Identification of suitable combinations of in vitro sperm-function test for the prediction of fertility in buffalo bull

The present study assessed sperm functional characteristics in the frozen-thawed semen of buffalo bulls and estimated their relationship with field fertility. Frozen semen samples from three different freezing operations each from nine Murrah buffalo bulls were used for the assessment of different sperm functions related to fertilizing potential. Bulls were classified into high (n = 2), medium (n = 5), and low (n = 2) fertile based on adjusted field fertility. The sperm functions estimated included membrane integrity using carboxyfluorescein diacetate-propidium iodide, acrosome reaction status using fluorescein isothiocyanate peanut agglutinine, status of apoptosis using Annexin-V, protamine deficiency using Chromomycin A₃, membrane stability using Merocyanine 540 and lipid peroxidation status using 4, 4-difluoro-4-bora-3a, 4a-diaza-s-indacene. The relationship between the proportion of live acrosome-intact spermatozoa and fertility was positive and significant (r = 0.59; P = 0.001). The proportion of moribund spermatozoa showed a significantly negative correlation with fertility (r = -0.50; P = 0.008). Similarly, the relationship of spermatozoa with unstable membrane (r = -0.51; P = 0.007), necrotic (r = - 0.42; P = 0.028), early necrotic (r = -0.42; P = 0.031), and apoptotic spermatozoa (r = -0.39; P = 0.046) with bull fertility was negative and significant. The correlation between the protamine-deficient spermatozoa and fertility was negative, but not significant. Among different combinations of tests, live acrosome-intact spermatozoa and lipid peroxidation status of spermatozoa revealed high positive correlation with buffalo bull fertility (adjusted R² = 0.73, C[p] = 0.80). These preliminary findings may help in developing tools for assessing fertility of buffalo bulls, once validated in more animals.

Assessment of sperm damages during different stages of cryopreservation in water buffalo by fluorescent probes

The present study was designed to investigate the sperm damages occurring in acrosome, plasma membrane, mitochondrial activity, and DNA of fresh, equilibrated and frozen-thawed buffalo semen by fluorescent probes. The stability of sperm acrosome and plasma membrane stability, mitochondrial activity and DNA status were assessed by fluorescein conjugated lectin Pisum sativum agglutinin, Annexin-V/propidium iodide, JC-1 and TUNEL assay, respectively, under the fluorescent microscope. The damages percentage of acrosome integrity was significantly increased during equilibration and freezing-thawing process. The stability of sperm plasma membrane is dependent on stability of phosphatidylserine (PS) on the inner leaflet of plasma membrane. The frozen-thawed sperm showed externalization of PS leading to significant increase in apoptotic, early necrotic and necrotic changes and lowered high mitochondrial membrane potential as compared with the fresh sperm but all these parameters were not affected during equilibration. However, the DNA integrity was not affected during equilibration and freezing-thawing procedure. In conclusion, the present study revealed that plasma membrane and mitochondria of buffalo sperm are more susceptible to damage during cryopreservation. Furthermore, the use of fluorescent probes to evaluate integrity of plasma and acrosome membranes, as well as mitochondrial membrane potential and DNA status increased the accuracy of semen analyses.

Royal jelly supplementation in semen extender enhances post-thaw quality and fertility of Nili-Ravi buffalo bull sperm

Two experiments were conducted to evaluate the effect of royal jelly (RJ) on post-thaw sperm quality, in vitro and in vivo fertility rate of cryopreserved buffalo bull sperm. The semen was collected from three mature regular donor buffalo bulls, ejaculates were pooled and semen evaluated initially. In Experiment 1, the ejaculates were extended in tris-citric acid diluter supplemented with different RJ concentrations (0, 0.05, 0.1, 0.2, 0.3 or 0.4%). The diluted semen was cooled to 4°C, packaged into 0.5 mL straws and frozen using standard procedure. The straws were thawed and assessed for sperm progressive motility, viability, plasma membrane, acrosome, and chromatin integrity. The results indicated that sperm progressive motility was significantly greater (P<0.05) in 0.05, 0.1, 0.2 and 0.3% RJ than 0.4% RJ supplemented and control groups. The sperm viability, plasma membrane and acrosome integrity were significantly improved (P<0.05) in 0.1% RJ supplemented group the compared to other treatment groups. In Experiment 2, cryopreserved sperm with 0.1% RJ supplementation and control (without RJ supplementation) were used to observe the in vitro fertilizing potential and in vivo fertility. In vitro fertilization method was applied to assess the cleavage rate; whereas, AI was performed in buffalo during in vivo fertility trial. The buffaloes were inseminated 12h after standing estrus and pregnancy diagnosis was performed through ultrasonography. The results revealed that the cleavage rate was higher (P<0.05) in 0.1% RJ as compared to control group. However, the pregnancy rate was similar (P>0.05) between 0.1% RJ supplemented and control groups. It is concluded that supplementation of RJ in freezing extender can improve the cryosurvival rate and in vitro fertilizing capacity of buffalo bull sperm.

Development and validation of most efficient RNA isolation method from buffalo bull spermatozoa

BACKGROUND

Being highly fragmented and low in concentration, isolation of good quality RNA from sperm cells is a big challenge. Attempts have been made to evaluate various sperm RNA isolation methods from purified buffalo bull sperm cells.

METHODS

Both, non-membrane and membrane-based methods have been evaluated for isolating RNA from Murrah buffalo sperms and compared for their respective efficacies. The traditional TRIzol, TRIzol-heat lysed (H-TRIzol) and cocktail of TCEP-RLT lysis buffer (Qiagen RNeasy mini kit)-TRIzol (C-TRIzol) based isopropanol isolation methods have been evaluated.

RESULTS

H-TRIzol yielded best results among conventional methods. The combined T-RLT RNA isolation protocol yielded best quality and quantity compared to other membrane-based methods, due to high lytic property of cocktail of lysis reagents, necessary for complete breakdown of sperm membrane and RNA binding membrane for RNA isolation. Combined lysis performed by treatment with RLT-T and T-RLT differing in order of reagents used were also evaluated. T-RLT combination giving better results compared to RLT-T due to high gDNA contamination and membrane clogging in later protocol steps.

CONCLUSION

Overall, in terms of total RNA quantity and quality per million spermatozoa, the heat-lysed TRIzol method (H-TRIzol) performs best among RNA separation techniques employed and is also quite easy to perform. This comparative evaluation of sperm RNA isolation protocols can be useful in deciding the best protocol for isolation of good quality and high concentration sperm RNA from buffalo semen, for transcriptome and other downstream studies.

Analysis of chromatin integrity and DNA damage of buffalo spermatozoa

This study was conducted to determine chromatin integrity and DNA damage by DNA electrophoresis and comet assays of buffalo fresh and frozen semen. Semen samples were collected from four buffalo bulls and evaluated after freezing for semen motility, viability, sperm abnormalities, chromatin integrity and DNA damage. A significant variation was found in semen parameters after thawing. Highly significant differences (P<0.001) in chromatin integrity were observed between fresh and frozen semen. For the fresh semen, there was no significant difference between the bulls for chromatin integrity; however, a significant variation (P<0.05) was detected in their frozen semen. No DNA fragmentation was observed by agarose gel electrophoresis. The percentage of sperm with damaged DNA detected by comet assay differed significantly between fresh and frozen semen. A significant negative correlation was recorded between motility and DNA damage (r=-0.68, P<0.05). Sperm abnormalities and DNA fragmentation were significantly positively correlated (r=0.59, P<0.05). In conclusion, DNA damage evaluation can provide reassurance about genomic normalcy and guide the development of improved methods of selecting spermatozoa with intact DNA to be used in artificial insemination.