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PubMed1989

Membrane remodelling during sperm maturation in the epididymis.

Identification of molecules or factors on spermatozoa that are involved in the recognition and binding to the zona pellucida of the egg is one of the central problems in current research on mammalian fertilization. This information is important, not just from the standpoint of scientific interest, but also for treatment of male infertility and design of future contraceptive technology. One of the most informative approaches to solving this puzzle has been to study the maturation of spermatozoa in the epididymis. The gradual development of motility and zona-binding capacity by spermatozoa after they leave the testis affords an opportunity to investigate what distinguishes a fertile from an infertile spermatozoon and what mechanisms are involved in the transformation from one state to the other. This chapter has reviewed some of the current information on sperm maturation in the epididymis and attempted to correlate it with concepts emerging from in vitro fertilization experiments. Emphasis has been placed on mechanistic aspects of maturation changes to the sperm plasma membrane, not only because in many species it is the surface membrane that encounters the zona and it is therefore likely to be the site of potential recognition molecules, but also because the plasma membrane influences many intracellular events and has a bearing on the maturation of the nucleus and axoneme as well. An example of the latter is shown by the induction of motility in demembranated testicular sperm by the addition of ATP and Mg2+ (Mohri and Yanagimachi 1980; White and Voglmayr 1986). This suggests that the motor apparatus for motility is essentially present in immature spermatozoa and that one of the requirements for it to become fully operative are subtle alterations to the permeability properties of the plasma membrane. A similar mechanism may also be true of the maturing sperm nucleus to which only passing reference has been made here. Very little is known about this aspect of sperm maturation beyond the increasing stabilization of the nucleoprotein by formation of disulphide bonds (Bedford 1975). The fact that isolated heads from immature spermatozoa fail to form pronuclei if injected directly into the egg (Uehara and Yanagimachi 1977) may explain, in part, the high embryonic mortality observed when not fully mature spermatozoa are induced to fertilize eggs (Orgebin-Crist et al. 1975). Thus maturation events within the nucleus are just as important as those on the surface membrane.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1998

Properties of a novel pH-dependent Ca2+ permeation pathway present in male germ cells with possible roles in spermatogenesis and mature sperm function.

Rises of intracellular Ca2+ ([Ca2+]i) are key signals for cell division, differentiation, and maturation. Similarly, they are likely to be important for the unique processes of meiosis and spermatogenesis, carried out exclusively by male germ cells. In addition, elevations of [Ca2+]i and intracellular pH (pHi) in mature sperm trigger at least two events obligatory for fertilization: capacitation and acrosome reaction. Evidence implicates the activity of Ca2+ channels modulated by pHi in the origin of these Ca2+ elevations, but their nature remains unexplored, in part because work in individual spermatozoa are hampered by formidable experimental difficulties. Recently, late spermatogenic cells have emerged as a model system for studying aspects relevant for sperm physiology, such as plasmalemmal ion fluxes. Here we describe the first study on the influence of controlled intracellular alkalinization on [Ca2+]i on identified spermatogenic cells from mouse adult testes. In BCECF [(2',7')-bis(carboxymethyl)- (5, 6)-carboxyfluorescein]-AM-loaded spermatogenic cells, a brief (30-60 s) application of 25 mM NH4Cl increased pHi by approximately 1.3 U from a resting pHi approximately 6.65. A steady pHi plateau was maintained during NH4Cl application, with little or no rebound acidification. In fura-2-AM-loaded cells, alkalinization induced a biphasic response composed of an initial [Ca2+]i drop followed by a two- to threefold rise. Maneuvers that inhibit either Ca2+ influx or intracellular Ca2+ release demonstrated that the majority of the Ca2+ rise results from plasma membrane Ca2+ influx, although a small component likely to result from intracellular Ca2+ release was occasionally observed. Ca2+ transients potentiated with repeated NH4Cl applications, gradually obliterating the initial [Ca2+]i drop. The pH-sensitive Ca2+ permeation pathway allows the passage of other divalents (Sr2+, Ba2+, and Mn2+) and is blocked by inorganic Ca2+ channel blockers (Ni2+ and Cd2+), but not by the organic blocker nifedipine. The magnitude of these Ca2+ transients increased as maturation advanced, with the largest responses being recorded in testicular sperm. By extrapolation, these findings suggest that the pH-dependent Ca2+ influx pathway could play significant roles in mature sperm physiology. Its pharmacology and ion selectivity suggests that it corresponds to an ion channel different from the voltage-gated T-type Ca2+ channel also present in spermatogenic cells. We postulate that the Ca2+ permeation pathway regulated by pHi, if present in mature sperm, may be responsible for the dihydropyridine-insensitive Ca2+ influx required for initiating the acrosome reaction and perhaps other important sperm functions.

Acrosome↗
PubMed1979

An evolutionary view of the male reproductive tract and sperm maturation in a monotreme mammal--the echidna, Tachyglossus aculeatus.

In exploring the evolution and adaptive significance of epididymal function, we have studied the male excurrent duct and spermatozoa of a monotreme mammal--the echidna. Sperm maturation in the echidna excurrent duct appears simpler than that in most therians examined. Furthermore, neither the duct nor the spermatozoa of the echidna display specific therian characteristics; they bear a much closer resemblance to those of non-passerine birds. The echidna spermatozoon is filiform, the sperm tail has no distinctive features, and the anterior seventh of the undulating nucleus is covered by a modest acrosome. Immediately behind this a restricted apposition between plasma membrane and nuclear envelope constitutes a post-acrosomal ring. This is evident also in some reptiles and marsupials, whereas in Eutheria such a membrane association appears as the posterior ring at the base of the sperm nucleus. Maturation of spermatozoa in the Wolffian duct of the echidna appears to be expressed only in a changing capacity for motility and in loss of the cytoplasmic droplet. Neither surface, structural nor acrosomal changes that characterize sperm maturation in therian mammals have been detected in maturing echidna spermatozoa. The echidna duct displays little of the regional complexity of the epithelium that typifies this duct in the Theria. Of five regions distinguishable on the basis of epithelial morphology, the first two appear to be counterparts of efferent ducts by virtue of a low columnar, partially ciliated epithelium. The tall pseudo-stratified Golgi-rich epithelium of the major portion of the duct broadly resembles that of the therian epididymis, but it displays only two structurally distinguishable regions, the more distal being the site of a dense luminal secretion. The foamy epithelial cells of the fifth and terminal region, characterized by a mass of supra-nuclear vesicles and rough ER, suggest a secretory function that may in some way contribute significantly to the ejaculate, for accessory glands are poorly developed in monotremes. The possibility is considered that the relative complexity of epididymal function and sperm structure in therian mammals could have been determined by evolutionary change in the milieu of the female tract, and/or in the character of the egg vestments that the fertilizing spermatozoon must penetrate.

Animals↗
PubMed2002

Sperm maturity and treatment choice of in vitro fertilization (IVF) or intracytoplasmic sperm injection: diminished sperm HspA2 chaperone levels predict IVF failure.

OBJECTIVE: To reexamine whether low sperm HspA2 ratios (formerly sperm CK-M ratio) are predictive for failure to cause pregnancies by in vitro fertilization (IVF) and to explore whether there are other male or female factors that may be predictive for IVF pregnancy outcome. DESIGN: Retrospective, cohort study. SETTING: University-based IVF program. PATIENT(S): In 119 IVF cycles, three patient groups were studied: 25 men had a <10% sperm HspA2 ratio and a lack of pregnancies (HS <10% group), 50 men had a >10% sperm HspA2 ratio and no pregnancies (HS >10%NP group), and another 44 couples had a >10% sperm HspA2 ratio but did achieve pregnancies (HS >10%P group). INTERVENTION(S): Sperm HspA2 ratio determinations within 1 year of the IVF cycles and analysis of male and female IVF cycle parameters. MAIN OUTCOME MEASURE(S): Sperm HspA2 ratio determinations within 1 year of the IVF cycles and analysis of male and female IVF cycle parameters. RESULT(S): In the three groups, male and female ages, number and maturation level of oocytes, and morphology of embryos were similar. In the HS < 10% group, mean sperm concentration and motility were close to normal, the fertilization and cleavage rates were lower, and cycles without any oocyte fertilization were higher. These parameters were similar in the two HS > 10% groups. The receiver operating characteristic curve in men with sperm HspA2 ratios of <17% (diminished and borderline sperm maturity) provided a cutoff value of 10.84% HspA2 ratio with a 100% positive predictive value for failure to achieve pregnancy, whether the men were oligospermic or normospermic. CONCLUSION(S): HspA2 ratios of <10% in the diminished sperm maturity range predict the failure to cause pregnancies by IVF. Thus, IVF should be bypassed in favor of ICSI. The occurrence of pregnancy with ICSI depends on the maturity of sperm selected, and it may not be as likely as in other indications for ICSI.

Adult↗
PubMedDate not supplied

Contribution of epididymal factors to sperm maturation and storage.

In fertile men, the majority of epididymal spermatozoa acquire the potential to fertilize (assessed with sperm function assays) on passage into the corpus and cauda regions of the epididymis. Although secretions of the epididymal epithelium are clearly important for sperm maturation and survival, their role in this process has yet to be fully determined. Alterations in epididymal sperm membranes may result from the incorporation of protein, sugar and lipid determinants. Most probably, factors of epididymal origin act in concert with constitutional changes to spermatozoa, which together permit full sperm function. Epididymal spermatozoa incubated with epididymal epithelial cell cultures can undergo some maturation in vitro, which can lead to the development of sperm fertilizing capacity. Co-incubations of human sperm with epididymal epithelial cultures, at 37 degrees C with medium replenished every other day, led to 50% of spermatozoa retaining motility after 8 days. In one case, a few spermatozoa survived for 17 days, the inherent maximal survival time of human spermatozoa in situ. An important aspect of coculture experiments is that close interactions between spermatozoa and epithelial cells can be examined in detail. This coculture technique may yield important information related to epididymal sperm maturation and storage.

Animals↗
PubMed2026

Integrating transcriptomics and metabolomics reveals the molecular landscape of sperm maturation driven by regional differentiation in the epididymis of Guizhou-Guiqian semi-fine wool sheep.

Epididymal regionalized differentiation is crucial for sperm maturation. However, little is known about the synergistic remodeling mechanisms of different epididymal segments at the transcriptional and metabolic levels during sexual maturation in ruminants (especially sheep). We investigated the caput, corpus, and cauda epididymidis of pre-pubertal (2-month-old) and post-pubertal (7-month-old) Guizhou-Guiqian semi-fine wool sheep using histology, RNA sequencing, and metabolomics. Post-pubertal tissues exhibited increased luminal diameters, cilia lengths, and abundant cauda spermatozoa. Transcriptomic analysis revealed increasing differentially expressed genes (DEGs) along the caput-corpus-cauda axis (4642, 6103, and 7698 DEGs, respectively). Metabolomics detected 786 unique differentially accumulated metabolites (DAMs). Region-specific analysis showed that in the caput, up-regulated pathways (fructose/mannose metabolism; HK2, ALDOA, HKDC1) provide energy and substrates for initial sperm motility. In the corpus, down-regulated genes associated with extracellular matrix and tight junctions suggested epithelial barrier remodeling to establish an immune-tolerant microenvironment. The cauda specifically up-regulated the pentose phosphate pathway (FBP1, GPI) and glutathione metabolism, maintaining redox homeostasis for long-term sperm storage. Additionally, glycerophospholipid metabolism was enriched across all segments, where PEMT, AGPAT5, and LCAT likely regulate sperm plasma membrane fluidity. In conclusion, during sexual maturation, the caput drives energy metabolism and glycosylation, the corpus establishes immune tolerance, and the cauda maintains antioxidant homeostasis. The glycerophospholipid network throughout the across all epididymal segments synergistically remodels sperm membrane. This study reveals the underlying multi-omics regulatory mechanisms of epididymal functional differentiation, providing a theoretical basis for elucidating the molecular mechanisms of sperm maturation in this breed and for the molecular breeding of early reproductive performance in rams.

Animals↗
PubMed1983

Sperm maturation, fluid transport, and secretion and absorption of protein in the epididymis of the echidna, Tachyglossus aculeatus.

Extratesticular sperm maturation in the echidna mainly occurs in the initial segment of the ductus epididymidis. The process involves the development of motility, migration and loss of the cytoplasmic droplet, a decrease in permeability to Congo red and the formation of sperm bundles. The spermatozoa are supported in the bundles by a matrix of electron-dense material; the bundles are very motile is undiluted samples of luminal fluids. Micropuncture studies of anaesthetized echidnas showed that the ductuli efferentes absorb 74% of the fluid and 46% of the soluble protein that enters them. The initial segment of the ductus epididymidis absorbs 83% of the fluid which enters it, and its secretions increase the concentration of protein in luminal fluid by 107%. Denatured, linear-gradient polyacrylamide gel electrophoresis of micropuncture samples showed that 1 protein (apparent M4 = 100 500) which is not present in blood plasma is present in rete testis fluid, and a glycoprotein which is present in rete testis fluid (apparent Mr = 78500) is absorbed by the ductuli efferentes. Six proteins which are not present in blood plasma are secreted into the initial segment of the ductus epididymidis; 5 are glycoproteins (apparent Mr = 48500, 39000, 32000, 20500 and 19000) and one (apparent Mr = 82500) is not. The most prominent electrophoresis bands corresponded to the glycoproteins with apparent molecular weights of 48500, 20500 and 19000.

Animals↗
PubMed2005

[Primary study on the method for separating mature sperms from human testicular tissue].

This study was aimed to explore a simple and applicable method of separating mature sperms from human testicular tissue for intracytoplasmic sperm injection and embryo transfer. The suspension of human testicular tissue was cultured in 10% human serum albumin and human tubule fluid with different concentrations (0 u/ml; 50 u/ml; 100 u/ml; 150 u/ml; 200 u/ml) of hyaluronidase for 24 h, and then the Percoll gradient centrifugation was processed to separate the sperms; meanwhile the sperms were counted and graded according to their motility. The difference in quality and quantity among the groups and the difference between the groups and the zero-hour culturing group were detected. It was shown that the four hyaluronidase-treated groups contained large quantity and high quality of sperms as compared with the two contrast groups (P<0.01). The groups in the solution of 50 u/ml, 100 u/ml and 150 u/ml concentrations of hyaluronidase had almost the same amount of sperms that displayed higher motility as compared against the sperms in the group treated with 200 u/ml concentration of hyaluronidase (P<0.01). There was no difference between the two contrast groups (P>0.05), or among the groups treated with 50 u/ml, 100 u/ml, and 150 u/ml of hyaluronidase concentration (P>0.05). This method of adopting hyaluronidase with Percoll gradient centrifugation in the process for separating mature sperms from human testicular tissue is applicable. It can increase the quantity and quality of sperms separated from testicular tissue suspensions when adequate concentrations of hyaluronidase is used.

Adult↗
PubMedDate not supplied

Sperm maturation and storage in the male rat after acute treatment with aflatoxin B1.

The effects of acute aflatoxicosis on sperm maturation in the rat were evaluated using sperm GOT, GPT and LDH activities as indices. The levels of these enzymes in sperm undergoing maturation were stable like the sperm populations in the testis and epididymis. Acute aflatoxicosis enhanced corpus epididymal sperm transaminase but not sperm transit.

Aflatoxin B1↗
PubMed1997

Systematic fine-needle aspiration of the testis: correlation to biopsy and results of organ "mapping" for mature sperm in azoospermic men.

OBJECTIVES: This study compares fine-needle aspiration (FNA) and testis biopsy for the ability to detect mature sperm in the testes of azoospermic men. In addition, we introduce the concept of testis "mapping" with FNA and apply it to detect sperm in men with severe testis failure. METHODS: Sixteen patients were evaluated for azoospermia in a university-based infertility clinic. All men had testis biopsies and FNAs from matched testicular sites to assess for the presence of spermatozoa. Adequacy criteria for FNA specimens were strictly defined, and correlative analysis of the two techniques was performed. In addition, a subset of 12 men with nonobstructive azoospermia (NOA) had systematic FNA mapping (more than four FNA sites per testis) to detect mature sperm for potential clinical use. RESULTS: Adequate FNA specimens were obtained in 115 (91.3%) of 126 FNA attempts. Of 34 paired biopsy FNA sites. FNA was seen to be more sensitive than, and equally specific as, testis biopsy for sperm detection. When compared with the biopsy touch imprint, FNA was equally as sensitive and specific. Among men with NOA who underwent FNA mapping, 4 (33%) of 12 had localized "patches" of sperm detected in areas distant from sperm-negative biopsy sites. In 1 case, a pregnancy was achieved with later biopsy and sperm extraction "directed" by previous FNA. CONCLUSIONS: For sperm detection, testis FNA provides equivalent or better information than a testis biopsy. FNA can localize areas of sperm production within the testis and accurately guide sperm extraction procedures in men with NOA.

Biopsy, Needle↗
PubMed1992

Fine structure of spermiogenesis in the coccid insect Aspidiotus perniciosus: late stages of differentiation and structure of the mature sperm bundles.

Spermatids of A. perniciousus are organized into bundles each containing 32 cells. During the process of differentiation, nuclear elongation and chromatin condensation take place. The mature sperm bundles are finally surrounded by the secondary sheath which is composed of a trilaminar membrane. The mature sperm is not differentiated into head, mid piece or tail but has two tapering ends and an electron dense central core. Centrioles, the nuclear membrane, mitochondria and a flagellum appear to be lacking. Microtubules are arranged in a spiral pattern forming the enveloping microtubular sheath.

Animals↗
PubMed2006

An infertile couple suffering from oligospermia by partial sperm maturation arrest: can phytoestrogens play a therapeutic role? A case report study.

We describe the case of a 30-year-old man with severe oligospermia, caused by partial sperm maturation arrest at spermatidic stage, who was given phytoestrogens. The couple had been trying to conceive for 3 years. The woman was normal at the clinical and endocrinological examination. No other parameters except sperm count, motility and morphology were altered in the male subject. Semen analysis was performed at baseline and after 3 and 6 months of therapy, which consisted of phytoestrogens 80 mg/day for 6 months. An additional semen analysis was performed 6 months after the termination of therapy (wash-out period). During the third month semen parameters improved drastically; therefore a reproductive technique (intrauterine insemination) was performed. This treatment resulted in pregnancy, and a healthy baby weighing 3300 g was born. After 6 months of treatment, sperm parameters ameliorated further. Conversely, after the wash-out period, they returned to baseline values. The appealing results strongly suggest a therapeutic role for phytoestrogens in the treatment of oligospermia. However, it is evident that a validation stage and randomized, controlled studies are essential in order to confirm this observation and verify that phytoestrogens can play an important role in male infertility.

Adult↗
PubMed1994

Rat epididymis-specific sperm maturation antigens. I. Evidence that the 26 kD 4E9 antigen found on rat caudal epididymal sperm tail is derived from a protein secreted by the epididymis.

Monoclonal antibody 4E9, which was raised against a partially purified detergent extract of rat caudal epididymal sperm, recognizes the tail of sperm from the cauda, but not from caput epididymidis, as well as epithelial cells in a restricted region of the distal caput/corpus epididymidis and proteins in epididymal fluid from corpus and cauda epididymidis. The antigen is apparently a glycoprotein, since it is retained on a Ricinus communis agglutinin I lectin column. Epididymal fluid antigens have apparent M(rs) of 38-26 kD, whereas the membrane-associated form of the molecule has an M(r) of 26 kD. Immunocytochemical data and Western immunoblot data suggest that the membrane antigen is derived from the fluid antigen, which, in turn, is secreted by the epididymal epithelium. Characterization of the membrane antigen indicates that it is tightly associated with the sperm surface, behaving as though it is an integral membrane protein. The antigen persists on ejaculated sperm.

Animals↗
PubMed1993

Olfactory receptors are displayed on dog mature sperm cells.

Olfactory receptors constitute a huge family of structurally related G protein-coupled receptors, with up to a thousand members expected. We have shown previously that genes belonging to this family were expressed in the male germ line from both dog and human. The functional significance of this unexpected site of expression was further investigated in the present study. We demonstrate that a few dog genes representative of various subfamilies of olfactory receptors are expressed essentially in testis, with little or no expression in olfactory mucosa. Other randomly selected members of the family show the expected site of expression, restricted to the olfactory system. Antibodies were generated against the deduced amino acid sequence of the most abundantly expressed olfactory receptor gene in dog testis. The purified serum was able to detect the gene product (DTMT receptor) in late round and elongated spermatids, as well as in the cytoplasmic droplet that characterizes the maturation of dog sperm cells, and on the tail midpiece of mature spermatozoa. Western blotting further confirmed the presence of a 40-kD immunoreactive protein in the membrane of mature sperm cells. Altogether , these results demonstrate that the main expression site of a subset of the large olfactory receptor gene family is not olfactory mucosa but testis. This expression correlates with the presence of the corresponding protein during sperm cell maturation, and on mature sperm cells. The pattern of expression is consistent with a role as sensor for unidentified chemicals possibly involved in the control of mammalian sperm maturation, migration, and/or fertilization.

Amino Acid Sequence↗
PubMed2002

Sperm membrane modulation by Sapindus mukorossi during sperm maturation.

AIM: To observe the alterations in the biochemical and biophysical changes in the sperm membrane during sperm maturation in male rats treated with the water extract of the fruit pericarp of S. mukorossi. METHODS: Adult male Sprague-Dawley rats were gavaged the aqueous extract of the fruit pericarp of S. mukorossi at a dose of 50 mg/kg/d for 45 days. On day 46, the sperm parameters were observed in different sections of the epididymis and the sperm superoxide dismutase and the lipid peroxidation was determined and compared with the controls. The testis and epididymis were routinely prepared for histological examination under the light microscope. RESULTS: No significant differences in the sperm number and morphology were observed between the control and treated groups. However, a significant inhibition (P<0.05-0.01) of sperm motility in the caput, corpus and cauda regions of the epididymis was seen in the treated group. No significant histopathological changes were found in the testis and epididymis. The important finding was that in the treated animals, the spermatozoa showed an abnormal distribution of the superoxide dismutase activity, being minimum in the caput and maximum in the corpus, which was just opposite to that of the controls. CONCLUSION: The study provides a unique observation where the plant extract alters the sperm membrane physiology without change the testicular and epididymal morphology.

Animals↗
PubMed2003

The effects of dietary vitamin B12 deficiency on sperm maturation in developing and growing male rats.

To evaluate the role of vitamin B12 on spermatogenesis, the effects of dietary vitamin B12 deficiency on sperm maturation in developing rat fetuses and young growing rats were examined. The vitamin B12-deficient diet was given to all the animals for three different periods: whole period (gestation to mature), gestation period (gestation to weaning), or immature period (3-12 weeks postnatal). Sperm examination revealed that the sperm count was markedly lower in male progeny (F1) that were vitamin B12-deficient during the whole period. In addition, a significantly higher number of abnormal sperm, such as tailless and amorphous sperm, was observed. In male rats that were vitamin B12-deficient during the immature period, the incidence of abnormal sperms was 14.4% and 4.8% for tailless and short tail, respectively. The motion rates, such as path velocity and straight line velocity, were decreased to 20-40% of the control value in rats that were vitamin B12-deficient both during the whole and gestation periods. However, no effects of vitamin B12 deficiency on sperm motility were observed during the immature and mature periods. From these findings, we suggest that dietary vitamin B12 deficiency during pregnancy may induce irreversible damage in the germ cells of embryos and affect the maturation of spermatozoa.

Animal Feed↗
PubMedDate not supplied

Role of exosomes in sperm maturation during the transit along the male reproductive tract.

Even tough differentiated spermatozoa are unable of transcriptional or translational activity; the sperm surface undergoes major modifications in macromolecules composition during the transit along the male reproductive tract. This is the result of sequential, well orchestrated interactions between the male reproductive tract secretions and the transiting male gamete. This is particularly true when spermatozoa transit along the epididymis. The epididymis is a long convoluted tubules in which the spermatozoa leaving the testis have to transit. The unraveled epididymal tubule can be as long as 80 m in stallion, and the transit time of spermatozoa is of 3-12 days depending on the species. The epididymis is usually divided in three segments: the caput (proximal part), the corpus, and cauda. While the cauda epididymides acts as a sperm reservoir, the caput and corpus are responsible for sperm maturation. This means that, under androgen control, the epididymal epithelium secretes proteins that will interact sequentially with sperm surface. Some of the sperm proteins acquired during maturation along the excurrent duct behave as integral membrane proteins. In fact, some epididymal originating proteins are glycosylphosphatidylinositol (GPI)-anchored to the sperm plasma membrane. Our laboratory has shown that some of these proteins are secreted in an apocrine manner by the epididymal epithelium and are associated to exosomes, called epididymosomes. Epididymosomes are rich in sphingomyelin and are characterized by a high cholesterol/phospholipids ratio. Many proteins are associated to epididymosomes, some of which are selectively transferred to spermatozoa during the epididymal transit. We have identified some of these exosomes associated proteins transferred to the maturing spermatozoa. These include two enzymes involved in the polyol pathway: an aldose reductase and a sorbitol dehydrogenase. A cytokine named MIF (macrophage migration inhibitory factor) is another protein associated to exosomes who is transferred to spermatozoa during the epididymal transit. We hypothesized that both the polyol pathway and MIF secreted in an apocrine fashion by the epididymal epithelium modulate sperm motility during the transit along the male reproductive tract. Finally, P25b, belonging to a family of sperm surface proteins (P26h/P34H) necessary for the binding to the surface of the egg, is also acquired through the interaction between epididymosomes and the male gamete. In vitro studies have defined the conditions of protein transfer when epididymal spermatozoa are co-incubated with epididymosomes. The transfer of selected proteins to specific membrane domains of spermatozoa is saturable, temperature and pH-dependent, being optimal at pH 6.5. The presence of zinc in the incubation medium, but not of calcium neither magnesium, significantly increases the efficiency of protein transfer. These results show that exosomes play a role in sperm epididymal maturation which is an essential event to produce male gametes with optimal fertilizing ability.

Cytoplasmic Vesicles↗
PubMed1986

The non-mature sperm cells: evaluation of surface markers and interaction in in vitro cultures.

The ejaculated human seminal plasma cells may be classified into subpopulations on the basis of spermatogenesis or biological features. In this paper we divided these cells into two main groups: one of them is obviously predestinated to fertilization as mature sperm cells, viable and motile ejaculated cells. Second group of unknown biological role is very heterogeneous; simplifying its variety we call them non-mature sperm cells. Morphological studies by electron microscopy and evaluation of surface markers of these cells by monoclonal antibodies did not reveal any known biological features or markers for cells of leukocyte origin. They did not express any antigenic determinants of HLA system and they did not react with autologous or allogeneic lymphocytes.

Antibodies, Monoclonal↗