Cervical Mucus Properties Stratify Risk for Preterm Birth

Background: Ascending infection from the colonized vagina to the normally sterile intrauterine cavity is a well-documented cause of preterm birth. The primary physical barrier to microbial ascension is the cervical canal, which is filled with a dense and protective mucus plug. Despite its central role in separating the vaginal from the intrauterine tract, the barrier properties of cervical mucus have not been studied in preterm birth. Methods and Findings: To study the protective function of the cervical mucus in preterm birth we performed a pilot case-control study to measure the viscoelasticity and permeability properties of mucus obtained from pregnant women at high-risk and low-risk for preterm birth. Using extensional and shear rheology we found that cervical mucus from women at high-risk for preterm birth was more extensible and forms significantly weaker gels compared to cervical mucus from women at low-risk of preterm birth. Moreover, permeability measurements using fluorescent microbeads show that high-risk mucus was more permeable compared with low-risk mucus. Conclusions: Our findings suggest that critical biophysical barrier properties of cervical mucus in women at high-risk for preterm birth are compromised compared to women with healthy pregnancy. We hypothesize that impaired barrier properties of cervical mucus could contribute to increased rates of intrauterine infection seen in women with preterm birth. We furthermore suggest that a robust association of spinnbarkeit and preterm birth could be an effectively exploited biomarker for preterm birth prediction.Massachusetts Institute of Technology. Charles E. Reed Faculty Initiative FundBurroughs Wellcome Fund (Preterm Birth Research Grant)National Science Foundation (U.S.). Graduate Research Fellowship Progra

Bacterial adhesion in structured environments

Thesis: Ph. D., Harvard-MIT Program in Health Sciences and Technology, 2014.Cataloged from PDF version of thesis.Includes bibliographical references.Biofilms-surface-bound communities of microbes-are a major medical concern, as they can be sources of infection that are difficult to eradicate. Their formation starts with the attachment of bacteria to available surfaces-often implantable biomaterials. The development of materials that prevent bacterial adhesion is therefore of paramount importance, and it requires a thorough understanding of the materials and bacterial surface properties that enable adhesive interactions. We herein design model surfaces and examine the interplay between micro-scale geometry, surface energy and bacterial surface properties with respect to adhesion, with the ultimate goal of understanding bacterial adhesion in structured environments, and establishing principles for design of novel surfaces that effectively repel bacteria. We first study adhesion of Escherichia coli to engineered surfaces possessing superficially unfavorable geometries. We show that cells can overcome geometric constraints with the aid of flagella, which are able to reach between narrow crevices, thus improving adhesion and expanding the range of surfaces to which cells can adhere. We examine binding of purified flagella to abiotic surfaces by means of quartz crystal microbalance (QCM) and show that flagella bind preferentially to hydrophobic surfaces, yet they do not appreciably bind to hydrophilic surfaces. Using mutant strains, we investigate the role of flagella in surface attachment of live cells and demonstrate that flagellated cells adhere best to hydrophobic substrates; however flagella may impede cell adhesion to hydrophilic surfaces. To further explore hydrophilic, structured environments with physiological relevance, we examine mucin-a natural hydrogel that typically harbors microbes in animals, while protecting the host. We purify mucins and use them in their native, three-dimensional configuration to probe bacterial swimming behavior and surface attachment in their presence. We demonstrate that mucins maintain-and possibly enhance-swimming ability for E. coli and Pseudomonas aeruginosa, and show that they greatly reduce adhesion to underlying substrates. Finally, we build on our established design principles and construct anti-adhesive surfaces by combining hydrophilic chemistries with topographic features smaller than cellular dimensions. This work suggests a path toward anti-adhesive materials that may be optimized for mechanical robustness, longevity and specific environments of application.by Ronn S. Friedlander.Ph. D

Chemo-Mechanically Regulated Oscillation of an Enzymatic Reaction

Chemistry and Chemical Biolog

Chemo-Mechanically Regulated Oscillation of an Enzymatic Reaction

Chemo-Mechanically Regulated Oscillation of an Enzymatic Reactio

(A) Diagram of shear rheology.

<p>Rotational shear force applied to cervical mucus sample. <b>(B) Example linear viscoelastic spectra of high risk and low risk cervical mucus samples.</b> Storage modulus G′ and loss modulus G” of low risk mucus is an order of magnitude greater than that of high-risk mucus, indicating that high-risk mucus is more weakly cross-linked than low-risk mucus.</p

Example time series of spinnbarkeit test at 2, 5, 10, 15, and 20 mm in low-risk and high-risk cervical mucus samples.

<p>Almost all high-risk samples could be stretched to at least 20 mm without breaking (exhibiting spinnbarkeit). In contrast, mucus from low-risk patients had an average break length of 13.8±2.4 mm.</p

Example scanning electron microscopy images.

<p>Cervical mucus samples from low-risk and high-risk patients were fixed and dehydrated for examination by electron microscopy. Scale bar: 200 nm.</p

Summary.

<p>In women at high risk of preterm birth (with a short and dilated cervix), we find that the cervical mucus does display spinnbarkeit, is more weakly cross-linked and is a less effective barrier.</p

Patient Characteristics.

<p>Expressed as Mean (+/− SD) or percentage; GBS: Group B Streptococcus.</p