Mesenchymal stem cell regulation of IL-8 and MMP-1 in inflammatory states

Abstract

Wound healing remains a challenge to many clinicians in spite of significant advances that have occurred in wound management in view of their significant social and economic impact on the ageing population (Velnar, Bailey and Smrkolj, 2009). During this study, an in vitro air-liquid interface wound model was set up to analyse the interactions between keratinocytes, fibroblasts and mesenchymal stem cells (MSC) and the changes in gene expression of Matrix Metalloproteinase-1 (MMP-1) and Interleukin-8 (IL-8) during wound healing with the help of growth factors.

The project involved cell culturing of primary human keratinocytes and fibroblasts from skin biopsies and culturing of primary human mesenchymal stem cells from peripheral blood. Characterisation of Mesenchymal stem cells was carried out by differentiation of mesenchymal stem cells into adipocytes, osteocytes and chondrocytes, flow cytometry and quantitative Polymerase Chain Reaction (qPCR). The in-vitro wound model, using an air-liquid interface, was assembled using keratinocytes and fibroblasts embedded in a leukocyte-depleted platelet-rich plasma scaffold. Tumour Necrosis Factor-alpha (TNF-α) and Mesenchymal Stem Cells were added to the wound model. Ribonucleic acid (RNA) extraction was carried out from the wound model, followed by cDNA synthesis. The gene expression of IL-8 and MMP-1 was then measured using quantitative PCR. This project described the implementation of an innovative skin equivalent that is devoid of leucocytes and capable of supporting added cells such as MSCs. This enabled quantification of selective expression of genes, in this case, MMP-1 and IL-8 on wounding. The addition of MSCs to the wound model showed downregulation of MMP-1 and IL-8 in day 2, in keeping with the immunosuppressive phenotype of MSCs. The MSCs overcame the acute inflammatory state produced by the TNF-α and helped anticipate the immune response in the study group. A significant result was noted between day 2 and day 4 where a substantial increase in mRNA levels of IL-8 and MMP-1 was noted in the study group. In the case of IL-8, this contrasted with the results in the treated group where there was a down-regulation of IL-8 gene expression.

The results showed that the role of mesenchymal stem cells is more complex than it was thought initially. Mesenchymal stem cells act as the “sensor and switcher of the immune system” (Jiang and Xu, 2019). These cells favour pro-inflammatory factors at the time of the inflammatory stage of repair and up regulate anti-inflammatory factors when the wound is healing (Iocono et al., 2000). Therefore, innovative wound therapies using mesenchymal stem cells, which promote regenerative medicine hold great potential for clinical management of problematic wounds.