Changes in cumulus–oocyte complexes of pregnant and non-pregnant camels (Camelus dromedarius) during maturation in vitro
Introduction
Development of techniques for assisted reproduction in camelids, such as artificial insemination and embryo transfer, has been slow in comparison to that for other livestock species. There is relatively limited information available on follicular growth and maturation in camels, and very little information on camelid oocyte physiology and oocyte maturation. To our knowledge, there have been no reports of attempts to establish IVF-techniques in old world camelids, although IVF has been reported in new world camelids [1].
Based on observation of follicular waves, the mean duration of the oestrous cycle (peak of one follicular wave to the peak of the next wave) in the dromedary camel has been reported to be 24 days in Egypt and 28 days in Sudan. The oestrous cycle does not have a luteal phase in the unmated camel, rather, the ovarian activity is strictly follicular [2]. Studies using ultrasonography have shown that these follicular waves are divided into a growth phase (10.5 days), a maturation phase (7.6 days) and a regression phase (11.9 days) [3].
All camelids are induced ovulators. Only after mating induces ovulation is the corpus luteum present, and it persists if the camel becomes pregnant [4], [5]. Presence of the corpus luteum is associated with a depression in the number of growing follicles.
There is a clear influence of season on ovarian follicular growth and maturation in camels. Sghiri and Driancourt [6] showed that the proportion of females with active ovaries (i.e. with follicles >5 mm) increased from 73.5% in October/December to 89% in January/May.
At present, three different methods are available for oocyte recovery from excised ovaries in farm animals: follicle aspiration, follicle dissection, and follicle slicing [7]. Aspiration of oocytes from follicles of slaughtered dromedary camels was shown to be the most efficient [8], resulting in 32 oocytes from eight ovaries. However, most oocytes were recovered without any cumulus mass.
Some progress has been made in the field of embryo freezing and transfer in dromedary camels [9] and, recently, in embryo transfer and oocyte recovery in llamas [10], [11], [12], [13] and alpacas [14]. Most of the work in assisted reproduction in camelidae has been focused on artificial insemination and storage of semen [15]. There have been some attempts to hybridize old and new world camelids using assisted reproductive techniques [16], [17].
The techniques of in vitro maturation (IVM) and fertilization offer opportunities to obtain information about the dynamics of reproduction in a particular species. The process of IVF involves maturation of oocytes, capacitation of spermatozoa, formation of zygotes (fusion) and subsequent embryo culture. In vitro maturation and fertilization have been extensively studied in many domestic species (cattle [18], buffalo [19], sheep [20], goat [21], pig [22], and horse [23]). Only few studies in this field are available in Camelus dromedarius [24].
The objective of the current study was to develop in vitro maturation methods for dromedary camel oocytes, by evaluating cumulus morphology, oocyte chromatin quality, and level of apoptosis in cumulus cells of cumulus–oocyte complexes (COCs) of pregnant and non-pregnant camels before and during in vitro maturation.
Section snippets
Materials and methods
Apparently normal ovaries of pregnant (n=47) and non-pregnant mature camels (n=43) older than 5 years of age were collected from an abattoir located in Cairo, Egypt. The reproductive status of the camels was characterized by examination of the uterus contents and estimating the age of the conceptus, if present. Ovaries from pregnant donors contained a corpus luteum, whereas ovaries from non-pregnant donors were without corpora lutea. Within 3 h after slaughter the ovaries were transported in
Results
A total of 1023 COCs were isolated after slicing of ovarian pairs of 43 non-pregnant and 47 pregnant camels. The average number of COCs recovered per donor did not differ significantly between non-pregnant and pregnant donors: 12.5 versus 10.3, respectively (Table 1). Non-pregnant camels yielded a greater mean number of COCs with a dispersed cumulus: 5.8 versus 4.0 for pregnant camels (P<0.05).
The morphology of camel COCs in relation to donor type is depicted in Table 2. In both donor types,
Discussion
The present study was conducted to monitor the changes in cumulus cells and oocyte chromatin of camel COCs during IVM, and to analyze the interaction between apoptosis of cumulus cells and meiotic progression in oocytes depending on pregnancy status of the donor.
Because of reported seasonal differences in ovarian activity and oocyte recovery rates [2], [6], [24] we recovered camel COCs only during October. Therefore, it was possible to ignore the seasonal influence and to focus on the influence
Acknowledgements
The authors thank Dr. Katrin Hinrichs, Texas A&M University, for the review of the manuscript. The work was supported by DAAD.
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In vitro embryo production (IVEP) in camelids: Present status and future perspectives
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Effect of roscovitine pretreatment on in vitro maturation of oocytes and their subsequent developmental after chemical activation in dromedary camel (Camelus dromedarius)
2020, TheriogenologyCitation Excerpt :However, in other studies, a higher concentration of 75 μM was found to be efficient to block GVBD in ovine [32] and 80 μM in swine [33] oocytes without any detrimental effect on development and quality of in vitro-produced embryos. The proportion of GV stage oocytes at the beginning of culture in the present study and those pre-cultured in 50 μM roscovitine was higher than 43–47% [34], 52% [35], and 74% [27] reported earlier in same species. The reasons for this disparity could be due to the number of ovaries processed at a given time, which could lead to the variation in time from harvesting of oocytes to their fixation/staining.
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2020, Reproductive Technologies in AnimalsDiverse patterns of cumulus cell expansion during in vitro maturation reveal heterogeneous cellular and molecular features of oocyte competence in dromedary camel
2018, TheriogenologyCitation Excerpt :This observation in agreement with the study of Rienzi et al. [43] suggests that a very dense corona radiata layer is a hallmark of poor oocyte competence. Recent studies in pig suggested that adhesion of COCs may be due to inferior cumulus matrix disassembly because of inadequate cleavage of versican in the expanded COC matrix by a disintegrin and metalloproteinase with thrombospondin-like repeats (ADAMTS-1) [17–19]. It has been also suggested that cyclic adenosine mono-phosphate (cAMP) mat reduce the occurrence of adherent COCs by up-regulating the expression of the ADAMTS-1 protein in the cumulus cells in pig [42].