Response to commentary on manuscript: “The impact of fresh versus cryopreserved testicular sperm on intracytoplasmic sperm injection (ICSI) pregnancy outcomes in men with azoospermia due to spermatogenic dysfunction: a meta-analysis”

9 12 2013

To the Editor:

We appreciate the insightful comments of Dr. Kim (1). As he correctly states, the use of fresh versus cryopreserved sperm has been controversial. While the use of frozen sperm from men with obstructive azoospermia appears to yield equivalent outcomes to fresh sperm, the application to men with nonobstructive azoospermia (NOA) is less certain (2). However, if proven equivalent, Dr. Kim correctly emphasizes the significant logistical and economic burdens that could be improved for couples. Additionally, we agree with his assessment on the importance of methodology. We as male reproductive specialists do not have a standardized, evidence-based protocol for the cryopreservation of sperm. As such, we believe that there should be some caution in mentioning an established detrimental effect of cryopreservation. The analyses that produced such findings suffer the same methodological dependence that is inherent within essentially any cryopreservation data to date (3). Moreover, as data from men with obstructive azoospermia suggest equivalent outcomes, it appears that cryopreservation does not irreparably impact sperm function (2). Read the rest of this entry »


Unknown risk of the reintroduction of malignant cells in a Danish cohort of women autotransplanted with ovarian tissue.

31 03 2011

To the Editor:

Ovarian cryopreservation appears to hold much promise for fertility preservation of women undergoing gonadotoxic therapy. In the Netherlands, cryopreservation of ovarian tissue has been performed for a number of cancer patients. No autotransplantation of ovarian tissue has been performed thus far, due (amongst other reasons) to concerns about the risk of reintroducing the malignancy with the transplant.

The available literature on this subject is not unequivocal. For example, Shaw et al. (1) have shown in a mouse model that lymphoma can be transmitted to the recipient by both fresh and frozen ovarian tissue grafts. Kim et al. (2), on the other hand, reassuringly demonstrated that none of the mice that were xenografted with human ovarian tissue fragments derived from patients with (non)Hodgkin lymphoma developed disease. Read the rest of this entry »

Vitrification with UV-sterilized super-cooled air

22 03 2011

To the Editor:

We read with interest the recent article by Larman and Gardner (1) regarding their alternative technique for vitrifying oocytes/embryos with the carrier Rapid-i. The authors proposed inserting the Rapid-i into the super-cooled air of a straw for instantaneous vitrification and then sealing the open end of the straw (postsealing method) in order to avoid direct contact with liquid nitrogen (LN2). We would like to point out that the super-cooled air inside the straws will be basically composed of nitrogen vapors, due to the nitrogen’s rapid evaporation and molecular weight. For this reason any microorganism accidentally present in the LN2 can also pass to the nitrogen vapor phase (2), and this may lead to the hypothetical contamination of the oocyte/embryos and the inner carrier of Rapid-I. Read the rest of this entry »

Xenografting fresh and cryopreserved human ovarian tissue (revised 10-31-08)

30 10 2008


To the Editor:

In a recent article by Schubert et al. (1), human ovarian cortical samples obtained from benign ovarian cysts were xenografted into SCID mice subcutaneously as either fresh or frozen-thawed pieces . Follicle counts in the grafts and their E2 production as a measure of endocrine function were assessed. While recognizing their valuable work and previous contributions to the field, there are certain points in their study that need to be clarified to the readers.  Read the rest of this entry »