OU-MRU Vol.13 August 2015

Okayama University Medical Research Updates （OU-MRU）

2015.08 Vol.13

Source: Okayama University, Center for Public Affairs and Communications
For immediate release: 05 August 2015
Okayama University research: Peptide directs artificial tissue growth(Okayama, 05 August) Studies on peptide-modified cultures demonstrate control overboth tissue growth and location in vitro.
“In vitro fabricated biological tissue would be a valuable tool to screen newly synthesized
drugs or understand the tissue development process,” explain Takuya Matsumoto and hiscolleagues in a recent report. However tissues grown so far have not reached the size andfinal shape of natural tissue. Matsumoto and colleagues at Okayama, Osaka and Kansai
Universities in Japan have now identified a tripeptide sequence that can be used toovercome both limitations. With hydrogel modified with the tripeptide they demonstrateenhanced tissue growth of a salivary gland both across a sheet of tissue and at specified
localised points.
The salivary gland studied - the submandibular gland - develops a branched structure
through budding and the elongation of ducts, which is also typical of other structures suchas lungs, kidneys, mammary glands and spleen. Previous research revealed the importanceof the glycoprotein fibronectin in the morphological development and growth of salivary
gland tissue. Consequently Matsumoto and colleagues focused their investigations on theeffects of the specific tripeptide sequence arginine-glycine aspartic acid (RGD) that acts as acell binding site on fibronectin.
The researchers studied the growth of salivary gland tissue on hydrogel both modified withdifferent concentrations of RGD and without and found significant growth enhancementsthat increased with RGD concentrations. They then experimented with RGD-modifiedhydrogel beads and demonstrated that localised growth enhancement occurred where thebeads were situated, which could provide control over morphology in artificial tissue growth.
Further studies also suggested that neuronal growth and the enhancement of growth factor
proteins were responsible for the enhanced gland tissue growth observed.
In their report of the work the researchers conclude, “This in vitro SMG tissue growthmodulation system can have a variety of uses including tissue arrays for drug screening andas a biologic tool to understand tissue development.”

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OU-MRU Vol.13 August 2015

Background
Tripeptide in previous studies
The shape development or morphogenesis of the submandibular gland develops throughthe formation of clefts that occur through a change in cell adhesion so that they bind to thesurrounding extracellular matrix instead of each other. Previous research has shown that
expression of the glycoprotein fibronectin is crucial for cleft formation.
Integrin is a receptor protein that bridges interactions between cells and the extracellularmatrix. The domain of fibronectin that binds to integrin is the tripeptide sequence arginineglycine aspartic acid (RGD) prompting studies of this tripeptide sequence on tissue growth.
Investigations have already shown that transplanting composites containing RGD peptides
onto the back of a mouse can result in the development of growth plates – the tissue at theends of bones in growing children and adolescents. However so far there have been nostudies into the growth and morphology of tissues in vitro. The ability to grow tissues invitro is particularly important for drug screening and studies to better understand tissuegrowth.
The role of FGFs
Fibroblast growth factors (FGFs) are a family of proteins involved in embryonic development,
wound healing and signalling pathways. Two specific FGFs play a crucial role in the growthof the two main tissue types in the submandible salivary gland – FGF7 induces budding in
the epithelial tissue and FGF10 induces the elongation of ducts in the mesenchymal tissue.
Matsumoto and colleagues imaged the salivary gland tissues grown in RGD-modifiedhydrogels using immunofluorescent staining and found both FGF7 and FGF10 were highly
expressed. Experiments to grow the salivary gland tissues in the presence of FGF7 andFGF10 antibodies revealed that these antibodies inhibited tissue growth. The RGD-modifiedhydrogel was also ineffective at enhancing tissue budding in isolated epithelial cells alone.
The role of neurites
Previous studies have also suggested that neuron outgrowths – ‘neurites’ – from a region
known as the parasympathetic ganglion in submandibular gland tissue are key to tissue
growth. The researchers observed an even distribution of the neurite network throughout
the gland tissues they had grown. Antibodies to the neurotrophic factors, which areresponsible for neuron growth and survival, also inhibited submandibular gland tissue
growth in RGD-modified hydrogels.

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OU-MRU Vol.13 August 2015

Figure captiona) Schematic illustration of the RGD-modified hydrogel (left) and the submandibular gland(SMG) tissue culture on hydrogel (right). b,c) SMG cultured on hydrogel sheets modifiedby introducing various RGD concentrations (0–0.18 mol/l), and SMG cultured on a tissue
culture dish without any hydrogel substrate as a negative control (Bar = 50 μ m). A stiffer
gel sheet normally attenuates SMG growth, but the SMG growth was enhanced whenRGD was introduced. The SMG growth changed in accordance with the introduced
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1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530 Japan© OKAYAMA University

OU-MRU Vol.13 August 2015

amount of RGD. SMG was completely dissociated when cultured on the traditional tissue
culture dish instead of hydrogel.
Reference
Hiroaki Taketa, Gulsan Ara Sathi, Mahmoud Farahat, Kazi Anisur Rahman, Takayoshi Sakai,
Yoshiaki Hirano, Takuo Kuboki, Yasuhiro Torii, Takuya Matsumoto. Peptide-modified
Substrate for Modulating Gland Tissue Growth and Morphology In Vitro. Scientific Reports 5,
Article number: 11468 (2015).
DOI: 10.1038/srep11468
http://www.nature.com/articles/srep11468
Correspondence toProfessor Takuya Matsumoto, D.D.S., Ph.D.
Department of Biomaterials, Okayama University,
2-5-1 Shikata-Cho, Okayama, 700-8558, Japan.
E-mail: tmatsu@md.okayama-u.ac.jp

Further information
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https://www.youtube.com/watch?v=KU3hOIXS5kkOkayama University Medical Research Updates （OU-MRU）
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OU-MRU Vol.13 August 2015

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About Okayama University
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Place sponsored by the Lord of Okayama
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