CellScale User Publication Highlight: Multifactorial Bottom-up Bioengineering Approaches to Develop Living Tissue Substitutes

CellScale User Publication Highlight: Multifactorial Bottom-up Bioengineering Approaches to Develop Living Tissue Substitutes

Bottom-up bioengineering is an approach to build tissue structures using cell-laden modules (such as extracellular matrix) as opposed to seeding cells into porous scaffolds. It has a higher level of biomimicry and has been used successfully in clinical settings for skin, cornea and blood vessel tissues. However, existing methods require a long culture time to produce the implantable construct. This causes phenotypic drift and eventually the loss of cells’ therapeutic potential. Dr Dimitrios Zeugolis and his team at the National University of Ireland-Galway looked at using macromolecular crowding (MMC) and mechanical loading to optimize cell conditions and ECM deposition in the eventual goal of fabricating biomimetic tissue substitutes.

 

In their experiment, cultured cells in MMC medium underwent uniaxial stretching using the CellScale MechanoCulture T6. Mechanical stimulation is important for tissues to regain functional mechanical properties. Scaffolds and cell constructs in vitro have seen improved mechanical properties even after short-term stimulation. The team varied 4 different cell types: human adult tenocytes, human neonatal dermal fibroblasts, human adult dermal fibroblasts and human bone marrow stem cells.

 

This paper thoroughly discusses the team’s results after studying cell morphology, ECM composition, gene expression, cell viability and more. In the image above, cytoskeleton and nuclei staining of tenocytes in varying days of culture and presence of MMCs shows perpendicular alignment to the load direction (white arrow). 

Read the full journal article here: https://doi.org/10.1096/fj.201802451R

Read about Dr Zeugolis’s research here:https://www.nuigalway.ie/engineering-informatics/biomedical-engineering/research/researchtopics/drdimitrioszeugolis/

To read about an engineered meniscus developed from Middle East Technical University in Turkey, click here.

 

CellScale User Publication Highlight: Investigating the Venous Valve Tissue Mechanical Properties and ECM

CellScale User Publication Highlight: Investigating the Venous Valve Tissue Mechanical Properties and ECM

A jugular venous valve functions to prevent retrograde blood flow. If it malfunctions or is incompetent, symptoms such as amnesia or stroke may occur. Moreover, there are no long-term remedy for jugular venous valve incompetence – surgery to replace a failed valve often uses a replacement with warped mechanical properties which in turn affects the valve performance. Dr. Hsiao-Ying Shadow Huang and her team at North Carolina State University wants to bridge the knowledge gap of mechanical properties of the venous valve tissues so as to address better choice of bioprosthetic venous valve replacements and venous valve incompetent treatment.

Her first approach is performing multi loading biaxial mechanical tests. Applying a stress in more than one direction better represents the physiological loading of the venous valve tissue, and various force loading ratios allows further characterization of the tissue’s fiber reorientation in extra-cellular matrix. Together with light microscopy imaging and scanning electron microscopy, this paper captures several firsts: images of the venous valve’s isolated elastin microstructure; explanation of the venous valve tissue’s anisotropic behavior; and characterization of crimp effects on venous valve mechanical properties.

The image above shows circumferential and radial stress-strain curves taken with the CellScale BioTester under the 3 force loading ratios. The paper also contains several high-contrast images of the bovine jugular venous valve tissue and its elastin microstructure.

Read the full journal article here: https://doi.org/10.3390/bioengineering6020045

Read about her research here: https://huang.wordpress.ncsu.edu/

Dr Huang is the recipient of the Presidential Early Career Award for Scientists and Engineers (PECASE) from the National Science Foundation. Read about the award here: http://bit.ly/2Jlpftm

To read about an onsite applications of valve tissue research, click here.

 

CellScale User Publication Highlight: Molecularly-ordered Hydrogels with Controllable Response

CellScale User Publication Highlight: Molecularly-ordered Hydrogels with Controllable Response

In the field of biosensors, artificial muscles and microfluidics, shape-morphing hydrogels are of significant interest. Isotropic materials can be morphed into complex shapes under aqueous stimuli by varying the material (embedding with stiff particulate such as carbon nanotubes for example) or the processing (angled lamination). While the challenge exists to create and control such hydrogels at a micro-size, Taylor Ware and his team at the University of Texas at Dallas have successfully created anisotropic hydrogels by polymerizing oriented chromonic liquid crystals. In  this paper, the team demonstrated control over magnitude of shape change, stimulus to which the gel responds, and complexity of the liquid crystal orientation.

Key to these anisotropic hydrogels is the patterned order imparted by chromonic liquid crystals. This patterned order was quantified by testing the axis-dependent mechanical properties, which is a difficult task in thin, compliant hydrogels. The team used the CellScale MicroTester with a temperature-controlled water bath setup to measure and subsequently derive the Young’s Modulus.

Stimulus in this experiment were pH and temperature, as determined by the choice of responsive comonomer. From the image below, approximately 70% and 50% dimensional changes are seen perpendicular to the alignment direction versus along the alignment direction in response to increased temperature. Varying the pH from acid to base saw approximately 100%/80% dimensional change (image above). Leveraging this knowledge, the team went further to create a microstructure that would exhibit positive or negative Gaussian curvature in response to certain conditions.

Read the full journal article here: https://doi.org/10.1039/C9SM00763F

To read about a research on biomechanical impact of localized corneal cross-linking, click here.

 

CellScale User Publication Highlight: Biomechanical Impact of Localized Corneal Cross-linking

Corneal Ectasia occurs when there are irregularities in the cornea which may lead to disturbances of vision. Astigmatism is a common outcome of corneal ectasia, but the disorder can also occur after refractive surgery (LASIK). It is the second leading cause of corneal transplantation worldwide. To treat it, the U.S. FDA approves of corneal cross-linking (CXL) to stop the ectatic process. This is a process that stiffens the cornea with a photosensitizer followed by uniform ultraviolet-A exposure. The additional chemical bonds created through this process increases the overall corneal strength.

Another recent approach is localized CXL. The risk of complication and infection is expected to diminish by limiting the irradiated area. Dr Giuliano Scarcelli and his team at the University of Maryland investigates localized CXL within and beyond the irradiated region in three-dimensions and worked with fresh porcine eyes acquired within 8 hours after the animal was killed.

The CellScale MicroTester was used to evaluate the mechanical properties of each corneal sample through a compression test, from which the Young’s Modulus could be derived from force and displacement data.

Image below: A parallel plate compression test of the corneal sample.

Read the full journal article here: https://doi.org/10.3928/1081597X-20190304-01

To read about another cornea research based in the IROC Institute in Switzerland, click here.

 

CellScale User Publication Highlight: IVD Regenerative Medicine featuring Pullulan Microbeads in an Injectable System

CellScale User Publication Highlight: IVD Regenerative Medicine featuring Pullulan Microbeads in an Injectable System

Dr Catherine Le Visage and her group at the Regenerative Medicine and Skeleton (INSERM U119) based in the School of Dental Surgery, University of Nantes – France has derived an ingenious way to treat discogenic low back pain, something several of us experience as we age. A common reason of low back pain is the degeneration of the intervertebral disc (IVD), which is a fibrocartilaginous tissue located between each vertebrae in our spine. Current treatment does not address the etiological cause of disc degenerative disease (DDD) thus regenerative medicine approaches are considered with deep interest – in particular, the stimulation of local cells by in situ injection of growth factors targeting IVD degenerative process.

Dr Le Visage’s approach is an injectable biphasic system of pullulan microbeads (PMBs) dispersed within a cellulose-based hydrogel (Si-HPMC). Pullulan is a neutral, linear and non-immunogenic polysaccharide that is widely used because of its natural properties (biodegradable, biocompatible, non-toxic). The research team demonstrated a sustained release of growth factors TGF-β1and GDF-5 in vitro for up to 28 days, while maintaining biological activity on human cells. In addition, they were able to measure for the first time the mechanical properties of the PMBs through a parallel plate compression test with the CellScale MicroTester.

Images above – 
Top left: Pullulan microbeads observed with a confocal microscopy
Bottom left: Pullulan microbeads observed with a scanning electron microscope
Right: Pullulan microbeads mechanical characterization. A hydrated single PMB was compressed between 2 plates using a MicroTester. Force and displacement data were recorded and a representative curve was presented.

This study is part of a larger comprehensive and continuous study to improve treatment options of DDD through regenerative medicine. You can read more about Dr Le Visage’s work here: https://rmes.univ-nantes.fr/

Read the full journal article here: https://doi.org/10.1080/10717544.2017.1340362

Read all other publications here: https://cellscale.com/publications/

 

To read about a collagenous bioscaffold for the treatment of cutaneous wounds, click here.

 

Interview with Peter Hammer at the Boston Children’s Hospital

Interview with Peter Hammer at the Boston Children’s Hospital

In our In the Lab blog series, we catch up with researchers using CellScale systems.

In this installment of the blog, Caleb Horst chats with Dr. Peter Hammer at the Boston Children’s Hospital. Peter is a staff scientist and an instructor in surgery, using the CellScale BioTester in his work.

Caleb Horst: You have a really interesting position. You are an engineer, but you work at a hospital with the surgeons. Can you tell us a little bit more about what that is like for you and what your role is here?

Peter HammerYeah, you’re right. It’s a bit of an unusual arrangement having an engineer working in a clinical department in the hospital. I’ve been working in research for many years. Several years ago I was hired by the department to work directly with clinicians, primarily cardiac surgeons to help bring some quantitative methods to bear some of the most challenging problems in cardiac surgeries.

CH: And what type of problems have you been tackling with regards to helping the surgeons do a better job with surgery?

PH: Mostly heart valves, helping to understand the biomechanics of heart valves but in a clinically relevant way. In other words, surgeons are faced with a reconstruction of a child’s heart valve – helping them understand what ways they can sort of measure or quantify the elements that go into a valve reconstruction to get more of a reliable result.

CH: You were telling me earlier how often the valves were taken from the patient’s own pericardium material, and you were trying to help them do a better job of harvesting that tissue and understanding how best to use the tissue that they have available?

PH: Yes, that’s right. In children, they typically will try to repair a valve rather than replace it. And repairing it means cutting and sewing the tissues that are already there in the child’s valve, or introducing materials, preferably the child’s own materials such as pericardium to reconstruct a leaflet, or even all the leaflets of the valve to get a working valve. And the challenge is that those materials, the properties of those replacement leaflet materials such as the child’s own pericardium, are not the same as the native valve leaflet so the surgeons has to make some alterations to the way he would size and shape a patch of a replacement leaflet and to do that, you really need to know the properties of that in a quantitative way.

CH: And so your research was to do mechanical testing not for the purposes of material modeling or generation of synthetic materials but just to provide that feedback to surgeons directly, and see that impact right away.

PH: That’s right, to help them understand if I use this type of material which is very stretchy, medium stretchy, not stretchy at all, depending on where it falls in that ‘stretchyness’ spectrum, how do we compensate when cutting and sizing patches and replacement leaflets to create a repair that’s robust and durable.

CH: And what was the workflow of the research then? You had to do mechanical testing so you needed samples, and you have that good communication with the surgeons, so how do you get samples? What kind of samples were they and what type of results were you able to get for the surgeons?

PH: When the surgeons operate on a heart valve, they know that they may need patch materials. They will harvest some of the patient’s own pericardium, put it aside, typically fix it to stabilize it using some type of chemical fix agent like glutaraldehyde. And then during a certain procedure, we’ll then cut a patch out of this to use during the procedure. They typically don’t use all of the patch they cut out and it just goes into the trash. I have told the surgeons that we can use those discarded operating room tissues. We’re able to test them in the lab here. We build a library of the properties of those different patch materials, with different amounts of fixation time or harvested from different sites. 

CH: You mentioned you were able to compare it to different fixation time in terms of how extensible it is and also compare it to other commercially available products and do some studies with the alignment of the tissue. How are your results fed back to the surgeons?

PH: First I can start by saying that there really are no standard techniques for harvesting and fixing these tissues. Every surgeon does it a little bit differently. Part of the goal is to put numbers on the different variables involved in this process. How long did they fix these tissues? How much did they stretch when they were being fixed? And also the harvest site of the pericardium, how does that affect the properties and how it behaves. Part of the challenge was to try and quantify all the different steps that affect the final result which is the ‘stretchyness’, the durability of these tissues. In terms of disseminating this information, after we collected a fairly large number of samples from the different fixation methods, we wrote this up in journal articles, submitted this to journals, not in engineering journals but the journals that the surgeons read and that was a bit of a challenge, taking these methods and approaches that are used typically in engineering fields and distilling it, relating it in a way that the surgeons can understand and could then apply to their own practice, so making it very practical.

CH: We’re certainly glad you’re doing this work and it’s nice to see such a direct application, the knowledge we’re getting from the equipment like the BioTester toward health outcomes in a very short term. I hope there are more roles like yours that continue to come into existence in the world and more close interactions with engineering and material science people and surgeons.

PH: Thank you, yes, meaningful work, and I’m also very happy to see a machine like this come along that really took the mechanical testing apparatus from every lab having their own home built system to something that can really take a lot of the nuts and bolts assembly and machining and software and controls engineering out of it to make that all a turnkey system. This has been a real asset to this type of lab.

CH: I’m glad its in capable hands and you’re doing good work. Thank you very much and thanks for talking to us, I really appreciate it.