Survival of primordial follicles following prolonged transportation of ovarian tissue prior to cryopreservation

BACKGROUND: Cryopreservation of ovarian tissue for fertility preservation is becoming increasingly common. Treatment of diseases that may deprive the ovaries of follicles is often performed at local hospitals that are without the necessary facilities and expertise to cryopreserve ovarian tissue. The aim of the present study was to evaluate whether primordial follicles of ovarian cortex survive transport for up to 4 h prior to cryopreservation. METHODS: Immediately after recovery of one ovary from each of four patients, the cortex was roughly isolated, placed in IVF culture medium, kept on ice and transported for 3-4 h to the centre where final dissection and cryopreservation took place. Transplantation of pieces of thawed ovarian cortex under the skin of ovariectomized immunodeficient mice for a period of 4 weeks was used to assess the survival of primordial follicles. RESULTS: After transplantation, ovarian tissue from each of the four patients contained surviving follicles. CONCLUSIONS: Transport of roughly isolated ovarian cortex cooled on ice for a period of up to 4 h allows survival of primordial follicles following cryopreservation and transplantation to immunodeficient mice.     

Assessment of the integrity of human oocytes retrieved from cryopreserved ovarian tissue after xenotransplantation

BACKGROUND: Previous studies showed that immature oocytes stored in ovarian tissue could develop to the mature stage after transplantation. However, the quality and competency of the oocytes developed in xenografted ovarian tissue have never been investigated. As a pilot study to investigate this uncharted issue, we evaluated microtubule organization and chromatin configuration of human oocytes harvested from xenografted frozen-thawed ovarian tissue. METHODS: Frozen-thawed human ovarian tissue was transplanted into severe combined immunodeficient mice. All animals were stimulated with gonadotrophin from 20 weeks after transplantation. Grafts were recovered 36 h after hCG administration. The oocytes were retrieved from the antral follicles (>2 mm diameter), cultured in vitro, stained for microtubule and chromatin localization. RESULTS: Five oocytes from 21 female mice and seven oocytes from nine male mice were retrieved. Immunocytochemical examinations of these oocytes after in vitro maturation revealed only two developed to the metaphase II stage. Most oocytes were between prophase and metaphase with abnormal microtubule organization and chromatin configuration. CONCLUSIONS: Immature oocytes in stored human ovarian tissue can grow to maturity in host animals after xenotransplantation. Retrieval of oocytes from the xenograft can be carried out and is reproducible. However, many oocytes, grown in host animals and further matured in vitro, showed aberrant microtubule organization and chromatin patterns.     

Reducing ischaemic damage in rodent ovarian xenografts transplanted into granulation tissue

BACKGROUND: Anti-cancer therapies frequently lead to ovarian damage and impaired fertility. To preserve fertility, cryopreservation and subsequent transplantation of the ovaries have been suggested. One of the challenges in ovarian graft transplantation is overcoming the initial ischaemic damage that depletes a significant fraction of the oocyte pool. METHODS AND RESULTS: Follicular survival in ovarian grafts was examined by magnetic resonance imaging (MRI) and fluorescence microscopy in a model system in which rat ovaries were transplanted into nude mice. Transplantation into angiogenic granulation tissue created during wound healing shortened the ischaemic period by 24 h and significantly increased the pool of healthy primordial follicles and the perfused area of the transplanted grafts. Functional blood vessels were detected within the grafts as early as 2 days after transplantation. Gain of function was demonstrated both by growth of the grafts and by the hormonal influence on the host uteri. CONCLUSION: Implantation of ovarian grafts into an angiogenic granulation tissue improved graft vascularization and follicular survival. This procedure/treatment may be used for reducing the ischaemic damage in ovarian transplants, thus prolonging graft functionality and increasing the yield of oocytes that can be easily recovered for fertilization.     

Angiogenesis of the Frozen‐Thawed Human Fetal Ovarian Tissue at the Early Stage after Xenotransplantation and the Positive Effect of Salviae miltiorrhizae

Cryopreserving ovarian tissue followed by transplantation has been suggested to preserve fertility for young cancer survivors. However, ischemia in the early stage after transplantation causes massive follicle loss. The aim was to investigate the histological and ultrastructural characteristics of the frozen‐thawed human fetal ovarian tissue after xenotransplantation and the effects of Salviae miltiorrhizae (SM) on the angiogenesis. The human fetal ovarian tissues were frozen‐thawed, xenografted into the immunodeficient nu/nu mice, and then collected 2, 7, and 28 days after transplantation. SM was administered. Compared with that of the frozen‐thawed ovarian tissue, the total follicle number of the grafts was greatly reduced. Nearly half of the primordial follicles were damaged at different levels on day 2. Moreover, edema was prevalent in the stroma during the first week after the graft, especially on day 2. The microvessel density of the grafts was increased on day 2, reached a peak on day 7, and then declined on day 28. Both healthy primordial follicle proportion and the total healthy primordial follicles pool in the SM group were significantly higher than those of the control group (P = 0.003 and P = 0.001). We found a statistically significant difference of microvessel density between the two groups on day 2 (P < 0.001). In the frozen‐thawed fetal ovarian grafts, angiogenesis has been begun on day 2, and the first week is the critical time for the grafts to regain their function, in which SM can facilitate graft vascularization and improve the preservation of primordial follicles. Anat Rec, 2010. © 2010 Wiley‐Liss, Inc.     

Diagnostic assessment of the developmental potential of human cryopreserved ovarian tissue from multiple patients using xenografting

BACKGROUND: Although ovarian tissue cryopreservation for women at risk of losing ovarian function is offered by many clinics, there is a lack of evidence relating to the developmental potential of the stored tissue and, therefore, its clinical potential. This study was designed to use xenografting of cryopreserved tissue from multiple patients to assess the reproducibility of preservating developmental potential, the variation in developing follicle profile and the relationship between pre-freeze histology and post-thaw development. METHODS: Using previously published methods, cryopreserved ovarian cortex from nine patients was thawed and grafted under the kidney capsules of immunodeficient mice. Development of follicles was assessed after 26 weeks and compared to histology prior to freezing. RESULTS: Multiple growing follicles including antral stages were observed in multiple grafts of tissue from all patients. Metaphase II oocytes (n=9) were observed in follicles in grafts from five patients. There was no relationship between pre-freeze histology and developing follicle profile in xenografts. CONCLUSIONS: The propanediol freezing method used in this study is capable of reproducibly preserving the developmental potential of human ovarian follicles. The developing follicle profile after cryopreservation cannot be accurately predicted from pre-freeze histology. Xenografting provides a powerful tool for assessing the potential of human cryopreserved ovarian tissue.     

Histopathological characteristics of human non-tumor thyroid tissues in a long-term model of adenomatous goiter xenografts in the NOD/Shi-scid,IL-2Rγnull mouse

There is a growing need for modeling the human thyroid to link data obtained from animals to humans because of its sensitivity to radiation exposure and endocrine disruption chemicals. In a scid mouse model produced by transplanting human thyroid tissues, leakiness and thymic lymphoma that occurs spontaneously in the scid mouse can complicate the interpretation of experimental results. Considering that the NOD.Cg-Prkdc^scid Il2rg^tm1Sug/Jic mouse (NOD/Shi-scid, IL-2Rγ^null or NOG mouse) may be a better host because this strain has low incidence of leakiness and thymic lymphoma, we have evaluated the potential of a model that allows long-term observation of non-tumor human thyroid tissues in this mouse. We transplanted tissues of human adenomatous goiter into NOG mice and examined the tissues histopathologically. The morphology of human adenomatous goiter tissues was maintained from 24 to 44 weeks after transplantation in NOG mice with no noted differences between donor-matched tissues or the weeks after transplantation. The tissues expressed thyroglobulin protein and mRNA as well as thyroperoxidase. Endothelial cells originating from human were found in the transplanted tissues and were thought to be a characteristic of this model. The intactness of the tissues before transplantation was found to affect the rate of tissue engraftment. From the present results we have concluded that transplanted thyroid tissues in NOG mice maintain the histopathological characteristics of their origin for long terms. Therefore this model was thought feasible for toxicity evaluation.     

Development of human primordial follicles to antral stages in SCID/hpg mice stimulated with follicle stimulating hormone

In contrast to the many detailed studies of Graafian follicles, the biology of small follicles in the human ovary is poorly understood and the trigger for follicular growth initiation remains unknown. No practical model exists to study preantral follicle growth in the human because of their slow growth rate and lack of an effective culture system. We therefore tested ovarian xenografts as a new strategy to study the early stages of ovarian follicular growth in vivo. Mice homozygous for severe combined immunodeficiency (SCID) and hypogonadism (hpg) received human ovarian xenografts under their kidney capsules. Follicle growth was assessed by morphology and proliferating cell nuclear antigen (PCNA) immunostaining. The grafts were recovered after 11 (short-term) and 17 weeks (long-term), and serially sectioned. During the last 6 weeks of long-term grafting, mice were randomized to receive either placebo or 1 IU of purified follicle stimulating hormone (FSH) s.c. on alternating days. After 11 weeks of grafting, the most advanced follicles had a maximum of two granulosa cell layers. In the absence of FSH administration, follicles did not progress beyond the two-layer stage even after 17 weeks of grafting, and the oestradiol levels remained undetectable. In the FSH-treated long-term grafts, follicles had grown to antral stages and resulted in oestradiol levels as high as 2070 pmol/l. Growth initiation indices did not differ between control and FSH-treated grafts. This study demonstrates that follicles can survive and grow in human ovarian tissue grafted under the renal capsules of immunodeficient mice for at least 17 weeks, and indicate that xenograft models are potentially useful for studying human follicle development. Using this physiological model, we showed that FSH is required for follicle growth beyond the two-layer stage, although growth initiation is independent of gonadotrophin stimulation.      

Reproduction of menstrual changes in transplanted human endometrial tissue in immunodeficient mice

BACKGROUND: Cultures of human endometrial tissue are useful for analysing the mechanisms underlying the menstrual cycle. However, long-term culture of endometrial tissue is difficult in vitro. Xenotransplantation of normal human endometrial tissue into immunodeficient mice could allow prolonged survival of the transplanted tissues. METHODS: Proliferative-phase endometrial tissue samples from three women were transplanted into the subcutaneous space of ovariectomized, immunodeficient, non-obese diabetic (NOD)/severe combined immunodeficiency (SCID)/gammaC(null) (NOG) mice. The mice were treated with 17beta-estradiol (E2) for the first 14 days after transplantation, followed by E2 plus progesterone for the next 14 days. The transplants were investigated morphologically and immunohistochemically at various times after implantation. RESULTS: The transplanted tissues contained large numbers of small glands, pseudostratification of the nuclei and dense stroma after treatment with E2 alone. After treatment with E2 plus progesterone, subnuclear vacuolation, luminal secretion and decidualization of the stroma were observed. When the hormone treatment ceased, tissue destruction occurred and the transplants returned to the proliferative phase. Lymphocytes were identified immunohistochemically: the numbers of CD56-positive and CD16-negative cells increased significantly in the stroma during the late secretory phase (day 28). CONCLUSIONS: Human endometrial tissue transplanted into NOG mice showed similar histological changes to eutopic endometrial tissue during treatment with sex steroid hormones for 1 month. Moreover, lymphocytes were produced in the transplanted human endometrial tissue. This system represents a new experimental model of the human endometrium in vivo.     

Anti-Müllerian hormone inhibits initiation of growth of human primordial ovarian follicles in vitro

BACKGROUND: Anti-Müllerian hormone (AMH) inhibits the initiation of the development and early growth of mouse ovarian follicles. Furthermore, the ovarian follicle pool diminishes prematurely in AMH-knockout mice. In this study, we examined whether AMH plays a similar role in humans, controlling ovarian follicle growth. METHODS: Human ovarian cortical tissue biopsy specimens were cut into small pieces and cultured for 7 days in medium containing rat recombinant AMH at 0, 10, 30 or 100 ng/ml. The developmental stages and viability of the follicles were evaluated from histological sections. RESULTS: Similar to previous studies, significant initiation of follicle growth was observed in almost all culture media, as demonstrated by a significantly smaller proportion of primordial follicles (14-26%) compared with non-cultured control tissue (56%). The exception was tissue in medium supplemented with AMH at 100 ng/ml. Here, the proportion of primordial follicles was not significantly different from that in non-cultured tissue; furthermore, it was significantly greater than that in vehicle control cultures and cultures containing AMH at 10 ng/ml, indicating the inhibition of growth initiation. Viability was unaffected by the presence of AMH when compared with tissues in control media. CONCLUSIONS: Recombinant AMH at a concentration of 100 ng/ml has an inhibitory effect on early human ovarian follicular development in vitro, suppressing the initiation of primordial follicle growth.     

Human ovarian tissue cryopreservation: indications and feasibility

BACKGROUND: The cryopreservation of ovarian tissue may enable women exposed to gonadotoxic treatments to have children at a later date. METHODS: Between April 1998 and October 2000, we evaluated the feasibility of long-term ovarian tissue cryopreservation in 51 women who were all at risk of becoming sterile following treatment. RESULTS: Ovarian tissue was not cryopreserved in 20 cases because of the woman's age or premature ovarian failure. In 31 patients, ovarian tissue was frozen by a slow cooling technique using DMSO and sucrose as cryoprotectants. The patients were aged 2.7-34 years and 16 of them were <18 years old. Cryopreservation could be performed in all cases. Ovarian cortex histology was performed for all patients to evaluate the concentration of follicles. The mean number of primordial and primary follicles per mm(2) was 20.36 +/- 19.03 before 10 years of age, 4.13 +/- 2.9 between 10 and 15 years of age and 1.63 +/- 3.35 after 15 years of age. An average mean number of 26 +/- 8.2 ovarian fragments (range 13-50) were cryopreserved per patient for future autografts or for in-vitro growth of follicles. CONCLUSION: Cryopreservation of ovarian tissue may be systematically proposed to young women and girls at risk of becoming sterile as a result of gonadotoxic treatment.     

Two novel techniques to detect follicles in human ovarian cortical tissue

BACKGROUND: Ovarian tissue cryopreservation and transplantation are becoming increasingly important issues for preserving female fertility as shown by recent successes in restoring ovarian activity and even fertility. Primordial follicle content before transplantation is a key issue for success. We investigated two novel methods to detect primordial follicles in human ovarian cortical tissue strips. METHODS: The first method used the fluorescent mitochondrial stain rhodamine 123 in combination with laser scanning confocal microscopy (LSCM). The first method used the fluorescent mitochondrial stain rhodamine 123 (R123) in combination with laser scanning confocal microscopy (LSCM). The second used a simple stereomicroscopic method with glass-bottom dishes for detecting primordial follicles in ovarian cortical tissue strips. Potential toxic effects of R123 and of the exposure to confocal laser were investigated in a mouse ovarian allograft model. RESULTS: Follicles were visible as white spots in thin cortical strips using LSCM in single and fast scanning at low magnification, allowing a fair estimation of the number of primordial follicles present. Using the second method, ovarian follicles were also visible using glass-bottom dishes under the stereomicroscope, although tissue thickness and density were limiting factors of its success. DISCUSSION: Follicles can be visualized in human cortical ovarian strips with R123 in combination with LSCM. Stereomicroscopy using glass-bottom dishes and transmitted illumination is a simple alternative method and has the advantage of allowing further safe clinical use of the analysed tissue.     

Human fetal tissues grafted to rodent hosts: structural and functional observations of brain,adrenal and heart tissues in oculo

Summary The potential for growth and development of human tissue grafts was explored by transplantation to the anterior chamber of the eye of rats and mice. Tissues were obtained from therapeutic abortions, performed in the eighth to twelfth week of gestation, using a slight modification of routine vacuum aspirations. Recipients were either adult rats immunosuppressed with cyclosporin A and protected with antibiotics, or nude immunodeficient Balb C mice. Catecholamine-rich tissues such as chromaffin cells from the adrenal medulla, sympathetic ganglia, central dopamine neuroblasts from the substantia nigra, and noradrenaline neuroblasts from the locus coeruleus all survived grafting, and in many cases formed nerve fibers that invaded the host iris. Similarly, central serotonin neurons from developing raphe nuclei grafts were able to innervate host irides. Human fetal cerebellar and cerebral cortical transplants continued their development in rat host eyes. Extracellular recordings from such cerebellar and cortical grafts revealed spontaneously active cells with immature action potential waveforms. Spinal cord grafts also survived and contained substance P-immunoreactive neurons. Dorsal root ganglia were able to form nerve fibers invading the host iris, as evidenced by neurofilament immunohistochemistry. Heart tissue survived and manifested spontaneous rhythmic contractions in oculo. Both human cortex cerebri and heart tissue grafts became innervated by sympathetic adrenergic nerve fibers from the rat host iris. Thus both graft-to-host and host-to-graft neuronal connections may be established between man and rat. Taken together, these data suggest that transplantation of human fetal nervous tissues to the anterior chamber of immunosuppressed or immunodeficient rodent hosts yields a unique model system for studies of human brain development, developmental disturbances, connectivity, and the action of drugs.     

Human ovarian tissue from cortex surrounding benign cysts: a model to study ovarian tissue cryopreservation

BACKGROUND: The scarcity of human ovarian tissue is a major problem in developing research on ovarian cryopreservation. We were interested in ovarian cortex surrounding benign ovarian cysts harvested during their requisite operations. METHODS: Ovarian tissue was collected from 25 women (mean age = 27.7 +/- 1.0 SEM) and frozen in serum-free cryoprotective medium. Histological and viability analysis were performed on fresh and frozen-thawed slices of tissue. RESULTS: Dermoid (n = 7), endometriosis (n = 13) and serous (n = 5) cysts were observed. Follicular densities (expressed per mm3) in ovarian cortex surrounding dermoid cysts were higher than in endometriosis and serous cysts for both histological (median of follicular densities: 13.04, 0.31 and 0.89 respectively) and viability analysis (2.93, 0.05 and 0.71 respectively). Freezing-thawing did not result in gross abnormality of follicle population either in number or morphology (80% of follicles preserved a normal pattern). However, a slight decrease of the density of living follicles (expressed per mm2) was reported. CONCLUSIONS: Ovarian cortex surrounding ovarian cysts, especially dermoid cysts, could be considered a source of ovarian tissue for future research. In our study, the cryopreservation procedure resulted in high follicular survival assessed by both histological and viability analysis. Nevertheless, further studies of in vivo and in vitro follicular maturation are needed to strengthen this model.     

Induction of human humoral immune responses in a novel HLA-DR-expressing transgenic NOD/Shi-scid/γcnull mouse

Mounting evidence has demonstrated that NOD-Shi/scid/γc(null) (NOG) mice are one of the most suitable mouse strains for humanized mouse technologies, in which various human cells or tissues can be engrafted without rejection and autonomously maintained. We have characterized and analyzed various features of the human immune system reconstituted in NOG mice by transplanting human hematopoietic stem cells (hu-HSC). One of the problems of the quasi-immune system in these hu-HSC NOG mice is that the quality of immune responses is not always sufficient, as demonstrated by the lack of IgG production in response to antigen challenge. In this study, we established a novel transgenic NOG sub-strain of mice bearing the HLA-DRA and HLA-DRB1:0405 genes, which specifically expresses HLA-DR4 molecules in MHC II-positive cells. This mouse strain enabled us to match the haplotype of HLA-DR between the recipient mice and human donor HSC. We demonstrated that T-cell homeostasis was differentially regulated in HLA-matched hu-HSC NOG mice compared with HLA-mismatched control mice, and antibody class switching was induced after immunization with exogenous antigens in HLA-matched mice. This novel mouse strain improves the reconstituted human immune systems that develop in humanized mice and will contribute to future studies of human humoral immune responses.     

Expression of cholinergic markers in transplants of immature mouse neocortex into adult mouse parietal cortex

Summary Cerebral cortex of embryonic and newborn mouse was removed and transplanted into adult mouse neocortex to investigate whether the development of cholinergic markers would proceed normally after transplantation. It is shown that both AChE and muscarinic receptors developed in transplanted mouse neocortex. However, while muscarinic receptor binding increased to adult levels in transplants from both pre- and postnatal donors AChE staining intensity only achieved adult levels in tissue from postnatal donors. These results are in accordance with the normal developmental time course of the two different cholinergic markers, since muscarinic receptors appear prenatally in cortex while AChE becomes histochemically detectable after birth. These data suggest that the prenatal donor tissue, unlike the postnatal transplants, lacks an environmental signal for the appearance of AChE stained elements, that is, presumably host AChE fiber ingrowth. Transplantation of immature donor CNS tissue into adult host thus appears to be a useful paradigm to study the regulation of differentiation processes.     

The female-to-male transsexual patient: a source of human ovarian cortical tissue for experimental use

We demonstrated that ovaries removed from female-to-male transsexuals can be used as research material for ovarian cryopreservation, grafting and culture studies. A 21 year old female-to-male transsexual individual, who had been treated with androgens for 12 months, donated her ovaries removed in the sex reversal operation. She had normal numbers of, and proportions of, primordial (98.6%) and primary (1.4%) follicles in her ovarian cortex. After freezing and thawing the ovarian tissue was grafted to immuno-incompetent mice, which were stimulated by human recombinant FSH for 14 days, 10 weeks after transfer. Initiation of growth had occurred in the grafts in which only 79.4% of follicles were primordial, 17.1% primary, and in which there were also secondary and pre-antral follicles. Because long-term androgen treatment does not appear to cause depletion of the primordial follicle pool or affect the developmental capacity of the follicles, ovaries from individuals who undergo sex-reversal operations are an excellent source of tissue for research and maybe even for oocyte donation in the future.     

cAIMP administration in humanized mice induces a chimerization-level-dependent STING response

It is well understood that the STING signalling pathway is critical for generating a robust innate immune response to pathogens. Human and mouse STING signalling pathways are not identical, however. For example, mice lack IFI16, which has been proven important for the human STING pathway. Therefore, we investigated whether humanized mice are an appropriate experimental platform for exploring the human STING signalling cascade in vivo. We found that NOG mice reconstituted with human cord blood haematopoietic stem cells (humanized NOG mice) exhibit human STING signalling responses to an analogue of the cyclic di-nucleotide cGAMP. There was an increase in the proportions of monocytes in the lungs of mice receiving cGAMP analogue. The most robust levels of STING expression and STING-induced responses were observed in mice exhibiting the highest levels of human chimerization. Notably, differential levels of STING in lung versus spleen following cGAMP analogue treatment suggest that there are tissue-specific kinetics of STING activation and/or degradation in effector versus inductive sites. We also examined the mouse innate immune response to cGAMP analogue treatment. We detected that mouse cells in the immunodeficient NOG mice responded to the cGAMP analogue and they do so with distinct kinetics from the human response. In conclusion, humanized NOG mice represent a valuable experimental model for examining in vivo human STING responses.     

Transplantation of a human ovarian cystadenocarcinoma into severe combined immunodeficient (SCID) mice — formation of metastases without significant alteration of the tumour cell phenotype

Human ovarian papillary cystadenocarcinoma cells were injected intraperitoneally into severe combined immunodeficient (SCID) mice. After intraperitoneal application the cells, designated SoTü, grew well in vivo , lodged on to the peritoneum, formed local metastatic deposits, led to the development of ascites in the mice and formed distant metastases in the lungs. If lodged in the ovary, the morphology of the SoTu¨ tumour remarkably resembled that of the primary tumour in the patient. In contrast, several attempts failed to maintain the SoTü cells in vitro . If SCID mouse ascites derived SoTü were transplanted subcutaneously in SCID mice, they formed cystic tumours which also metastasized into the lungs. Immunophenotypical analysis of cell adhesion molecule expression, cell proliferation markers, various oncoproteins, keratin, vimentin, and lectin binding site expression all showed striking similarity between the primary tumour and the SCID mouse explants. In particular, expression of binding sites for the lectin Helix pomatia agglutinin (HPA), which has been shown to be an index of metastatic potential in several human carcinomas, was found on the primary tumour as well as on tumour cells grown in SCID mice, indicating that HPA might be a prognostic indicator in ovarian carcinoma as well. Our results demonstrate that the human/SCID mouse system can mimic growth and distant metastasis formation of human ovarian carcinoma. Although the formation of distant metastases is a relatively rare event in patients, this model system might help to elucidate mechanisms of metastasis formation in ovarian cancer.     

冻融人胎儿卵巢组织异种移植后早期血管生成的实验观察

目的 石观察冻融人胎儿卵巢组织异种移植后1个月内移植物形态学改变,动态了解微血管情况. 方法 将难免流产胎儿的卵巢组织经过冻融,异种移植至18只裸鼠肾被膜下,分别于移植后2d、7d和28d回收移植物.将新鲜、冻融以及移植后不同时间的卵巢组织进行光镜、电镜观察,RT-PCR检测血管相关基因的表达. 结果 移植后2d卵巢组织的微血管密度显著上升,部分血管处于扩张状态;移植后7d微血管密度达到相对高峰且扩张的血管腔消失,微小血管恢复正常形态;移植后28d微血管密度出现轻微下降.电镜观察发现,移植卵巢内多数原始卵泡结构完整;移植后2d间质水肿,血管内红细胞淤积;移植后7d及28d的间质水肿逐渐消退,大量微小血管生长.移植卵巢的人血管内皮生长因子(VEGF)和血管生成素2(Ang-2)mKNA表达均呈双向改变,即在移植后2d上升到高值.此后表达下降. 结论 冻融人胎儿卵巢组织移植后的血管重建在移植后1个月内基本完成,移植后l周是采取措施提高冻融人胎儿卵巢移植效果的关键时期.     

Cryopreservation of oocytes from pre-antral follicles

Cryobiology is a very important tool in reproductive biology. Research in this area focuses on the possibility of restoring fertility in women with reproductive problems or after cancer treatments. Another goal is to establish a genetic resource bank for endangered or commercially important animal species. Cryopreservation of oocytes from pre-antral follicles has been studied during the past decade. Procedures can be divided between the cryopreservation of either ovarian tissue or isolated follicles. Most studies describe a slow freezing/rapid thawing protocol to cryopreserve ovarian fragments. Histology shows that the follicles maintain their morphological integrity, and transplantation of ovarian tissue demonstrates that the follicles can restart their growth and eventually ovulate. Some research groups have obtained offspring using this procedure in mice and sheep. With regard to the cryopreservation of isolated follicles, the few studies reported in this area used the same freezing protocol, and some of them described follicular growth using in-vitro culture. The best result was obtained in mice, with animal birth after follicular cryopreservation and culture. However, additional studies are necessary for a better understanding of the events during follicular cryopreservation and to establish a standard protocol for ovarian transplantation or follicle culture.