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International Journal of Bioprinting Biomimetic scaffolds for tendon healing

Figure 6. Results of cell viability assay. Fluorescence micrographs of live/dead-stained tissue constructs. The live (green) and dead (red) cells can be seen
at the different time points and cells densities (4×). Scale bar: 500 µm.

reason is that when the tenocyte phenotype is established, of Fn1 in tenocytes embedded in the scaffold did not
the expression of this gene ceases to change. The Tnc gene change with time.
encodes a glycoprotein that is essential during tendon Under normal conditions, the major component
regeneration because it is related to collagen fiber alignment of tendons is collagen, specifically type I collagen.
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and tissue homeostasis. 72,74 Although an increasing When an injury occurs in this tissue, during the first
tendency was detected over time, it was not statistically
significant. It has been previously reported that this gene is phase of the regeneration process, collagen III is the
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mechanosensitive, so its expression increases over time in one that is predominantly produced. In later phases,
response to the mechanical stimulation to which the cells this collagen is replaced by type I collagen, indicating
are subjected when they are embedded in the hydrogel. greater maturity and mechanical resistance of the
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The maintenance of Scx expression and the slight increase tissue. This is why the expression of both collagens,
in Tnc expression suggest that cell dedifferentiation is not as well as their proportion, is of great importance. In
occurring over time. 76 the developed tissue constructs, tenocytes presented a
significant increase in the expression of Col3a1 on day
c-Fos is a member of a family of intermediate early 12. In the case of Col1a1, its expression exhibited very
genes involved in a large number of biochemical processes. slight and not significant changes. This result indicates
Its transcription is increased as a response to growth that, during the first 12 days, the tenocytes embedded in
factors and during cell proliferation, differentiation, and the scaffold are still in an “initial” phase of production
transformation, among others. In the tissue constructs, of the tendon’s own ECM. It is necessary to mention
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the expression of this gene increased significantly over time. that these genes, Col1a1 and Col3a1, have also been
This allows authors to hypothesize that the cells increase used in many occasions as markers that indicate the
their proliferation rate over time within the scaffold, in differentiation or dedifferentiation of tenocytes.
agreement with the results observed in cell viability and
metabolic activity assays. On the other hand, Fn1 is a In addition to the analysis of the variation of gene
gene that encodes fibronectin. Its function is related to the expression over time, it is also interesting to analyze the
processes of cell adhesion and migration. The expression relationship between the expressions of the different genes.
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Volume 10 Issue 3 (2024) 457 doi: 10.36922/ijb.2632