The potential role of gap junction communication between cumulus cells and bovine oocytes during in vitro maturation

Abstract

Preliminary studies in our laboratory have indicated that modulating cumulus expansion early or late during culture has a profound influence on the subsequent development of cumulus-enclosed oocytes. Our objectives were to evaluate the effect of short term exposure to recombinant human follicle-stimulating hormone (r-hFSH) during in vitro maturation (IVM) on cumulus expansion and developmental competence of bovine oocytes. A highly significant (P < 0.0001) improvement in blastocyst development rate as a proportion of cleaved oocytes after IVM of oocytes was observed in the presence of r-hFSH for the first 6 hr of culture. To demonstrate the importance of the functional coupling between the oocyte and the cumulus compartment during that period of 6 hr, cumulus-oocyte complexes (COCs) were matured with r-hFSH for the first 6 hr followed by 18 hr in presence of 1-heptanol or 1-octanol (gap junction inhibitors) to block the communication between the two. With the coupling inhibitors, the blastocyst yield was significantly decreased (P < 0.05). A brief treatment (30 min) with the weak base methylamine, known to reverse the gap junction inhibitors effect, significantly (P < 0.05) reversed the inhibitory action of these agents on the blastocyst rate. Gap junction communication between the oocyte and surrounding cumulus cells was further studied using microinjection of the fluorescent dye Lucifer Yellow. Morphological evidences (dye transfer) were obtained that support the presence of functional coupling for a longer period with the FSH short exposure. In conclusion, high developmental rates of bovine oocytes can be achieved with a short exposure to r-hFSH. This effect is believed to be mediated through gap junctions as developmental competence of oocytes is compromised by the inhibition of their function.

The Effects of Gap Junction Modulators on the Rhythmic Contractions in Aortas Isolated from Rats Subjected with Sinoaortic Denervation

“…Moreover, gap junctions inhibitors disrupts electrical communications between smooth muscle cells 25) and thus this fact could be blocking the RCs, as observed in other study. 8,14,23) Although heptanol is relatively reliable in blocking gap junctions in a selective mode, 16,17,26,27) 31,32) bovine oocytes, 33) ciliary body 34) and human HeLa cells, 35) heptanol has been either shown 30,32) or assumed 33,34) to act as specific gap junction blocker over a range of concentration (Յ10 mmol/l), substantially larger than those used in our study (0.5 mmol/l). Taken together, the results obtained in this study suggest that heptanol, acting via gap junctions, inhibits the RCs and reveal an important participation of these junctions on oscillations.…”

Impact of anisosmotic conditions on structural and functional integrity of cumulus–oocyte complexes at the germinal vesicle stage in the domestic cat

“…Although not always comparable to results achieved under less extreme conditions, there was rather striking success in these oocytes having the capacity to mature, fertilize and advance to blastocyst stages in vitro. Interestingly, exposure of cat oocytes to the excessive 2,000 mOsm treatment was not as detrimental to COC functionality as denuding all cumulus cells or artificially disrupting communications with the oocyte by other artificial means (Vozzi et al, 2001;Atef et al, 2005;Luciano et al, 2005). This shows that a minimum of communications (not detectable by Lucifer Yellow diffusion) were retained within the COC exposed to 2,000 mOsm which allowed producing viable appearing embryos.…”

Simple gene transfer technique based on I-SceI meganuclease and cytoplasmic injection in IVF bovine embryos

“…The poor development rates for the groups injected before IVM seemed to be related to the lack of cumulus cells during maturation. It is well known that the presence of the cumulus cells is crucial for nuclear and cytoplasmic maturation [41]; consequently, removal of cumulus cells before injection and to IVM, reduced embryo viability. That injection of the transgene before IVM can result in transgene expression up to the blastocyst stage, could be very useful for the study of early maturation events, through injection of interference RNAs, exogenous DNAs, or mRNAs.…”