Cumulus cell expansion and ultrastructural changes in in vitro matured bovine oocytes under heat stress

Document Type: Full paper (Original article)


1 Division of Veterinary Physiology and Biochemistry, Faculty of Veterinary Sciences & Animal Husbandry, Sher-e-Kashmir University of Agricultural Sciences & Technology-Jammu, RS Pura-181102, Jammu & Kashmir, India

2 Division of Veterinary Pathology, Faculty of Veterinary Sciences & Animal Husbandry, Sher-e-Kashmir University of Agricultural Sciences & Technology-Jammu, RS Pura-181102, Jammu & Kashmir, India

3 Department of Veterinary Physiology, College of Veterinary Science, Assam Agricultural University, Guwahati-781022, Assam, India

4 Department of Animal Reproduction, Gynaecology and Obstetrics, College of Veterinary Science, Assam Agricultural University, Guwahati-781022, Assam, India

5 State Biotech Hub, College of Veterinary Science, Assam Agricultural University, Guwahati-781022, Assam, India


Cumulus-oocyte complexes (COCs) from cows were matured under normal (38.5°C) and elevated temperatures (41°C) simulating heat stress and their maturation was assessed based on measurement of cumulus expansion in both groups. There was a significant reduction (P<0.01) in maturation rate in the heat stressed oocytes. The ultrastructural events associated with in vitro oocyte maturation and changes associated with elevated temperature were also studied by transmission electron microscopy (TEM). Normal maturation cellular events were marked by migration of Golgi and mitochondria from the cortical regions, and conversely by a migration of cortical granules from the inner regions to a sub-perivitelline zone. Heat stressed oocytes (41°C) were not only marked by a reduction in rate and less cumulus cell expansion, but also by a reduction in cortical granule migration. The mitochondria appeared swollen with cristolysis. Ribosomal disruption and an abundance of free ribosomes were also seen. Changes in the cumulus cells include nuclear chromatin margination, condensation and karyolysis, formation of nuclear and cell membrane blebs, and typical membrane bound vesicles enclosing cell fragments indistinguishable from apoptosis. Evidently, heat stress can be associated with reduced cytoplasmic events of oocyte maturation, thereby decreasing the oocyte competence and can be associated with apoptosis of the cumulus cells and therefore compromise the survival of the oocyte itself.


Ahmed, JA; Dutta, D and Nashiruddullah, N (2016). Comparative efficacy of antioxidant retinol, melatonin, and zinc during in vitro maturation of bovine oocytes under induced heat stress. Turk. J. Vet. Anim. Sci., 40: 365-373.

Cetica, PD; Pintos, LN; Dalvit, GC and Beconi, MT (2001). Antioxidant enzyme activity and oxidative stress in bovine oocyte in vitro maturation. IUBMB Life. 51: 57-64.

Ealy, AD; Howell, JL; Monterroso, VH; Aréchiga, CF and Hansen, PJ (1995). Developmental changes in sensitivity of bovine embryos to heat shock and use of antioxidants as thermoprotectants. J. Anim. Sci., 73: 1401-1407.

Edwards, JL and Hansen, PJ (1996). Elevated temperature increases heat shock protein 70 synthesis in bovine two-cell embryos and compromises function of maturing oocyte. Biol. Reprod., 55: 340-346.

Edwards, JL; Saxton, AN; Lawrence, JL; Payton, RR and Dunlap, JR (2005). Exposure to a physiologically relevant elevated temperature hastens in vitro maturation of bovine oocytes. J. Diary Sci., 88: 4326-4333.

Ferreira, EM; Vireque, AA; Adona, PR; Meirelles, FV; Ferriani, RA and Navarro, PA (2009). Cytoplasmic maturation of bovine oocytes: structural and biochemical modifications and acquisition of developmental com-petence. Theriogenology. 71: 836-848.

Hansen, PJ (2013). Cellular and molecular basis of therapies to ameliorate effects of heat stress on embryonic development in cattle. Anim. Reprod., 10: 322-333.

Hosoe, M and Shioya, Y (1997). Distribution of cortical granules in bovine oocytes classified by cumulus complex. Zygote. 5: 371-376.

Hyttel, P; Fair, T; Callesen, H and Greve, T (1997). Oocyte growth, capacitation and final maturation in cattle. Theriogenology. 47: 23-32.

Jainudeen, MR; Wahid, H and Hafez, ESE (2008). Ovulation induction, embryo production and transfer. In: Hafez, ESE and Hafez, B (Eds.), Reproduction in farm animals. (7th Edn.), Blackwell Publishing. P: 418.

Ju, JC; Jiang, S; Tseng, JK; Parks, JE and Yang, X (2005). Heat shock reduces developmental competence and alters spindle configuration of bovine oocytes. Theriogenology. 64: 1677-1689.

Ju, JC and Tseng, JK (2004). Nuclear and cytoskeletal alterations of in vitro matured porcine oocytes under hyperthermia. Mol. Reprod. Dev., 68: 125-133.

Krisher, RL and Bavister, BD (1998). Responses of oocytes and embryos to the culture environment. Theriogenology. 49: 103-114.

Lawrence, JL; Payton, RR; Godkin, JD; Saxton, AM; Schrick, FN and Edwards, JL (2004). Retinol improves development of bovine oocytes compromised by heat stress during maturation. J. Dairy Sci., 87: 2449-2454.

Maya-Soriano, MJ (2012). Heat stress and antioxidant agents: effects on gamete development. Ph.D. Dissertation, Universtat Autonoma de Barcelona (Autonomous University of Barcelona), Spain. PP: 41-47.

Nabenishi, H; Ohta, H; Nishimoto, T; Morita, T; Ashizawa, K and Tsuzuki, Y (2012a). The effects of cysteine addition during in vitro maturation on the developmental competence, ROS, GSH and apoptosis level of bovine oocytes exposed to heat stress. Zygote. 20: 249-259.

Nabenishi, H; Takagi, S; Kamata, H; Nishimoto, T; Morita, T; Ashizawa, K and Tsuzuki, Y (2012b). The role of mitochondrial transition pores on bovine oocyte competence after heat stress, as determined by effects of cyclosporin A. Mol. Reprod. Dev., 79: 31-40.

Qu, P; Tian, W; Li, T; Jiang, Z; Gao, S; Tian, Z and Wang, M (2009). Development competence and ultrastructural changes of heat-stressed mouse early blastocysts produced in vitro. Curr. Zool., 55: 61-66.

Rivera, RM; Kelly, KL; Erdos, GW and Hansen, PJ (2004). Reorganization of microfilaments and microtubules by thermal stress in two-cell bovine embryos. Biol. Reprod., 70: 1852-1862.

Roth, Z and Hansen, PJ (2004). Involvement of apoptosis in disruption of developmental competence of bovine oocytes by heat shock during maturation. Biol. Reprod., 71: 1898-1906.

Roth, Z and Hansen, PJ (2005). Disruption of nuclear maturation and rearrangement of cytoskeletal elements in bovine oocytes exposed to heat shock during maturation.
Reproduction. 129: 235-244.

Schrock, GE; Saxton, AM; Shrick, FN and Edwards, JL (2007). Early in vitro fertilization improves development of bovine ova heat stressed during in vitro maturation. J. Dairy Sci., 90: 4297-4303.

Soto, P and Smith, LC (2009). BH4 peptide derived from Bcl-xL and Bax-inhibitor peptide suppresses apoptotic mitochondrial changes in heat stressed bovine oocytes. Mol. Reprod. Dev., 76: 637-646.

Stojkovic, M; Machado, SA; Stojkovic, P; Zakhartchenko, V; Hutzler, P; Goncalves, PB and Wolf, E (2001). Mitochondrial distribution and adenosine triphosphate content of bovine oocytes before and after in vitro maturation: correlation with morphological criteria and developmental capacity after in vitro fertilization and culture. Biol. Reprod., 64: 904-909.

Tanghe, S; Van Soom, A; Nauwynck, H; Coryn, M and DeKruif, A (2002). Minireview: functions of the cumulus oophorus during oocyte maturation, ovulation, and fertilization. Mol. Reprod. Dev., 61: 414-424.

Warnes, GM; Moor, RM and Johnson, MH (1977). Changes in protein synthesis during maturation of sheep oocytes in vivo and in vitro. J. Reprod. Fertil., 49: 331-335.