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Human eosinophils stimulate DNA synthesis and matrix production in dermal fibroblasts
T P Birkland1, M D Cheavens, S H Pincus
1Department of Dermatology, State University of New York at Buffalo.
Abstract:
Fibrosis is frequently found in diseases exhibiting tissue eosinophilia, such as some parasitic worm infections, eosinophilia-myalgia syndrome, and eosinophilic fasciitis. Previously, eosinophil extracts have been shown to induce proliferation in neonatal foreskin fibroblasts in vitro. To determine if living eosinophils can induce synthesis of DNA and components of the extracellular matrix in dermal fibroblasts, we cultured purified human eosinophils for 2 or 7 days in the presence of the eosinophil-active cytokines granulocyte/macrophage colony stimulating factor, interleukin-3, or interleukin-5, and added eosinophil-conditioned medium to cultures of dermal fibroblasts. Using flow cytometry, we found that eosinophil-conditioned medium increased by two-fold the percentage of fibroblasts in S-phase. This stimulation of fibroblast DNA synthesis was corroborated using a standard tritiated thymidine assay and the two methods were shown to correlate well with each other. Eosinophil-conditioned medium stimulation of DNA synthesis was dose dependent and conditioned medium from eosinophils treated with any one of the three cytokines induced increased DNA synthesis. Treatment of fibroblasts with cytokines alone did not induce enhanced DNA synthesis. Eosinophil-conditioned medium also affected fibroblast matrix production. Eosinophil-conditioned medium induced a two-fold increase in soluble and cell-associated fibroblast glycosaminoglycan production and a 76% increase in collagen production. These observations support the concept that eosinophils may be active contributors to the pathophysiology of eosinophil-associated fibrotic disease.
Insights
Eosinophils, immune cells often found in fibrotic diseases, can stimulate fibroblast DNA synthesis and extracellular matrix production. This suggests eosinophils actively contribute to fibrotic conditions like eosinophilic fasciitis.
Area of Science:
- Immunology
- Cell Biology
- Dermatology
Background:
- Fibrosis, a hallmark of many diseases, is often associated with tissue eosinophilia.
- Previous in vitro studies indicated eosinophil extracts promote fibroblast proliferation.
Purpose of the Study:
- To investigate if living human eosinophils can induce DNA synthesis and extracellular matrix component production in dermal fibroblasts.
- To determine the role of eosinophil-active cytokines in mediating these effects.
Main Methods:
- Cultured purified human eosinophils with granulocyte/macrophage colony stimulating factor, interleukin-3, or interleukin-5.
- Applied eosinophil-conditioned medium to dermal fibroblast cultures.
- Assessed fibroblast proliferation using flow cytometry and tritiated thymidine assays.
- Quantified glycosaminoglycan and collagen production.
Main Results:
- Eosinophil-conditioned medium significantly increased fibroblast DNA synthesis (S-phase) by two-fold.
- This stimulation was dose-dependent and observed with conditioned medium from cytokine-treated eosinophils.
- Eosinophil-conditioned medium elevated glycosaminoglycan production by two-fold and collagen production by 76%.
Conclusions:
- Living eosinophils, through conditioned medium, actively stimulate fibroblast DNA synthesis and extracellular matrix production.
- These findings support the hypothesis that eosinophils are key contributors to the pathophysiology of eosinophil-associated fibrotic diseases.