It is worth noting that single-cell atlas analysis has revealed that S100A9 and MMP9 play significant roles respectively in psoriasis-related CD8-IL17A T cells and M2-like macrophages, and further clarified the functional characteristics of S100A9 in the temporal development process of psoriasis fibroblasts and keratinocytes.<h4>Conclusions</h4>In summary, our findings confirm the efficacy and safety of hAMSCs in the treatment of psoriasis and elucidate the underlying mechanisms of their therapeutic action. Here, MMP9 is linked to psoriasis.