Mesenchymal stem cells (MSCs) are potentially useful cells for musculoskeletal tissue engineering. However, controlling MSC differentiation and tissue formation in vivo remains a challenge. There is a significant need for well-defined and efficient protocols for directing MSC behaviors in vivo. We hypothesize that morphogenetic signals from chondrocytes may regulate MSC differentiation. In micromass culture of MSCs, incubation with chondrocyte-conditioned medium (CCM) significantly enhanced the production of cartilage specific matrix including type II collagen. In addition, incubation of MSCs with conditioned medium supplemented with osteogenic factors induced more osteogenesis and accumulation of calcium and increased ALP activity. These findings reveal that chondrocyte-secreted factors promote chondrogenesis as well as osteogenesis of MSCs during in vitro micromass culture. Moreover, when MSCs expanded with chondrocyte-conditioned medium were encapsulated in hydrogels and subsequently implanted into athymic mice, basophilic extracellular matrix deposition characteristic of neocartilage was evident. These results indicate that articular chondrocytes produce suitable morphogenetic factors that induce the differentiation program of MSCs in vitro and in vivo.

Tissue engineering provides a venue to investigate tissue development of mutant or diseased cells and potential therapeutics.

In an effort to improve the physiologic relevance of existing in vitro models for alveolar cells, we present a microfluidic platform which provides an air-interface in a dynamic system combining microfluidic and suspended membrane culture systems. Such a system provides the ability to manipulate multiple parameters on a single platform along with ease in cell seeding and manipulation. The current study presents a comparison of the efficacy of the hybrid system with conventional platforms using assays analyzing the maintenance of function and integrity of A549 alveolar epithelial cell monolayer cultures. The hybrid system incorporates bio-mimetic nourishment on the basal side of the epithelial cells along with an open system on the apical side of the cells exposed to air allowing for easy access for assays.

This paper describes the fabrication and application of microfluidic devices containing collagen vitrigel (CV) used as both a functional and sacrificial cell growth substrate for the development of corneal microtissue patches. Within the device, vacuum fixation of the CV in a dehydrated state enables quick integration with standard multilayer soft lithographic techniques, while on-chip rehydration results in a gel-like collagen substrate for microfluidic cell culture. Fluidic connectivity to both the apical and basal side of the CV permits bilayered culture of epithelium and supporting stromal cell layers. In addition, microfluidic introduction of a collagenase etching media enables sacrificial degradation of the supporting CV membrane for development of barrier tissue constructs containing minimal synthetic substrate. The utility of this platform was evaluated by miniaturizing the standard transepithelial permeability (TEP) assay in order to measure the integrity of an array of corneal tissue micropatches.

We demonstrate single biomolecule detection and quantification within sub-nanolitre droplets through application of Cylindrical Illumination Confocal Spectrosocpy (CICS) and droplet confinement within a retractable microfluidic constriction.Droplet-based microfluidic platforms offer the distinct advantages of fast sample mixing, limited reagant dispersion, and lower sample loss or contamination when compared to traditional microfluidic devices. 1, 2 In addition, simple control stategies for kHz frequency droplet generation, transportation, storage, and sorting give the platform a propensity for high throughput analysis. While initial applications have been shown in a range of research disciplines, including biochemical analysis 3 , chemical and material synthesis 4 , and chemical reactions 5 , more recent applications have emerged that seek to expand this high throughput capability to the analysis of individual biological entities, such as single cells 6-8 or biomolecules. 9,10 In single cell experiments, in vitro compartmentalization in droplets enables rapid accumulation of secreted cellular factors 11 , and provides both chemical isolation and a unique means of cell selection and control. 12 Alternately, single molecule compartmentalization enables nucleic acid analysis through single-copy DNA PCR, extending the high throughput capacity of droplet-based microfluidics to digital PCR assays. 7, 9, 10 However, the current dependence on amplification techniques (e.g. PCR or fluorogenic substrate) 1 for detection of low concentration biomolecules presents limitations in droplet-based platforms; these include decreased throughput and added complexity involved with enzymatic amplification. These limitations point towards the need for integration of a highly sensitive detection platform for amplification-free detection of lowabundance biomolecules.Confocal Fluorescence Spectroscopy (CFS) has traditionally been used for fluorescence based single molecule detection (SMD). [13][14][15][16][17][18] Resolution of single fluorophores is accomplished through reduction of a laser-illuminated probe volume to femtolitre size, thus minimizing background noise. Although well suited for SMD in continuous sample streams,