IMSI For Selection of Healthy Sperms
What is IMSI?
Intracytoplasmic morphologically selected sperm injection (IMSI) removes sperm with abnormal morphology that arises after spermatogenesis. IMSI may improve implantation, can lead to higher pregnancy rates and diminished abortion rates.
The resulting magnification was based on 4 parameters:
Objective magnification x100
Magnification selector x1.5
Video coupler magnification x0.99
Calculated video magnification (ccd x monitor diagonal dimension) x 44.45
TOTAL MAGNIFICATION: 100 x 1.5 x 0.99 x 44.45 = x 6600 !!!
SPERM MORPHOLOGY
Sperm is a male haploid gamete.
It measures about 60μm in length.
It contains three regions as head, middle piece and tail.
Head: The head of the sperm is oval in shape, contains a large haploid nucleus. Anteriorly nucleus is covered by a cap like structure called acrosome. It is formed by Golgi complex. It contains the lytic enzymes to dissolve the egg membrane during fertilization
SPERM MORPHOLOGY
Neck: Below the head is a small neck. It contains a proximal and distal centriole.
Middle piece: The distal centriole gives rice to axial filament and becomes basal bodies.The axial filament is surrounded spirally by mitochondria and forms middle piece. The mitochondria provides energy for motility of sperm.
Tail: The tail is divided into principal piece and end piece. The principal piece has axial filament surrounded by plasma membrane.The end piece lacks the protoplasmic sheath.The tail is used for swimming movement in the liquid media
SPERM MORPHOLOGY – MICROSCOPIC VIEW
Defects
Head abnormalities mainly responsible for sperm fertilization deficiency
Flagellar abnormalities haven’t been shown to have any impact on fertilization (Berkovitz et al., 2006; Chemes et al., 2003)
Sperm nuclear DNA damage is closely related to male- derived repeated failed ICSI attempts (Tesarik et al., 2004; Tesarik 2005)
Presence of large nuclear vacuoles: negatively associated with natural male fertility potential (Bartoov et al., 1994; Mundi et al., 1994)
IMSI EQUIPMENT
IMSI can be achieved on a Nikon inverted microscope equipped with high resolution Nomarski optics (100x or 60x oil Plan Apo VC) enhanced by a videozoom and digital imaging. The final magnification of the system can be calculated as follows: (objective) X (magnification changer) X (videozoom) X (diagonal of image camera CCD chip diagonal)
ICSI vs IMSI
IMSI – Sperm Assessment
Vacuoles & DNA fragmentation
Vacuole: concavity extending from the surface of the sperm head to the nucleus through the acrosome
• Spermatozoa with large vacuoles should be avoided)
• Spermatozoa with large vacuoles (>50% of the sperm head) & other potential abnormalities were described as having higher DNA fragmentation levels than normal spermatozoa
• Spermatozoa with multiples vacuoles (>4% of the head area) have higher DNA fragmentation levels than normal spermatozoa
• No difference in DNA fragmentation between normal ones & morphometrically normal ones with a single, large vacuole (15%-25% of head area)
Sperm grading
Grade I: absence of vacuoles
Grade II: max. of 2 small vacuoles
Grade III: >2 small vacuoles or at least 1 large
Grade IV: abnormal head shapes or other abnormalities with or without vacuoles (identified even at x400 magnification)
Sperm preparation techniques
• Both SUP & DGP efficient in recovering lower percentage of sperm cells with vacuolization
• POOR SPERM MOTILITY : temperature 37°C, no PVP and supplemented with 6% of human serum albumin
• HIGH SPERM MOTILITY : temperature 20°C and concentration of PVP about 8%.
Benefits
Sperm nucleus morphological normalcy assessed at high magnification could decrease the prevalence of major fetal malformations in ICSI childre
Concerns
• Prolonged exposure to 37°C during IMSI could impair the morphological integrity of the sperm nuclei
• The No of spermatozoa without vacuoles in humans is extremely small and trying to find and then inject such cells is a very difficult & time-consuming process.