+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Ultrastructural observations of enzymatically treated human blastocysts: Zona-free blastocyst transfer and rescue of blastocysts with hatching difficulties



Ultrastructural observations of enzymatically treated human blastocysts: Zona-free blastocyst transfer and rescue of blastocysts with hatching difficulties



Human Reproduction 16(3): 540-546



Enzymatic treatment of the zona pellucida to either soften or remove totally the zona before blastocyst transfer has resulted in high implantation rates. The zona is usually completely dissolved after 1.5 min exposure with 10 IU pronase at 37 degrees C. Since there may be concerns that pronase treatment for periods of 1.5 min or longer may cause adverse effects on the trophectoderm (TE) and inner cell mass (ICM), the changes to human blastocysts exposed to different time intervals of pronase were investigated. Of 18 blastocysts exposed to pronase for 1.5 min, the zona was completely dissolved and no changes were observed by light microscopy (LM) or transmission electron microscopy (TEM), compared with 11 naturally hatched untreated blastocysts (controls). In another five blastocysts exposed to pronase for 2 min, no LM changes were observed but subtle TEM changes such as fewer bundles of tonofibrils attached to desmosomes were observed. When three other blastocysts were exposed to pronase for 5 min, the blastocoele collapsed, and the TE cells started to show blebbing under LM. Under TEM, the cytoplasm of TE cells was extensively vacuolated and many TE cells showed cytoplasmic blebbing towards the blastocoele. However, the epithelium was uninterrupted with intact tight junctions and desmosomes. Of a separate group of 44 blastocysts cultured in vitro, 54.5% had hatching difficulties when monitored from day 5 to day 8 and 80% of these could be rescued by removal of the zona with pronase for 1.5 min prior to extensive degeneration taking place. The results confirm that the optimal time for softening or complete removal of the zona before transfer was around 1.5 min and that enzymatic treatment was a safe, non-invasive procedure to remove the zona of blastocysts. The human embryonic TE is a very hardy, robust epithelium that withstands pronase treatment.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 011609600

Download citation: RISBibTeXText

PMID: 11228226

DOI: 10.1093/humrep/16.3.540


Related references

Vitrification of zona-free rabbit expanded or hatching blastocysts: a possible model for human blastocysts. Human Reproduction 18(10): 2151-2156, 2003

Glycosaminoglycans Improves Early Development of Zona-free 8-cell Rat Embryos to Blastocysts in a Chemically Defined Medium, but Not the Pregnancy Rate Following Transfer of the Blastocysts. Journal of Reproduction and Development 58(3): 295-301, 2012

Glycosaminoglycans improves early development of zona-free 8-cell rat embryos to blastocysts in a chemically defined medium, but not the pregnancy rate following transfer of the blastocysts. Journal of Reproduction and Development 58(3): 295-301, 2012

Ongoing normal pregnancy after transfer of zona-free blastocysts: implications for embryo transfer in the human. Human Reproduction 12(3): 557-560, 1997

Transfer of completely hatched euploid blastocysts results in signficiantly lower pregnancy outcomes compared to euploid expanded or hatching blastocysts. Fertility and Sterility 110(4): e44-e45, 2018

Zona-free versus laser zona-assisted hatching blastocyst transfer: a comparison of outcomes. Fertility and Sterility 91(5): 1959-1962, 2008

Birth of cloned pigs from zona-free nuclear transfer blastocysts developed in vitro before transfer. Cloning and Stem Cells 8(4): 283-293, 2007

Births after transfer of zona-free blastocysts in oocyte donation cycles. Journal of Assisted Reproduction and Genetics 18(3): 156-159, 2001

Trypsin-like hatching enzyme of mouse blastocysts: Evidence for its participation in hatching process before zona shedding of embryos. Development Growth & Differentiation 36(2): 149-154, 1994

Collection in vitro of a ribonucleic acid (RNA) precursor (5-3H-uridine) by rat blastocyst; differences between normal blastocysts and blastocysts in diapause. Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences. Serie D: Sciences Naturelles 268(1): 188-190, 1969

Single blastocyst transfer (SET) and pregnancy outcome of day 5 and day 6 human blastocysts vitrified using a closed device. Cryobiology 84: 40-45, 2018

High implantation and pregnancy rates with transfer of human hatching day 6 blastocysts. Fertility and Sterility 75(4): 832-833, 2001

Transfer of nonassisted hatched and hatching human blastocysts after in vitro fertilization. Fertility & Sterility 74(1): 163-165, 2000

Pregnancy and live birth following the transfer of vitrified-warmed blastocysts derived from zona- and corona-cell-free oocytes. Reproductive Biomedicine Online 21(4): 527-532, 2011

Atypical hatching of a cow blastocyst leading to separation of complete twin half blastocysts. Veterinary Record 112(13): 301-301, 1983