Study of the effect of equine type I collagen preparation on the process of collagenesis in an experimental model using gene expression measurements and histological assessment of tissues

Objective: Evaluation of the effect of equine type I collagen on the collagenesis process in a mouse model by measuring gene expression in mouse skin (genes: COL1, COL3, MMP1, MMP3, ELN, VCAN, IL-6, TNFα, TGFβ) and performing histological examination of tissues.

Materials and methods: The study used female BALB/C mice aged 6–8 weeks. The animals were kept under standard vivarium conditions at controlled temperature (22 ± 2 °C), humidity (50 ± 10%) and 12/12-hour light regime with access to water and food ad libitum. Experimental animals were shaved with two skin areas of ~3 cm² on the dorsal surface using a trimmer (day 0). On the next day (day 1), 100 μl of sterile saline (0.9% NaCl, control) were injected intradermally into one area, and 100 μl of equine collagen type I solution diluted in sterile saline according to the manufacturer’s instructions into the other ones. On day 1 of the experiment (24 hours after the first injection of the drug), one of the animals was sacrificed and skin areas in the injection areas were excised. Gene expression was measured using real-time polymerase chain reaction with reverse transcription (RT-rtPCR).

Histological analysis was performed on the 21st, 35th, and 53rd days.

Results: On day 1 of the experiment (24 hours after the first injection of equine collagen type I), a statistically significant increase in the expression of the COL1 and COL3 genes encoding collagen types I and III, the main structural proteins of the dermis, was observed in the tissues. This clearly indicates the initiation of new collagen synthesis by fibroblasts. Additionally, a significant increase in the TGFβ expression was recorded, which is one of the key regulators of fibroblast activity and differentiation, which is also known as a powerful inducer of collagenesis. Histological data confirm these molecular observations: on the 21st day, a higher ratio of fibroblasts to the total number of dermal cells and a denser organization of collagen fibers were found in the experimental samples than in the control group. Considering that fibroblasts are the main producers of extracellular matrix components, inclu-ding collagen, their high density in the dermis serves as an indirect sign of activation of the synthetic function of the skin under the influence of the drug.

A tendency towards an increase in the thickness of the dermis on the 35th day was also revealed in the experimental group, which may reflect the accumulation of a new matrix and structural reorganization of the tissue. At the same time, the structure of collagen fibers on the 35th and 53rd days remained compact and dense, which indicates stabilization of the remodeled matrix.