Is there a future for spermatid injections?

Abstract

Microinjection of spermatids into oocytes has proven to be a successful assisted reproduction procedure in the animal model. In the human, low fertilization and cleavage to the 4-cell stage were reported after intracytoplasmic sperm injection (ICSI) with round spermatids. In comparison with a conventional ICSI-testicular sperm extraction (TESE) programme, the implantation rate after round spermatid injection is dramatically low. Different problems have been encountered during the development of the spermatid injection technique and they could be partially responsible for the lower outcome when using round spermatids. Compared with the round spermatid cells, spermatids in the elongation phase are easy to isolate and identify from other round cells present in a wet preparation. The morphological identification does not reveal anything about the viability or the genetic normality of the round spermatids. Severe testicular dysfunction may have consequences on the quality of the few spermatogenic cells present. Others factors, such as the pathology of the patient, play an important role in the successful treatment. Even if the results are extremely low, spermatid injection seems more favourable for men who have already proven their capacity to produce some spermatozoa. A spermatogenic block at the round spermatid level has led to early abortions, increasing the suspicion of the role of a genetic factor. In order for this technique to be safe for use in clinics, more intensive work is needed to improve the selection and handling of cells and to ascertain the genomic imprinting and gene expression necessary for embryonic development. Hence, when using immature cells for conception, the screening of the patient and the follow-up of the pregnancies and babies should be mandatory.