An engraved surface induces weak adherence and high proliferation of nonadherent cells and microorganisms during culture

When cells are cultured in a Petri dish, the adherent cells attach to the bottom of the dish; whereas, the nonadherent cells float in the culture medium. It was observed that nonadherent cells could be induced to adherent-like cells when cultured in an engraved plastic dish (biosimulator). The adherence of these cells to the engraved surface could be prevented with inhibitors specific for adhesion. It was also observed that culturing microorganisms of the environment in a biosimulator induced weak adhesion and high proliferation. Analysis of the microbiome using 16S rRNA profiling demonstrated that the biosimulator was more efficient in inducing proliferation of several phyla of microorganisms compared with culture by conventional techniques.

Positioning of inner cell mass determines the development of mouse blastocysts in vitro

We have explanted mouse blastocysts into culture dishes and studied the positioning of the inner cell mass (ICM) at the time of attachment in order to establish what effect the location of the inner cell mass has on the subsequent development of embryos in vitro. We show that blastocysts may attach to the substrate with any portion of the trophectoderm. The location of ICM within the attaching blastocysts is unpredictable. The directions of egg-cylinder development may be either upward or downward. The axis assumed by a developing egg cylinder in vitro depends to a large extent on the initial positioning of the ICM at the time of attachment. Egg cylinders grown from blastocysts that have the ICM in the lower position (close to the plastic dish) reach advanced stages of development in greater numbers than egg cylinders grown from blastocyst with their ICM's in the upper lateral or upper position. Only upward-growing egg cylinders can develop further into somitic stage (which is equivalent to 8½- or 9-day in vivo embryos). In contrast, downward growing egg cylinders become thwarted in their further development by the surrounding trophectoderm. If the downward growing egg cylinders are freed of trophectoderm and repositioned to face upwards they will develop in a manner similar to the originally upward growing egg cylinders. These findings indicate that the initial positioning of the ICM at the time of attachment is an important factor in governing the development of blastocysts to somite stage in vitro.

A correlation between membrane fluidity and the critical temperature for cell adhesion.

BHK 21 cells can adhere to a protein-coated plastic dish in the presence of Ca2+ at temperatures above 12 degrees C. However, they cannot adhere below 8 degrees C. The ESR spectrum of cells spin-labeled with a stearic acid label indicated that the membrane fluidity changed characteristically at 10 degrees C, 20 degrees C, and 30 degrees C. The critical temperature for cell adhesion coincided well with one of the characteristic temperatures for the membrane fluidity change. In the case of adhesion in the presence of Mg2+, no such correlation was observed.