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To compare the frequency of Y-chromosome microdeletions in Japanese and African azoospermic …
Biology Articles » Reproductive Biology » Prospective assessment of Y-chromosome microdeletions and reproductive outcomes among infertile couples of Japanese and African origin » Discussion
This study shows the frequency of microdeletion in the AZF region of the Y-chromosome to be 6.2% among Japanese males with azoospermia and oligozoospermia. Our findings are consistent with prior reports which found a microdeletion frequency of 1% to 35%, depending on the male subfertility definition used for inclusion and on the choice of sequence tagged sites used for screening [6,14,28,36,37]. In our populaton, the majority of Y-chromosome microdeletions (~70%) occurred in the AZFc region of the AZF region and is in agreement with other investigations [27,38]. Previous studies on Y-chromosome microdeletion frequency in Japanese males [15-22] suggested a range of 7.6% – 17.0%. Separating these Japanese patients with deletions into azoospermic and oligozoospermic cases revealed frequencies of 15.4 % and 3.4%, respectively.
We excluded from analysis two study patients with Y-chromosome microdeletions at sY202 and sY243. Indeed, no known location has been ascertained so far for sY202 and sY243 is found in several locations both inside and outside DAZ. Nevertheless, the frequency observed in our population is consistent with previous data describing a 15%-20% microdeletion frequency in men with idiopathic azoospermia and a 7%-10% frequency in men with severe idiopathic oligozoospermia [15,23,38,39]. Interestingly, no microdeletions were documented among the 49 African males with azoospermia or severe oligozoospermia. Since ours is the first study of Y-chromosome microdeletion frequency to be undertaken on an African population, a comparison with earlier data sets from this group was not possible.
The absence of Y-chromosome microdeletions in our African study population may be due to limited sampling. However, this finding is in general agreement with the few studies conducted in other parts of Africa that found frequencies of male infertility secondary to oligozoospermia or azoospermia to be much lower (~20%) in Africa than elsewhere [40-48]. Unlike some other regions, the most common cause of male infertility in Africa was found to be infection. Yeboah et al. reported on 595 infertile African males and found ~70% of them to have inflammatory testicular lesion due to STD . A multi-center study by Cates et al. demonstrated that >50% of African couples had secondary infertility due to STD , which was a rate much higher than in non-African countries (i.e.,
In our study all active STD cases were excluded, although the association between male infertility and STD remains controversial. Some investigators have shown that treatment of infection directly improved the sperm quality in oligozoospermia [42,43] while others did not see any improvement in sperm quality after treatment [44,45]. It is difficult to know the precise frequency of azoospermia and oligozoospermia in Africa as certain cultural factors (e.g., polygamy) are more common than in other parts of the world . Therefore, an azoospermic man may have children whose actual biological father was another man if the wife had extramarital intersourse with a fertile male [47,48]. Financial constraints did not enable testing to confirm paternity when babies were born after infertility treatments at our centers.
All 5 cases with Y-chromosome microdeletion in the AZFc region had successful outcomes following IVF+ ICSI. A comparison of reproductive outcomes between couples with AZFc microdeletion and couples with an intact Y-chromosome showed no statistically significant difference. Our results confirm previous studies showing that Y-chromosome microdeletions do not appear to adversely affect fertilization and pregnancy rates (either in azoospermic or severe oligozoospermic men) when sperm are successfully retrieved [26-33,36]. The concerns that IVF+ICSI might yield poorer results in the setting of Y-chromosome microdeletions were not seen in previous reports [26-30]. However, Van Volde et al.  found fertilization and embryo quality to be significantly lower in couples with Y-chromosome microdeletions compared to couples without Y-chromosome microdeletions; pregnancy and take home baby rates were not statistically different.
In conclusion, our investigation did not detect any Y-chromosome microdeletions in azoospermic or severely oligozoospermic men of African origin. This was in contrast to seven cases of Y-chromosome microdeletion identified in Japanese males. Furthermore, comparison of embryo characteristics in Japanese couples with Y-chromosome microdeletion and control couples (those with no Y-chromosome microdeletion) revealed no statistically significant difference. We regard it as premature to conclude definitively that Y-chromosome microdeletion in azoospermic and oligozoospermic African males is not as common as in other races, due to limited sampling. We hope to continue this investigations with a larger patient population to provide additional information on the overall frequency of azoospermia/oligozoospermia in African males, as well as the association of these conditions with Y-chromosome microdeletions.
Acknowledgements We wish to thank Dr. Takafumi Utsunomiya, Yoko Kumasako and Keiko Hirotsuri of St. Luke hospital for their advice and technical help ; We also wish to thank Prof. Kensuke Yamamoto, Dr. Kazuo Aoki, Prof. Junichi Misumi and Akira Kono of Oita University school of Medicine for their help in study design and constant examination of our data; Drs. Ramzy E. Kisanga and Godfrey Lema of Muhimbili University of college science, Dar-es-salaam, Tanzania for their technical assistance while in Tanzania and San Francisco Edit http://www.sfedit.net for editing this manuscript.
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