Survival, re-expansion, and pregnancy outcome following vitrification of dromedary camel cloned blastocysts: A possible role of vitrification in improving clone pregnancy rate by weeding out poor competent embryos

Chemical activation of mammalian oocytes and its application in camelid reproductive biotechnologies: A review

Mammalian oocyte activation is a critical process occurring post-gamete fusion, marked by a sequence of cellular events initiated by an upsurge in intracellular Ca2+. This surge in calcium orchestrates the activation/deactivation of specific kinases, leading to the subsequent inactivation of MPF and MAPK activities, alongside PKC activation. Despite various attempts to induce artificial activation using distinct chemical compounds as Ca2+ inducers and/or Ca2+-independent agents, the outcomes have proven suboptimal. Notably, incomplete suppression of MPF and MAPK activities persists, necessitating a combination of different agents for enhanced efficiency. Moreover, the inherent specificity of activation methods for each species precludes straightforward extrapolation between them. Consequently, optimization of protocols for each species and for each technique, such as PA, ICSI, and SCNT, is required. Despite recent strides in camelid biotechnologies, the field has seen little advancement in chemical activation methods. Only a limited number of chemical agents have been explored, and the effects of many remain unknown. In ICSI, despite obtaining blastocysts with different chemical compounds that induce Ca2+ and calcium-independent increases, viable offspring have not been obtained. However, SCNT has exhibited varying outcomes, successfully yielding viable offspring with a reduced number of chemical activators. This article comprehensively reviews the current understanding of the physiological activation of oocytes and the molecular mechanisms underlying chemical activation in mammals. The aim is to transfer and apply this knowledge to camelid reproductive biotechnologies, with emphasis on chemical activation in PA, ICSI, and SCNT.

A Modified Handmade Cloning Method for Dromedary Camels

Camels play very important economic and sociocultural roles for communities residing in arid and semi-arid countries. The positive impacts of cloning on genetic gain in camel species are indisputable, considering the unique ability of cloning to produce a large number of offspring of a predefined sex and genotype using somatic cells obtained from elite animals, live or dead, and within any age category. However, the current low efficiency of camel cloning seriously limits its commercial applicability. We have systematically optimized technical and biological factors for dromedary camel cloning. In this chapter, we present the details of our current standard operating procedure for dromedary camel cloning, namely, "modified handmade cloning (mHMC)."

Blastocyst formation, embryo transfer and breed comparison in the first reported large scale cloning of camels

Cloning, through somatic cell nuclear transfer (SCNT), has the potential for a large expansion of genetically favorable traits in a population in a relatively short term. In the present study we aimed to produce multiple cloned camels from racing, show and dairy exemplars. We compared several parameters including oocyte source, donor cell and breed differences, transfer methods, embryo formation and pregnancy rates and maintenance following SCNT. We successfully achieved 47 pregnancies, 28 births and 19 cloned offspring who are at present healthy and have developed normally. Here we report cloned camels from surgical embryo transfer and correlate blastocyst formation rates with the ability to achieve pregnancies. We found no difference in the parameters affecting production of clones by camel breed, and show clear differences on oocyte source in cloning outcomes. Taken together we demonstrate that large scale cloning of camels is possible and that further improvements can be achieved.

Vitrification of camel oocytes transiently impacts mitochondrial functions without affecting the developmental potential after intracytoplasmic sperm injection and parthenogenetic activation

Oocyte vitrification preserves the female genetic resources of elite dromedary camels. In the current study, we aimed to explore the effects of vitrification of camel oocytes on mitochondrial activity, redox stress, and expression of genes related to mitochondrial function, apoptosis, pluripotency, and cytoskeleton. Moreover, we investigated developmental competence of vitrified oocytes after parthenogenetic activation. Oocytes vitrified with the Cryotop method were compared with the fresh oocytes. Our results showed that vitrification led to increased ROS production in oocytes as evidenced by an increase in the DCFDHA fluorescence intensity, and lower mitochondrial activity. At the molecular level, vitrification reduced mRNA expression of many genes, including those related to mitochondrial function (TFAM, MT-CO1, MFN1, ATP1A1, NRF1), pluripotency (SOX2 and POU5F1), and apoptosis (p53 and BAX). In contrast, expression of KLF4 and cytoskeleton-related genes (ACTB and KRT8) was not affected. However, we found no difference in the rates of oocyte survival, cleavage, and blastocyst development, and blastocyst hatching between fresh and vitrified oocytes after warming. Our results indicate that although vitrification of camel metaphase II (MII) oocytes adversely affected mitochondrial functions, the effect was transient without compromising the developmental potential of the oocytes after parthenogenetic activation.

Pregnancy and Calving Rates of Cloned Dromedary Camels Produced by Conventional and Handmade Cloning Techniques and In Vitro and In Vivo Matured Oocytes

Despite practical implication of cloning in camelids, its broad application has been hampered by technical and biological problems. Method of somatic cell nuclear transfer (SCNT) and oocyte competence are the principal technical and biological factors, respectively, that determine the cloning efficiency. This study, therefore, investigated differential contributions of two SCNT methods [modified handmade cloning (mHMC) vs. conventional (cNT)] and two recipient oocyte sources [abattoir-derived (Vitro) vs. FSH-stimulated (Vivo)] on the efficiency of dromedary camel cloning. The mHMC method supported similar rates of fusion, cleavage, and total blastocyst development, compared to conventional NT (cNT) (94, 89.1, and 68.5% vs. 78.9, 92, and 73.5%, respectively) when Vivo oocytes are used. However, using Vitro oocytes, mHMC supported significantly higher rates for these criteria, except for the cleavage, compared to cNT (95.5, 76.2, 25.2% vs. 75.3, 76.7, and 13.9%, respectively). A total of seven clones were born from mHMC/Vitro (four calves), mHMC/Vivo (one calf), cNT/Vitro (one calf), and mHMC/Vivo&Vivo (one calf)-derived embryos with overall efficiencies of 31.9, 26.6, 20, and 30% for initial pregnancy, 10.6, 6.6, 7.5, and 5% for development to term, and 8.5, 6.6, 2.5, 5% for development to weaving, respectively. To conclude, the quality of recipient oocyte greatly impacts cloning efficiency in vitro with no apparent carrying over effect on cloning efficiency in vivo, but the efficiency of SCNT method may compensate for the initial poor oocyte competence during in vitro and in vivo development of cloned embryos. The introduced mHMC could be a superior alternative to conventional method for simple, fast, and efficient production of cloned offspring in camelids.

Platelet rich plasma efficiently substitutes the beneficial effects of serum during in vitro oocyte maturation and helps maintain the mitochondrial activity of maturing oocytes

Platelets contain most of the potent mitogenic factors present in serum and follicular fluid and intraovarian injection of autologous platelet rich plasma (PRP) was shown to improve ovarian function and development of preantral follicles. This study evaluated the effect of PRP on caprine oocyte maturation in vitro and subsequent fertilization and embryonic development. Cumulus oocyte complexes were cultured in a maturation medium supplemented with (1) fetal bovine serum (FBS, control), (2) PRP, extracted from healthy female goats, (3) polyvinyl alcohol (PVA), and (4) PVA plus PRP (PVA-PRP). The degree of cumulus expansion was scored, and denuded oocytes were used for assessment of nuclear maturation, mitochondrial activity, lipid content, redox status, yield and quality of in vitro embryo development, and cryosurvival of the resulting blastocysts. PRP supported the same beneficial effects of FBS on cumulus expansion, nuclear maturation, in vitro developmental competence of oocytes, and survival of vitrified-warmed blastocysts. Moreover, PRP protected oocytes from undesirable effects FBS exerted on the mitochondrial activity and intracytoplasmic lipid content of maturing oocyte. Although PVA could support the same beneficial effects of neither FBS nor PRP on oocyte maturation, its combined addition with PRP improved the yield and quality of oocyte maturation at rates closely similar to PRP. PRP efficiently substitutes beneficial effects of serum during in vitro oocyte maturation and helps maintain the mitochondrial activity of maturing oocytes.