The objective of this thesis was to investigate and expand the use of testis tissue xenografting as means of maintaining the developmental potential of donor testis tissue. The objective of the first study was to investigate the effect of donor age on spermatogenesis in canine testis tissue after xenografting into immunodeficient recipient mice. Fragments of testis tissue from 12 dogs of different ages were xenografted under the back skin of mice. Donors were categorized based on testis developmental status at the time of grafting into: less than four months (immature), four to six months (young), and greater than six months of age (adult). The grafts were evaluated at four, six or eight months post-grafting. At four months post-grafting, immature and young groups had higher graft recovery rates (92 ± 5.8 and 88 ± 4.4% versus 69 ± 3.5%; P = 0.001 and P = 0.001), graft weights (34 ± 8.1 and 32 ± 11.0 mg versus 7 ± 2.6 mg; P = 0.001 and P = 0.02), vesicular gland indices (1.1 ± 0.20 and 0.6 ± 0.18% versus 0.1 ± 0.03%; P < 0.0001 and P = 0.02), seminiferous tubule numbers (517 ± 114.8 and 364 ± 161.0 versus 10 ± 5.1; P < 0.0001 and P = 0.03), and larger seminiferous tubular diameters (140 ± 17.8 and 130 ± 3.4 µm versus 55 ± 21.9 µm; P = 0.003 and P = 0.001), compared to adult donor xenografts. Xenografts from immature donors maintained the growth and development for eight months, as exhibited by greater graft weights (17 ± 4.6 mg, P = 0.002), seminiferous tubule numbers (547 ± 210.3, P < 0.01) and tubular diameters (93 ± 15.9 µm, P < 0.0001), and induced greater vesicular gland indices (1.5 ± 0.46%, P = 0.0005), compared to adult donor xenografts. The growth and development of testis tissue xenografts from immature and young donors were not different after eight months (P > 0.05). Young donor xenografts had greater seminiferous tubule number and diameter compared to adult donor xenografts (P = 0.009 and P = 0.004, respectively) at eight months post-grafting. Elongated spermatids were the most advanced germ cell type present at four and eight months post-grafting in the testis grafts of immature and young age groups.<p> The objective of the second study was to evaluate three different strategies to preserve/cryopreserve immature porcine testis tissue. Immature porcine testes were cooled at 4 °C for 24, 48 or 72 hours, and testis tissue fragments were cryopreserved using programmed slow freezing with dimethyl sulfoxide (DMSO), glycerol, or ethylene glycol, or vitrified using DMSO or glycerol at 5, 15 or 30 min exposure time. In vitro cell viability was determined by trypan blue exclusion, and in vivo developmental potential was evaluated by xenografting into immunodeficient mice. Compared to fresh tissue, short-term cooling of porcine testis tissue resulted in similar in vitro cell survival rates (93 ± 2.2% for fresh versus 95 ± 0.3, 93 ± 1.7 and 87 ± 4.3% after 24, 48 and 72 hours at 4 °C, respectively; P = 0.74) and in vivo development, with generation of elongated spermatids and sperm after four months of grafting. Cryopreservation of testis tissue with programmed slow freezing using glycerol and vitrification with DMSO (5 min equilibration) or glycerol (5 or 15 min equilibration) did not compromise the developmental competence of xenografts when compared to fresh tissue (control), characterized by the formation of elongated spermatids and sperm.<p> These findings suggest that canine testis tissue from immature donors and cooling of immature porcine testis tissue to refrigerator temperature for up to 72 hours or cryopreservation with slow controlled freezing or vitrification could be suitable methods to restore male fertility following xenografting.

The objective of this thesis was to investigate and expand the use of testis tissue xenografting as means of maintaining the developmental potential of donor testis tissue. The objective of the first study was to investigate the effect of donor age on spermatogenesis in canine testis tissue after xenografting into immunodeficient recipient mice. Fragments of testis tissue from 12 dogs of different ages were xenografted under the back skin of mice. Donors were categorized based on testis developmental status at the time of grafting into: less than four months (immature), four to six months (young), and greater than six months of age (adult). The grafts were evaluated at four, six or eight months post-grafting. At four months post-grafting, immature and young groups had higher graft recovery rates (92 ± 5.8 and 88 ± 4.4% versus 69 ± 3.5%; P = 0.001 and P = 0.001), graft weights (34 ± 8.1 and 32 ± 11.0 mg versus 7 ± 2.6 mg; P = 0.001 and P = 0.02), vesicular gland indices (1.1 ± 0.20 and 0.6 ± 0.18% versus 0.1 ± 0.03%; P < 0.0001 and P = 0.02), seminiferous tubule numbers (517 ± 114.8 and 364 ± 161.0 versus 10 ± 5.1; P < 0.0001 and P = 0.03), and larger seminiferous tubular diameters (140 ± 17.8 and 130 ± 3.4 µm versus 55 ± 21.9 µm; P = 0.003 and P = 0.001), compared to adult donor xenografts. Xenografts from immature donors maintained the growth and development for eight months, as exhibited by greater graft weights (17 ± 4.6 mg, P = 0.002), seminiferous tubule numbers (547 ± 210.3, P < 0.01) and tubular diameters (93 ± 15.9 µm, P < 0.0001), and induced greater vesicular gland indices (1.5 ± 0.46%, P = 0.0005), compared to adult donor xenografts. The growth and development of testis tissue xenografts from immature and young donors were not different after eight months (P > 0.05). Young donor xenografts had greater seminiferous tubule number and diameter compared to adult donor xenografts (P = 0.009 and P = 0.004, respectively) at eight months post-grafting. Elongated spermatids were the most advanced germ cell type present at four and eight months post-grafting in the testis grafts of immature and young age groups.<p> The objective of the second study was to evaluate three different strategies to preserve/cryopreserve immature porcine testis tissue. Immature porcine testes were cooled at 4 °C for 24, 48 or 72 hours, and testis tissue fragments were cryopreserved using programmed slow freezing with dimethyl sulfoxide (DMSO), glycerol, or ethylene glycol, or vitrified using DMSO or glycerol at 5, 15 or 30 min exposure time. In vitro cell viability was determined by trypan blue exclusion, and in vivo developmental potential was evaluated by xenografting into immunodeficient mice. Compared to fresh tissue, short-term cooling of porcine testis tissue resulted in similar in vitro cell survival rates (93 ± 2.2% for fresh versus 95 ± 0.3, 93 ± 1.7 and 87 ± 4.3% after 24, 48 and 72 hours at 4 °C, respectively; P = 0.74) and in vivo development, with generation of elongated spermatids and sperm after four months of grafting. Cryopreservation of testis tissue with programmed slow freezing using glycerol and vitrification with DMSO (5 min equilibration) or glycerol (5 or 15 min equilibration) did not compromise the developmental competence of xenografts when compared to fresh tissue (control), characterized by the formation of elongated spermatids and sperm.<p> These findings suggest that canine testis tissue from immature donors and cooling of immature porcine testis tissue to refrigerator temperature for up to 72 hours or cryopreservation with slow controlled freezing or vitrification could be suitable methods to restore male fertility following xenografting.

Testis tissue xenografting (TTX) provides a novel in vivo model for the study of testis function, and a previously-unavailable opportunity to produce spermatozoa in the grafts from immature donors of diverse species. The overall objectives of this thesis were to examine a number of factors that potentially affect the outcome of TTX, and to apply TTX using immature bison and deer donors as models for endangered ungulates. The objective of the first experiment was to examine the effects of recipient mouse strain, gender and gonadal status on the outcome of TTX. Eight small fragments of neonatal porcine testis tissue (~5 mg each) were grafted under the back skin of immunodeficient mice of different strains (SCID vs. nude), gender (male vs. female), and gonadal status (intact vs. gonadectomised), using a 2×2×2 factorial design (8 groups, n = 7 mice/group). The xenografts were recovered at 8 mo post-grafting and evaluated for gross and histological attributes. Gonadectomy of the recipients did not affect any of the measured outcomes of TTX (P > 0.05), and data were pooled into four groups based on recipient strain and gender. Overall, male recipient mice had grafts with higher mean (+SEM) recovery rate (97 ± 2.3% vs. 88 ± 2.4%, P = 0.004), weight (348 ± 26.3 vs. 104 ± 27.0 mg, P < 0.001), seminiferous tubular diameter (150 ± 3.3 vs. 108 ± 5.3 mg, P < 0.001), percentage of tubules containing spermatozoa (32 ± 3.2 vs. 6 ± 1.8%, P < 0.001), elongated spermatids (13 ± 1.4% vs. 4 ± 0.8%, P < 0.001), and round spermatids (10 ± 1.2% vs. 6 ± 1.1%, P = 0.006) than female mice. Overall, SCID mice had grafts with higher recovery rate (98 ± 2.4% vs. 87 ± 2.3%, P = 0.001), average weight (292 ± 27.0 vs. 160 ± 26.3 mg, P = 0.001), tubular density (44 ± 3.3 vs. 33 ± 2.1, P = 0.02), percentage of tubular cross-sections containing spermatocytes (27 ± 3.7% vs. 13 ± 2.3%, P = 0.003) than nude mice. Among the four groups of recipients, the grafts from male SCID mice had the highest weight (P < 0.05) and percentage of tubules containing spermatozoa (P < 0.05).<p> The objective of the second experiment was to evaluate the effect of using different numbers of donor testis tissue fragments on the outcome of TTX. Fragments of donor piglet testis tissue were grafted subcutaneously under the back skin of four groups of castrated male nude mice (n = 10/group). Each group of recipient mice received 2, 4, 8, or 16 fragments per mouse. Mice were sacrificed at 8 mo post-grafting, and xenografts were evaluated for physical growth and histological development. The relative weight of the vesicular gland (index) was also determined as a measure of bioactive androgen production by grafts in castrated recipient mice. The overall graft recovery rate was ~94% (range 86-98%) which did not differ among the groups (P > 0.05). The group of mice that received 16 testis tissue fragments had higher mean (+ SEM) graft weights (278 ± 39.4 vs. 106 ± 38.0, P = 0.02), total graft weight (2,443 ± 338.8 vs. 192 ± 76.2, P < 0.001), vesicular gland index (0.5 ± 0.06 vs. 0.1 ± 0.06, P = 0.007), and percentage of seminiferous tubules with round spermatids (11 ± 1.5 vs. 3 ± 1.3, P = 0.03) than the group of mice that received two testis tissue fragments. The objective of the third experiment was to assess the use to salvage testis tissue from neonatal/immature bison or deer donors using TTX into immunodeficient recipient mice as models for closely-related rare or endangered ungulates. Donor testis tissue fragments from two newborn bison calves (Bison bison bison) and a 2-mo-old white-tailed deer fawn (Odocoileus virginianus) were grafted under the back skin of gonadectomised nude mice (n = 15 and n = 7 for bison and deer groups, respectively, 8 testis fragments/mouse). To examine the potential effect of individual donors, we grafted four testis tissue fragments from one bison calf on one side of the recipient and four fragments from the second bison calf on the other side. Single grafts were surgically removed from representative recipient mice every 2 mo for up to 16- and 14 mo post-grafting, for bison and deer groups, respectively. The overall graft recovery rates were 69% and 63% for bison and deer groups, respectively. For bison grafts, a donor effect on efficiency of spermatogenesis was also observed. The weight of bison testis tissue xenografts increased (P < 0.02) ~4-fold by 2 mo and ~10-fold by 16 mo post-grafting, and gradual maturational changes were evident in the form of seminiferous tubule expansion starting at 2 mo, first appearance of spermatocytes at 6 mo, round spermatids at 12 mo, and elongated spermatids at 16 mo post-grafting. Testis tissue xenografts from donor white-tailed deer also showed a gradual development starting with tubular expansion by 2 mo and presence of spermatocytes by 6 mo post-grafting, round and elongated spermatids by 8 mo, followed by fully-formed spermatozoa by 12 mo post-grafting. The timing of complete spermatogenesis roughly corresponded to the reported timing of sexual maturation in these species.<p> Taken together, the findings in this thesis suggest that male SCID mice provide a more suitable recipient model for TTX with neonatal porcine testis tissue; recipient mice can be grafted with as many as 16 testis tissue fragments for optimal results; and that TTX is a feasible strategy for salvaging genetic materials from immature males of rare or endangered ungulates that die prematurely.

Testis tissue xenografting (TTX) provides a novel in vivo model for the study of testis function, and a previously-unavailable opportunity to produce spermatozoa in the grafts from immature donors of diverse species. The overall objectives of this thesis were to examine a number of factors that potentially affect the outcome of TTX, and to apply TTX using immature bison and deer donors as models for endangered ungulates. The objective of the first experiment was to examine the effects of recipient mouse strain, gender and gonadal status on the outcome of TTX. Eight small fragments of neonatal porcine testis tissue (~5 mg each) were grafted under the back skin of immunodeficient mice of different strains (SCID vs. nude), gender (male vs. female), and gonadal status (intact vs. gonadectomised), using a 2×2×2 factorial design (8 groups, n = 7 mice/group). The xenografts were recovered at 8 mo post-grafting and evaluated for gross and histological attributes. Gonadectomy of the recipients did not affect any of the measured outcomes of TTX (P > 0.05), and data were pooled into four groups based on recipient strain and gender. Overall, male recipient mice had grafts with higher mean (+SEM) recovery rate (97 ± 2.3% vs. 88 ± 2.4%, P = 0.004), weight (348 ± 26.3 vs. 104 ± 27.0 mg, P < 0.001), seminiferous tubular diameter (150 ± 3.3 vs. 108 ± 5.3 mg, P < 0.001), percentage of tubules containing spermatozoa (32 ± 3.2 vs. 6 ± 1.8%, P < 0.001), elongated spermatids (13 ± 1.4% vs. 4 ± 0.8%, P < 0.001), and round spermatids (10 ± 1.2% vs. 6 ± 1.1%, P = 0.006) than female mice. Overall, SCID mice had grafts with higher recovery rate (98 ± 2.4% vs. 87 ± 2.3%, P = 0.001), average weight (292 ± 27.0 vs. 160 ± 26.3 mg, P = 0.001), tubular density (44 ± 3.3 vs. 33 ± 2.1, P = 0.02), percentage of tubular cross-sections containing spermatocytes (27 ± 3.7% vs. 13 ± 2.3%, P = 0.003) than nude mice. Among the four groups of recipients, the grafts from male SCID mice had the highest weight (P < 0.05) and percentage of tubules containing spermatozoa (P < 0.05).<p> The objective of the second experiment was to evaluate the effect of using different numbers of donor testis tissue fragments on the outcome of TTX. Fragments of donor piglet testis tissue were grafted subcutaneously under the back skin of four groups of castrated male nude mice (n = 10/group). Each group of recipient mice received 2, 4, 8, or 16 fragments per mouse. Mice were sacrificed at 8 mo post-grafting, and xenografts were evaluated for physical growth and histological development. The relative weight of the vesicular gland (index) was also determined as a measure of bioactive androgen production by grafts in castrated recipient mice. The overall graft recovery rate was ~94% (range 86-98%) which did not differ among the groups (P > 0.05). The group of mice that received 16 testis tissue fragments had higher mean (+ SEM) graft weights (278 ± 39.4 vs. 106 ± 38.0, P = 0.02), total graft weight (2,443 ± 338.8 vs. 192 ± 76.2, P < 0.001), vesicular gland index (0.5 ± 0.06 vs. 0.1 ± 0.06, P = 0.007), and percentage of seminiferous tubules with round spermatids (11 ± 1.5 vs. 3 ± 1.3, P = 0.03) than the group of mice that received two testis tissue fragments. The objective of the third experiment was to assess the use to salvage testis tissue from neonatal/immature bison or deer donors using TTX into immunodeficient recipient mice as models for closely-related rare or endangered ungulates. Donor testis tissue fragments from two newborn bison calves (Bison bison bison) and a 2-mo-old white-tailed deer fawn (Odocoileus virginianus) were grafted under the back skin of gonadectomised nude mice (n = 15 and n = 7 for bison and deer groups, respectively, 8 testis fragments/mouse). To examine the potential effect of individual donors, we grafted four testis tissue fragments from one bison calf on one side of the recipient and four fragments from the second bison calf on the other side. Single grafts were surgically removed from representative recipient mice every 2 mo for up to 16- and 14 mo post-grafting, for bison and deer groups, respectively. The overall graft recovery rates were 69% and 63% for bison and deer groups, respectively. For bison grafts, a donor effect on efficiency of spermatogenesis was also observed. The weight of bison testis tissue xenografts increased (P < 0.02) ~4-fold by 2 mo and ~10-fold by 16 mo post-grafting, and gradual maturational changes were evident in the form of seminiferous tubule expansion starting at 2 mo, first appearance of spermatocytes at 6 mo, round spermatids at 12 mo, and elongated spermatids at 16 mo post-grafting. Testis tissue xenografts from donor white-tailed deer also showed a gradual development starting with tubular expansion by 2 mo and presence of spermatocytes by 6 mo post-grafting, round and elongated spermatids by 8 mo, followed by fully-formed spermatozoa by 12 mo post-grafting. The timing of complete spermatogenesis roughly corresponded to the reported timing of sexual maturation in these species.<p> Taken together, the findings in this thesis suggest that male SCID mice provide a more suitable recipient model for TTX with neonatal porcine testis tissue; recipient mice can be grafted with as many as 16 testis tissue fragments for optimal results; and that TTX is a feasible strategy for salvaging genetic materials from immature males of rare or endangered ungulates that die prematurely.

Submitted by Socorro Pontes (socorrop@ufersa.edu.br) on 2017-05-12T15:29:10Z No. of bitstreams: 1 EricaCGP_DISSERT.pdf: 2673309 bytes, checksum: c441c049726d8b3cc5250d4dbb83b8ea (MD5) / Made available in DSpace on 2017-05-12T15:29:10Z (GMT). No. of bitstreams: 1 EricaCGP_DISSERT.pdf: 2673309 bytes, checksum: c441c049726d8b3cc5250d4dbb83b8ea (MD5) Previous issue date: 2017-02-17 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objective of the present thesis was to use the manipulation of oocytes enclosed in preantral follicles (MOIFOPA) as a tool for the female gametes rescue and conservation, from wild species agouti (Dasyprocta leporina). The dissertation was divided into two experimental phases. At first, it was performed solid surface vitrification (SSV) using different concentrations of cryoprotectant agents (CPAs) in which the effects of the 3 and 6 M concentrations of dimethylsufoxide (DMSO) and ethylene glycol (EG) were verified, as well as the association of both CPAs in the high concentration (6 M) under morphology, viability and apoptosis cell on the in situ PFs. A total of 865 PFs was analyzed before and after vitrification, it was observed an average of 80.7 ± 5.21% of morphologically normal follicles in the control group and after SSV, indifferent the CPA used, it was possible to preserve until 76.7% ± 5.4 OF PFs. At viability analysis, DMSO 3 M, DMSO 6 M, EG 3, EG 6 M (70.0%, 81.11%, 76.6% and 71.11%, respectively) presented similar values to the control group (79.0%). No apoptotic cells (TUNEL positive) were found before and after vitrification. At second, vitrification was performed using the association of CPAs, followed by xenografting of ovarian tissue in C57Bl/6 SCID Black mice. Through vaginal washing monitoring, was observed that 80% mice of the xeno-fresh group and 42% of the xeno-vitrified group returned to ovarian activity, confirmed by hormonal measures. Microscopically, primordial, primary and transitional follicles were observed in the grafts, and all had normal morphology for the species studied. However, major primordial and primary follicles were observed in transplants. The NORs revealed that after transplantation a significant reduction (1.66 ± 0.25) occurred when compared to the control groups (group fresh control: 7.19 ± 1.23 and xeno-fresh group: 9.10 ± 0.64). Apoptotic cells (TUNEL positive) were found only after transplantation of samples vitrified and the healthy follicles (TUNEL negative) observed in other groups (TUNEL negative). Thus, as the general conclusion, the use of MOIFOPA in agouti allowed the knowledge of aspects related to its reproductive morphology and physiology, enabling the germplasm conservation, with the possibility of germplasm bank formation, as the elucidation of mechanisms related to the PF survive and in vivo development / O objetivo do presente estudo foi utilizar a manipulação de oócitos inclusos em folículos ovarianos pré antrais (MOIFOPA) como ferramenta para o resgate e conservação do uso de gametas femininos de cutias (Dasyprocta leporina). A dissertação foi dividida em duas fases experimentais. Na primeira, foi realizada a vitrificação em superfície sólida (SSV) utilizando diferentes concentrações de agentes crioprotetores (ACPs), na qual foram verificados os efeitos das concentrações de 3 e 6 M de dimetilsufoxido (DMSO) e etilenoglicol (EG), bem como a associação de ambos os ACPs na concentração maior (6 M) sob a morfologia, viabilidade e apoptose celular de folículos ovarianos pré-antrais in situ (FOPAs). Um total de 865 FOPAs foi analisado antes e após a vitrificação. No grupo controle, foi observado 80,7 ± 5,21% de FOPA morfologicamente normais. Após SSV, independentemente do ACP utilizado, foram obtidos até 76,7% ± 5,4 de FOPAS. Na análise de viabilidade, DMSO 3 M, DMSO 6 M, EG 3, EG 6 M (70,0%; 81,11%; 76,6% e 71,11%; respectivamente) apresentaram valores semelhantes de FOPAS viáveis ao grupo controle (79,0%). Na segunda fase, foi realizada a SSV utilizando a associação dos ACPs (DMSO e EG), seguido do xenotransplante de tecido ovariano de cutias em camundongas C57Bl/6 SCID. Através do monitoramento do lavado vaginal, observou-se que 80% das camundongas do grupo controle e 42% do grupo vitrificado retornaram à atividade ovariana, confirmada pela dosagem hormonal. Microscopicamente, folículos primordiais, primários, transição e secundários foram observados nos enxertos, e todos tinham morfologia normal para as espécies estudadas. No entanto, os folículos primordiais e primários foram observados em maior quantidade após transplante. As Regiões organizadoras de nucléolos (NORs) revelaram que após o transplante ocorreu uma redução significativa de NORs no grupo vitrificado-xenotranplantado (1,66 ± 0,25) quando comparados aos grupos controles (grupo controle fresco: 7,19 ± 1,23; grupo controle xenotransplantado: 9,10 ± 0,64). As células apoptóticas (TUNEL positivo) foram encontradas somente após o transplante das amostras vitrificadas e folículos saudáveis foram encontrados nos outros grupos tratado (TUNEL negativo). Assim, como conclusão geral, o uso da MOIFOPA em cutias permitiu o conhecimento de aspectos relacionados a sua morfofisiologia reprodutiva, possibilitando tanto a conservação do material genético, com a possibilidade de formação de bancos de germoplasma; e ainda a elucidação dos mecanismos relacionados à sobrevivência e ao desenvolvimento dos FOPA in vivo / 2017-05-12

Made available in DSpace on 2016-08-15T20:31:29Z (GMT). No. of bitstreams: 1 FernandaAS_DISSERT.pdf: 1414995 bytes, checksum: e7e006bb87888d5b4777f2f259d7afd8 (MD5) Previous issue date: 2015-09-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Ovarian xenografting is an auxiliary reproductive technique that allows the conservation of germplasm of high value livestock or endangered species. The use of exogenous gonadotropins assists in developing these xenografted tissues and obtaining viable follicles for in vitro embryo production (IVEP), however this use has not been reported in xenograftings of cats ovaries with C57BL/6 SCID female mice as recipients. Thus, the aim of this study was to evaluate the response of xenografting of domestic cat ovaries to equine chorionic gonadotropin (eCG) when grafted into C57BL/6 SCID female mice. Therefore, domestic cats ovarian cortex fragments were grafted under the kidney capsule of fifteen C57BL/6 SCID mice after bilateral ovariectomy. At the end of 45 days, the female mice were divided into two groups and those who did not receive hormone induction (eCG ) were euthanized at the time of induction. Females who received hormonal induction (eCG +) were euthanized after 48 hours. All collected tissues were taken for histologic processing. The proportions between the different ovarian follicles were compared by the chi-square test. The morphometric analysis of the follicles were compared between the experimental groups by the Tukey test (primordial follicles, primary and secondary) and Kruskal-Wallis (antral follicles). Macroscopically, it was possible to observe a low number (16%) of antral follicles with more than 1mm in transplants treated with eCG. In the microscopic analysis, follicles from all categories were observed in transplants and all had normal morphology and morphometry for the studied species (Felis catus), being however observed larger primordial and primary follicles in those eCG + transplants. There was a decrease in primordial follicles percentages and an increase in subsequent categories, mainly in antral follicles of eCG + group, and this condition is proposed here characterized as Follicular Right Shift (FRS). Luteinized follicles were also observed in transplants treated with eCG. Thus, it is concluded that the treatment with eCG is effective when it comes to follicular development, but it did not show a good superovulatory response / Xenotransplante ovariano é uma técnica reprodutiva auxiliar que permite a conservação do germoplasma de espécies de alto valor zootécnico ou em perigo de extinção. O uso de gonadotrofinas exógenas auxilia no desenvolvimento desses tecidos xenotransplantados e na obtenção de folículos viáveis para produção in vitro de embriões (PIVE), entretanto esse uso não foi relatado em xenotransplante de ovários de gatas com fêmeas C57BL/6 SCID como receptora. Dessa forma, o objetivo desse trabalho foi avaliar a resposta do xenotransplante ovariano de gata doméstica à gonadotrofina coriônica equina (eCG) quando transplantados em fêmeas C57BL/6 SCID. Para tanto, fragmentos de córtex ovariano de gatas domésticas foram transplantados sob a cápsula renal de quinze camundongas C57BL/6 SCID após ovariectomia bilateral. Ao final de 45 dias, as fêmeas foram divididas em dois grupos e aquelas que não receberam indução hormonal (eCG ) foram eutanasiadas no momento da indução. As fêmeas que receberam indução hormonal (eCG +) foram eutanasiadas 48h após. Todos os tecidos colhidos foram levados para processamento histológico. As proporções entre os diferentes folículos ovarianos foram comparadas pelo teste de qui-quadrado. A análise morfométrica dos folículos foi comparada entre os grupos experimentais pelo teste de Tukey (folículos primordial, primário e secundário) e Kruskal-Wallis (folículo antral). Macroscopicamente foi possível observar um baixo número (16%) de folículos antrais com mais de 1mm nos transplantes tratados com eCG. Na análise microscópica, folículos de todas as categorias foram observados nos transplantes e todos apresentaram morfologia e morfometria normais para a espécie estudada (Felis catus), sendo, porém observado folículos primordiais e primários maiores naqueles transplantes eCG +. Houve uma redução nas porcentagens de folículos primordiais e aumento nas categorias subsequentes, principalmente nas de folículos antrais do grupo eCG +, sendo essa condição caracterizada como Follicular Right Shift (FRS). Folículos luteinizados também foram observados nos transplantes tratados com eCG. Dessa maneira, conclui-se que o tratamento com eCG foi eficaz em se tratando de desenvolvimento folicular, mas não apresentou boa resposta superovulatória