AG and RM collected the data and drafted the manuscript. DC analyzed the data, drafted the representative results, performed the statistics and revised the manuscript. FMU and LR provided critical discussion of the results and of the whole manuscript.

The protocol for human blastocyst biopsy, here described, follows the guidelines of G.EN.E.R.A. Human Research Ethic Committee.
NOTE: Refer to the Table of Materials for materials required. Further material required entails laboratory footwear and outfit, surgical facemask, hair cover, surgical gloves, a permanent non-toxic marker, forceps and disinfectant. The use of surgical gown, disposable surgical gloves, facemask, hair cover is mandatory to prevent risk ...

<ol>
	<li>Glujovsky, D., Farquhar, C., Quinteiro Retamar, A. M., Alvarez Sedo, C. R., Blake, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cleavage+stage+versus+blastocyst+stage+embryo+transfer+in+assisted+reproductive+technology.">Cleavage stage versus blastocyst stage embryo transfer in assisted reproductive technology.</a> Cochrane Database of Systematic Reviews. (6), CD002118 (2016).</li><li>Dahdouh, E. M., Balayla, J., Garcia-Velasco, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comprehensive+chromosome+screening+improves+embryo+selection:+a+meta-analysis.">Comprehensive chromosome screening improves embryo selection: a meta-analysis.</a> Fertility and Sterility. 104 (6), 1503-1512 (2015).</li><li>Cimadomo, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Impact+of+Biopsy+on+Human+Embryo+Developmental+Potential+during+Preimplantation+Genetic+Diagnosis.">The Impact of Biopsy on Human Embryo Developmental Potential during Preimplantation Genetic Diagnosis.</a> Biomedical Research International. 2016, 7193075 (2016).</li><li>Capalbo, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+between+standard+blastocyst+morphology,+euploidy+and+implantation:+an+observational+study+in+two+centers+involving+956+screened+blastocysts.">Correlation between standard blastocyst morphology, euploidy and implantation: an observational study in two centers involving 956 screened blastocysts.</a> Human Reproduction. 29 (6), 1173-1181 (2014).</li><li>Capalbo, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Implementing+PGD/PGD-A+in+IVF+clinics:+considerations+for+the+best+laboratory+approach+and+management.">Implementing PGD/PGD-A in IVF clinics: considerations for the best laboratory approach and management.</a> Journal of Assisted Reproduction and Genetics. , (2016).</li><li>McArthur, S. J., Leigh, D., Marshall, J. T., de Boer, K. A., Jansen, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pregnancies+and+live+births+after+trophectoderm+biopsy+and+preimplantation+genetic+testing+of+human+blastocysts.">Pregnancies and live births after trophectoderm biopsy and preimplantation genetic testing of human blastocysts.</a> Fertility and Sterility. 84 (6), 1628-1636 (2005).</li><li>Kokkali, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Birth+of+a+healthy+infant+following+trophectoderm+biopsy+from+blastocysts+for+PGD+of+beta-thalassaemia+major.">Birth of a healthy infant following trophectoderm biopsy from blastocysts for PGD of beta-thalassaemia major.</a> Human Reproduction. 20 (7), 1855-1859 (2005).</li><li>Rienzi, L., Ubaldi, F., Anniballo, R., Cerulo, G., Greco, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preincubation+of+human+oocytes+may+improve+fertilization+and+embryo+quality+after+intracytoplasmic+sperm+injection.">Preincubation of human oocytes may improve fertilization and embryo quality after intracytoplasmic sperm injection.</a> Human Reproduction. 13 (4), 1014-1019 (1998).</li><li>Wale, P. L., Gardner, D. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+chemical+and+physical+factors+on+mammalian+embryo+culture+and+their+importance+for+the+practice+of+assisted+human+reproduction.">The effects of chemical and physical factors on mammalian embryo culture and their importance for the practice of assisted human reproduction.</a> Human Reproduction Update. 22 (1), 2-22 (2016).</li><li>Rienzi, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oocyte,+embryo+and+blastocyst+cryopreservation+in+ART:+systematic+review+and+meta-analysis+comparing+slow-freezing+versus+vitrification+to+produce+evidence+for+the+development+of+global+guidance.">Oocyte, embryo and blastocyst cryopreservation in ART: systematic review and meta-analysis comparing slow-freezing versus vitrification to produce evidence for the development of global guidance.</a> Human Reproduction Update. 23 (2), 139-155 (2017).</li><li>Cimadomo, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Associations+of+blastocyst+features,+trophectoderm+biopsy+and+other+laboratory+practice+with+post-warming+behavior+and+implantation.">Associations of blastocyst features, trophectoderm biopsy and other laboratory practice with post-warming behavior and implantation.</a> Human Reproduction. , (2018).</li><li>Evans, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fresh+versus+frozen+embryo+transfer:+backing+clinical+decisions+with+scientific+and+clinical+evidence.">Fresh versus frozen embryo transfer: backing clinical decisions with scientific and clinical evidence.</a> Human Reproduction Update. 20 (6), 808-821 (2014).</li><li>Capalbo, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consistent+and+reproducible+outcomes+of+blastocyst+biopsy+and+aneuploidy+screening+across+different+biopsy+practitioners:+a+multicentre+study+involving+2586+embryo+biopsies.">Consistent and reproducible outcomes of blastocyst biopsy and aneuploidy screening across different biopsy practitioners: a multicentre study involving 2586 embryo biopsies.</a> Human Reproduction. 31 (1), 199-208 (2016).</li><li>Cimadomo, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Failure+mode+and+effects+analysis+of+witnessing+protocols+for+ensuring+traceability+during+PGD/PGS+cycles.">Failure mode and effects analysis of witnessing protocols for ensuring traceability during PGD/PGS cycles.</a> Reproductive Biomedicine Online. 33 (3), 360-369 (2016).</li><li>Gardner, D. K., Schoolcraft, B., Jansen, R., Mortimer, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Towards Reproductive Certainty: Infertility and Genetics Beyond 1999. , 377-388 (1999).</li><li>Cimadomo, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inconclusive+chromosomal+assessment+after+blastocyst+biopsy:+prevalence,+causative+factors+and+outcomes+after+re-biopsy+and+re-vitrification.+A+multicenter+experience.">Inconclusive chromosomal assessment after blastocyst biopsy: prevalence, causative factors and outcomes after re-biopsy and re-vitrification. A multicenter experience.</a> Human Reproduction. , (2018).</li><li>de Boer, K. A., Catt, J. W., Jansen, R. P., Leigh, D., McArthur, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Moving+to+blastocyst+biopsy+for+preimplantation+genetic+diagnosis+and+single+embryo+transfer+at+Sydney+IVF.">Moving to blastocyst biopsy for preimplantation genetic diagnosis and single embryo transfer at Sydney IVF.</a> Fertility and Sterility. 82 (2), 295-298 (2004).</li><li>Capalbo, A., Rienzi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosaicism+between+trophectoderm+and+inner+cell+mass.">Mosaicism between trophectoderm and inner cell mass.</a> Fertility and Sterility. 107 (5), 1098-1106 (2017).</li><li>McCoy, R. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+of+Selection+against+Complex+Mitotic-Origin+Aneuploidy+during+Preimplantation+Development.">Evidence of Selection against Complex Mitotic-Origin Aneuploidy during Preimplantation Development.</a> PLoS Genetics. 11 (10), e1005601 (2015).</li><li>Scott, R. T., Upham, K. M., Forman, E. J., Zhao, T., Treff, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cleavage-stage+biopsy+significantly+impairs+human+embryonic+implantation+potential+while+blastocyst+biopsy+does+not:+a+randomized+and+paired+clinical+trial.">Cleavage-stage biopsy significantly impairs human embryonic implantation potential while blastocyst biopsy does not: a randomized and paired clinical trial.</a> Fertility and Sterility. 100 (3), 624-630 (2013).</li><li>Lee, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Live+births+after+transfer+of+rebiopsy+and+revitrification+of+blastocyst+that+had+&#8220;no+diagnosis&#8221;+following+trophectoderm+biopsy.">Live births after transfer of rebiopsy and revitrification of blastocyst that had &#8220;no diagnosis&#8221; following trophectoderm biopsy.</a> Fertility and Sterility. 106 (3), e164 (2016).</li><li>Capalbo, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnostic+efficacy+of+blastocoel+fluid+and+spent+media+as+sources+of+DNA+for+preimplantation+genetic+testing+in+standard+clinical+conditions.">Diagnostic efficacy of blastocoel fluid and spent media as sources of DNA for preimplantation genetic testing in standard clinical conditions.</a> Fertility and Sterility. 110 (5), 870-879 (2018).</li><li>Hammond, E. R., Shelling, A. N., Cree, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nuclear+and+mitochondrial+DNA+in+blastocoele+fluid+and+embryo+culture+medium:+evidence+and+potential+clinical+use.">Nuclear and mitochondrial DNA in blastocoele fluid and embryo culture medium: evidence and potential clinical use.</a> Human Reproduction. 31 (8), 1653-1661 (2016).</li><li>Vera-Rodriguez, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Origin+and+composition+of+cell-free+DNA+in+spent+medium+from+human+embryo+culture+during+preimplantation+development.">Origin and composition of cell-free DNA in spent medium from human embryo culture during preimplantation development.</a> Human Reproduction. 33 (4), 745-756 (2018).</li></ol>

Only well-experienced skilled embryologists who have completed their training period should perform both TE biopsy and blastocyst vitrification. Furthermore, a witness is required to monitor the procedures and guarantee an efficient traceability during i) the movements of the biopsied blastocyst from the biopsy dish (Supplementary Figure 1) to the post-biopsy dish (Supplementary Figure 1), then to the vitrification plate (Supplementary Figure 1) and lastly to the vitrifi...

The main goal of modern human embryology is to maximize the number live births per stimulated cycle and reduce costs, time and efforts to achieve a pregnancy. To accomplish this goal, validated approaches for embryo selection should be employed to identify reproductively competent embryos within a cohort obtained during an IVF cycle. According to the latest evidences, blastocyst culture1 combined with comprehensive chromosomal testing and vitrified-warmed euploid embryo transfer (ET) is the most efficient framework to increase IVF efficiency2. Clearly, aneuploidy testing requires an embryonic specimen, which at present is mostly represented from few cells retrieved from the trophectoderm (TE), i.e., the section of the blastocyst that gives origin to embryo annexes (e.g., the placenta) during pregnancy. Beyond karyotype analysis, also single gene mutations might be assessed from a TE biopsy as part of a clinical strategy known as preimplantation genetic testing (PGT; -A for aneuploidies, -SR for structural chromosomal rearrangements, -M for monogenic diseases). Other oocyte/embryo biopsy methods have been theorized and adopted clinically across the last decades, namely polar bodies biopsy and blastomere biopsy. However, their use is reduced nowadays since their procedural drawbacks (e.g., higher workload and risk for reproductive impact) and diagnostic limitations (e.g., single cell analysis issues) implicitly hinder a sufficient balance between costs, risks and benefits (for a review see3).
In this paper, one of the main protocols for TE biopsy is thoroughly described together with the subsequent vitrification, warming and transfer procedures required. The workflow here outlined is ideal for a busy PGT unit.
As already described previously by our group4,5, the procedure involves the sequential opening of the zona pellucida of fully-expanded blastocysts and removal of few TE cells (on average 7-8). Compared to the day 3 laser-assisted hatching-based blastocyst biopsy method6, this procedure might ease the daily schedule of an IVF unit where delicate procedures, such as blastocyst biopsy and vitrification, must be timely performed. As soon as the blastocyst reaches its full expansion, the biopsy can be carried out by selecting the TE cells to remove, thereby preventing the risk of herniation of the inner cell mass (ICM), which would otherwise render the procedure challenging. In literature, a third protocol of blastocyst biopsy has been also described, which involves laser-assisted hatching being performed once the embryo has already reached the blastocyst stage, few hours before the procedure5,7. However, this approach is more time-consuming and mainly suits IVF units that are implementing TE biopsy in the hands of limitedly experienced operators and in view of a moderate-low daily workload.
Intracytoplasmatic sperm injection (ICSI)8 should be a consolidated technique if aiming at conducting genetic analyses in IVF. Similarly, a proper culture system to safely harvest embryos to the blastocyst stage is crucial for the implementation of TE biopsy strategy. An adequate number of incubators, as well as the use of low oxygen tension are key prerequisites to this end, not to compromise the blastocyst rate9. At the same time, an efficient cryopreservation program is needed to safely manage a PGT cycle. In the last decade, the implementation of vitrification has boosted embryo cryo-survival rates even up to &#62;99%10,11. This provided sufficient time to perform genetic testing and postpone embryo transfer to the following menstrual cycle, on a non-stimulated and probably more receptive endometrium12.
Both TE biopsy and vitrification are demanding tasks requiring stringent skills and their effectiveness might vary across unexperienced operators. A specific training period is therefore advocated before allowing each operator to perform these procedures clinically; moreover, the maintenance of the operators&#8217; skills should be assessed periodically by monitoring key performance indicators (KPI) for cryopreservation and biopsy procedures. Each IVF clinic should set internal KPIs to this end, which must approximate the ones published by international consortia and/or the outcomes published by reference laboratories.
TE biopsy, vitrification-warming and witnessing procedures are validated techniques at our unit, that have been standardized across all the operators involved as reported in three previous publications11,13,14.

<table>
	<tbody>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cold tube rack</td>
			<td>Biocision</td>
			<td>XTPCR96</td>
			<td></td>
		</tr>
		<tr>
			<td>Electronic pipette controller</td>
			<td>Fisher Scientific</td>
			<td>710931</td>
			<td></td>
		</tr>
		<tr>
			<td>Flexipet adjustable handle set</td>
			<td>Cook</td>
			<td>G18674</td>
			<td>Stripper holder</td>
		</tr>
		<tr>
			<td>Gilson Pipetman</td>
			<td>Gilson</td>
			<td>66003</td>
			<td>p20</td>
		</tr>
		<tr>
			<td>IVF Electronic Witness System</td>
			<td>CooperSurgical Fertility &#38; Genomic Solutions</td>
			<td></td>
			<td>RI Witness ART Management System</td>
		</tr>
		<tr>
			<td>Inverted microscope</td>
			<td>Nikon</td>
			<td>Eclipse TE2000-U</td>
			<td></td>
		</tr>
		<tr>
			<td>Laminar Flow Hood</td>
			<td>IVF TECH</td>
			<td></td>
			<td>Grade A air flow</td>
		</tr>
		<tr>
			<td>Laser objective</td>
			<td>RI</td>
			<td>Saturn 5</td>
			<td></td>
		</tr>
		<tr>
			<td>Microinjectors</td>
			<td>Nikon Narishige</td>
			<td>NT-88-V3</td>
			<td></td>
		</tr>
		<tr>
			<td>Mini centrifuge for PCR tubes</td>
			<td>Eppendorf</td>
			<td>CSLQSPIN</td>
			<td>for 0.2ml PCR tubes</td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Leica</td>
			<td>Leica M80</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermostat</td>
			<td>Panasonic</td>
			<td>MCO-5AC-PE</td>
			<td></td>
		</tr>
		<tr>
			<td>Tri-gas incubator</td>
			<td>Panasonic</td>
			<td>MCO-5M-PE</td>
			<td>02/CO2</td>
		</tr>
		<tr>
			<td>Consumables</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Biopsy pipette</td>
			<td>RI</td>
			<td>7-71-30FB35720</td>
			<td>30&#181;m ID, flat 35&#176;C</td>
		</tr>
		<tr>
			<td>Cryolock</td>
			<td>Cryolock</td>
			<td>CL-R-CT</td>
			<td></td>
		</tr>
		<tr>
			<td>CSCM complete</td>
			<td>Irvine Scientific</td>
			<td>90165</td>
			<td>IVF culture medium supplemented with HSA</td>
		</tr>
		<tr>
			<td>Embryo Transfer Catheter</td>
			<td>Cook</td>
			<td>G17934</td>
			<td></td>
		</tr>
		<tr>
			<td>Flexipet pipette</td>
			<td>Cook</td>
			<td>G26712</td>
			<td>140&#181;m stripping pipette tip</td>
		</tr>
		<tr>
			<td>Flexipet pipette</td>
			<td>Cook</td>
			<td>G46020</td>
			<td>300&#181;m stripping pipette tips</td>
		</tr>
		<tr>
			<td>Holding pipette</td>
			<td>RI</td>
			<td>7-71-IH35/20</td>
			<td>30&#181;m ID, flat 35&#176;C</td>
		</tr>
		<tr>
			<td>Human Serum Albumin</td>
			<td>Irvine Scientific</td>
			<td>9988</td>
			<td></td>
		</tr>
		<tr>
			<td>IVF One well dish</td>
			<td>Falcon</td>
			<td>353653</td>
			<td></td>
		</tr>
		<tr>
			<td>Mineral Oil for embryo culture</td>
			<td>Irvine Scientific</td>
			<td>9305</td>
			<td></td>
		</tr>
		<tr>
			<td>Modified HTF Medium</td>
			<td>Irvine Scientific</td>
			<td>90126</td>
			<td>Hepes-Buffered medium</td>
		</tr>
		<tr>
			<td>Nuclon Delta Surface</td>
			<td>Thermofisher scientific</td>
			<td>176740</td>
			<td>IVF dish 4-well plate with sliding lid</td>
		</tr>
		<tr>
			<td>Primaria Cell culture dish</td>
			<td>Corning</td>
			<td>353802</td>
			<td>60x15mm</td>
		</tr>
		<tr>
			<td>Reproplate</td>
			<td>Kitazato</td>
			<td>83016</td>
			<td></td>
		</tr>
		<tr>
			<td>Serological pipette</td>
			<td>Falcon</td>
			<td>357551</td>
			<td>10ml</td>
		</tr>
		<tr>
			<td>Sterile disposable Gilson tips</td>
			<td>Eppendorf</td>
			<td>0030 075.021</td>
			<td>200&#181;l</td>
		</tr>
		<tr>
			<td>Tubing Kit</td>
			<td>Provided by the genetic lab</td>
			<td></td>
			<td>PCR tubes (0.2mL), loading solution, biopsy washing solution</td>
		</tr>
		<tr>
			<td>Vitrification media</td>
			<td>Kitazato</td>
			<td>VT801</td>
			<td>Equilibration and vitrification solutions</td>
		</tr>
		<tr>
			<td>Warming media</td>
			<td>Kitazato</td>
			<td>VT802</td>
			<td>Thawing and dilution solutions</td>
		</tr>
	</tbody>
</table>

human blastocyst biopsy and vitrification

Blastocyst biopsy is performed to obtain a reliable genetic diagnosis during IVF cycles with preimplantation genetic testing. Then, the ideal workflow entails a safe and efficient vitrification protocol, due to the turnaround time of the diagnostic techniques and to transfer the selected embryo(s) on a physiological endometrium in a following natural cycle. A biopsy approach encompassing the sequential opening of the zona pellucida and retrieval of 5-10 trophectoderm cells (ideally 7-8) limits both the number of manipulations required and the exposure of the embryo to sub-optimal environmental conditions. After proper training, the technique was reproducible across different operators in terms of timing of biopsy (~8 min, ranging 3-22 min based on the number of embryos to biopsy per dish), conclusive diagnoses obtained (~97.5%) and live birth rates after vitrified-warmed euploid blastocyst transfer (&#62;40%). The survival rate after biopsy, vitrification and warming was as high as 99.8%. The re-expansion rate at 1.5 h from warming was as high as 97%, largely dependent on the timing between biopsy and vitrification (ideally &#8804;30 min), blastocyst morphological quality and day of biopsy. In general, it is better to vitrify a collapsed blastocyst; therefore, in non-PGT cycles, laser-assisted artificial shrinkage might be performed to induce embryo collapse prior to cryopreservation. The most promising future perspective is the non-invasive analysis of the IVF culture media after blastocyst culture as a putative source of embryonic DNA. However, this potential avant-garde is still under investigation and a reliable protocol yet needs to be defined and validated.

Figure 6 represents a scheme of all the outcomes of a biopsy procedure that can be adopted to standardize the protocol and monitor the performance of each operator. The main procedural outcome is the timing to complete the biopsy/biopsies; the main technical outcome is the quality of the plot produced after genetic testing that might result in either a conclusive or inconclusive diagnosis, the latter of which requires a re-biopsy of the undiagnosed blastocyst...

Watch this Scientific Journal Video about Human Blastocyst Biopsy and Vitrification at JoVE.com

Human Blastocyst Biopsy and Vitrification

Blastocyst biopsy and vitrification are required to efficiently conduct preimplantation genetic testing. An approach entailing the sequential opening of the zona pellucida and retrieval of 7-8 trophectoderm cells in day 5-7 post-insemination limits both the number of manipulations required and the exposure of the embryo to sub-optimal environmental conditions.

Blastocyst biopsy is performed to obtain a reliable genetic diagnosis during IVF cycles with preimplantation genetic testing. Then, the ideal workflow ...

Both blastocyst biopsy and vitrification have been a revolution in IVF, in vitro fertilization, allowing embryologists from all around the world to perform preimplantation genetic testing on human embryos with minimal risk for the embryo. Trophectoderm biopsy has allowed the retrieval of about seven cells from a fully grown embryo, thereby enabling robust downstream genetic analysis. Moreover, no impact has been shown, to date, for this approach.The clinical efficiency of this workflow allows patients with monogenic conditions and all those patients with increased risk of chromosomal abnormalities within their blastocyst to benefit from preimplantation genetic testing. There is still room for improving the current strategies of embryo selection. For instance, miRNomic and proteomic profiling represent intriguing options to complement preimplantation genetic testing on a single trophectoderm biopsy.Unexperienced operators often struggle with opening and penetrating the zona pellucida. It's just a matter of focus. The blastocyst, laser objective, and pipettes should be on the same focal plane.After labeling the biopsy dish with the patient's details, with a permanent, non-toxic marker, number each 10-microliter drop of HEPES-buffered medium with the embryo and cycle ID.Using a 300-micrometer stripping pipette, transfer a viable, fully expanded blastocyst to the first drop of the biopsy dish and rinse the drop to remove the excess culture medium, before moving the blastocyst into the second drop in the dish. Place the dish under an inverted microscope, and prime the biopsy pipette with medium from the third drop of the biopsy dish. Under a 20 times magnification, orient the blastocyst to obtain a clear view of the inner cell mass at seven o'clock, and secure the embryo on the holding pipette.Focus on the zona pellucida so that both the pipettes and the blastocyst are on the same focal plane. Switch to the laser objective, and position the laser pointer on the zona pellucida at the opposite side of the inner cell mass. Drill the zona pellucida with two to three laser pulses, and gently press the biopsy pipette against the zona pellucida to allow medium to be blown through the breach to detach the trophectoderm cells from the internal surface.When the trophectoderm is detached, enter through the hole and aspirate seven to eight trophectoderm cells into the biopsy pipette with gentle suction. While applying a moderate suction to stretch the target cells, slightly move the biopsy pipette backwards and direct the laser towards the thinnest part of the aspirated cells. Fire two to five laser pulses at the junctions between the cells to separate the target cells from the body of the embryo.When the trophectoderm fragment has been separated from the blastocyst, release the fragment into the same biopsy drop far from the blastocyst to prevent the fragment from being sucked back into the biopsy pipette. Release the blastocyst from the holding pipette, and promptly raise both pipettes to prevent the fragment from sticking to pipettes. Then image the biopsied fragment for quality control purposes.When all of the blastocysts have been biopsied as just demonstrated, move the biopsy dish back to the laminar flow hood and label the post-biopsy culture dish with the couple ID and each drop with the embryo and cycle IDs. In presence of a witness, rinse the blastocyst in clean IVF medium and move the blastocyst to its corresponding drop in the post-biopsy dish. Then place the post-biopsy dish to a 37-degree Celsius, 6%carbon dioxide, and 5%oxygen incubator.In the presence of the witness and inside a laminar flow hood at room temperature, label the PCR tubes with a permanent, non-toxic marker. Label the lid of a 60 x 15-millimeter tubing culture dish with the biopsied embryo IDs, and add two 10-microliter drops of biopsy washing solution to the dish. Prime a 140-micrometer stripping pipette with biopsy washing solution from the second drop of the tubing dish under the stereo microscope to visualize the trophectoderm fragments.Gently release some biopsy washing solution upon the trophectoderm fragment, and load the fragment into the stripping pipette. Move the fragment to the second drop of biopsy washing solution, and carefully rinse the tissue two to three times. Transfer the trophectoderm fragment to the bottom of the appropriately labeled PCR tube with loading solution, taking care to avoid touching the walls of the tube with the tip of the stripping pipette.When all of the fragments have been added to their tubes, spin all of the tubes in a mini centrifuge for a few seconds to sediment the fragments. Then store the samples at minus 20 degrees Celsius until they are shipped to the referring genetic laboratory for testing. Within 30 minutes of trophectoderm biopsy, label a vitrification plate with the patient's details and the IDs of the blastocysts that must be vitrified.Using special cold temperature-resistant cryolabels, label the vitrification supports with patient's name and surname, couple ID, ID of the embryo that will be loaded on to it, and the date of the procedure. At room temperature, dispense 300 microliters of equilibration solution for each blastocyst that will be vitrified and, in the presence of a witness, use a 300-micrometer stripping pipette to move the blastocyst into one volume of equilibration solution. Leave the blastocyst in the equilibration solution for 13 to 15 minutes.After an initial shrinkage of the volume, a gradual re-expansion will be observed. At the end of the equilibration, add 300 microliters of vitrification solution to the second well of the vitrification plate and transfer the completely re-expanded blastocyst to the vitrification solution for one minute. At the end of the incubation, rinse the blastocyst to dilute the equilibration solution and, in the presence of a witness, load the blastocyst on the vitrification support.Remove the excess of vitrification solution. A subtle film of solution should surround the blastocyst. Plunge the vitrification support into liquid nitrogen, and vigorously move the support to reduce the risk of bubble formation close to the specimen.Then place the protective cap on the support while the vitrification support is still submerged in liquid nitrogen. Of the 1, 544 trophectoderm biopsy procedures conducted over this representative two-year period, between one to four blastocysts were biopsied per procedure for between three to 22 minutes per procedure. In these plots, the mean timing of the biopsy for each operator along the study trimesters are shown, with a mean overall value of 8.24 minutes.It is helpful to acquire an image of each biopsied fragment for quality control purposes to evaluate whether the cause of inconclusive diagnoses was imputable to the dimension and/or quality of the fragment, to the tubing, or to some issues in the processing of the sample in the genetic laboratory. In this study, 572 euploid blastocysts were warmed to undergo an embryo transfer after a diagnosis of euploidy. All the blastocysts vitrified within 30 minutes, with 2.4%of the blastocysts not re-expanding between 31 and 90 minutes and 4.9%not re-expanding beyond 90 minutes from rewarming.Especially for poor quality and/or day seven blastocysts, the timing between biopsy and vitrification seems crucial to achieve re-expansion after warming. Take care to focus before opening the zona pellucida when exposing the junction between the trophectoderm cell and firing, and take care also to prevent blastocyst re-expansion before vitrification. Two other blastocyst biopsy approaches exist, both entailing zona pellucida opening and waiting for a spontaneous arching of the trophectoderm cells.These approaches are easier but require more manipulations and are more time-consuming. The efficacy of this workflow allows the implementation of molecular technologies in IVF in order to try to select the blastocyst with the highest chance to implant before the embryo transfer. Remember not to use any device or solution that might be toxic to the embryos and to prevent DNA contamination by using DNA-free materials.

human-blastocyst-biopsy-and-vitrification

Research

JoVE Journal

Developmental Biology

21.7K ビュー.  G.EN.E.R.A. Centers for Reproductive Medicine. 胚盤胞生検とガラス化の両方がIVFの革命であり、体外受精の両方であり、世界中の胚学者が胚のリスクを最小限に抑えてヒト胚に着床前遺伝子検査を行うことを可能にした。栄養細胞化生検は、完全に成長した胚から約7個の細胞を取り出すことを可能にし、それによって堅牢な下流遺伝子解析を可能にした。さらに、このアプローチに対する影響は、現在までに示され?...