely innervated by the sympathetic nervous system. Contraction of CE smooth muscle via α₁-adrenoceptors (α₁-ARs) plays a key role during the seminal emission phase of ejaculation and α₁-AR antagonism has been suggested as a nonhormonal and reversible male contraceptive target. Since the α₁-AR subtype mediating contraction of rat CE is not known, this study investigates the expression and role of α₁-AR subtypes on the proximal and distal rat CE duct contraction to norepinephrine in vitro. Alpha_1a, α_1b, and α_1d transcripts were detected by real-time quantitative polymerase chain reaction in proximal and distal CE segments and α_1a and α_1d were shown to predominate over α_1b The inhibition of [³H]prazosin specific binding to intact CE segments from proximal and distal CE by RS 100329 and 5-methylurapidil (α_1A-selective) and BMY 7378 (α_1D-selective) showed that α_1A- and α_1D-ARs are expressed at similar densities. Norepinephrine-induced contractions of CE were competitively antagonized with high affinity by RS 100329 (pK_B ≈ 9.50) and 5-methylurapidil (pK_B ≈ 9.0) and with low affinity by BMY 7378 (pK_B ≈ 7.0) and the α_1B-selective L-765,314 (pA₂ < 7.0), suggesting contractions are mediated by α_1A-ARs. The clinically used α_1A/D-ARs antagonist tamsulosin potently (pA₂ ≈ 10.0) inhibited the norepinephrine-induced CE contractions. Altogether, our results show that α_1A- and α_1D-ARs are expressed in the CE duct and α_1A-AR is the main subtype mediating contraction to norepinephrine. Our results highlight the importance of α_1A-AR in the peripheral control of ejaculation and strengthen the α_1A-AR as a target for a nonhormonal approach to male contraception.

Opinions and Attitudes About Vasectomy of Married Couples Living in Turkey

This study was conducted as a descriptive study, designed to determine the opinions and attitudes of married couples living in Turkey about vasectomy. The sample consisted of 350 women. Researchers used a questionnaire to collect data. Descriptive statistics and chi-square analysis were used. The results showed that 14% of women and 43.0% of men were of the opinion that undergoing a vasectomy procedure was a sin. Chi-square analysis determined statistically significant differences between the male and female groups ( p < .05). More than 88.0% of the men were not willing to have vasectomy and 35.4% thought that vasectomy had a negative effect on marriage and sexual health. In addition, 58.9% thought that vasectomy had a negative effect on men's health. Women were more likely than men to see vasectomy as merely a cultural taboo instead of a sin. Sociocultural factors, such as ideas that contraception is the woman's responsibility, that sterilized men lose status in society, or that sterilized men lose authority in the family, as well as misconceptions about vasectomy such as concerns about sexual functioning, psychological effects, and effects on physical strength, were determined to be the main barriers for vasectomy use in Turkish culture. The study recommends determining strategies for overcoming sociocultural barriers by raising awareness and increasing the utilization of vasectomy. Couple-specific family planning programs can make an important contribution toward improving awareness of the benefits of vasectomy.

Recombinant production of enzymatically active male contraceptive drug target hTSSK2 - Localization of the TSKS domain phosphorylated by TSSK2

The testis-specific serine/threonine kinase 2 (TSSK2) has been proposed as a candidate male contraceptive target. Development of a selective inhibitor for this kinase first necessitates the production of highly purified, soluble human TSSK2 and its substrate, TSKS, with high yields and retention of biological activity for crystallography and compound screening. Strategies to produce full-length, soluble, biologically active hTSSK2 in baculovirus expression systems were tested and refined. Soluble preparations of TSSK2 were purified by immobilized-metal affinity chromatography (IMAC) followed by gel filtration chromatography. The biological activities of rec.hTSSK2 were verified by in vitro kinase and mobility shift assays using bacterially produced hTSKS (isoform 2), casein, glycogen synthase peptide (GS peptide) and various TSKS peptides as target substrates. Purified recombinant hTSSK2 showed robust kinase activity in the in vitro kinase assay by phosphorylating hTSKS isoform 2 and casein. The ATP Km values were similar for highly and partially purified fractions of hTSSK2 (2.2 and 2.7 μM, respectively). The broad spectrum kinase inhibitor staurosporine was a potent inhibitor of rec.hTSSK2 (IC50 = 20 nM). In vitro phosphorylation experiments carried out with TSKS (isoform 1) fragments revealed particularly strong phosphorylation of a recombinant N-terminal region representing aa 1-150 of TSKS, indicating that the N-terminus of human TSKS is phosphorylated by human TSSK2. Production of full-length enzymatically active recombinant TSSK2 kinase represents the achievement of a key benchmark for future discovery of TSSK inhibitors as male contraceptive agents.

Human Adenine Nucleotide Translocase (ANT) Modulators Identified by High-Throughput Screening of Transgenic Yeast

Transport of ADP and ATP across mitochondria is one of the primary points of regulation to maintain cellular energy homeostasis. This process is mainly mediated by adenine nucleotide translocase (ANT) located on the mitochondrial inner membrane. There are four human ANT isoforms, each having a unique tissue-specific expression pattern and biological function, highlighting their potential as drug targets for diverse clinical indications, including male contraception and cancer. In this study, we present a novel yeast-based high-throughput screening (HTS) strategy to identify compounds inhibiting the function of ANT. Yeast strains generated by deletion of endogenous proteins with ANT activity followed by insertion of individual human ANT isoforms are sensitive to cell-permeable ANT inhibitors, which reduce proliferation. Screening hits identified in the yeast proliferation assay were characterized in ADP/ATP exchange assays employing recombinant ANT isoforms expressed in isolated yeast mitochondria and Lactococcus lactis as well as by oxygen consumption rate in mammalian cells. Using this approach, closantel and CD437 were identified as broad-spectrum ANT inhibitors, whereas leelamine was found to be a modulator of ANT function. This yeast "knock-out/knock-in" screening strategy is applicable to a broad range of essential molecular targets that are required for yeast survival.

Yeast cell-based analysis of human lactate dehydrogenase isoforms

Human lactate dehydrogenase (LDH) has attracted attention as a potential target for cancer therapy and contraception. In this study, we reconstituted human lactic acid fermentation in Saccharomyces cerevisiae, with the goal of constructing a yeast cell-based LDH assay system. pdc null mutant yeast (mutated in the endogenous pyruvate decarboxylase genes) are unable to perform alcoholic fermentation; when grown in the presence of an electron transport chain inhibitor, pdc null strains exhibit a growth defect. We found that introduction of the human gene encoding LDHA complemented the pdc growth defect; this complementation depended on LDHA catalytic activity. Similarly, introduction of the human LDHC complemented the pdc growth defect, even though LDHC did not generate lactate at the levels seen with LDHA. In contrast, the human LDHB did not complement the yeast pdc null mutant, although LDHB did generate lactate in yeast cells. Expression of LDHB as a red fluorescent protein (RFP) fusion yielded blebs in yeast, whereas LDHA-RFP and LDHC-RFP fusion proteins exhibited cytosolic distribution. Thus, LDHB exhibits several unique features when expressed in yeast cells. Because yeast cells are amenable to genetic analysis and cell-based high-throughput screening, our pdc/LDH strains are expected to be of use for versatile analyses of human LDH.

Male Contraception: Research, New Methods, and Implications for Marginalized Populations

The majority of research on contraception has focused on manipulating the female reproductive system. Recent studies have identified novel contraceptives for males, including hormonal- and nonhormonal-based therapeutics. Although these new contraceptives are still undergoing clinical trials, their development and potential future use in society necessitate serious consideration of their implications for reproductive health. Through my analysis of the research conducted on male contraception over time and the current therapeutics available, it is clear that male contraception has the potential to shift societal gender dynamics and provide males with greater control over their own reproduction. This article also identifies the implications of these novel contraceptives for marginalized populations, especially men of color and men of lower socioeconomic positions. To overcome barriers to contraception among these populations, public policy efforts are needed in order to motivate the development of programs that facilitate coverage of these new male contraceptives by health plans and to increase their availability to underserved communities. Health care providers will be responsible for educating patients about these novel male contraception options and the need to continue using existing methods (e.g., condoms) in order to prevent sexually transmitted infections. This article analyzes the research conducted on male contraception and identifies the implications of these novel therapeutics for marginalized groups of men in the United States to identify the interventions that will be necessary to help ensure that all men have access to these promising scientific innovations.