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Epididymis-on-a-chip device : a unique approach to study tight barriers in the human male reproductive system using ex vivo tissue

Burgers, T. (2019) Epididymis-on-a-chip device : a unique approach to study tight barriers in the human male reproductive system using ex vivo tissue.

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Abstract:The male reproductive organ is composed of a convoluted network of tubules. Spermatozoa differentiate from germ cells into spermatozoa in the seminiferous tubules and consecutively travel through the epididymis where the spermatozoa mature. Upon maturation the ability to fertilize an oocyte (egg) is enhanced. Spermatozoa are not labeled as body-self, the body identifies them as antigens and hence triggers an auto-immune response towards them. To prevent this, spermatozoa in the male reproductive organ are protected by a strong physiological barrier with the blood, testes-blood and blood-epididymis barrier respectively (BTB and BEB). Dysfunction of this barrier can lead to infertility, globally affecting 30 million men with a prevalence estimated between 5 and 10 percent depending on the continent. Infertility is defined as “the inability of a sexually active, non-contracepting couple to achieve pregnancy in one year” (World Health Organization). The cause for infertility is not understood for half of the cases (15 million men). In this report we propose a real-time BEB study tool using human ex vivo tissue originating from patients with gender dysphoria undergoing sex reassignment surgery. In this work we designed and fabricated a microfluidic chip to construct an organ-on-a-chip device for the epididymis. The research field of organ-on-a-chip utilizes microfluidic chip technology to construct physiological relevant microenvironments. Conventional in vitro cell culture are too simplistic since it results in non-physiological 2D cell layers. An alternative physiological relevant technique is the use of animal models but is time consuming and raises ethical concerns. Research on the male reproductive organs translates poorly to the human situation. We focused on creating a platform to gain more knowledge on the BEB to find an explanation for the unexplained infertility cases. Microfluidic devices were designed in SOLIDWORKS and fabricated by softlithography of polydimethylsiloxane (PDMS) using 3D-printed molds. The final platform was composed of a 3D-printed cartridge on which an epididymal tubule of about 5-10 millimeter could be placed. The tubule was kept in place by trapping pillars that seal the lumen at the endings. This ensures that the BEB is the only way luminal fluids interact with the surrounding media. This 3D-printed cartridge can be inserted in a two layer PDMS chip (PDMS housing) that is bonded through plasma activation. As a result the epididymal tubule is confined in a chamber of about 15μL. The nutrients in this chamber get replenished by diffusion through an array of micrometer sized channels that are connected to 1.5mL cell culturing medium (DMEM, 10% FBS, 1% pen/strep). Chemicals or fluorescent dyes can be inserted into the luminal environment by injecting the epididymal tubule with a dye filled glass-pulled needle through a needle entry designed into the 3D-printed cartridge. Our epididymis-on-a-chip platform is able to maintain small epididymal tubules of 5-10 millimeter ex vivo viable for at least 11 days with in-tact tubule structure. As a comparison when epididymal tissue (5-10 mm tubule) was cultured in a in vitro dish (1.5mL) cell survival was lower and tubule structure disappears. Adding 10% fetal bovine serum to the cell culture media (Dulbecco’s Modified Eagle’s Medium, 1% penicillin/streptomycin) increased the cell survival. This unique epididymis-on-a-chip platform is the first platform to provide luminal access of human epididymal tubules, with the ability to measure the effect of pertubations in their micro- and luminal environment. The low quantity of sample needed for testing allows to do at least 150 experiments with one sample. Another advantage of the platform is that the tubules can be extracted for off-chip analysis or imaging. Studying the BEB using this platform it can be discovered what can disturb the barrier, how it functions. A better understanding of the BEB might also lead to a better understanding is can lead to a better understanding
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:02 science and culture in general, 30 exact sciences in general, 42 biology, 50 technical science in general
Programme:Biomedical Engineering MSc (66226)
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