A genetic system for Akkermansia muciniphila reveals a role for mucin foraging in gut colonization and host sterol biosynthesis gene expression.

Akkermansia muciniphila, a mucophilic member of the gut microbiota, protects its host against metabolic disorders. Because it is genetically intractable, the mechanisms underlying mucin metabolism, gut colonization and its impact on host physiology are not well understood. Here we developed and applied transposon mutagenesis to identify genes important for intestinal colonization and for the use of mucin.

Microbiota responses to different prebiotics are conserved within individuals and associated with habitual fiber intake.

Background: Short-chain fatty acids (SCFAs) derived from gut bacteria are associated with protective roles in diseases ranging from obesity to colorectal cancers. Intake of microbially accessible dietary fibers (prebiotics) lead to varying effects on SCFA production in human studies, and gut microbial responses to nutritional interventions vary by individual. It is therefore possible that prebiotic therapies will require customizing to individuals.

Interindividual Variation in Dietary Carbohydrate Metabolism by Gut Bacteria Revealed with Droplet Microfluidic Culture.

Culture and screening of gut bacteria enable testing of microbial function and therapeutic potential. However, the diversity of human gut microbial communities (microbiota) impedes comprehensive experimental studies of individual bacterial taxa. Here, we combine advances in droplet microfluidics and high-throughput DNA sequencing to develop a platform for separating and assaying growth of microbiota members in picoliter droplets (MicDrop).

Antibiotic-induced changes in the microbiota disrupt redox dynamics in the gut.

How host and microbial factors combine to structure gut microbial communities remains incompletely understood. Redox potential is an important environmental feature affected by both host and microbial actions. We assessed how antibiotics, which can impact host and microbial function, change redox state and how this contributes to post-antibiotic succession.

Improving the permeability of lyophilized collagen-hydroxyapatite scaffolds for cell-based bone regeneration with a gelatin porogen.

Bone tissue engineering using biomaterial scaffolds and culture-expanded osteoprogenitor cells has been demonstrated in several studies; however, it is not yet a clinical reality. One challenge is the optimal design of scaffolds for cell delivery and the identification of scaffold parameters that can delineate success and failure in vivo. Motivated by a previous experiment in which a batch of lyophilized collagen-hydroxyapatite (HA) scaffolds displayed modest bone formation in vivo, despite having large pores and high porosity, we began to investigate the effect of scaffold permeability on bone formation.

Imaging mass spectrometry of elements in forensic cases by LA-ICP-MS.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was performed to map elements in thin formalin-fixed paraffin-embedded tissue sections of two forensic cases with firearm and electrocution injuries, respectively. In both cases, histological examination of the wounded tissue regions revealed the presence of exogenous aggregates that may be interpreted as metallic depositions. The use of imaging LA-ICP-MS allowed us to unambiguously determine the elemental composition of the observed aggregates assisting the pathologist in case assessments.

Comparison of the Osteogenic Potential of Mineral Trioxide Aggregate and Endosequence Root Repair Material in a 3-dimensional Culture System.

Introduction: The ability to promote osteoblast differentiation is a desirable property of root-end filling materials. Several in vitro studies compare the cytotoxicity and physical properties between mineral trioxide aggregate (MTA) and Endosequence root repair material (ERRM), but not their osteogenic potential. Three-dimensional cultures allow cells to better maintain their physiological morphology and better resemble in vivo cellular response than 2-dimensional cultures.

Effects of cell-attachment and extracellular matrix on bone formation in vivo in collagen-hydroxyapatite scaffolds.

Cell-based tissue engineering can be used to replace missing or damaged bone, but the optimal methods for delivering therapeutic cells to a bony defect have not yet been established. Using transgenic reporter cells as a donor source, two different collagen-hydroxyapatite (HA) scaffolds, and a critical-size calvarial defect model, we investigated the effect of a cell-attachment period prior to implantation, with or without an extracellular matrix-based seeding suspension, on cell engraftment and osteogenesis. When quantitatively compared, the in-house scaffold implanted immediately had a higher mean radiopacity than in-house scaffolds incubated overnight.

Bone tissue engineering with a collagen-hydroxyapatite scaffold and culture expanded bone marrow stromal cells.

Osteoprogenitor cells combined with supportive biomaterials represent a promising approach to advance the standard of care for bone grafting procedures. However, this approach faces challenges, including inconsistent bone formation, cell survival in the implant, and appropriate biomaterial degradation. We have developed a collagen-hydroxyapatite (HA) scaffold that supports consistent osteogenesis by donor-derived osteoprogenitors, and is more easily degraded than a pure ceramic scaffold.

Visualizing osteogenesis in vivo within a cell-scaffold construct for bone tissue engineering using two-photon microscopy.

Tissue-engineering therapies have shown early success in the clinic, however, the cell-biomaterial interactions that result in successful outcomes are not yet well understood and are difficult to observe. Here we describe a method for visualizing bone formation within a tissue-engineered construct in vivo, at a single-cell resolution, and in situ in three dimensions using two-photon microscopy. First, two-photon microscopy and histological perspectives were spatially linked using fluorescent reporters for cells in the skeletal lineage.

Growth of primary embryo cells in a microculture system.

We present optimal perfusion conditions for the growth of primary mouse embryonic fibroblasts (mEFs) and mouse embryonic stem cells (mESCs) using a microfluidic perfusion culture system. In an effort to balance nutrient renewal while ensuring the presence of cell secreted factors, we found that the optimal perfusion rate for culturing primary embryonic fibroblasts (mEFs) in our experimental setting is 10 nL/min with an average flow velocity 0.55 microm/s in the microchannel.