IntroductionInfertility treatment prior to 1978 proved challenging to both patients and their physicians. The birth of Louise Brown through in vitro fertilization (IVF) was the result of decades-long research in both the basic and clinical sciences and followed hundreds of failed attempts at human IVF [1]. With IVF's successful introduction, related and supportive technologies soon emerged including IVF and the use of donor eggs, cryopreservation and frozen embryo transfer (FET), gamete intra-fallopian transfer (GIFT), zygote intra-fallopian transfer (ZIFT), intra-cytoplasmic sperm injection (ICSI) and less invasive procedures aided by enhancements in equipment, such as transvaginal ultrasound guided oocyte retrieval. It may be hard to recall now that technologies such as IVF, the use of donor eggs, and ICSI were, at first, controversial but so successful in improving outcomes that they were most often adopted into clinical practice without any demonstrated benefit in randomized controlled clinical trials [2].Despite the technical enhancements introduced over time that have resulted in unprecedented cumulative IVF pregnancy rates, a significant percentage of women continue to fail repeated attempts at IVF. While cumulative pregnancy rates increase with increasing cycle number (approximately 75% of women will achieve a live birth by the sixth IVF cycle), per cycle IVF success rates tend to decrease with increasing cycle number. The age blended probability of a live birth is approximately 25% in a woman's first cycle (range [9-33%]), 20% per cycle during her second and third cycles and decreases to less than 20% per cycle during cycles four through six [3]. IVF success rates drop dramatically as women age. Therefore, a patient population exists that will fail to respond to all lines of treatment, including repeated cycles of IVF. For this patient population, IVF using a donor egg or adoption have, until recently, represented the only remaining option(s) [4].The causes of repeated IVF failure are often complex and poorly understood. In contrast, the decrease in fertility observed in women with increasing maternal age has been attributed to a decline in egg and embryo quality as well as increased rates of aneuploidy [5]. Other causes of poor egg/embryo quality beyond age-related factors include medical conditions such as type II diabetes, obesity, polycystic ovary syndrome (PCOS), as well as other genetic and environmental factors [6,7]. Over the past 25 years, an increasing body of clinical and preclinical data has demonstrated that the decline in egg quality is largely due to a reduction in energy production [8][9][10][11]. In the 1990s, there were attempts at improving egg and embryo quality by injecting cytoplasm from young,

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Testicular tissue extraction (TESE) to obtain spermatozoa for use with intracytoplasmic sperm injection (ICSI) has recently been employed in patients with non-obstructive azoospermia. Standard protocol is to retrieve a new sample of testis tissue on the day of oocyte recovery. Unfortunately, approximately 30% of men will possess no spermatozoa in their tissue, making ICSI an impossibility. We investigated whether testicular tissue that was intentionally obtained well before any planned ICSI cycle and cryopreserved could then serve as an efficacious sperm source in a subsequent ICSI cycle. This study reports on 10 men with non-obstructive azoospermia who did have spermatozoa found within their testis tissue at the time of TESE and who chose to use their frozen samples as the source of spermatozoa for a later cycle of ICSI. In 19 cycles the overall fertilization rate was 48%. Embryo transfer occurred in 89% of cycles. Two couples have achieved pregnancy (one ongoing, one delivered). All patients except one had multiple vials of frozen tissue remaining following their first cycle. This approach is offered as an alternative to repeated testicular tissue sampling, as the availability of spermatozoa is assured prior to the initiation of ovulation induction. This tissue can be harvested at the same time as diagnostic biopsy, thereby minimizing the number of surgical procedures.