Evaluation of rat sperm by flow cytometry: simultaneous analysis of sperm count and sperm viability

Validation of the volumetric flow cytometry for bovine sperm concentration

Sperm concentration is a stronghold of the andrological evaluation and the production of insemination doses. The use of haemocytometers, although considered the gold standard, is difficult to apply in field conditions because it is subjective and time-consuming. The present study was designed to validate the volumetric flow cytometry (volFC) in order to estimate bovine sperm concentration, comparing it with the performances of haemocytometer, NucleoCounter, and flow cytometry with the use of fluorospheres. Compared with other methods, volFC appeared less affected by large dilution of the sample, with similar concentrations calculated in the range of dilution 1:200-1:800. Using volFc the population detected on the basis of morphological criteria and fluorescence of DNA better represents the real concentration of sperm in the sample. The volFC showed high repeatability compared with the haemocytometer (coefficient of variation 1.85% and 4.52%, respectively) and stable performances with cryopreserved samples, with negligible effects of the medium components. The present study showed that volFC is as accurate and precise as other techniques to estimate sperm concentration in bovine fresh and frozen semen, but it is less affected by operative conditions, such as sample dilution. The possibility to quantify sperm functional subpopulations by volFC could potentially implement the study of the relationship between sperm attributes and fertility.

Skin Inflammation and Testicular Function: Dermatitis Causes Male Infertility via Skin-Derived Cytokines

The medical comorbidities including skin diseases are associated with male infertility. The most common cause of male infertility is the inability of testes to produce sperm; however, the influence of persistent dermatitis on testicular function has not been elucidated so far. We investigated the relationship between skin inflammation and impaired sperm production using a spontaneous dermatitis mouse model. We examined the breeding records of dermatitis mice and their wild-type littermates. Sperm count, motility, and viability were analyzed by direct microscopic observation and flow cytometry. In addition, testis and epididymis were histologically examined. Finally, sperm viability was evaluated in another dermatitis mouse model and in wild-type mice in which inflammatory cytokines were intraperitoneally administered. Compared to wild-type littermate mice, the number of children born was lower in mice with dermatitis. The body weight and testis size were decreased age-dependently. In the skin disease group, the sperm count and movement ratio were clearly decreased, and reduced sperm viability was observed. Histological examination revealed the detachment of Sertoli cells and reduced spermatogenesis. The fibrosis of epididymal stroma was severe, and it might affect defective sperm maturation in the epididymis. In addition, this phenomena was reproduced by a hapten applied dermatitis mouse model and the intraperitoneal administration of inflammatory cytokines. Once the skin is inflamed, inflammatory cytokines are produced and released, which may affect testicular and sperm function. Additional studies are needed to determine the relationship between male infertility and severe dermatitis in human.

A Flow Cytometric Method for Rapid Determination of Sperm Concentration and Viability in Mammalian and Avian Semen

A new flow cytometric method has been developed to rapidly determine sperm concentration and viability in semen from bulls and boars. Sperm viability was determined on the basis of staining with SYBR-14 and propidium iodide (PI), and this allowed detection of live (membrane-intact) sperm, dying (moribund) sperm, as well as dead cells. Fluorescent microspheres (beads) were used to determine sperm concentration. The use of SYBR-14 at 50 nM and PI at 12 micro M in combination with the FACSCount diluent in the counting tubes resulted in a uniform staining after 2.5-5 minutes at room temperature. Reagent staining was reproducible enough to allow subsequent semiautomated analysis of data using Attractors software. In experiment 1, this method was used to analyze semen from boars, rams, rats, rabbits, humans, and turkeys. In experiment 2, Attractors analysis was performed by the FACSCount AF flow cytometer, and sperm concentration determination with this system was compared with results obtained by a spectrophotometer and an electronic cell counter, which is routinely used by bull artificial insemination centers. When compared to microscopic counting in a hemocytometer, the FACSCount AF flow cytometer was two and four times more accurate than the spectrophotometer and the electronic cell counter, respectively. In addition, the FACSCount AF flow cytometer determined both sperm concentration (coefficient of variation 3.3%) and sperm viability (coefficient of variation 0.7%) with high precision.

Is flow cytometry really adapted to the determination of sperm concentration?

It has been reported that flow cytometry can be used as a reference procedure to determine sperm concentrations in quality control schemes in andrology laboratories, but there are no convincing quality control data. To understand comprehensively whether flow cytometry can be used to determine sperm concentration, sperm concentrations of 85 human semen samples were detected using three different methods, namely flow cytometry, computer-assisted semen analysis (CASA) and manual counting with a cell-VU chamber. The bead concentrations of both low [(18+/-2.5)x10(6)/mL] and high [(35+/-5)x10(6)/mL] pre-calibrated standard latex bead solutions were also determined with flow cytometry. The results showed that bead concentrations of both low and high pre-calibrated standard latex bead solutions counted five times with flow cytometry were (21.37+/-0.85)x10(6)/mL and (45.95+/-1.76)x10(6)/mL, respectively. Coefficient variances (CVs) and relative errors (REs) were 4%, 15.51% and 3.84%, 31.3% for low and high latex bead solutions, respectively. The overall correlation between values measured with flow cytometry and values measured with the cell-VU chamber and the CASA system was significant. However, flow cytometry overestimated the sperm concentration by 109% compared to the results with the cell-VU chamber. Moreover, for the azoospermic samples analysed, the sperm concentration was estimated at 0.12 (range from 0.04 to 0.24)x10(6)/mL. In conclusion, the data demonstrated that flow cytometry can result in an overestimation of both bead counting and sperm concentration, suggesting that flow cytometry is an inappropriate method for sperm counting, especially in the case of azoospermia.

Effect of chronic treatment with three varieties of Lepidium meyenii (Maca) on reproductive parameters and DNA quantification in adult male rats

The aim of this study was to evaluate the chronic effect of different varieties of Lepidium meyenii (Red Maca, Yellow Maca and Black Maca). Male rats were treated by gavage with aqueous extract of each variety of maca equivalent to 1 g hypocotyl kg(-1) body weight (BW) for 84 days. At the end of the treatment, daily sperm production (DSP), epididymal sperm count (ESC) and sperm count in vas deferens (SCVD) were assessed. In addition, testis DNA quantification was also determined. Any toxic effect was assessed in liver and spleen by histological studies. The results indicate that Yellow Maca and Black Maca improved ESC and that three varieties of maca increased the SCVD without affecting DSP. Moreover, testis DNA levels were not affected by treatment with any of the three varieties of maca. Histological picture of the liver in animals treated with the three varieties of maca was similar to that observed in controls. In conclusion, Yellow and Black Maca increased epididymal sperm count after 84 days of treatment without affecting DSP. Maca seems to act as a modulator of sperm count at the reproductive tract level.

Discrepancies in the determination of sperm concentration using Bürker-Türk, Thoma and Makler counting chambers

Determination of sperm concentration by use of a haemocytometer or counting chamber is an important step in semen evaluation and is also used for calibration or validation of instruments. Three experiments were carried out to determine the precision and accuracy of the Makler chamber, the Thoma haemocytometers (50 and 100 microm deep, TH-50, TH-100) and the Bürker-Türk (BT) haemocytometer. The first experiment confirmed that precision in sperm count by use of the haemocytometers (TH-50 and BT) can be increased if a higher number of sperm are counted. In contrast, the precision of the Makler chamber was relatively unaffected by the number of sperm counted and the coefficient of variation for this chamber was significantly (P < 0.05) higher than for the two haemocytometers. Experiment 2 confirmed the low precision of the Makler chamber and also showed that the TH-50 haemocytometer underestimated sperm concentration by approximately 25% in comparison to the Makler chamber and the BT haemocytometer. Experiment 3 demonstrated a slight underestimation of sperm count by the TH-100 haemocytometer in comparison to the BT haemocytometer, but both haemocytometers yielded acceptable precision (coefficients of variation were 10.4% and 9.4%, respectively). In comparison, the precision of the Makler chamber was significantly poorer (coefficient of variation 18.6%). When used for validation of a flow cytometric method which determines sperm concentration, the Makler chamber caused a higher degree of scattering of the points around the regression line than when the flow cytometric method was validated against the BT haemocytometer. It thus appears that the poor precision of the Makler chamber also affects the accuracy. It is concluded that duplicate counts by at least two technicians is recommended to achieve high precision but, that particular caution should be exerted with regard to the precision and accuracy of the used counting device.

Evaluation of mitochondrial function and membrane integrity by dual fluorescent staining for assessment of sperm status in rats

Dual fluorescent staining (DFS) with calcein acetoxy methyl ester (CAM), which labels the cellular esterase activity that is a major component of energy metabolism in cellular mitochondria, and with ethidium homodimer-1 (EthD-1) was used to evaluate mitochondrial function and membrane integrity in rat spermatozoa. The spermatozoa stained by DFS could be classified into three different populations microscopically when excited at 490 nm after 60 min incubation. 1) Spermatozoa, which were stained with CAM alone and had maintained either mitochondrial function or membrane integrity, were identified as live during incubation. 2) Spermatozoa, which were stained with EthD-1 alone and had lost either mitochondrial function or membrane integrity, were identified as already dead at the beginning of incubation. 3) Spermatozoa, which were stained with both CAM and EthD-1 and had maintained mitochondrial function with membrane breached, were identified as having died during incubation. Two toxicological tests, an in vitro triton X-100 experiment and an in vivo nitrobenzene experiment, were done. All spermatozoa were immobilized and lost either mitochondrial function or membrane integrity by 1.0% triton X-100 treatment. Almost no motile sperm were found at 0.1% in the triton X-100 group and in the groups treated with 60 and 40 mg/kg/day of nitrobenzene, and these spermatozoa maintained their mitochondrial function but had their membrane breached. In conclusion, the DFS procedure, which uses CAM and EthD-1, can clearly and visually identify the population of viable and dead spermatozoa simultaneously by fluorescence microscopy in rats. This is a useful technique to characterize sperm status, which is determined by the mitochondrial function assessed by CAM and membrane integrity evaluated by EthD-1.

Fluorescent probes and flow cytometry to assess rat sperm integrity and mitochondrial function

Fluorescent assessment of cellular integrity and mitochondrial function by flow cytometry can provide a rapid and precise means of determining the functional status of large numbers of spermatozoa. In the present study, rat sperm viability was assessed with SYBR-14 and PI and sperm mitochondria were differentially labeled with JC-1. Sperm samples of variable viability were prepared using varying proportions of fresh and frozen spermatozoa. SYBR-14 stained sperm correlated well with expected sperm viability (r = 0.98). Motile sperm stained with JC-1 appeared orange in the midpiece indicating a high mitochondrial membrane potential whereas immotile sperm with a low membrane potential stained green. The percentage of spermatozoa staining orange was highly correlated (r = 0.99) with expected sperm viability. Flow cytometry using specific fluorescent probes is a useful technique for detecting changes in rat sperm plasma membrane integrity and mitochondrial function in large numbers of spermatozoa.

A C-terminal-truncated PrP isoform is present in mature sperm

PrP(C), the normal isoform of the prion component PrP(Sc), is a 33-35-kDa glycophosphatidylinositol-anchored glycoprotein expressed in the plasma membrane of many cells and especially in the brain. The specific role of PrP(C) is unknown, although lately it has been shown to bind copper specifically. We show here that PrP(C) is present even in mature sperm cells, a polarized cell that retains only the minimal components required for DNA delivery, movement, and energy production. As opposed to PrP(C) in other cells, PrP in ejaculated sperm cells was truncated in its C terminus in the vicinity of residue 200. Sperm PrP, although membrane-bound, was not released by phosphatidylinositol phospholipase C as well as not localized in cholesterol-rich microdomains (rafts). Although no infertility was reported for PrP-ablated mice in normal situations, our results suggest that sperm cells originating from PrP-ablated mice were significantly more susceptible to high copper concentrations than sperm from wild type mice, allocating a protective role for PrP in specific stress situations related to copper toxicity. Since the functions performed by proteins in sperm cells are limited, these cells may constitute an ideal system to elucidate the function of PrP(C).