In Vivo and In Vitro Impact of Carbohydrate Variation on Human Follicle-Stimulating Hormone Function

Follicle-stimulating hormone sweetness: How carbohydrate structures impact on the biological function of the hormone

Follicle-stimulating hormone (FSH), or follitropin, exists in multiple molecular forms due largely to its protein-carbohydrate composition and the complexity of the glycans attached to the protein core. The heterogeneity of gonadotropins exists in two forms, macroheterogeneity, which results from the absence of one or two oligosaccharide chains in the ß-subunit, and microheterogeneity which results from variation in the structures and complexity of the glycans attached to the hormone. In the clinical arena, FSH compounds are widely used by fertility specialists to promote ovarian follicle growth and maturation to a preovulatory follicle containing a fertilization-competent oocyte. Several genetically engineered recombinant human FSH preparations have been added to the arsenal of follitropin preparations in several countries for the treatment of infertility, particularly in women attending assisted reproduction clinics. Although the primary structure of these recombinant proteins is identical to that of naturally occurring FSH, the cell context and variations in the production and purification processes may impact the glycosidic profile of the recombinant FSH macro- and micro-heterogeneity, which may potentially influence the pharmacokinetics and pharmacodynamics of the compound. This review concentrates on the structure-function correlates of follitropin, with emphasis on the physiological and biological importance of the carbohydrates attached to its protein core, including its pharmacokinetics and biological activity. Emphasis is placed on pituitary FSH, and the available data on the various recombinant FSH preparations employed in therapeutics are also discussed, considering that this gonadotropin represents the cornerstone for the treatment of infertility in modern assisted reproduction.

Hormonal and Allosteric Regulation of the Luteinizing Hormone/Chorionic Gonadotropin Receptor

Luteinizing hormone (LH) and human chorionic gonadotropin (CG), like follicle-stimulating hormone, are the most important regulators of the reproductive system. They exert their effect on the cell through the LH/CG receptor (LHCGR), which belongs to the family of G protein-coupled receptors. Binding to gonadotropin induces the interaction of LHCGR with various types of heterotrimeric G proteins (Gs, Gq/11, Gi) and β-arrestins, which leads to stimulation (Gs) or inhibition (Gi) of cyclic adenosine monophosphate-dependent cascades, activation of the phospholipase pathway (Gq/11), and also to the formation of signalosomes that mediate the stimulation of mitogen-activated protein kinases (β-arrestins). The efficiency and selectivity of activation of intracellular cascades by different gonadotropins varies, which is due to differences in their interaction with the ligand-binding site of LHCGR. Gonadotropin signaling largely depends on the status of N- and O-glycosylation of LH and CG, on the formation of homo- and heterodimeric receptor complexes, on the cell-specific microenvironment of LHCGR and the presence of autoantibodies to it, and allosteric mechanisms are important in the implementation of these influences, which is due to the multiplicity of allosteric sites in different loci of the LHCGR. The development of low-molecular-weight allosteric regulators of LHCGR with different profiles of pharmacological activity, which can be used in medicine for the correction of reproductive disorders and in assisted reproductive technologies, is promising. These and other issues regarding the hormonal and allosteric regulation of LHCGR are summarized and discussed in this review.

Differential effects of follicle-stimulating hormone glycoforms on the transcriptome profile of cultured rat granulosa cells as disclosed by RNA-seq

It has been documented that variations in glycosylation on glycoprotein hormones, confer distinctly different biological features to the corresponding glycoforms when multiple in vitro biochemical readings are analyzed. We here applied next generation RNA sequencing to explore changes in the transcriptome of rat granulosa cells exposed for 0, 6, and 12 h to 100 ng/ml of four highly purified follicle-stimulating hormone (FSH) glycoforms, each exhibiting different glycosylation patterns: a. human pituitary FSH18/21 (hypo-glycosylated); b. human pituitary FSH24 (fully glycosylated); c. Equine FSH (eqFSH) (hypo-glycosylated); and d. Chinese-hamster ovary cell-derived human recombinant FSH (recFSH) (fully-glycosylated). Total RNA from triplicate incubations was prepared from FSH glycoform-exposed cultured granulosa cells obtained from DES-pretreated immature female rats, and RNA libraries were sequenced in a HighSeq 2500 sequencer (2 x 125 bp paired-end format, 10-15 x 106 reads/sample). The computational workflow focused on investigating differences among the four FSH glycoforms at three levels: gene expression, enriched biological processes, and perturbed pathways. Among the top 200 differentially expressed genes, only 4 (0.6%) were shared by all 4 glycoforms at 6 h, whereas 118 genes (40%) were shared at 12 h. Follicle-stimulating hormone glycocoforms stimulated different patterns of exclusive and associated up regulated biological processes in a glycoform and time-dependent fashion with more shared biological processes after 12 h of exposure and fewer treatment-specific ones, except for recFSH, which exhibited stronger responses with more specifically associated processes at this time. Similar results were found for down-regulated processes, with a greater number of processes at 6 h or 12 h, depending on the particular glycoform. In general, there were fewer downregulated than upregulated processes at both 6 h and 12 h, with FSH18/21 exhibiting the largest number of down-regulated associated processes at 6 h while eqFSH exhibited the greatest number at 12 h. Signaling cascades, largely linked to cAMP-PKA, MAPK, and PI3/AKT pathways were detected as differentially activated by the glycoforms, with each glycoform exhibiting its own molecular signature. These data extend previous observations demonstrating glycosylation-dependent distinctly different regulation of gene expression and intracellular signaling pathways triggered by FSH in granulosa cells. The results also suggest the importance of individual FSH glycoform glycosylation for the conformation of the ligand-receptor complex and induced signalling pathways.

Effectiveness of recombinant human FSH: recombinant human LH combination treatment versus recombinant human FSH alone for assisted reproductive technology in women aged 35-40 years

RESEARCH QUESTION

According to real-world data, is recombinant human FSH (r-hFSH) combined with recombinant human LH (r-hLH) or r-hFSH alone more effective for women of advanced maternal age (AMA) in terms of live birth?

DESIGN

Non-interventional study comparing the effectiveness of r-hFSH and recombinant r-hLH (2:1 ratio) versus r-hFSH alone for ovarian stimulation during ART treatment in women aged 35-40 years, using real-world data from the Deutsches IVF-Register.

RESULTS

Overall clinical pregnancy (29.8%, 95% CI 28.2 to 31.6 versus 27.8%, 95% CI 26.5 to 29.2) and live birth (20.3%, 95% CI 18.7 to 21.8 versus 18.0%, 95% CI 16.6 to 19.4) rates were not significantly different between the combined r-hFSH and r-hLH group and the r-hFSH alone group (P = 0.269 and P = 0.092, respectively). Treatment effect was significantly higher for combined r-hFSH and r-hLH compared with r-hFSH alone for clinical pregnancy (33.1%, 95% CI 31.0 to 35.0 versus 28.5%, 95% CI 26.6 to 30.4; P = 0.001, not adjusted for multiplicity) and live birth (22.5%, 95% CI 20.5 to 24.2 versus 19.4%, 95% CI 17.6 to 20.9; P = 0.014, not adjusted for multiplicity) in a post-hoc analysis of women with five to 14 oocytes retrieved (used as a surrogate for normal ovarian reserve), highlighting the potential benefits of combined r-hFSH and r-hLH for ovarian stimulation in women aged 35-40 years with normal ovarian reserve.

CONCLUSIONS

Women of AMA with normal ovarian response benefit from treatment with combined r-hFSH and r-hLH in a 2:1 ratio versus r-hFSH alone in terms of live birth rate. The effectiveness of treatments is best assessed by RCTs; however, real-world data are valuable for examining the effectiveness of fertility treatment, especially among patient groups that are not well represented in clinical trials.

Complex N-glycosylation of mGluR6 is required for trans-synaptic interaction with ELFN adhesion proteins

Synaptic transmission from retinal photoreceptors to downstream ON-type bipolar cells (BCs) depends on the postsynaptic metabotropic glutamate receptor mGluR6, located at the BC dendritic tips. Glutamate binding to mGluR6 initiates G-protein signaling that ultimately leads to BC depolarization in response to light. The mGluR6 receptor also engages in trans-synaptic interactions with presynaptic ELFN adhesion proteins. The roles of post-translational modifications in mGluR6 trafficking and function are unknown. Treatment with glycosidase enzymes PNGase F and Endo H demonstrated that both endogenous and heterologously expressed mGluR6 contain complex N-glycosylation acquired in the Golgi. Pull-down experiments with ELFN1 and ELFN2 extracellular domains revealed that these proteins interact exclusively with the complex glycosylated form of mGluR6. Mutation of the four predicted N-glycosylation sites, either singly or in combination, revealed that all four sites are glycosylated. Single mutations partially reduced, but did not abolish, surface expression in heterologous cells, while triple mutants had little or no surface expression, indicating that no single glycosylation site is necessary or sufficient for plasma membrane trafficking. Mutation at N445 severely impaired both ELFN1 and ELFN2 binding. All single mutants exhibited dendritic tip enrichment in rod BCs, as did the triple mutant with N445 as the sole N-glycosylation site, demonstrating that glycosylation at N445 is sufficient but not necessary for dendritic tip localization. The quadruple mutant was completely mislocalized. These results reveal a key role for complex N-glycosylation in regulating mGluR6 trafficking and ELFN binding, and by extension, function of the photoreceptor synapses.

Oocyte quality is enhanced by hypoglycosylated FSH through increased cell-to-cell interaction during mouse follicle development

Macroheterogeneity in follicle-stimulating hormone (FSH) β-subunit N-glycosylation results in distinct FSH glycoforms. Hypoglycosylated FSH21 is the abundant and more bioactive form in pituitaries of females under 35 years of age, whereas fully glycosylated FSH24 is less bioactive and increases with age. To investigate whether the shift in FSH glycoform abundance contributes to the age-dependent decline in oocyte quality, the direct effects of FSH glycoforms on folliculogenesis and oocyte quality were determined using an encapsulated in vitro mouse follicle growth system. Long-term culture (10-12 days) with FSH21 (10 ng/ml) enhanced follicle growth, estradiol secretion and oocyte quality compared with FSH24 (10 ng/ml) treatment. FSH21 enhanced establishment of transzonal projections, gap junctions and cell-to-cell communication within 24 h in culture. Transient inhibition of FSH21-mediated bidirectional communication abrogated the positive effects of FSH21 on follicle growth, estradiol secretion and oocyte quality. Our data indicate that FSH21 promotes folliculogenesis and oocyte quality in vitro by increasing cell-to-cell communication early in folliculogenesis, and that the shift in in vivo abundance from FSH21 to FSH24 with reproductive aging may contribute to the age-dependent decline in oocyte quality.

Differential effects of follicle-stimulating hormone glycoforms on the transcriptome profile of cultured rat granulosa cells as disclosed by RNA-seq

It has been documented that variations in glycosylation on glycoprotein hormones, confer distinctly different biological features to the corresponding glycoforms when multiple in vitro biochemical readings are analyzed. We here applied next generation RNA sequencing to explore changes in the transcriptome of rat granulosa cells exposed for 0, 6, and 12 h to 100 ng/ml of four highly purified follicle-stimulating hormone (FSH) glycoforms, each exhibiting different glycosylation patterns: human pituitary FSH18/21 and equine FSH (eqFSH) (hypo-glycosylated), and human FSH24 and chinese-hamster ovary cell-derived human recombinant FSH (recFSH) (fully-glycosylated). Total RNA from triplicate incubations was prepared from FSH glycoform-exposed cultured granulosa cells obtained from DES-pretreated immature female rats, and RNA libraries were sequenced in a HighSeq 2500 sequencer (2 × 125 bp paired-end format, 10-15 × 106 reads/sample). The computational workflow focused on investigating differences among the four FSH glycoforms at three levels: gene expression, enriched biological processes, and perturbed pathways. Among the top 200 differentially expressed genes, only 4 (0.6%) were shared by all 4 glycoforms at 6 h, whereas 118 genes (40%) were shared at 12 h. Follicle-stimulating hormone glycocoforms stimulated different patterns of exclusive and associated up regulated biological processes in a glycoform and time-dependent fashion with more shared biological processes after 12 h of exposure and fewer treatment-specific ones, except for recFSH, which exhibited stronger responses with more specifically associated processes at this time. Similar results were found for down-regulated processes, with a greater number of processes at 6 h or 12 h, depending on the particular glycoform. In general, there were fewer downregulated than upregulated processes at both 6 h and 12 h, with FSH18/21 exhibiting the largest number of down-regulated associated processes at 6 h while eqFSH exhibited the greatest number at 12 h. Signaling cascades, largely linked to cAMP-PKA, MAPK, and PI3/AKT pathways were detected as differentially activated by the glycoforms, with each glycoform exhibiting its own molecular signature. These data extend previous observations demonstrating glycosylation-dependent differential regulation of gene expression and intracellular signaling pathways triggered by FSH in granulosa cells. The results also suggest the importance of individual FSH glycoform glycosylation for the conformation of the ligand-receptor complex and induced signalling pathways.

RNA-seq analysis identifies age-dependent changes in expression of mRNAs - encoding N-glycosylation pathway enzymes in mouse gonadotropes

Follicle-stimulating hormone (FSH) is a glycoprotein that is assembled as a heterodimer of α/β subunits in gonadotropes. Each subunit contains two N-glycan chains. Our previous in vivo genetic studies identified that at least one N-glycan chain must be present on the FSHβ subunit for efficient FSH dimer assembly and secretion. Moreover, macroheterogeneity observed uniquely on human FSHβ results in ratiometric changes in age-specific FSH glycoforms, particularly during menopausal transition. Despite the recognition of many prominent roles of sugars on FSH including dimer assembly and secretion, serum half-life, receptor binding and signal transduction, the N-glycosylation machinery in gonadotropes has never been defined. Here, we used a mouse model in which gonadotropes are GFP-labeled in vivo and achieved rapid purification of GFP+ gonadotropes from pituitaries of female mice at reproductively young, middle, and old ages. We identified by RNA-seq analysis 52 mRNAs encoding N-glycosylation pathway enzymes expressed in 3- and 8-10-month-old mouse gonadotropes. We hierarchically mapped and localized the enzymes to distinct subcellular organelles within the N-glycosylation biosynthetic pathway. Of the 52 mRNAs, we found 27 mRNAs are differentially expressed between the 3- and 8-10-month old mice. We subsequently selected 8 mRNAs which showed varying changes in expression for confirmation of abundance in vivo via qPCR analysis, using more expanded aging time points with distinct 8-month and 14-month age groups. Real time qPCR analysis indicated dynamic changes in expression of N-glycosylation pathway enzyme-encoding mRNAs across the life span. Notably, computational analysis predicted the promoters of genes encoding these 8 mRNAs contain multiple high probability binding sites for estrogen receptor-1 and progesterone receptor. Collectively, our studies define the N-glycome and identify age-specific dynamic changes in mRNAs encoding N-glycosylation pathway enzymes in mouse gonadotropes. Our studies suggest the age-related decline in ovarian steroids may regulate expression of N-glycosylation enzymes in mouse gonadotropes and explain the age-related N-glycosylation shift previously observed on human FSHβ subunit in pituitaries of women.

Follicle-Stimulating Hormone Biological Products: Does Potency Predict Clinical Efficacy?

Follicle-stimulating hormone (FSH), together with luteinizing hormone (LH) and human chorionic gonadotropin (hCG), plays a fundamental role in human reproduction. The discovery of FSH and other gonadotropins was a defining moment in our understanding of reproduction and led to the development of many treatments for infertility. In this regard, exogenous FSH has been used to treat infertility in women for decades. Today, several recombinant and highly purified urinary forms of FSH are used in medically assisted reproduction (MAR). However, differences in the macro- and micro-heterogeneity of FSH result in a variety of FSH glycoforms, with glycoform composition determining the bioactivity (or potency), pharmacokinetic/pharmacodynamic (PK/PD) profiles, and clinical efficacy of the different forms of FSH. This review illustrates how the structural heterogeneity of FSH glycoforms affects the biological activity of human FSH products, and why potency does not predict effects in humans in terms of PK, PD, and clinical response.

Effectiveness of recombinant human follicle-stimulating hormone (r-hFSH): recombinant human luteinizing hormone versus r-hFSH alone in assisted reproductive technology treatment cycles among women aged 35-40 years: A German database study

This non-interventional study compared the effectiveness of recombinant human follicle-stimulating hormone (r-hFSH) and recombinant human luteinizing hormone (r-hLH) (2:1 ratio) versus r-hFSH alone for ovarian stimulation (OS) during assisted reproductive technology treatment in women aged 35-40 years, using real-world data from the Deutsches IVF-Register (D·I·R). Numerically higher clinical pregnancy (29.8% [95% CI 28.2, 31.6] vs. 27.8% [26.5, 29.2]) and live birth (20.3% [18.7, 21.8] vs. 18.0% [16.6, 19.4]) rates were observed with r-hFSH:r-hLH versus r-hFSH alone. The treatment effect was consistently higher for r-hFSH:r-hLH compared with r-hFSH alone in terms of clinical pregnancy (relative risk [RR] 1.16 [1.05, 1.26]) and live birth (RR 1.16 [1.02, 1.31]) in a post-hoc analysis of women with 5-14 oocytes retrieved (used as a surrogate for normal ovarian reserve), highlighting the potential benefits of r-hFSH:r-hLH for OS in women aged 35-40 years with normal ovarian reserve.

Biological Assay to Determine Gonadotropin Potency: From In Vivo to In Vitro Sustainable Method

Various preparations of follicle-stimulating hormone (FSH) are commercially available; however, they differ in glycoforms composition and purity owing to their respective sources. Additional chemical/physical changes can also be introduced during manufacturing and can impact their biological activity (biopotency), which is routinely assessed using an in vivo bioassay (Steelman-Pohley). This study aimed to determine whether an in vitro bioassay could assess biopotency by distinguishing between r-hFSH chemical/physical variants with similar ability to the in vivo bioassay. The specific activity (units of biological activity per mg of product) of variants of r-hFSH generated through enrichment (acidic/basic), stress (oxidative/acidic pH) and enzymatic treatment (desialylation and desialylation/degalactosylation) was compared using the in vivo and in vitro bioassays. The in vitro bioassay reliably detected potential chemical/physical modifications in r-hFSH variants that may impact biopotency. Overall, the methods demonstrated a comparable ability to detect changes in specific activities due to chemical/physical differences in r-hFSH variants. These data indicate that the in vitro bioassay is suitable to replace the in vivo bioassay.

Two Synthetic Peptides Corresponding to the Human Follicle-Stimulating Hormone β-Subunit Promoted Reproductive Functions in Mice

A follicle stimulating hormone (FSH) is widely used in the assisted reproduction and a synthetic peptide corresponding to a receptor binding region of the human (h) FSH-β-(34−37) (TRDL) modulated reproduction. Furthermore, a 13-amino acid sequence corresponding to hFSH-β-(37−49) (LVYKDPARPKIQK) was recently identified as the receptor binding site. We hypothesized that the synthetic peptides corresponding to hFSH-β-(37−49) and hFSH-β-(34−49), created by merging hFSH-β-(34−37) and hFSH-β-(37−49), modulate the reproductive functions, with the longer peptide being more biologically active. In male or female prepubertal mice, a single injection of 200 μg/g BW ip of hFSH-β-(37−49) or hFSH-β-(34−49) hastened (p < 0.05) puberty, whereas the same treatments given daily for 4 d promoted (p < 0.05) the gonadal steroidogenesis and gamete formation. In addition of either peptide to the in vitro cell cultures, promoted (p < 0.05) the proliferation of primary murine granulosa cells and the estradiol production by upregulating the expression of Ccnd2 and Cyp19a1, respectively. In adult female mice, 200 μg/g BW ip of either peptide during diestrus antagonized the FSH-stimulated estradiol increase and uterine weight gain during proestrus. Furthermore, hFSH-β-(34−49) was a more potent (p < 0.05) reproductive modulator than hFSH-β-(37−49), both in vivo and in vitro. We concluded that hFSH-β-(37−49) and especially hFSH-β-(34−49), have the potential for reproductive modulation.

Lactobacillus, glycans and drivers of health in the vaginal microbiome

A microbiome consists of microbes and their genomes, encompassing bacteria, viruses, fungi, protozoa, archaea, and eukaryotes. These elements interact dynamically in the specific environment in which they reside and evolve. In the past decade, studies of various microbiomes have been prevalent in the scientific literature, accounting for the shift from culture-dependent to culture-independent identification of microbes using new high-throughput sequencing technologies that decipher their composition and sometimes provide insights into their functions. Despite tremendous advances in understanding the gut microbiome, relatively little attention has been devoted to the vaginal environment, notably regarding the ubiquity and diversity of glycans which denote the significant role they play in the maintenance of homeostasis. Hopefully, emerging technologies will aid in the determination of what is a healthy vaginal microbiome, and provide insights into the roles of Lactobacillus, glycans and microbiome-related drivers of health and disease.

Hypo-glycosylated hFSH drives ovarian follicular development more efficiently than fully-glycosylated hFSH: enhanced transcription and PI3K and MAPK signaling

STUDY QUESTION

Does hypo-glycosylated human recombinant FSH (hFSH18/21) have greater in vivo bioactivity that drives follicle development in vivo compared to fully-glycosylated human recombinant FSH (hFSH24)?

SUMMARY ANSWER

Compared with fully-glycosylated hFSH, hypo-glycosylated hFSH has greater bioactivity, enabling greater follicular health and growth in vivo, with enhanced transcriptional activity, greater activation of receptor tyrosine kinases (RTKs) and elevated phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and Mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling.

WHAT IS KNOWN ALREADY

Glycosylation of FSH is necessary for FSH to effectively activate the FSH receptor (FSHR) and promote preantral follicular growth and formation of antral follicles. In vitro studies demonstrate that compared to fully-glycosylated recombinant human FSH, hypo-glycosylated FSH has greater activity in receptor binding studies, and more effectively stimulates the PKA pathway and steroidogenesis in human granulosa cells.

STUDY DESIGN, SIZE, DURATION

This is a cross-sectional study evaluating the actions of purified recombinant human FSH glycoforms on parameters of follicular development, gene expression and cell signaling in immature postnatal day (PND) 17 female CD-1 mice. To stimulate follicle development in vivo, PND 17 female CD-1 mice (n = 8-10/group) were treated with PBS (150 µl), hFSH18/21 (1 µg/150 µl PBS) or hFSH24 (1 µg/150 µl PBS) by intraperitoneal injection (i.p.) twice daily (8:00 a.m. and 6:00 p.m.) for 2 days. Follicle numbers, serum anti-Müllerian hormone (AMH) and estradiol levels, and follicle health were quantified. PND 17 female CD-1 mice were also treated acutely (2 h) in vivo with PBS, hFSH18/21 (1 µg) or hFSH24 (1 µg) (n = 3-4/group). One ovary from each mouse was processed for RNA sequencing analysis and the other ovary processed for signal transduction analysis. An in vitro ovary culture system was used to confirm the relative signaling pathways.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The purity of different recombinant hFSH glycoforms was analyzed using an automated western blot system. Follicle numbers were determined by counting serial sections of the mouse ovary. Real-time quantitative RT-PCR, western blot and immunofluorescence staining were used to determine growth and apoptosis markers related with follicle health. RNA sequencing and bioinformatics were used to identify pathways and processes associated with gene expression profiles induced by acute FSH glycoform treatment. Analysis of RTKs was used to determine potential FSH downstream signaling pathways in vivo. Western blot and in vitro ovarian culture system were used to validate the relative signaling pathways.

MAIN RESULTS AND THE ROLE OF CHANCE

Our present study shows that both hypo- and fully-glycosylated recombinant human FSH can drive follicular growth in vivo. However, hFSH18/21 promoted development of significantly more large antral follicles compared to hFSH24 (P < 0.01). In addition, compared with hFSH24, hFSH18/21 also promoted greater indices of follicular health, as defined by lower BAX/BCL2 ratios and reduced cleaved Caspase 3. Following acute in vivo treatment with FSH glycoforms RNA-sequencing data revealed that both FSH glycoforms rapidly induced ovarian transcription in vivo, but hypo-glycosylated FSH more robustly stimulated Gαs and cAMP-mediated signaling and members of the AP-1 transcription factor complex. Moreover, hFSH18/21 treatment induced significantly greater activation of RTKs, PI3K/AKT and MAPK/ERK signaling compared to hFSH24. FSH-induced indices of follicle growth in vitro were blocked by inhibition of PI3K and MAPK.

LARGE SCALE DATA

RNA sequencing of mouse ovaries. Data will be shared upon reasonable request to the corresponding author.

LIMITATIONS, REASONS FOR CAUTION

The observations that hFSH glycoforms have different bioactivities in the present study employing a mouse model of follicle development should be verified in nonhuman primates. The gene expression studies reflect transcriptomes of whole ovaries.

WIDER IMPLICATIONS OF THE FINDINGS

Commercially prepared recombinant human FSH used for ovarian stimulation in human ART is fully-glycosylated FSH. Our findings that hypo-glycosylated hFSH has greater bioactivity enabling greater follicular health and growth without exaggerated estradiol production in vivo, demonstrate the potential for its development for application in human ART.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by NIH 1P01 AG029531, NIH 1R01 HD 092263, VA I01 BX004272, and the Olson Center for Women's Health. JSD is the recipient of a VA Senior Research Career Scientist Award (1IK6 BX005797). This work was also partially supported by National Natural Science Foundation of China (No. 31872352). The authors declared there are no conflicts of interest.

Comparative effectiveness of recombinant human follicle-stimulating hormone alfa (r-hFSH-alfa) versus highly purified urinary human menopausal gonadotropin (hMG HP) in assisted reproductive technology (ART) treatments: a non-interventional study in Germany

BACKGROUND

This study compared the effectiveness of recombinant human follicle-stimulating hormone alfa (r-hFSH-alfa; GONAL-f^®) with urinary highly purified human menopausal gonadotropin (hMG HP; Menogon HP^®), during assisted reproductive technology (ART) treatments in Germany.

METHODS

Data were collected from 71 German fertility centres between 01 January 2007 and 31 December 2012, for women undergoing a first stimulation cycle of ART treatment with r-hFSH-alfa or hMG HP. Primary outcomes were live birth, ongoing pregnancy and clinical pregnancy, based on cumulative data (fresh and frozen-thawed embryo transfers), analysed per patient (pP), per complete cycle (pCC) and per first complete cycle (pFC). Secondary outcomes were pregnancy loss (analysed per clinical pregnancy), cancelled cycles (analysed pCC), total drug usage per oocyte retrieved and time-to-live birth (TTLB; per calendar week and per cycle).

RESULTS

Twenty-eight thousand six hundred forty-one women initiated a first treatment cycle (r-hFSH-alfa: 17,725 [61.9%]; hMG HP: 10,916 [38.1%]). After adjustment for confounding variables, treatment with r-hFSH-alfa versus hMG HP was associated with a significantly higher probability of live birth (hazard ratio [HR]-pP [95% confidence interval (CI)]: 1.10 [1.04, 1.16]; HR-pCC [95% CI]: 1.13 [1.08, 1.19]; relative risk [RR]-pFC [95% CI]: 1.09 [1.05, 1.15], ongoing pregnancy (HR-pP [95% CI]: 1.10 [1.04, 1.16]; HR-pCC [95% CI]: 1.13 [1.08, 1.19]; RR-pFC [95% CI]: 1.10 [1.05, 1.15]) and clinical pregnancy (HR-pP [95% CI]: 1.10 [1.05, 1.14]; HR-pCC [95% CI]: 1.14 [1.10, 1.19]; RR-pFC [95% CI]: 1.10 [1.06, 1.14]). Women treated with r-hFSH-alfa versus hMG HP had no statistically significant difference in pregnancy loss (HR [95% CI]: 1.07 [0.98, 1.17], were less likely to have a cycle cancellation (HR [95% CI]: 0.91 [0.84, 0.99]) and had no statistically significant difference in TTLB when measured in weeks (HR [95% CI]: 1.02 [0.97, 1.07]; p = 0.548); however, r-hFSH-alfa was associated with a significantly shorter TTLB when measured in cycles versus hMG HP (HR [95% CI]: 1.07 [1.02, 1.13]; p = 0.003). There was an average of 47% less drug used per oocyte retrieved with r-hFSH-alfa versus hMG HP.

CONCLUSIONS

This large (> 28,000 women), real-world study demonstrated significantly higher rates of cumulative live birth, cumulative ongoing pregnancy and cumulative clinical pregnancy with r-hFSH-alfa versus hMG HP.

Reduced FSH and LH action: implications for medically assisted reproduction

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) play complementary roles in follicle development and ovulation via a complex interaction in the hypothalamus, anterior pituitary gland, reproductive organs, and oocytes. Impairment of the production or action of gonadotropins causes relative or absolute LH and FSH deficiency that compromises gametogenesis and gonadal steroid production, thereby reducing fertility. In women, LH and FSH deficiency is a spectrum of conditions with different functional or organic causes that are characterized by low or normal gonadotropin levels and low oestradiol levels. While the causes and effects of reduced LH and FSH production are very well known, the notion of reduced action has received less attention by researchers. Recent evidence shows that molecular characteristics, signalling as well as ageing, and some polymorphisms negatively affect gonadotropin action. These findings have important clinical implications, in particular for medically assisted reproduction in which diminished action determined by the afore-mentioned factors, combined with reduced endogenous gonadotropin production caused by GnRH analogue protocols, may lead to resistance to gonadotropins and, thus, to an unexpected hypo-response to ovarian stimulation. Indeed, the importance of LH and FSH action has been highlighted by the International Committee for Monitoring Assisted Reproduction Technologies (ICMART) in their definition of hypogonadotropic hypogonadism as gonadal failure associated with reduced gametogenesis and gonadal steroid production due to reduced gonadotropin production or action. The aim of this review is to provide an overview of determinants of reduced FSH and LH action that are associated with a reduced response to ovarian stimulation.

Recent advances in understanding gonadotropin signaling

Gonadotropins are glycoprotein sex hormones regulating development and reproduction and bind to specific G protein–coupled receptors expressed in the gonads. Their effects on multiple signaling cascades and intracellular events have recently been characterized using novel technological and scientific tools. The impact of allosteric modulators on gonadotropin signaling, the role of sugars linked to the hormone backbone, the detection of endosomal compartments supporting signaling modules, and the dissection of different effects mediated by these molecules are areas that have advanced significantly in the last decade. The classic view providing the exclusive activation of the cAMP/protein kinase A (PKA) and the steroidogenic pathway by these hormones has been expanded with the addition of novel signaling cascades as determined by high-resolution imaging techniques. These new findings provided new potential therapeutic applications. Despite these improvements, unanswered issues of gonadotropin physiology, such as the intrinsic pro-apoptotic potential to these hormones, the existence of receptors assembled as heteromers, and their expression in extragonadal tissues, remain to be studied. Elucidating these issues is a challenge for future research.

FGDB: Database of follicle stimulating hormone glycans

Glycomics, the study of the entire complement of sugars of an organism has received significant attention in the recent past due to the advances made in high throughput mass spectrometry technologies. These analytical advancements have facilitated the characterization of glycans associated with the follicle-stimulating hormones (FSH), which play a central role in the human reproductive system both in males and females utilizing regulating gonadal (testicular and ovarian) functions. The irregularities in FSH activity are also directly linked with osteoporosis. The glycoanalytical studies have been tremendously helpful in understanding the biological roles of FSH. Subsequently, the increasing number of characterized FSH glycan structures and related glycoform data has thrown a challenge to the glycoinformatics community in terms of data organization, storage and access. Also, a user-friendly platform is needed for providing easy access to the database and performing integrated analysis using a high volume of experimental data to accelerate FSH-focused research. FSH Glycans DataBase (FGDB) serves as a comprehensive and unique repository of structures, features, and related information of glycans associated with FSH. Apart from providing multiple search options, the database also facilitates an integrated user-friendly interface to perform the glycan abundance and comparative analyses using experimental data. The automated integrated pipelines present the possible structures of glycans and variants of FSH based on the input data, and allow the user to perform various analyses. The potential application of FGDB will significantly help both glycoinformaticians as well as wet-lab researchers to stimulate the research in this area. FGDB web access: https://fgdb.unmc.edu/.

Uterine artery Doppler indices: pulsatility index and resistance index as predictive tools for the incidence of heavy menstrual bleeding related to copper intrauterine contraceptive device

Objectives

To assess the predictive value of the initial uterine artery Doppler indices, the pulsatility index (PI), and resistance index (RI) in the prediction of heavy menstrual bleeding before and after copper intrauterine contraceptive device (IUCD) insertion.

Methods

The current prospective clinical study included 100 women who intended to use a copper IUCD (Cu T-380A) and met the inclusion criteria. Uterine artery Doppler PI and RI indices were calculated before IUCD insertion and at three and six months after insertion. Based on the presence or absence of menorrhagia, all women were classified into two groups: non-bleeding (n=52) and extreme menstrual bleeding (n=48). Receiver operating curve analysis was used to determine the predictive value of uterine artery PI and RI in patients with menorrhagia relevant to IUCD.

Results

The PI and RI indices displayed a highly significant difference between the IUCD groups at three and six months after insertion (P<0.001). Uterine artery PI ≤2.02 (sensitivity of 95.8%, specificity of 100%, and area below the curve [AUC] of 0.97 at P-value<0.001) and RI ≤0.83 (sensitivity of 93.8%, specificity of 100%, and AUC of 0.949 at P-value<0.001) were correlated with significant menstrual bleeding following insertion of IUCD.

Conclusion

The presented results confirmed our assumption that the initial studies of uterine artery Doppler can predict heavy-menstrual bleeding associated with IUCD and therefore, should be conducted in women pursuing reversible long-acting contraception.

Discovery and Preclinical Development of Orally Active Small Molecules that Exhibit Highly Selective Follicle Stimulating Hormone Receptor Agonism

An orally active follicle stimulating hormone receptor allosteric agonist would provide a preferred treatment for over 16 million infertile women of reproductive age in low complexity methods (ovulation induction-intrauterine insemination) or in high complexity methods (controlled ovarian stimulation-in vitro fertilization). We present two oral follicle stimulating hormone receptor allosteric agonist compounds that have the desired pharmacology, drug metabolism, pharmacokinetics, and safety profile for clinical use. These molecules provide a single agent suitable for ovulation induction-intrauterine insemination or controlled ovarian stimulation-in vitro fertilization that is more convenient for patients and achieves similar preclinical efficacy as rec-hFSH. TOP5668, TOP5300 were evaluated in vitro in Chinese hamster ovary cells transfected with individual glycoprotein receptors measuring cAMP (FSHR, LH/CGR, thyroid stimulating hormone receptor). TOP5668 was found to have solely follicle stimulating hormone receptor allosteric agonist activity while TOP5300 was found to have mixed follicle stimulating hormone receptor allosteric agonist and LHR-AA activity. Both compounds stimulated concentration-dependent increases in estradiol production from cultured rat granulosa cells in the presence or absence of low dose rec-hFSH, while only TOP5300 stimulated testosterone production from rat primary Leydig cells. In pooled human granulosa cells obtained from patients undergoing controlled ovarian stimulation-in vitro fertilization, TOP5300 stimulated 7-fold greater maximal estradiol response than rec-hFSH and TOP5668 was 10-fold more potent than TOP5300. Both TOP5300 and TOP5668 stimulated follicular development in immature rat to the same efficacy as recombinant follicle stimulating hormone. In mice treated with TOP5300, in the presence of low dose of follicle stimulating hormone, there were no differences in oocyte number, fertilization rate, and hatched blastocyst rate in mice with TOP5300 and low dose follicle stimulating hormone vs. reference proteins pregnant mare serum gonadotropin or high dose rec-hFSH. ADME/PK and safety profiles were favorable. In addition, there was no appreciable activity on thyroid hormones by TOP5300 in 14-days toxicological study in rat or dog. The selected lead compound, TOP5300 stimulated a more robust increase in estradiol production from granulosa-lutein cells from women with polycystic ovarian syndrome patient compared to rec-hFSH. Conclusions: Two novel oral FSHR allosteric agonist, TOP5668 and TOP5300, were found to mimic the biological activity of rec hFSH in preclinical studies. Both compounds led to folliculogenesis and superovulation in rat and mice. Specifically, TOP5300 led to a similar number of ovulated oocytes that fertilized and developed into hatched blastocysts in mice when compared to rec-hFSH. The safety profile demonstrated lack of toxicity.

Pharmacogenomic Biomarkers of Follicle-Stimulating Hormone Receptor Malfunction in Females with Impaired Ovarian Response-A Genetic Survey

Follicle-stimulating hormone receptor (FSHR) plays an essential role as one of the most important molecules in response to some of infertility related medications. Impaired ovarian reserve and poor response to such treatments are partially dependent on the FSHR molecule itself. However, the function and drug sensitivity for this receptor may change due to various allele and polymorphisms in the FSHR gene. Studies indicated some of the FSHR-mediated treatments utilized in clinical centers display different outcomes in specific populations, which may arise from FSHR altered genotypes in certain patients. To support the increased demands for reaching the personalized drug and hormone therapy in clinics, focusing on actionable variants through Pharmacogenomic analysis of this receptor may be necessary. The current study tries to display a perspective view on genetic assessments for Pharmacogenomic profiling of the FSHR gene via providing a systematic and critical overview on the genetics of FSHR and its diverse responses to ligands for infertility treatment in females with impaired ovarian responses and show the potential effects of the patient genetic make-up on related binding substances efficacy. All identified functional drug-related alleles were selected through a comprehensive literature search and analyzed. Advanced technologies for the genetic evaluation of them are also discussed properly.

Optimising Follicular Development, Pituitary Suppression, Triggering and Luteal Phase Support During Assisted Reproductive Technology: A Delphi Consensus

BACKGROUND

A Delphi consensus was conducted to evaluate global expert opinions on key aspects of assisted reproductive technology (ART) treatment.

METHODS

Ten experts plus the Scientific Coordinator discussed and amended statements plus supporting references proposed by the Scientific Coordinator. The statements were distributed via an online survey to 35 experts, who voted on their level of agreement or disagreement with each statement. Consensus was reached if the proportion of participants agreeing or disagreeing with a statement was >66%.

RESULTS

Eighteen statements were developed. All statements reached consensus and the most relevant are summarised here. (1) Follicular development and stimulation with gonadotropins (n = 9 statements): Recombinant human follicle stimulating hormone (r-hFSH) alone is sufficient for follicular development in normogonadotropic patients aged <35 years. Oocyte number and live birth rate are strongly correlated; there is a positive linear correlation with cumulative live birth rate. Different r-hFSH preparations have identical polypeptide chains but different glycosylation patterns, affecting the biospecific activity of r-hFSH. r-hFSH plus recombinant human LH (r-hFSH:r-hLH) demonstrates improved pregnancy rates and cost efficacy versus human menopausal gonadotropin (hMG) in patients with severe FSH and LH deficiency. (2) Pituitary suppression (n = 2 statements): Gonadotropin releasing hormone (GnRH) antagonists are associated with lower rates of any grade ovarian hyperstimulation syndrome (OHSS) and cycle cancellation versus GnRH agonists. (3) Final oocyte maturation triggering (n=4 statements): Human chorionic gonadotropin (hCG) represents the gold standard in fresh cycles. The efficacy of hCG triggering for frozen transfers in modified natural cycles is controversial compared with LH peak monitoring. Current evidence supports significantly higher pregnancy rates with hCG + GnRH agonist versus hCG alone, but further evidence is needed. GnRH agonist trigger, in GnRH antagonist protocol, is recommended for final oocyte maturation in women at risk of OHSS. (4) Luteal-phase support (n = 3 statements): Vaginal progesterone therapy represents the gold standard for luteal-phase support.

CONCLUSIONS

This Delphi consensus provides a real-world clinical perspective on the specific approaches during the key steps of ART treatment from a diverse group of international experts. Additional guidance from clinicians on ART strategies could complement guidelines and policies, and may help to further improve treatment outcomes.

New Human Follitropin Preparations: How Glycan Structural Differences May Affect Biochemical and Biological Function and Clinical Effect

It is well accepted that pituitary follitropin is secreted into the circulation as a mixture of variants, which differ not in primary structure but rather at the level of glycosylation. These glycosidic forms vary in the number of glycosylation sites filled, complexity of glycosidic chains, and sialylation and sulfation. It is generally agreed that high sialylation, 2,3 sialic acid capping of terminal N-acetyl galactosamine or galactose leads to longer circulating half-life, by blocking binding of asialoglycoprotein receptor (ASGPR) in the liver. In contrast, 2,6 sialic acid found in humans does not prevent recognition of galactose and N-acetyl galactosamine by ASGPR. Few studies on clinical outcomes comparing differences in sialylation of follitropin found in commercially available preparations are available. Thus, there is a clear need for a consortium of open data to address this unmet need. Recently, FSH glycosylation, primarily on the β-subunit, which varies as women age, has emerged as a key modifier of follitropin action, with profound biological effects in vivo in animal models. To date, limited information of recombinant follitropin hormone preparations is available. Thus, most of the studies with FSH that is well characterized biochemically have been done in vitro, with engineered non gonadal host cells bearing recombinant receptors or in animal models. Since limited studies in human granulosa cells are available, a question is whether structural differences in glycosylation in commercially available follitropin affects biological function and clinical effect in humans. The presence of fucose, for example, has not been studied greatly even though, in the case of antibody therapy it has been shown to have a large effect on antibody targeting. This review on glycosidic variability of follitropin from the biochemical/structural point of view reflects on this question and presents an assessment in the context of available published data. If clinical differences are to be expected or not, the readers will have a better understanding of the evidence for and limitations of such expectations.

Differential FSH Glycosylation Modulates FSHR Oligomerization and Subsequent cAMP Signaling

Follicle-stimulating hormone (FSH) and its target G protein-coupled receptor (FSHR) are essential for reproduction. Recent studies have established that the hypo-glycosylated pituitary FSH glycoform (FSH21/18), is more bioactive in vitro and in vivo than the fully-glycosylated variant (FSH24). FSH21/18 predominates in women of reproductive prime and FSH24 in peri-post-menopausal women, suggesting distinct functional roles of these FSH glycoforms. The aim of this study was to determine if differential FSH glycosylation modulated FSHR oligomerization and resulting impact on cAMP signaling. Using a modified super-resolution imaging technique (PD-PALM) to assess FSHR complexes in HEK293 cells expressing FSHR, we observed time and concentration-dependent modulation of FSHR oligomerization by FSH glycoforms. High eFSH and FSH21/18 concentrations rapidly dissociated FSHR oligomers into monomers, whereas FSH24 displayed slower kinetics. The FSHR β-arrestin biased agonist, truncated eLHβ (Δ121-149) combined with asparagine56-deglycosylated eLHα (dg-eLHt), increased FSHR homomerization. In contrast, low FSH21/18 and FSH24 concentrations promoted FSHR association into oligomers. Dissociation of FSHR oligomers correlated with time points where higher cAMP production was observed. Taken together, these data suggest that FSH glycosylation may modulate the kinetics and amplitude of cAMP production, in part, by forming distinct FSHR complexes, highlighting potential avenues for novel therapeutic targeting of the FSHR to improve IVF outcomes.

Controlled delivery of follicle-stimulating hormone in cattle

Embryo transfer in cattle is a key issue requiring in vivo production of several mature follicles as opposed to the normal production of only one. In vivo produced embryos can then be transferred to recipient cows for gestation to occur. To obtain a large number of transferable embryos, the superovulation step is crucial. To allow the growth of ovarian follicles, the most commonly used protocol consists of 2 intramuscular injections per day over 4 days of a saline solution of the follicle-stimulating hormone. To reduce workload, technical errors in the injected dose and animal stress, different strategies have been investigated to sustain the release of this hormone over 4 days in 1 or 2 injections. This review introduces the physicochemical properties of the follicle-stimulating hormone and discusses the limitations of marketed products and all the research that has been conducted to overcome these limitations. In particular, the field of subcutaneous administrations, the development of new formulations such as viscous solutions, implants and microspheres and the modification of the structure of the follicle-stimulating hormone are overviewed and discussed.

Bioactivity of recombinant hFSH glycosylation variants in primary cultures of porcine granulosa cells

Previous studies have reported hypo-glycosylated FSH and fully-glycosylated FSH to be naturally occurring in humans, and these glycoforms exist in changing ratios over a woman's lifespan. The precise cellular and molecular effects of recombinant human FSH (hFSH) glycoforms, FSH21 and FSH24, have not been documented in primary granulosa cells. Herein, biological responses to FSH21 and FSH24 were compared in primary porcine granulosa cells. Hypo-glycosylated hFSH21 was significantly more effective than fully-glycosylated hFSH24 at stimulating cAMP accumulation and protein kinase A (PKA) activity, leading to the higher phosphorylation of CREB and β-Catenin. Compared to fully-glycosylated hFSH24, hypo-glycosylated hFSH21 also induced greater levels of transcripts for HSD3B, STAR and INHA, and higher progesterone production. Our results demonstrate that hypo-glycosylated hFSH21 exerts more robust activation of intracellular signals associated with steroidogenesis than fully-glycosylated hFSH24 in primary porcine granulosa cells, and furthers our understanding of the differing bioactivities of FSH glycoforms in the ovary.

Prospects for FSH Treatment of Male Infertility

CONTEXT

Despite the new opportunities provided by assisted reproductive technology (ART), male infertility treatment is far from being optimized. One possibility, based on pathophysiological evidence, is to stimulate spermatogenesis with gonadotropins.

EVIDENCE ACQUISITION

We conducted a comprehensive systematic PubMed literature review, up to January 2020, of studies evaluating the genetic basis of follicle-stimulating hormone (FSH) action, the role of FSH in spermatogenesis, and the effects of its administration in male infertility. Manuscripts evaluating the role of genetic polymorphisms and FSH administration in women undergoing ART were considered whenever relevant.

EVIDENCE SYNTHESIS

FSH treatment has been successfully used in hypogonadotropic hypogonadism, but with questionable results in idiopathic male infertility. A limitation of this approach is that treatment plans for male infertility have been borrowed from hypogonadism, without daring to overstimulate, as is done in women undergoing ART. FSH effectiveness depends not only on its serum levels, but also on individual genetic variants able to determine hormonal levels, activity, and receptor response. Single-nucleotide polymorphisms in the follicle-stimulating hormone subunit beta (FSHB) and follicle-stimulating hormone receptor (FSHR) genes have been described, with some of them affecting testicular volume and sperm output. The FSHR p.N680S and the FSHB -211G>T variants could be genetic markers to predict FSH response.

CONCLUSIONS

FSH may be helpful to increase sperm production in infertile men, even if the evidence to recommend the use of FSH in this setting is weak. Placebo-controlled clinical trials, considering the FSHB-FSHR haplotype, are needed to define the most effective dosage, the best treatment length, and the criteria to select candidate responder patients.

Human Recombinant FSH and Its Biosimilars: Clinical Efficacy, Safety, and Cost-Effectiveness in Controlled Ovarian Stimulation for In Vitro Fertilization

Exogenous human follicle-stimulating hormone (hFSH), either derived from extraction and purification from the urine or obtained by recombinant technology in the form of follitropin α, β and δ (rFSH), has been used for decades in the treatment of infertility. The main applications of FSH treatment in the woman have been, and still are, ovulation induction in oligo-anovulatory subjects, and stimulation of the development of a cohort of follicles in patients undergoing controlled ovarian stimulation (COS) for in vitro fertilization (IVF). In the last years, two biosimilars of follitropin alfa, rFSH compounds structurally and functionally similar to the originator, have been approved and marketed for clinical use in Europe. Moreover, some other rFSH biosimilars are currently under investigation. The objective of this article is to review the available evidences comparing the efficacy, safety, and cost-effectiveness of rFSH follitropin alpha originator with its biosimilars, discussing the clinical trials that allowed biosimilars to get registration and marketing authorization.

Use of Biosimilar Follicle-Stimulating Hormone in Asthenozoospermic Infertile Patients: A Multicentric Study

There is increasing data in favour of follicle-stimulating hormone (FSH) therapy in patients with oligo-asthenozoospermia and normal-range gonadotropins in order to increase sperm count and above all sperm motility. Some studies showed an improvement in DNA fragmentation and spontaneous pregnancy. Recently, biosimilar FSH has been marketed with the same indications. We performed a retrospective multicentric case-control study involving 147 asthenozoospermic patients between 18 and 45 years of age. A total of 97 patients were treated with biosimilar FSH 150 UI three times a week for 3 months, while 50 control subjects received no treatment. Patients were evaluated at baseline and after 3 months with semen analysis including DNA fragmentation, testicular colour Doppler ultrasound, and blood tests. Spontaneous pregnancies were recorded during a further follow-up period of 6 months. Treated patients showed after treatment a statistically significant increase in sperm concentration, total sperm count, and total motile sperm, as well as improved progressive motility and non-progressive motility. DNA fragmentation showed a significant reduction. Conversely, in the control group, no significant change was found. Pregnancy rate was significantly higher in treated patients. These data suggest comparable efficacy of biosimilar FSH in the treatment of male infertility; however, larger studies are needed to confirm our results.

FSH for the Treatment of Male Infertility

Follicle-stimulating hormone (FSH) supports spermatogenesis acting via its receptor (FSHR), which activates trophic effects in gonadal Sertoli cells. These pathways are targeted by hormonal drugs used for clinical treatment of infertile men, mainly belonging to sub-groups defined as hypogonadotropic hypogonadism or idiopathic infertility. While, in the first case, fertility may be efficiently restored by specific treatments, such as pulsatile gonadotropin releasing hormone (GnRH) or choriogonadotropin (hCG) alone or in combination with FSH, less is known about the efficacy of FSH in supporting the treatment of male idiopathic infertility. This review focuses on the role of FSH in the clinical approach to male reproduction, addressing the state-of-the-art from the little data available and discussing the pharmacological evidence. New compounds, such as allosteric ligands, dually active, chimeric gonadotropins and immunoglobulins, may represent interesting avenues for future personalized, pharmacological approaches to male infertility.

Follicle-Stimulating Hormone Glycobiology

FSH glycosylation varies in two functionally important aspects: microheterogeneity, resulting from oligosaccharide structure variation, and macroheterogeneity, arising from partial FSHβ subunit glycosylation. Although advances in mass spectrometry permit extensive characterization of FSH glycan populations, microheterogeneity remains difficult to illustrate, and comparisons between different studies are challenging because no standard format exists for rendering oligosaccharide structures. FSH microheterogeneity is illustrated using a consistent glycan diagram format to illustrate the large array of structures associated with one hormone. This is extended to commercially available recombinant FSH preparations, which exhibit greatly reduced microheterogeneity at three of four glycosylation sites. Macroheterogeneity is demonstrated by electrophoretic mobility shifts due to the absence of FSHβ glycans that can be assessed by Western blotting of immunopurified FSH. Initially, macroheterogeneity was hoped to matter more than microheterogeneity. However, it now appears that both forms of carbohydrate heterogeneity have to be taken into consideration. FSH glycosylation can reduce its apparent affinity for its cognate receptor by delaying initial interaction with the receptor and limiting access to all of the available binding sites. This is followed by impaired cellular signaling responses that may be related to reduced receptor occupancy or biased signaling. To resolve these alternatives, well-characterized FSH glycoform preparations are necessary.

Gain-of-Function Genetic Models to Study FSH Action

Follicle-stimulating hormone (FSH) is a pituitary-derived gonadotropin that plays key roles in male and female reproduction. The physiology and biochemistry of FSH have been extensively studied for many years. Beginning in the early 1990s, coincident with advances in the then emerging transgenic animal technology, and continuing till today, several gain-of-function (GOF) models have been developed to understand FSH homeostasis in a physiological context. Our group and others have generated a number of FSH ligand and receptor GOF mouse models. An FSH GOF model when combined with Fshb null mice provides a powerful genetic rescue platform. In this chapter, we discuss different GOF models for FSH synthesis, secretion and action and describe additional novel genetic models that could be developed in the future to further refine the existing models.

Hormonal Regulation of Follicle-Stimulating Hormone Glycosylation in Males

The Follicle-Stimulating Hormone plays an important role in the regulation of gametogenesis. It is synthesized and secreted as a family of glycoforms with differing oligosaccharide structure, biological action, and half-life. The presence of these oligosaccharides is absolutely necessary for the full expression of hormone bioactivity at the level of the target cell. The endocrine milieu modulates the glycosylation of this hormone. During male sexual development a progressive increase in FSH sialylation and in the proportion of glycoforms bearing complex oligosaccharides are the main features in this physiological condition. In late puberty, FSH oligosaccharides are largely processed in the medial- and trans-Golgi cisternae of the gonadotrope and remain without changes throughout adult life. In experimental models, the absence of gonads severely affects FSH sialylation; androgen administration is able to restore the characteristics observed under physiological conditions. The expression of ST6 beta-galactoside alpha-2,6-sialyltransferase 1 is hormonally regulated in the male rat; it decreases after short periods of castration but increases markedly at longer periods of androgen deprivation. Although ST3 beta-galactoside alpha-2,3-sialyltransferase 3 is expressed in the male rat pituitary it is not influenced by changes in the endocrine milieu. The oligosaccharide structure of FSH has an impact on the Sertoli cell endocrine activity. In more advanced stages of Sertoli cell maturation, both sialylation and complexity of the oligosaccharides are involved in the regulation of inhibin B production; moreover, FSH glycoforms bearing incomplete oligosaccharides may enhance the stimulatory effect exerted by gonadal growth factors. In this review, we discuss available information on variation of FSH glycosylation and its hormonal regulation under different physiological and experimental conditions, as well as the effect on Sertoli cell endocrine activity.

Intracellular Follicle-Stimulating Hormone Receptor Trafficking and Signaling

Models of G protein-coupled receptor (GPCR) signaling have dramatically altered over the past two decades. Indeed, GPCRs such as the follicle-stimulating hormone receptor (FSHR) have contributed to these new emerging models. We now understand that receptor signaling is highly organized at a spatial level, whereby signaling not only occurs from the plasma membrane but distinct intracellular compartments. Recent studies in the role of membrane trafficking and spatial organization of GPCR signaling in regulating gonadotropin hormone receptor activity has identified novel intracellular compartments, which are tightly linked with receptor signaling and reciprocally regulated by the cellular trafficking machinery. Understanding the impact of these cell biological mechanisms to physiology and pathophysiology is emerging for certain GPCRs. However, for FSHR, the potential impact in both health and disease and the therapeutic possibilities of these newly identified systems is currently unknown, but offers the potential to reassess prior strategies, or unveil novel opportunities, in targeting this receptor.