Document Type : Full Research Paper


1 PhD Candidate, Mechanical Engineering School, Iran University of Science & Technology

2 Assistant Professor, Mechanical Engineering School, Iran University of Science & Technology

3 Assistant Professor, Department of Embryology, Infertility and IVF Unit, Royan Institute

4 Assistant Professor, School of Mechanics, Aerospace and Civil Engineering, University of Manchester



Recently, considerable biomedical attention has centered on the mechanical properties of living tissues at the single cell level. Stiffness is an important parameter in determining the physical properties of living tissues. Indeed, stiffness changes of the ovum as a single cell pose a unique challenge in determining the sequence of fertilization. The ovum's extracellular layer has been reported to be altered following fertilization in a process described as Zona reaction. In the present study, the Young's modulus of Zona Pellucida of the mouse ovum was evaluated using micropipette aspiration technique. By incorporating exact engineering principles into the cell mechanics and extract appropriate formula, the Young's modulus of metaphase II (MII) and pronuclear (PN) was measured. The experimental results clearly demonstrated that the mouse Zona Pellucida hardened following fertilization. This study involves the contents of Reproductive Biology and Mechanics, and opens up a new trail of thought for evaluating the quality of mammalian oocytes and embryos. 


Main Subjects

[1]     Kania G., The structure properties and function of the zona pellucida of mammalian ovums; Medycynan Weterynaryjna 1999; vol. 55; 5:295–299.
[2]     Schroeder A.C., Schultz R.M., Kopf G.S., Taylor F.R., Becker R.B., and Eppig J.J., Fetuin inhibits zona pellucida hardening and conversion of Zp2 to Zp2f during spontaneous mouse oocyte maturation in vitro in the absence of serum, Biol. Reproduction 1990; vol. 43, 5:891–897.
[3]     Demeestere I., Barlow P., and Leroy F., Hardening of zona pellucida of mouse oocytes and embryos in vivo and in vitro, Int. J. Fertil. Womens Med. 1997; vol. 42, 3:219–222.
[4]     Braden A.W., Austin C.R., The reaction of the zona pellucida to sperm penetration, Australian J. Biol. Sci. 1954; 7:391-409.
[5]     Hatanaka Y. Nagagai T., Tobita T., Changes in the properties and composition of zona pellucida of pigs during fertilization in vitro, J. Reprod Fertil 1992; 95:431-40.
[6]     Iwamoto K., Ikeda K., Yonezawa N., Disulfide formation in bovine zona pellucida glycoproteins during fertilization, J. Reprod Fertil 1999; 117:395- 402.
[7]     Schmell E.D., Gulyas B.J., Egg surface changes during fertilization, J.F. Hartmann, New York 1983; 356-413.
[8]     Drobnis E.Z., Andrew J.B., Katz D.F., Biophysical properties of the zona pellucida measured by capillary suction: Is zona hardening a mechanical phenomenon?,  J. Exp. Zool 1988; 245:206-19.
[9]     Sun Y., Wan K. T., Roberts K. P., Bishof C., Mechanical Property Characterization of Mouse Zona Pellucida, IEEE Transactions on Nanobioscience 2003; 2:279-286.
[10] Murayama Y., Constantinio C.E., Omata S., Fabrication of micro tactile sensore for measurement of micro-scale elasticity, Sens Actuators 2004; 109:202-7.
[11] Murayama Y., Constantinio C.E., Omata S., Mechanical property Characterization of mouse zona pellucida, IEEE UFFC 2005; 52:434-8.
[12] Lim, C.T. Single cell mechanics study of the human disease malaria, J. Biomech. Sci. & Engrg. 2006; 1:82– 92.
[13] Suresh, S., et al., Connections between single-cell biomechanics and human disease states: gastrointestinal cancer and malaria, Acta Biomater 2005; 1:15–30.
[14] Van Vliet K.J., Bao G., Suresh S., The biomechanics toolbox:experimental approaches to living cells and biomolecules, Acta Mater 2003; 51:5881–905.
[15] Lim, C.T., et al., Experimental techniques for single cell and single molecule biomechanics, Mat. Sci. Eng. 2006; 26: 1278 1288.
[16] Hochmuth, R.M., Micropipette aspiration of living cells, J. Biomech. 2000; 33:15–22.
[17] Sato, M., Levesque, M.J., Nerem, R.M., Micropipette aspiration of cultured bovine aortic endothelial cells exposed to shear stress, Arteriosclerosis 1987; 7:276- 286.
[18] Jones, W.R., Ting-Beall, H.P., Lee, G.M, Kelley, S.S., Hochmuth, R. M., Guilak, F.,. Alterations in the Young's modules and volumetric properties of chondrocytes isolate from normal and osteoarthritic human cartilage, J. Biomech. 1999; 32:119–127.
[19] Evans, E.A., New membrane concept applied to the analysis of fluid shear and micropipette-deformed red blood cells, Biophysical Journal 1973; 13:941-954.
[20] Evans, E., Ritchie, K., Merkel, R., Sensitive force technique to probe molecular adhesion and structural linkages at biological interfaces., Biophysical Journal 1995; 68:2580-2587.
[21] Lim, C.T., et al., Mechanical models for living cells – a review, J. Biomech. 2006; 39:195–216.