Researchers at
the Indian Institute of Technology (IIT) Delhi have for the first time
developed a 3D scar-tissue model through tissue engineering. The two-member
team led by Prof. Sourabh Ghosh from the Department of Textile Technology at
IIT Delhi was successful in replicating the early inflammatory microenvironment
that initiates a cascade of events that lead to scar development.
Drugs currently
available to reduce scarring in the case of deep wounds that affect all the
layers of the skin have limitations owing to poor understanding of scar tissue
formation and the signalling pathways responsible for its development. This is
particularly so as results of scar tissue models created in animals have
limitations when extrapolated to humans. Also, the European Union directive to
find alternatives to animals testing makes Prof. Ghosh’s relatively
simple in vitro scar-tissue model ideal for drug testing.
Optimised
cocktail
The researchers
first encapsulated fibroblasts from healthy human skin within the collagen gel.
Three days after an optimised cocktail of three cytokines were added to the
media, differentiation of dermal fibroblasts into myofibroblasts was triggered.
Myofibroblasts are bigger in size than fibroblasts and have greater contractile
power, something that is essential to close the wound. Scar-specific proteins
are expressed by myofibroblasts.
“There was an
increase in the scar-specific proteins and gene expression with increasing
duration of culture. By day 14, scar-tissue similar to what formed naturally on
human skin was formed,” says Shikha Chawla from the Department of Textile
Technology at IIT Delhi and first author of a paper published in the
journal Acta Biomaterialia.
Typical features
In addition to
the differentiation of fibroblasts into myofibroblasts, the researchers
witnessed other typical features that cause scar formation. For instance,
during the wound-healing process, excessive fibrous extracellular matrix is
produced.
While there is
excessive production of extracellular matrix proteins, the secretion of matrix
metalloproteinase, whose role is to degrade certain proteins such as ECM, is
reduced. As a result, the tightly regulated balance between synthesis and
degradation of matrix components get disturbed, and the skin gets thicker and stiffer.
There was also increased expression of alpha smooth muscle actin, a
cytoskeleton protein, in the in vitro scar model. “The alpha smooth muscle
actin is a characteristic marker of myofibroblasts. The cytoskeleton protein is
expressed as a thick bundle that stretches the cell thereby causing
contraction,” says Chawla.
“All these
features that make the scar tissue thicker and stiffer in humans are already
known. Using tissue engineering strategies, we are now able to replicate these
features in the in vitro 3D model,” says Prof. Ghosh.
“In addition to
these five features, the scar model was also able to replicate two important
cellular signalling pathways through which scar tissue are formed,” says Prof.
Ghosh. “Since the scar tissue formed in vitro followed similar
signalling pathways as natural scar tissue, new drug molecules and
immunomodulatory strategies designed to manipulate one or both the pathways
might help in modulating scar tissue formation.”
Implications
Creating scar
tissue in the lab has great implications for the pharmaceutical industry. “The
cosmetic and pharmaceutical industries, which are developing anti-fibrosis or
anti-scar medicines, need not have to test them on animals. They can use our
tissue-engineered model instead,” he says.
The team is now
using selective peptide domains and a 3D bioprinting strategy to develop
progressively more complex in vitro scar tissue, which would
recapitulate more hallmark features that are critical for tissue fibrosis.
Source:THE HINDU-25th February,2018
