Senescent dermal fibroblasts negatively influence fibroblast extracellular matrix-related gene expression partly via secretion of complement factor D.
Level 5 - mechanism / opinion, no new human data
In vitro cell culture and ex vivo tissue analysis (bench research)
PubMed 31026383 · doi:10.1002/biof.1512
What was done
Researchers investigated how senescent dermal fibroblasts affect younger dermal fibroblasts using a Transwell coculture model separated by a semipermeable membrane. Young (low-passage) and senescent (high-passage) fibroblasts were evaluated for changes in extracellular matrix-related gene expression. Secretory factor candidates upregulated by at least 2.5-fold in senescent cells were targeted with siRNA across 11 genes, including complement factor D (CFD). Complement factor D was also tested directly in monocultures, and its expression was compared in skin tissue specimens from aged (>70 years) versus young (<20 years) human donors.
What was found
Coculture with senescent fibroblasts decreased collagen type I alpha 1 chain and elastin gene expression while increasing matrix metalloproteinase 1 (MMP1) gene expression in young fibroblasts. Knockdown of CFD in senescent fibroblasts significantly attenuated the increase of MMP1 in cocultured young fibroblasts. In monoculture, adding CFD to young fibroblasts increased MMP1 expression, whereas knocking down CFD in senescent fibroblasts reduced MMP1 expression. CFD production was elevated in conditioned media from senescent fibroblasts, and both CFD gene and protein expression were higher in dermal tissue from aged human subjects compared to young subjects. The abstract did not report exact numerical values or effect sizes.
Why it matters
This study identifies complement factor D as a paracrine mediator within the senescent secretome that promotes extracellular matrix degradation in neighboring dermal fibroblasts, pointing to a potential mechanism for age-related dermal thinning.
Limits
The work relies primarily on in vitro monoculture and Transwell models, which do not fully replicate the complex 3D architecture, mechanical forces, or vascular environment of human skin in vivo. The abstract does not provide exact sample sizes, numerical fold-changes, or statistical confidence intervals, nor does it quantify total protein-level matrix degradation in intact skin.
Cited by
- supports Senescent cells produce high levels of proteases that degrade collagen.