Human Reproduction, Vol. 15, No. 9, 2057,
September 2000
© 2000 European Society of Human Reproduction and Embryology
Letters to the Editor |
Telomerase activity in testicular biopsy material
Department of Urology, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Hindenburgdamm 30, 12200 Berlin, Germany
Dear Sir,
We read with great interest the recent paper (Yamamoto et al., 1999a
) in which the exact determination of telomerase activity by a telomeric repeat amplification protocol and an automatic DNA sequencer analysis is presented as a suitable technique for differentiating between various gametogenic impairments. The authors thought that the determination of telomerase activity levels could be used to distinguish between gametogenic impairments with detection of haploid germ cells and maturation arrest at the level of diploid germ cells. They thus called into question a previous study (Fujisawa et al., 1998) reporting the opposite results largely on the basis of a different analytic technique (quantitative ELISA versus DNA sequencer). The experience gained from our own studies leads us to take a critical view of the differentiation technique postulated by Yamamoto et al. (1999a).
- (i) As described by the authors, focal islands of spermatogenesis are frequently overlooked during the conventional diagnostic work-up with haematoxylin–eosin staining. This is partly due to the fact that not every diagnostic biopsy in hypergonadotrophic patients is representative for the entire testicle, as evidenced by the different results obtained from multiple biopsies of the same testicle (Schulze et al., 1999). This suggests that, in hypergonadotrophic patients with islands of spermatogenesis adjacent to Sertoli cell-only areas, the assessment of telomerase activity cannot reliably predict whether haploid germ cells are detectable, since the non-homogeneity of the biopsy limits the identification of focal spermatogenesis with mature gametes by an increased telomerase value.
- (ii) Another point that supports these doubts is the decrease of telomerase activity with increasing gamete differentiation. It has not yet been clarified whether haploid germ cells do evidence telomerase activity and, if so, at what level. This was called into question in a study (Ravindranath et al., 1997
), not discussed by the authors. There is consensus on the statement also made by the authors that telomerase activity is highest in primary spermatocytes and decreases as germ cell differentiation increases, mature spermatids and spermatozoa showing none at all. This reduces the likelihood of a significant difference between patients with maturation arrest at the primary spermatocyte level and those with focally complete gametogenesis.
- (iii) We obtained discrepant results when classifying telomerase activity and gametogenic impairments, particularly in hypergonadotrophic patients with strongly reduced spermatogenesis (Figure 1
). Telomerase activity, determined according to the formula mentioned by the authors (Yamamoto et al., 1999b), was in five of 12 patients with a Johnsen Score of 2–5 higher than in those (n = 14) with focally complete gametogenesis. The possibility of some measurement inaccuracy due to the competitive and nonlinear amplification of the telomeric repeat amplification products and the internal standard cannot be ruled out. However, the results are in contrast to those postulated by the authors.
- (ii) Another point that supports these doubts is the decrease of telomerase activity with increasing gamete differentiation. It has not yet been clarified whether haploid germ cells do evidence telomerase activity and, if so, at what level. This was called into question in a study (Ravindranath et al., 1997
|
Despite the above points of criticism, the study by Yamamoto et al. presents impressive results for assessing gametogenic impairments by determination of telomerase activity. We think that determination of telomerase subunits by quantitative real-time RT-PCR may open up new perspectives for assessing gametogenic impairments. Though this approach cannot change the physiological factors described under points (i) and (ii), it avoids the methodological problems in determining telomerase activity mentioned under point (iii).
Notes
1 To whom correspondence should be addressed E-mail: schrader{at}medizin.fu-berlin.de 
References
Fujisawa, M., Tanaka, H., Tatsumi, N. et al. (1998) Telomerase activity in the testis of infertile patients with selected causes. Hum. Reprod., 13, 1476–1479.
Ravindranath, N., Dalal, R., Solomon, B. et al. (1997) Loss of telomerase activity during male germ cell differentiation. Endocrinology, 138, 4026–4029.
Schulze, W., Thoms, F. and Knuth, U.A. (1999) Testicular sperm extraction: comprehensive analysis with simultaneously performed histology in 1418 biopsies from 766 subfertile men. Hum. Reprod., 14, (Suppl. 1), 82–96.
Yamamoto, Y., Sofikitis, N., Mio, Y. et al. (1999a) Highly sensitive quantitative telomerase assay of diagnostic testicular biopsy material predicts the presence of haploid spermatogenic cells in therapeutic testicular biopsy in men with Sertoli cell-only syndrome. Hum. Reprod., 14, 3041–3047.
Yamamoto, Y., Sofikitis, N., Ono, K. et al. (1999b) Postmeiotic modifications of spermatogenic cells are accompanied by inhibition of telomerase activity. Urol. Res., 27, 336–345.[Web of Science][Medline]
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  M. Sousa, N. Cremades, J. Silva, C. Oliveira, L. Ferraz, J.T. da Silva, P. Viana, and A. Barros Predictive value of testicular histology in secretory azoospermic subgroups and clinical outcome after microinjection of fresh and frozen-thawed sperm and spermatids Hum. Reprod., July 1, 2002; 17(7): 1800 - 1810. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Schrader, M. Muller, W. Schulze, R. Heicappell, H. Krause, B. Straub, and K. Miller Quantification of the expression level of the gene encoding the catalytic subunit of telomerase in testicular tissue specimens predicts successful sperm recovery Hum. Reprod., January 1, 2002; 17(1): 150 - 156. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||