Author: Sara Gómez
"LAVA is a non-invasive technique that affects neither the sperm membrane nor DNA integrity".
Fig 1: Immotile spermatozoa (yellow arrow) that had responded to the laser shot (red) by either a curling reaction of the tail or sudden head displacement were considered to be likely viable, and thus retrieved for injection into the oocyte. Watch the next video for more information: https://download-tls-cdn.edge-cdn.net/videodb/5501/videodb_5501_77706_10917412_hp.mp4 (1).
The ability of sperm to pass through both the uterus and the Fallopian tube and fertilise an egg depends on sperm motility and progression. The flagellum confers motility on the sperm but, sometimes, spermatozoa present an abnormal axoneme ultrastructure and so they cannot swim (asthenozoospermia). The axoneme, the “scaffolding” of the flagellum, is composed of 9+2 microtubules pairs and provided with dynein arms, which conforms the major motor protein and provides flagella with movement. Certain autosomal recessive genetic disorders affect the structure (hence function) of specific motor proteins and, therefore, they result in the impaired action of cilia and flagella.
Kartagener syndrome (KS) is caused by different mutations in various genes that encode proteins necessary for ciliary structure and function. Not only these patients suffer from respiratory tract diseases, but also their sperm exhibit an abnormal structure of the axoneme that makes it impossible for the flagellum to beat. Consequently, these patients are infertile.
Motility in a sperm sample is one of the markers for viability when it comes to sperm selection in ART. Live and dead sperm are equally subjected to selection in KS patients since both types are immotile, and so the result may end up being unfertilised oocytes or poor quality embryos. In order to avoid such outcomes, there are currently several options to offer to these patients, like promotion of sperm motility, oocyte activation, testis biopsy, hypo-osmotic test, sperm tail flexibility test (STFT) or donor sperm. Nowadays, the most commonly used technique is probably the administration of pentoxifylline, a drug demonstrated to enhance sperm motility (2). However, there are cases in which the patient is resistant to pentoxifylline, and so any effort to improve sperm motility is in vain. What to do in such a situation?
In a recent study led by Sinain Ozkavuku at Ankara University School of Medicine (Turkey) (1), a new solution known as LAVA (laser assisted viability assessment) has been proposed. Even though this technique has been known since 2004, when reported by Aktan et al (3), this is the first time it has been applied on a KS patient. LAVA consists in shooting the so-called “end-piece” of the sperm flagellum with a non-contact diode laser pulse of 350 µs with an outcome wavelength of 1480 nm. By doing so, the shot would cause an immediate tail curling or a sudden displacement of the head on a live spermatozoon, whereas dead sperm would remain non-reactive (Fig. 1).
This study reports a couple that had gone through 9 years of infertility (no pregnancy). The male partner was diagnosed with Kartagener syndrome, had a history of oligoasthenoteratozoospermia with total immotile sperm and was pentoxifylline-resistant. Different approaches were carried out to confirm the syndrome: transmission electron microscopy (TEM) reported the absence of dynein arms on the axoneme at the ultrastructural level (Fig. 2), and next generation sequencing (NGS) analysis revealed different mutations, all related to KS cases. Moreover, viability test showed 54% of viable sperm (1).
Usually, sperm selection for ICSI (intracytoplasmatic sperm injection) in KS or total asthenozoospermic patients is made at random. However, for this study the authors made use of LAVA to select live viable sperm in order to guarantee good-quality embryos and high implantation rates. The ICSI day, 22 mature oocytes were microinjected, resulting in four blastocysts on day 5 and 6 (which indicates a proper timing for embryo development). One 4AB and one 2AA blastocysts (=good-quality embryos) were transferred, but one of them subsequently divided into two embryos, and so three babies were born.
Does LAVA represent the next approach in the future for this type of patients? Even though it is certainly possible, this solution is limited to IVF centres that count on laser equipment, and to be used mostly with high-viability sperm samples. Nevertheless, in their study the authors concluded that LAVA allowed for a practical and effective selection of viable spermatozoa, and that negative impact on embryo development or implantation was never observed. Moreover, LAVA is a non-invasive technique that affects neither the sperm membrane nor DNA integrity (4).
Despite LAVA's limitations in the clinic as a practical approach, it may increase the chances of having a child for patients suffering from Kartagener syndrome or total sperm immotility. This would certainly bring new hopes to couples who, until recently, had few or no options to become parents.
1. Ozkavukcu S, Celik-Ozenci C, Konuk E, Atabekoglu C. Live birth after Laser Assisted Viability Assessment (LAVA) to detect pentoxifylline resistant ejaculated immotile spermatozoa during ICSI in a couple with male Kartagener’s syndrome. Reproductive Biol Endocrinol. 2018; 16(1):10.
2. Shen MR, Chiang PH, Yang RC, Hong CY, Chen SS. Pentoxifylline stimulates human sperm motility both in vitro and after oral therapy. Br J Clin Pharmacol. 1991; 31(6):711–4.
3. Aktan TM, Montag M, Duman S, Gorkemli H, Rink K, Yurdakul T. Use of a laser to detect viable but immotile spermatozoa. Andrologia. 2004; 36(6):366–9.
4. Ortega C, Verheyen G, Raick D, Camus M, Devroey P, Tournaye H. Absolute asthenozoospermia and ICSI: what are the options? Hum Reprod Update. 2011; 17(5):684–92.
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