Biobanking and use of gonadal tissues - a promising strategy for conserving wildlife from the Caatinga biome

Biological Resource Banks (BRB) or Genetic Resource Banks (GRB) are critical tools for the conservation of animal biodiversity. According to the International Union for Conservation of Nature, more than 38,500 species are threatened with extinction, out of a total of 138,300 surveyed species. These banks are repositories of biological samples and data recovered and preserved for the long term by zoos, universities, research centers and other conservation organizations. In recent years, BRB have increasingly included ovarian and testicular tissues as additional options to rescue and propagate wild species, especially those at risk of extinction. After in vitro culture or grafting, gonadal tissues are potential sources of matured gametes that can be used for Assisted Reproduction Technologies while informing about gametogenesis or mechanisms involved in infertility. It therefore is crucial to properly recover, cryopreserve, and culture these tissues using species-specific protocols. Developing BRBs is currently one of the strategies to preserve species from the Caatinga biome - an exclusively Brazilian biome with a rich wild fauna that suffers from anthropogenic activities. Among wild species from this biome, studies have been primarily conducted in collared peccaries, agoutis, cavies, and armadillos to preserve their ovarian and testicular tissues. Additionally, domestic species such as the domestic cat and donkeys have been proposed as models for wild species that are phylogenetically close. This review addresses the main technical aspects involved in obtaining BRB derived from gonadal tissues in some wild species of the Caatinga biome. It reports recent advances and perspectives to use these biological materials for wildlife conservation.

Resurrecting biodiversity: advanced assisted reproductive technologies and biobanking

Biodiversity is defined as the presence of a variety of living organisms on the Earth that is essential for human survival. However, anthropogenic activities are causing the sixth mass extinction, threatening even our own species. For many animals, dwindling numbers are becoming fragmented populations with low genetic diversity, threatening long-term species viability. With extinction rates 1000–10,000 times greater than natural, ex situ and in situ conservation programmes need additional support to save species. The indefinite storage of cryopreserved (−196°C) viable cells and tissues (cryobanking), followed by assisted or advanced assisted reproductive technology (ART: utilisation of oocytes and spermatozoa to generate offspring; aART: utilisation of somatic cell genetic material to generate offspring), may be the only hope for species’ long-term survival. As such, cryobanking should be considered a necessity for all future conservation strategies. Following cryopreservation, ART/aART can be used to reinstate lost genetics back into a population, resurrecting biodiversity. However, for this to be successful, species-specific protocol optimisation and increased knowledge of basic biology for many taxa are required. Current ART/aART is primarily focused on mammalian taxa; however, this needs to be extended to all, including to some of the most endangered species: amphibians. Gamete, reproductive tissue and somatic cell cryobanking can fill the gap between losing genetic diversity today and future technological developments. This review explores species prioritisation for cryobanking and the successes and challenges of cryopreservation and multiple ARTs/aARTs. We here discuss the value of cryobanking before more species are lost and the potential of advanced reproductive technologies not only to halt but also to reverse biodiversity loss.

Prolonged use of letrozole causes morphological changes on gonads in Galea spixii

Letrozole is used as a therapeutic agent in reproductive disorders caused by high estrogen levels. Letrozole inhibits cytochrome P450 aromatase and reduces estrogen levels. However, the effects of long-term use on reproductive traits are unknown. The aim of this study was to evaluate the prolonged use of letrozole in the gonads of rodents (Spix's yellow-toothed cavy; Galea spixii). Forty-eight rodents (24 males and 24 females) were randomly divided into the treated and control groups. Letrozole administration started at 15 days of age and continued weekly until 30, 45, 90, and 120 days of age. The body, testis, and ovary weights were analyzed, as well as the morphological progression of spermatogenesis and folliculogenesis. Macroscopically, body weight gain and gonads weight were increased in the letrozole group. Microscopically, the ovaries of treated females showed stratified epithelium and a cellular disorder of the tunica albuginea. In the testes of treated males, the development of seminiferous tubules was delayed and sperm was absent. The collective findings indicate that the prolonged use of letrozole alters secondary sexual characteristics, and causes weight gain, reproductive changes, and male infertility.

Establishment, characterization, and cryopreservation of cell lines derived from red-rumped agouti (Dasyprocta leporina Linnaeus, 1758) - A study in a wild rodent

Somatic cells can be used for rescuing wild mammals of ecological and economic importance, such as red-rumped agouti, through their application in advanced technologies. Thus, appropriate cell isolation, culture, and storage through cryopreservation can ensure the future safe use of these cells. We aimed to establish and evaluate the effects of culture time (second, fifth, and eighth passages) and cryopreservation on the morphology, viability, metabolism, proliferative activity, reactive oxygen species (ROS) levels, mitochondrial membrane potential (ΔΨm), and apoptosis on somatic cells derived from red-rumped agouti skin. Initially, we identified six dermal fibroblast lines by morphology, immunophenotyping, and karyotyping assays. In vitro culture after the second, fifth, and eighth passages, as well as the cryopreservation conditions used did not affect the metabolism or level of apoptosis. Nevertheless, cells in the fifth passage featured a reduction in proliferative activity and an increase in ROS levels when compared to second and eighth passage cells. Moreover, cryopreservation resulted in reduced ΔΨm when compared to non-cryopreserved cells. Additionally, cryopreserved cells showed a reduction in viability immediately after thawing; nevertheless, the viability of these cells was re-established after 11 days of in vitro culture and was similar to that of non-cryopreserved cells. In conclusion, we have shown that viable fibroblasts can be obtained from red-rumped agouti skin, featuring minimal changes after eight passages in in vitro culture systems. Additionally, adjustments to the cryopreservation protocol are necessary to reduce cellular oxidative stress caused by low temperatures.

Comparison of different intracellular cryoprotectants on the solid surface vitrification of red-rumped agouti (Dasyprocta Leporina Lichtenstein, 1823) ovarian tissue

In contributing to the conservation of wild rodents, the aim of this study was to evaluate the use of distinct cryoprotectants, separately or in combination, for solid surface vitrification (SSV) of red-rumped agouti ovarian tissue. Ovarian cortex from nine females was recovered and fragmented. Fresh fragments (control) were used to analyse the pre-antral follicle (PF) morphology using a histologic procedure, viability using the Trypan blue test, cell proliferation by counting the argyrophilic nucleolar organizing regions (Ag-NORs technique) and DNA integrity using the TUNEL assay. The remaining fragments were vitrified using SSV method with 3 M or 6 M ethylene glycol (EG) or dimethyl sulfoxide (DMSO), or in combination (3 M EG/3 M DMSO), and further evaluated as reported for the fresh samples. All cryoprotectants were effective at preserving PFs morphology compared to the control group (80.7 ± 5.21%), except 6 M EG and 3 M DMSO that provoked a significant (p < .05) decrease on the values of morphologically normal primary (60.0 ± 19.0%) and primordial (44 ± 4.5%) follicles, respectively. Regarding viability, all cryoprotectants provided values similar to that verified for the control group (79.0%), but a significant decrease (p < .05) was observed with EG/DMSO combination (59%). Using Ag-NORs technique, the highest (p < .05) cell proliferative capacity was detected when using EG at each tested concentration. The TUNEL proved the preservation of DNA integrity regardless of the cryoprotectant. In summary, we suggest the use of 3 M EG for the solid surface vitrification of red-rumped agouti ovarian tissue.

Vitrification of collared peccary ovarian tissue using open or closed systems and different intracellular cryoprotectants

This study aimed to evaluate different vitrification methods using distinct cryoprotectants (CPAs) for the preservation of collared peccary ovarian preantral follicles (PFs). Ovarian pairs from six females were fragmented and three fragments (fresh control group) were immediately evaluated for morphology, viability, cell proliferation capacity (assessed by quantifying the number of argyrophilic nucleolus organizer regions - NORs), and apoptosis (by the identification of activated caspase-3 expression). The remaining 18 fragments were vitrified using the solid surface vitrification (SSV) method or the ovarian tissue cryosystem (OTC) with 3 M ethylene glycol (EG), 3 M dimethylsulfoxide (DMSO), or a combination of the two (1.5 M EG/1.5 M DMSO). After two weeks, samples were rewarmed and evaluated as described previously. The OTC with any of the CPAs provided a similar conservation of morphologically normal PFs as the fresh control group (75.6 ± 8.6%); however, the SSV was only efficient with DMSO alone (63.9 ± 7.6%). Regarding the viability or cell proliferation, all tested groups provided post rewarming values similar to those observed for the fresh control group, 84.0 ± 2.9% viable cells with 2.0 ± 0.2 NORs. Related to apoptosis analysis, only the OTC with EG (46.7%) and the SSV method with EG (43.4%) or the combination of EG and DMSO (33.4%) provided similar values to those found for the fresh control group (36.7%). Our findings indicate the utilization of a closed system, the OTC, with 3 M EG as the CPA for the vitrification of collared peccary ovarian tissue.

Ovarian features in white-tailed deer (Odocoileus virginianus) fawns and does

The knowledge about ovarian reserve is essential to determine the reproductive potential and to improve the methods of fertility control for overpopulated species, such as white-tailed deer (Odocoileus virginianus). The goal of this study was to evaluate the effect of age on the female reproductive tract of white-tailed deer, focusing on ovarian features. Genital tracts from 8 prepubertal and 10 pubertal females were used to characterize the preantral follicle population and density, morphology, distribution of follicular classes; stromal cell density; and apoptosis in the ovary. In addition, uterus and ovary weights and dimensions were recorded; and the number and the size of antral follicles and corpus luteum in the ovary were quantified. Overall, fawns had a greater (P < 0.05) preantral follicle population, percentage of normal follicles, and preantral follicle density than does. The mean stromal cell density in ovaries of fawns and does differed among animals but not between age groups. The apoptotic signaling did not differ (P > 0.05) between the ovaries of fawns and does. However, apoptotic ovarian cells negatively (P < 0.001) affected the preantral follicle morphology and density, and conversely, a positive correlation was observed with stromal cell density. As expected, the uteri and ovaries were larger (P < 0.002) and heavier (P < 0.001) in does than in fawns. In conclusion, this study has shown, for the first time, the preantral follicle population and distribution of classes, rate of morphologically normal follicles, and density of preantral follicles and stromal cells in white- tailed deer. Therefore, the findings herein described lead to a better understanding of the white-tailed deer ovarian biology, facilitating the development of new methods of fertility control.