MicroSort® Separation of X- and Y-chromosome bearing sperm: ongoing clinical trial results after intrauterine insemination (IUI), in-vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI).

Abstract

Objective: The purpose of this study is to evaluate the efficacy of flow cytometric separation of X- and Y-bearing sperm (MicroSort), clinical pregnancy rate after IUI, IVF, and ICSI, and birth gender following conception with sperm sorted for the X chromosome (XSort®) and Y chromosome (YSort®). This study also evaluates the proportion of female embryos conceived after XSort, determined by preimplantation embryo diagnosis (PGD), to reduce the probability of X-linked genetic disorders. Design: Prospective Institutional Review Board (IRB) approved clinical trial study to determine the efficacy and safety of flow cytometric separation of X- and Y-bearing human sperm. Materials/Methods: The primary patient inclusion criteria includes married couples sorting to reduce the probability of X-linked disorders or for Family Balancing (sorting for the less represented sex of children in the family). Fresh and frozen semen specimens were stained with 9μM Hoechst 33342 for 1 hour at 35°C and subsequently sorted through a modified FACS® Vantage equipped with an ultra violet laser operating at 100 mW power. The sorted specimen was either used immediately or frozen for subsequent use with IVF or ICSI. A small unused portion of the sorted sample was analyzed by fluorescence in-situ hybridization (FISH) using alpha satellite DNA probes specific for the X and Y chromosomes. Results: Between June 1994 and January 2001, 881 patients had 1245 IUI cycles, 45 IVF cycles, 285 ICSI cycles, and 34 frozen embryo transfer (FET) cycles after MicroSort sperm separation. The overall average pregnancy rate per cycle for IUI, IVF, ICSI, and FET was 14% (174/1245), 26.7% (12/45), 26.3% (75/285), and 29.4% (10/34) respectively. For the year 2000, the average IUI pregnancy rate was 21.4% (86/401) per cycle using an average of 201,000 motile sperm and the average IVF/ICSI pregnancy rate was 36.7% (29/79) per cycle. Of the 881 total patients, 667 had 1278 XSort cycles and 214 patients had 331 YSort cycles. The overall FISH results indicated an average purity of 87.5% after XSort and 67.8% after YSort. Pregnancies with known gender after XSort and YSort resulted in 89.5% (145/162) girls and 70.0% (21/30) boys respectively. MicroSort to reduce the probability of X-linked disorders resulted in 89.7% (245/273) female embryos after XSort and PGD, 21 clinical pregnancies and 13 unaffected babies born so far. A total of 271 clinical pregnancies from 1609 cycles have resulted in 156 babies born so far. Conclusions: MicroSort sperm separation provides a substantial enrichment of X- and Y-bearing sperm as determined by DNA analysis. The use of MicroSort sperm with IUI, IVF and ICSI results in pregnancy rates comparable to the use of sperm reported in the literature without MicroSort. The resulting birth gender after MicroSort is comparable to the proportion of X- and Y-bearing sperm enrichment after XSort and YSort. The use of XSort to reduce the probability of X-linked disorders provides a substantial increase in the proportion of female (unaffected) embryos available for replacement after PGD.