Mechanical zona pellucida removal of vitrified-warmed human blastocysts does not affect the clinical outcome.

RESEARCH QUESTION: Does complete mechanical removal of the zona pellucida modify the outcome of transfer of vitrified-warmed human blastocysts? DESIGN: In a prospective randomized controlled study, 419 couples were allocated to either zona pellucida-free (n = 209) or zona intact (n = 210) vitrified-warmed embryo transfer. Main outcome measures included clinical pregnancy, implantation and ongoing pregnancy rates. RESULTS: Transfer of zona pellucida-free blastocysts resulted in clinical pregnancy, implantation and ongoing pregnancy rates (35,9%, 33,9% and 32,1%, respectively), similar to those achieved with zona intact control embryos (39%, 36,4% and 33,1%, respectively). CONCLUSION: Total mechanical removal of the zona pellucida did not affect the tested parameters of clinical outcomes.

Controlling cell length.

Control of cell dimensions is an important but poorly understood aspect of morphogenesis. In this review, our primary focus is on control of cell length in different types of cells and cytoskeletal regulation of this parameter. Cell length is not a constant characteristic of certain cell type but of cells of fibroblastic morphology. Since cytoskeleton organization can change during different processes of morphogenesis changes in length control during cell spreading, epithelio-mesenchymal transformation and also in neoplastic transformation are discussed.

Transformation by RAS oncogene decreases the width of substrate-spread fibroblasts but not their length.

We compared morphometric parameters of the contours of cells in four pairs of non-transformed mouse and rat lines and of the same lines transformed by oncogenes of the RAS family. As expected, the mean areas of all RAS-transformed lines were much smaller than those of their non-transformed counterparts. At the same time the average length of cell projection did not regularly decrease after transformation. These results show that transformation induced by expression of RAS oncogene selectively affect only one component of spreading, namely transversal spreading and not longitudinal spreading; these changes result in an increase of antero-posterior polarity of transformed fibroblasts.

Length control is determined by the pattern of cytoskeleton.

In our previous experiments with linear strips of adhesive substrate, we found that elongated cultured fibroblasts preserve their length regardless of cell width and the number of cytoplasmic processes. This constancy of length was called 'length control'. In contrast to fibroblasts, single cultured epitheliocytes have nearly discoid shape on the plane substrata and have no length-controlling mechanism: their length on the narrow strips of adhesive substrate increased significantly in comparison with the diameter on the plane substrate. These results suggested that control of length is cell specific. An alternative suggestion is that length control is associated not with the cell type but with the cell cytoskeletal pattern (namely, with epithelioid circular actin bundles or straight actin bundles). Experiments described in this paper were made to choose between these two suggestions. Mouse embryo fibroblasts spreading on the planar substrate first acquire discoid epithelioid shape with a circular actin bundle. Only later did they acquire a polarized shape with straight actin bundles. Polarized, fully spread fibroblasts temporarily acquire discoid epithelioid shape when treated with the Taxol, disorganizing microtubules. However, epithelial discoid cells can be transformed into elongated fibroblast-like cells by scatter factor (HGF/SF; a cytokine) and by agents inhibiting Rho kinase. These reversible transitions from fibroblastic to epithelioid shape and vice versa were accompanied by a corresponding disappearance and appearance of length control. Fibroblasts with stress fibers destroyed by the Rho-kinase inhibitor Y27632 became considerable longer on the adhesive strips than on the plane while retaining a near-polarized shape. Thus, length control is typical not of the cell origin but of the cell phenotype (i.e. for polarized cells with microtubules and intact actin cytoskeleton).