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.
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.
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.”
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.