Lab on a Chip Blog

Lance Munn and co-workers at Massachusetts General Hospital have developed tissue isolation chambers that can be implanted into the brain or skin of mice beneath a transparent window, to allow host-tumour interactions to be observed over a timescale of weeks to months. A small tumour fragment from a donor mouse was placed within the shallow ‘tumour isolation chamber’ and implanted into another mouse, forcing any vasculature and connective tissue (stroma) to occur in an essentially 2D space. Fluorescent reporters were then used to visualise specific components of the tissue.

Different implantable tissue isolation chambers that were developed. a) 'raft' model; b) 'hole' model; c) 'pillar' model; d) transparent window models in the dorsal skin or brain

By using a shallow chamber, this new method overcomes some of the limitations of other systems used for studying tumour microenvironments and stromal remodelling processes. Other in vivo mouse models use fluorescent reporter and even transparent windows, however the penetration depth of optical microscopy is only a few hundred micrometers, preventing observations below this depth in the tissue. By using tissue chambers of around 150 µm, this issue is circumvented. Another problem can be in visualising structures that extend in the z­ direction, as they may overlap and be hidden; this is overcome in this work by allowing freedom of movement in the x-y plane, while restricting movement or growth in the z direction.

In the studies carried out by the authors, tumour angiogenesis was clearly observed and was found to show the same properties usually observed in tumours. It was also found that migrating blood vessel sprouts were closely associated with bundles of collagen fibres, providing the first evidence for matrix-guided sprouting in tumour angiogenesis. The tissue isolation chambers also allowed analysis of processes that are difficult to study through other methods, due to either the short distances involved, low frequency of occurrence, or rapid dynamics.

Image sequence showing the expansion of vessel sprouts and vascular loops in the tumour isolation chamber. D1=day 1, etc. Pillar structure is indicated by an asterix.

One potential application of this technology highlighted by the authors, is to provide vascularised tissues for transplantation, allowing good blood supply to the transplanted tissue immediately after implantation. In the experiments reported in this paper, stable and mature vasculature was formed that remained functional for more than 2 months after the tissue chambers were implanted. Although these initial findings are very positive, further studies would need to be carried out on a wide range of tissue types.

To download the full article for free* click the link below:

Implantable tissue isolation chambers for analyzing tumor dynamics in vivo
Gabriel Gruionu, Despina Bazou, Nir Maimon, Mara Onita-Lenco, Lucian G. Gruionu, Peigen Huang and Lance L. Munn
Lab Chip, 2016,16, 1840-1851
DOI: 10.1039/C6LC00237D

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About the webwriter

Claire Weston is a PhD student in the Fuchter Group, at Imperial College London. Her work is focused on developing novel photoswitches and photoswitchable inhibitors.

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It takes about 14 years and 2 billion dollars to bring a successful drug from laboratory to clinic. A large portion of this time period includes in vitro culture tests, animal tests, and clinical trials. The overall success rate of a new drug molecule making it through this entire process is only around 10%. To improve this situation, there has been a tremendous amount of work in recent years on developing in vitro organ-on-chip models. Many organ-on-chip platforms (including heart, lung, kidney, liver, and intestine) have shown to mimic organ functions on the microscale, offering the possibility to eliminate animal testing, shorten long development times, and reduce costs. More importantly, such platforms can offer personalized medicine, enabling drug molecules to be tested directly on individual patient cells without adverse side-effects or harm.

Figure 1. The concept of elastomeric endothelialized blood vessels for interconnecting multiple organs on chip systems (liver, heart, and lung modules as illustrated).

Although existing organ-on-chip models have been shown to function well individually, integrating all models into a single fluidic circuitry (or “body-on-a-chip”) remains a necessary goal to recapitulate multi-physiological functions (Figure 1). Passive tube connections and chip-based vessels have thus far been utilized for this purpose. However, bulky dead volumes created in connections, and unbalanced scaling of the volumes between organ models and chip-based vessels, seem counterintuitive to the miniaturized nature of microscale platforms. These methods may also result in miscommunication between the organ models due to the dilution of the signal molecules secreted by the cells.

This fundamental problem has recently been addressed in a practical way by Khademhosseini and co-workers, who are the first to develop polydimethylsiloxane (PDMS) hollow tubes in a range of different sizes and wall thicknesses which mimic the physio-anatomical properties of blood vessels. The fabrication of the PDMS tubes was enabled by two different strategies, including both hard and soft templating (Figure 2a). After fabrication, the tube’s interior surface was coated with human umbilical vein endothelial cells (HUVEC) to introduce biological functions (Figure 2b). The biofunctionality of the elastomeric blood vessels was demonstrated by the expression of an endothelial biomarker and dose-dependent responses in the secretion of von Willebrand factor. The endothelialized PDMS tubes were also utilized for assessing a panel of drugs, including the anti-cancer drug doxorubicin, immunosuppressive drug rapamycin, and vasodilator medication minoxidil, as well as amiodarone, acetaminophen, and histamine (Figure 2c). Functional elastomeric blood vessels can be fabricated up to 20 cm in length, which is sufficient for interconnecting the organ-on-chip models. Moreover, tailorable wall thicknesses enable the opportunity to study various disease models, such as the effect of diabetes or hyperlipidemia on blood vessels. The elastomeric blood vessels are expected to replace the current technologies in assembling human organ-on-chip models.

To download the full article for free* click the link below:

Elastomeric free-form blood vessels for interconnecting organs on chip systems
Weijia Zhang, Yu Shrike Zhang, Syeda Mahwish Bakht, Julio Aleman, Kan Yue, Su-Ryon Shin, Marco Sica, João Ribas, Margaux Duchamp, Jie Ju, Ramin Banan Sadeghian, Duckjin Kim, Mehmet Remzi Dokmeci, Anthony Atala, and Ali Khademhosseini
Lab Chip, 2016, 16, 1579-1586
DOI: 10.1039/C6LC00001K, Advance Article

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About the webwriter

Burcu Gumuscu is a PhD researcher in BIOS Lab on a Chip Group at University of Twente in The Netherlands. Her research interests include development of microfluidic devices for second generation sequencing, organ-on-chip development, and desalination of water on the micron-scale.

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*Access is free until 17/06/2016 through a registered RSC account.