Abstract resulted in an increase in number

Abstract

     
This work was carried out to evaluate  the quality and developmental competence of
the in vitro produced buffalo embryos under different culture conditions as co
culture with cumulus cell and buffalo oviductal cell monolayers (BOCM) or
supplementation of lactoferrin to the culture medium. Oocytes were aspirated
and classified according to their quality into grades 1, 2, 3. Oocytes were matured
in TCM 199 for 24 hrs at 38.5°C in a CO2 incubator. After
maturation, oocytes were in vitro fertilized by frozen thawed sperms capacitated in vitro by caffeine at final concentration 2
million sperm /ml.  The sperm-oocytes were incubated in TALP
medium for 24 hrs. Fertilized oocytes were cultured in  Cell free media or co cultured with cumulus
cell or oviductal cell monolayers (EXP1), CR1aa with addition of   lactoferrin with different concentrations (EXP2) inside CO2  incubator 
with 5% CO2  at
38°C.  Addition of BOCM  to culture media resulted in a significant
increase  in morula and blastocyst
compared with cell free media and media with cumulus cell monolayer and also resulted
in a significant increase in number of  cells
and mitochondrial function of in vitro produced buffalo embryos. Addition of lactoferrin by concentration 50µg/ml to culture media resulted in a significant increase   in rates of cleavage, morula and blastocyst compared
with control or other concentrations and also resulted in an increase in number
of cell and mitochondrial function of in vitro produced buffalo embryos. It
could be concluded that, addition of oviductal cells (monolayer) or lactoferrin
to culture medium significantly improved the quality of in vitro produced
buffalo embryos.

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Key words: In vitro fertilization, Buffalo embryos,
BOCM, Lactoferrin, Quality.

Introduction

     Buffaloes  represent 
a  vital part of the agricultural
economy in Egypt. But, they have lower fertility rate  which may be attributed to lower follicular
number in the ovary, low response to superovulation  and higher number of atretic follicles.
Recently efforts are established  to
enhance the reproductive efficiency  of
these animals using reproductive biotechnology such as in vitro fertilization
(IVF) technology and  embryo transfer
(ET) (1).

       Reproductive biotechnologies as IVEP and ET may
enhance genetic improvement and are needed as a tool to obtain large number of
offspring of superior animals. So, it has been expected that there is a
positive relationship between the use of these technologies and production (2).
Buffalo embryos can be cultured under different conditions and it is indicated
that the culture system and the composition of the medium influence embryo
quality (3). Some studies have been demonstrated that
the quality of the oocyte is the most important factor that influences the
blastocyst rate and that the in vitro culture medium in which the embryos are
cultured is the most important determinant of the quality of blastocyst (4). Several authors favour 
the co-culture of embryos with cumulus and oviductal epithelial cells  or with cell lines as Buffalo rat liver (BRL) for production of  buffalo embryos. It was demonstrated that cellular
co culture produces specific embryo trophic factors which improve the in
vitro embryo development (1).

     The
evaluation of quality of embryo is one of the most critical factors, which
determine the output of embryo transfer. Its significance is attributed to the
essential relationship between embryo quality and its developmental stage (5). Thus, this study contributed to study the effect of cellular
co culture (cumulus or oviductal cells monolayers) and lactoferrin additives to
improve  the quality of in vitro produced
buffalo embryos.

Materials and methods

Oocytes recovery:

     
Ovaries were collected within a few minutes after the slaughter of the
animals from Bahteem slaughter house. They were put in a well-sealed container
containing physiological saline and traces of Streptomycin and Penicillin at a
temperature 28-33°C. Oviducts also were dissected from the mesosalpinix.

 

     
Transportation of the ovaries and oviducts to the laboratory occurred within
2 hrs from slaughtering of buffalo,  then
 washed in warm physiological saline
several times at 37°C   until obtaining
clear saline and put in water bath at 37 °C during collection of oocyte (6). Before oocytes recovery, drying of the  ovaries with sterile towel paper was necessary.
Aspiration of oocytes from follicles (2-8mm) carried out by using a needle of 18
gauge attached to a 10 ml plastic syringe containing few Millis of warmed
aspiration medium (7). The examination and
classification of recovered oocytes occurred according to their quality into:
grade 1 (good), 2 (fair), 3 (poor) (8).

In vitro maturation of oocytes:

    Washing
of selected oocytes three times in warmed aspiration medium should be applied  and finally washing  by IVM medium before their  transfer to IVM medium. Oocytes were cultured
in groups (5–15 oocytes) in 50 µl of  IVM
medium under paraffin oil in a CO2 incubator (5% CO2 and
90–95% relative humidity) at 38.5°C for 
24 hrs (7).

In vitro fertilization:

       
Partial denudation of the cumulus cells surrounding the oocytes should
be applied   to facilitate penetration of the sperm cells
to the oocytes. Washing of  oocytes two
times in warmed IVF medium was very necessary.  Microdroplet (100µl) of F-TALP medium
containing BSA and caffeine with 2 million sperm/ ml was prepared to
accommodate 10 oocytes. Co-incubation of sperm with oocyte was carried out in a
humidified environment with 5% CO2 and 38.9°C temperature for 24 hrs
(9).

In vitro culture of fertilized oocytes:

    
Washing of oocytes four times in culture medium should be applied  before their 
transfer to the  in vitro culture
medium. Oocytes were transferred to the in vitro culture medium. In vitro
embryo culture was applied  inside
incubator with 5% CO2 at 38°C humidified air.

 

 

Experimental design:

1- Influence of monolayer on the quality
and in vitro produced buffalo embryos development (EXP1):

Fertilized oocytes were cultured in:

a. Cell free media (CR1aa) and Cellular
media by co-cultured in (Granulosa cells monolayers (GCM) and  Bovine oviductal cell  monolayers 
(BOCM)).

2- Influence of  lactoferrin on the quality and in vitro produced
buffalo embryos development (EXP 2):

   
Fertilized oocytes were cultured in CR1aa with addition of lactoferrin
with different concentrations of 10, 20, 50 and 100 µg /ml.   The cleavage rate was observed after the
begining of in vitro culture by 24 hrs. The development of in vitro produced
embryo was observed 7 to 9 days of in vitro culture.

Evaluation of in vitro produced embryos:

1.      Morphometric
evaluation:

      The evaluation of embryo quality is
applied under a stereomicroscope according to morphological criteria of in
vitro produced embryos. The most important criteria during the morphological
evaluation of embryos include damage and fracture of the zona pellucida, shape,
size, colour and the number of damaged blastomeres and the presence of granules
in the subvitelline space (5).

 

2.      Nuclear
Staining with Hoechst 33342:

Preparation of Embryos:

      Embryos were removed from culture medium and were
washed 2 times in 100 ?l of phosphate buffer saline containing 1 mg/ml
polyvinyl pyrrolidone.  The embryos were
fixed in 100 ?l of paraformaldehyde solution for 1 h at room temperature. Embryos
were washed in 100 ?l phosphate buffer saline / polyvinyl pyrrolidone for 3
times.

Staining the Embryo:

  
Staining should be carried out with dimmed lights.  Embryos were transfered to a 50 ?l of working
solution.  The cells were stained for 10
minutes. The embryos were washed two times by using 100 ?l of phosphate buffer
saline – polyvinyl pyrrolidone.

Mounting Embryos to Slides:

     Clean
slides were prepared by putting them in a 1:10 poly-L-lysine solution for few
minutes. They were allowed to dry.  Embryos
were transferred to a slide coated with poly-L-lysine and embryos were allowed
to dry for 20 minutes at room temperature. 
Cover slip was put over the slide and was allowed to dry for 2 hrs in a
dark place. The cells  were counted under
the fluorescent microscope with ultraviolet (UV) filter. Nuclei had blue color
(10).

3. Evaluation by MTT:

    
This test was carried out  by
incubating embryos with 0.25 mg/ml MTT in the culture media for 3 hrs at 37 °C.
Insoluble formazan products were solubilized by overnight incubation in 50%
N,N-dimethyl formamide, 20% sodium dodecyl sulfate, pH 4.8 (11).
Quantitative measurement of the absorbance of this colored solution can be performed  at wave length 575 nm by ELISA reader.

Statistical analysis:

    
Each experiment was replicated at least three times. The data were
expressed as means ± SEM. The statistical significant difference was analyzed
by ANOVA using SPSS. Values with different letters across treatments differed
significantly. Differences of P