# Lipopolysaccharide-Activated Macrophages Suppress Cellular Senescence and Promote Rejuvenation in Human Dermal Fibroblasts

## TL;DR

LPS-activated macrophages reduce aging signs in skin cells, suggesting a potential strategy for reversing skin aging.

## Contribution

Demonstrates that LPS-activated macrophages can suppress senescence and promote rejuvenation in human dermal fibroblasts.

## Key findings

- Conditioned medium from LPS-activated macrophages reduced P16 and P21 levels in senescent fibroblasts.
- LPS-activated macrophage supernatant increased Ki-67 expression, indicating partial rejuvenation of old cells.
- Unstimulated macrophage supernatants or LPS alone did not produce these effects.

## Abstract

Tissue-resident macrophages are essential for skin homeostasis. This study investigated whether lipopolysaccharide (LPS)-activated macrophages affect senescence and rejuvenation in human dermal fibroblasts. Human monocytic THP-1 cells were stimulated with Pantoea agglomerans–derived LPS (1–1000 ng/mL), and culture supernatants were collected. These were applied to two NB1RGB fibroblast populations: young, actively dividing cells (Young cells) and senescent cells with high population doubling levels and reduced proliferation (Old cells). Senescence markers P16, P21, and Ki-67 were analyzed at gene and protein levels. Conditioned medium from Old cells induced senescence in Young cells, increasing P16 and P21 expression levels. This effect was suppressed by cotreatment with LPS-activated THP-1 supernatant. Old cells treated with the LPS-activated supernatant exhibited decreased P16 and P21 levels as well as increased Ki-67 expression, indicating partial rejuvenation. These effects were not observed following treatment with unstimulated THP-1 supernatants or LPS alone. Overall, these findings suggest that secretory factors from LPS-activated macrophages can suppress cellular senescence and promote human dermal fibroblast rejuvenation, highlighting the potential role of macrophage activation in regulating cellular aging and offering a promising strategy for skin aging intervention.