A Novel Testicular Germ Cell Maturation Model for Fertility Preservation in Pre-p

描述(申请人提供)：2005年，美国约4%的癌症患者年龄在35岁以下(seer.ancer.gov)。随着癌症治疗的显著进步，生存对许多人来说是一个现实的结果(seer.ancer.gov)，最大限度地减少治疗的非靶标效应的重要性已成为患者管理的首要问题。化疗和放射治疗等治疗方式可以对生育率产生深远和不可逆转的影响。随着我们治疗方法的改进，越来越多的年轻癌症患者存活下来，这引发了关于长期幸存者的生活质量的重要问题。生殖能力的保存正成为这些生活质量问题中最重要的问题之一。为了保护即将接受癌症治疗的年轻男性的生育力，最广泛使用的策略是降低癌症治疗的毒性，并为未来的辅助生殖技术冷冻保存配子。不幸的是，青春期前的男孩不会产生成熟的精子，所以我们没有为这一群体冷冻精子的选择。我们对癌症治疗对男性生育能力的影响知之甚少。特别是，我们对青春期前男孩的影响的了解非常初级。几乎所有的实验室工作都使用动物模型来研究癌症治疗对生育能力的影响。将动物研究的数据外推到人类睾丸是有明显缺陷的。此外，对动物模型的研究主要集中在化疗对成熟成人睾丸的影响。在我们的实验室里，我们利用人胚胎睾丸移植到小鼠体内，建立了一种独特的人类青春期前睾丸模型。移植的胎儿睾丸存活和发育，在组织学上与青春期前的睾丸非常相似。这一模型为我们提供了直接研究化疗药物对青春期前人类睾丸的影响的机会。在研究的第一部分，我们将对睾丸移植的小鼠给予不同浓度的常用化疗药物环磷酰胺，以研究这种化疗对人类青春期前睾丸的影响。我们项目的第二部分是在我们的人睾丸异种移植模型中用促性腺激素刺激来诱导精子发生。青春期的启动涉及一系列复杂的内分泌事件，最终导致促性腺激素的增加和随后的精子发生的诱导。在促性腺激素水平低下/缺乏的男性中，如Kallman综合征患者，有青春期前的睾丸；外源性促性腺激素可以成功地诱导精子发生。在这个项目中，我们打算使用类似的策略，在我们的人类睾丸异种移植模型中使用外源性促性腺激素来刺激精子发生。如果成功，这将是人类生殖细胞在人体外成熟的第一个报告。该项目的主要优势是我们建立了人胚胎睾丸异种移植模型。这个模型是一个独特而强大的系统，它使我们能够直接探索癌症治疗对青春期前睾丸的影响，并开始了解如何减少或预防毒性。我们还建议在这个人类睾丸模型中使用不同的策略来诱导精子发生，以产生一个成熟的人类睾丸模型。对于任何生殖毒理学研究来说，这都将是一个极其强大的系统，但也将让我们深入了解成熟青春期前睾丸的技术，这些信息将对接受癌症治疗的青春期前男孩保持生育能力至关重要。 公共卫生相关性：我们这个项目的目标有两个：(1)验证我们的人类睾丸异种移植模型是研究常用癌症化疗药物对人类睾丸毒性效应的有用工具(S)，以及(2)在我们强大的异种移植模型中，刺激青春期人类睾丸向成熟精子发育。如果成功，我们将有一种直接的方法来评估任何性腺毒素的影响，探索将其对人类生育能力的有害影响降至最低的机会，并开发出第一个人-鼠异种移植系统，以恢复人类青春期前种群的生育能力。Vcolin 2009年10月14日

DESCRIPTION (provided by applicant): In 2005, approximately 4% of cancer patients were under the age of 35 in the United States (seer.cancer.gov). With the remarkable advances in cancer therapy, survival is a realistic outcome for many (seer.cancer.gov) and the importance of minimizing off-target effects of therapy has come to the forefront in patient management. Treatment modalities such as chemotherapy and radiotherapy can have a profound and irreversible impact on fertility. As our therapies improve, an increasing number of young cancer patients survive, leading to important questions about the quality of life of the long term survivors. Preservation of reproductive ability is becoming one of the most important of these quality of life issues. The most widely used strategies to preserve fertility in young men about to undergo cancer therapy are to reduce the toxicity of the cancer therapies and cryopreservation of gametes for future assisted reproductive technology. Unfortunately, pre-pubertal boys do not produce mature sperm, so we do not have the option to cryopreserve sperm for this group. We have limited knowledge about the effects of cancer therapy on male fertility. In particular, our knowledge about the effects on pre-pubertal boys is very rudimentary. Virtually all of the laboratory work has used animal models to study the effects of cancer therapy on fertility. There are obvious pitfalls in extrapolating data from animal studies to human testis. In addition, studies on animal models have concentrated on the effects of chemotherapy on mature adult testis. In our laboratory, we have developed a unique human pre-pubertal testis model using human fetal testis transplanted into mice. The transplanted fetal testis survives and develops to become histologically very similar to pre-pubertal testis. This model provides us with the opportunity to directly study the effects of chemotherapeutic agents on pre-pubertal human testes. For the first part of the study, we will administer different concentrations of the commonly used chemotherapy agent, cyclophosphamide, to the mice with the testis transplant to study the effects of this chemotherapy on human pre-pubertal testis. The second part of our project is to induce spermatogenesis in our human testis xenotransplantation model with gonadotropin stimulation. The initiation of puberty involves a series of complex endocrine events culminating in an increase in gonadotropins and the subsequent induction of spermatogenesis. In men with low/absent gonadotropins, such as in Kallman's syndrome, have pre-pubertal testis; exogenous gonadotropins can successfully induce spermatogenesis. In this project, we intend to use a similar strategy by using exogenous gonadotropins to stimulate spermatogenesis in our human testis xenotransplantation model. If successful, this will be the first report of human germ cell maturation outside the human body. The major strength of this project is our established human fetal testis xenotransplantation model. This model is a unique and powerful system which allows us to directly probe the effects of cancer therapies on pre- pubertal testis and begin to understand how toxicity may be reduced or prevented. We also propose to use different strategies to induce spermatogenesis in this human testis model to produce a mature human testis model. This would again be an extremely powerful system for any studies on reproductive toxicology, but would also give us insights into techniques to mature pre-pubertal testis, information which will be critical to the fertility preservation of pre-pubertal boys having cancer therapy. PUBLIC HEALTH RELEVANCE: Our goals for this project are twofold: (1) Validate our human testis xenotransplantation model as a useful tool to study the toxic effect(s) of commonly used cancer chemotherapeutic agents on human testis and (2) hormonally stimulate per-pubertal human testis to develop towards mature sperm in our robust xenotransplantation model. If successful, we will have a direct method to evaluate the impact of any gonadotoxic agent, explore opportunities to minimize their harmful effects on human fertility, and develop the first human-mouse xenotransplant system to restore fertility in the human pre-pubescent population. vcolin 14 October 2009