p38 MAPK Regulates Cavitation and Tight Junction Function in the Mouse Blastocyst

Abstract

Blastocyst formation is essential for implantation and maintenance of pregnancy and is dependent on the expression and coordinated function of a series of proteins involved in establishing and maintaining the trans-trophectoderm ion gradient that enables blastocyst expansion. These consist of Na/K-ATPase, adherens junctions, tight junctions (TJ) and aquaporins (AQP). While their role in supporting blastocyst formation is established, the intracellular signaling pathways that coordinate their function is unclear. The p38 MAPK pathway plays a role in regulating these proteins in other cell types and is required for embryo development at the 8–16 cell stage, but its role has not been investigated in the blastocyst.Hypothesisp38 MAPK regulates blastocyst formation by regulating blastocyst formation gene expression and function.MethodsEmbryos were cultured from the early blastocyst stage for 12 h or 24 h in the presence of a potent and specific p38 MAPK inhibitor, SB 220025. Blastocyst expansion, hatching, gene family expression and localization, TJ function and apoptosis levels were analyzed.ResultsInhibition of the p38 MAPK pathway reduced blastocyst expansion and hatching, increased tight junction permeability, affected TJP1 localization, reduced Aqp3 expression, and induced a significant increase in apoptosis.ConclusionThe p38 MAPK pathway coordinates the overall events that regulate blastocyst formation.

Binding of FGF2 to FGFR2 in an autocrine mode in trophectoderm cells is indispensable for mouse blastocyst formation through PKC-p38 pathway

“…18 In addition to the indispensability of correct lineage segregation, FGFs activated FGF signaling pathways, characterized by the expression of adherens junctions (AJ), tight junctions (TJ), ion channels and AQPs, are essential for fluid accumulation and formation of the blastocyst cavity in the development of a proper blastocyst. 4,18,19 We found that some human embryos could develop to expanded blastocysts without ICM in our in vitro fertilization (IVF) laboratory. This phenomenon may infer that blastocyst formation is independent of ICM.…”

“…The stimulation of PKC-activated p38 mitogen-activated protein kinase (MAPK) or ERK1/2 MAPK, is linked to the induction of blastocyst development. 4,29,30 To test this link, we studied the phosphorylated (p-) of p38 or ERK1/2 and their transport between the cytoplasm and nucleus using an immunofluorescence confocal technique. As shown in Figure 5B, p-p38 translocated to the nucleus of TEs in blastocysts that were transfected with scrambled (control) RNA.…”

“…2,3 Functional tight junctions form a seal between the cells of the TE, which is essential for fluid accumulation and formation of the blastocyst cavity. 4,5 The Na-K ATPase is also a critical mediator of blastocyst formation as it establishes a transtrophectoderm ionic gradient that directs fluid movement across the epithelium of the TE. 4,6,7 Aquaporins (AQP3 and AQP9) in the TE membrane facilitate the movement of fluids across the TE from the 'outside' to the 'inside' of the blastocyst cavity, along the ionic gradient established by the Na-K ATPase localized on the baso-lateral membrane.…”

“…4,5 The Na-K ATPase is also a critical mediator of blastocyst formation as it establishes a transtrophectoderm ionic gradient that directs fluid movement across the epithelium of the TE. 4,6,7 Aquaporins (AQP3 and AQP9) in the TE membrane facilitate the movement of fluids across the TE from the 'outside' to the 'inside' of the blastocyst cavity, along the ionic gradient established by the Na-K ATPase localized on the baso-lateral membrane. 4,8 After segregation of the early lineages is complete, the blastocyst emerges from the zona pellucida to invade the maternal uterine endometrium, where it implants.…”

“…4,6,7 Aquaporins (AQP3 and AQP9) in the TE membrane facilitate the movement of fluids across the TE from the 'outside' to the 'inside' of the blastocyst cavity, along the ionic gradient established by the Na-K ATPase localized on the baso-lateral membrane. 4,8 After segregation of the early lineages is complete, the blastocyst emerges from the zona pellucida to invade the maternal uterine endometrium, where it implants. 9,10,11 Generally, the development of the blastocyst is guided by highly organized interactions of multiple growth factors.…”