Development of a modified method of handmade cloning in dromedary camel

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.

Comparison of Umbilical Cord Mesenchymal Stem Cells and Fibroblasts as Donor Nuclei for Handmade Cloning in Sheep Using a Single-Cell Transcriptome

Oocytes are efficient at reprogramming terminally differentiated cells to a totipotent state. Nuclear transfer techniques can exploit this property to produce cloned animals. However, the overall efficiency is low. The use of umbilical cord mesenchymal stem cells (UC-MSCs) as donor nuclei may increase blastocyst rates, but the exact reasons for this remain unexplored. A single-cell transcriptomic approach was used to map the transcriptome profiles of eight-cell embryos that were in vitro-fertilized and handmade-cloned using umbilical cord mesenchymal stem cells and fibroblasts as nuclear donors. Differences were examined at the chromatin level, the level of differentially expressed genes, the level of histone modifications and the level of DNA methylation. This research provides critical information regarding the use of UC-MSCs as a preferred donor nucleus for nuclear transfer techniques. It also offers unique insights into the mechanism of cellular reprogramming.

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)."

Strategies to Improve the Efficiency of Somatic Cell Nuclear Transfer

Mammalian oocytes can reprogram differentiated somatic cells into a totipotent state through somatic cell nuclear transfer (SCNT), which is known as cloning. Although many mammalian species have been successfully cloned, the majority of cloned embryos failed to develop to term, resulting in the overall cloning efficiency being still low. There are many factors contributing to the cloning success. Aberrant epigenetic reprogramming is a major cause for the developmental failure of cloned embryos and abnormalities in the cloned offspring. Numerous research groups attempted multiple strategies to technically improve each step of the SCNT procedure and rescue abnormal epigenetic reprogramming by modulating DNA methylation and histone modifications, overexpression or repression of embryonic-related genes, etc. Here, we review the recent approaches for technical SCNT improvement and ameliorating epigenetic modifications in donor cells, oocytes, and cloned embryos in order to enhance cloning efficiency.

The Resurrection of Mabrokan: Production of Multiple Cloned Offspring from Decade-Old Vitrified Tissue Collected from a Deceased Champion Show Camel

Somatic cell nuclear transfer (SCNT) provides a unique opportunity to reproduce animals with superior genetics. Viable cell lines are usually established from tissues collected by biopsy from living animals in the SCNT program. In the present study, tissues were collected and preserved from a suddenly deceased champion camel. We established cell lines from these decade-old tissues and used them as nuclear donors. After 42 h of in vitro maturation, 68.00 ± 2.40% of oocytes reached the metaphase II (M II) stage while 87.31 ± 2.57% in vivo collected oocytes were matured at collection (p < 0.05). We observed a higher blastocyst formation rate when in vivo matured oocytes (43.45 ± 2.07%) were used compared to in vitro matured oocytes (21.52 ± 1.74%). The live birth rate was 6.45% vs. 16.67% for in vitro and in vivo matured oocytes, respectively. Microsatellite analysis of 13 camel loci revealed that all the SCNT-derived offspring were identical to each other and with their somatic cell donor. The present study succeeded in the resurrection of 11 healthy offspring from the decade-old vitrified tissues of a single somatic cell donor individual using both in vitro and in vivo matured oocytes.

Application of the modified handmade cloning technique to pigs

Although somatic cell nuclear transfer (SCNT) is frequently employed to produce cloned animals in laboratories, this technique is expensive and inefficient. Therefore, the handmade cloning (HMC) technique has been suggested to simplify and advance the cloning process, however, HMC wastes many oocytes and leads to mitochondrial heteroplasmy. To solve these problems, we propose a modified handmade cloning (mHMC) technique that uses simple laboratory equipment, i.e., a Pasteur pipette and an alcohol lamp, applying it to porcine embryo cloning. To validate the application of mHMC to pig cloning, embryos produced through SCNT and mHMC are compared using multiple methods, such as enucleation efficiency, oxidative stress, embryo developmental competence, and gene expression. The results show no significant differences between techniques except in the enucleation efficiency. The 8-cell and 16-cell embryo developmental competence and Oct4 expression levels exhibit significant differences. However, the blastocyst rate is not significantly different between mHMC and SCNT. This study verifies that cloned embryos derived from the two techniques exhibit similar generation and developmental competence. Thus, we suggest that mHMC could replace SCNT for simpler and cheaper porcine cloning.

In vitro embryo production (IVEP) in camelids: Present status and future perspectives

Camels are a fundamental livestock resource with a significant role in the agricultural economy of dry regions of Asia and Africa. Similarly, llamas and alpacas are an indigenous resource considered as beasts of burden in South America because of their surefootedness and ability to adapt. Camel racing, a highly lucrative and well-organized sport, camel beauty contests, and high demand for camel milk lead to a steady interest in the multiplication of elite animals by in vitro embryo production (IVEP) in this species during the last few decades. Although offspring have been produced from in vitro produced embryos, the technique is still not that well developed compared with other domestic animal species such as cattle. IVEP involves many steps, including the collection of oocytes from either slaughterhouse ovaries or live animals through ultrasound-guided transvaginal aspiration; in vitro maturation of these collected oocytes; collection and preparation of semen for fertilization; culture and passaging of cells for nuclear transfer, chemical activation of the reconstructed embryos, and in vitro culture of embryos up to the blastocyst stage for transfer into synchronized recipients to carry them to term. This review discusses the present status of all these steps involved in the IVEP of camelids and their future perspectives.

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.