Viability Morphokinetic Markers
Viability of the embryo correlates with the embryo’s competence to implant and is expressed by its ability to develop to blastocyst stage in 5-6 days of in-vitro cultivation and to start the process of hatching.
We distinguish between three groups of morphokinetic properties with an impact on viability:
- Morphokinetics indicating ability to produce relevant number of cells
- Morphokinetics indicating differentiation of ICM cells into trophectoderm
- Morphokinetics indicating embryo's ability to Blastocyst Hatching
Morphokinetics Indicating Ability to Produce Relevant Number of Cells
The time (t) interval (hrs) between ICSI fertilisation (tCSI) and the occurrence of the cell Cleavage . The cleavage of the cells occur within a specific time frame and is influenced by specific processes of early embryo development.
The dynamic of the cell shape changes is recognized and expressed by Activity Graph.
At present the inherited and meiotic genetic anomalies are not recognisable without preimplantation or prenatal testing. On the other side, the abnormal cleavages (the major source of mitotic aneuploidies responsible for developmental arrest, implantation failure and early miscarriages) can be detected by time‑lapse imaging system.
| Number of cells | Abbreviation |
|---|---|
| 1 cell | t1 |
| 2 cells | t2 |
| 3 cells | t3 |
| 4 cells | t4 |
| 5 cells | t5 |
| 8 cells | t8 |
| 9 cells | t9 |
| 17 cells | t17 |
| 33 cells | t33 |
| 65 cells | t65 |
| 129 cells | t129 |
An interval between the cleavage of the first and the last daughter cells of the same mitotic sequence . This is the duration of the mitotic sequence expressed in hours. The more synchronous cell cleavage is, the more homogeneous developmental competencies of the resulting daughter cells are achieved. Synchronous cell cleavage in a given mitotic sequence is exhibited by a short cleavage interval, and vice-versa.
The 3rd mitotic sequences are influenced by embryonic genome activation.
| Parameter | Abbreviation | Formula |
|---|---|---|
| 2 cells cleavage interval | CI1 | t2 - tsyng |
| 3-4 cells cleavage interval | CI3-4 | t4 - t3 |
| 5-8 cells cleavage interval | CI5-8 | t8 - t5 |
CI3-4 and CI5-8cleavage intervals can be monitored with existing time‑lapse systems.
Mitotic cycle is a process in which the cells duplicate themselves to create genetically identical copies (daughter cells). The process is accomplished through cell division. The phases of MC are: interphase and mitosis (M-phase).
The more mitotic cycles occur in 5-6 days, the more cells the embryo will have and the better chances for blastocyst expansion/hatching can be achieved.
Learn more about formulas to calculate lengths of mitotic cycles.
| Parameter | Abbreviation | Formula |
|---|---|---|
| Length of 1st mitotic cycle | MC1 | t2 - tICSI |
| Length of 2nd mitotic cycle | MC2 | t3-t2 |
| Length of 3rd mitotic cycle | MC3 | t5-t3 |
| Length of 4th mitotic cycle | MC4 | t9-t5 |
| Length of 5th mitotic cycle | MC5 | t17-t9 |
| Length of 6th mitotic cycle | MC6 | t33-t17 |
| Length of 7th mitotic cycle | MC7 | t65-t33 |
| Length of 8th mitotic cycle | MC8 | t129-t65 |
Mitotic sequences (MSeq) are series of cleavages occurring from the same generation of the cells. The product of each MSeq is a new generation of daughter cells. The more synchronous the timing of MSeq is (expressed as CI), the more uniform developmental competencies of the resulting daughter cells are achieved.
| Mitotic Sequences | The result |
|---|---|
| 1st mitotic sequence (1st MSeq) | 2-cells embryo |
| 2st mitotic sequence (2st MSeq) | 4-cells embryo |
| 3st mitotic sequence (3st MSeq) | 8-cells embryo |
| 4st mitotic sequence (4st MSeq) | 16-cells embryo |
| 5st mitotic sequence (5st MSeq) | 32-cells embryo |
| 6st mitotic sequence (6st MSeq) | 64-cells embryo |
| 7st mitotic sequence (7st MSeq) | 128-cells embryo |
Morphokinetics Indicating Differentiation of ICM Cells into Trophectoderm
Fluid build-up in the blastocoel cavity increases its volume, causing blastocoel expansion and blastocyst growing (i.e. increase of the embryo’s diameter). The blastocoel formation is a proof of TE and ICM differentiation. It is also an essential condition to break Zona Pellucida (ZP) that ultimately has an impact on hatching ability.
The Compaction is a prerequisite step for cell differentiation.
Compaction is not currently detected by CATI.
Morphokinetics Indicating Embryo´s Ability to Hatch
The fluid accumulation in blastocoel cavity increases its volume what causes a blastocoel expansion and blastocyst growing (increase of the embryo diameter). The blastocoel formation is a proof of TE and ICM differentiation. It is also an essential condition to break Zona Pellucida (ZP) which has an impact on hatching ability (link).
A negative effect on embryo’s ability to hatch. Embryos that exhibit collapse are as likely to hatch as those that do not, but are less likely to implant.
We distinguish between four types of collapses.
| Name | Description | Segmentation drops by |
|---|---|---|
| Big Collapse | Big drop of segmentation induced by apoptotic cells elimination — consequence of prior abnormal cleavages | >=41% |
| Medium Mitotic Pulse | Medium collapses or mitotic pulses caused by physiological cell changes during mitotis | 21-40% |
| Small Mitotic Pulse | Small collapses or mitotic pulses caused by physiological cell changes during mitotis | 11-20% |
| Extra Small Mitotic Pulse | Extra small collapses or mitotic pulses caused by physiological cell changes during mitotis | 0-10% |
Blastocyst hatching is a natural proces of embryo escaping from its envelope - zona pellucida (ZP) after 5 - 6 days of development. This is a prerequisite step before implantation. In time‑lapse records we see the initial phases of hatching as herniation of trophoectodermic (TE) cells occuring frequently on the place of ICSI needle penetration of ZP.