Lymphedema-Associated Fibroblasts Are Related to Fibrosis and Stage Progression in Patients and a Murine Microsurgical Model.

BACKGROUND

The driver of secondary lymphedema (SL) progression is chronic inflammation, which promotes fibrosis. Despite advances in preclinical research, a specific effector cell subpopulation as a biomarker for therapy response or stage progression is still missing for SL.

METHODS

Whole skin samples of 35 murine subjects of a microsurgically induced SL model and 12 patients with SL were collected and their fibroblasts were isolated. These lymphedema-associated fibroblasts (LAFs) were cultured in a collagen I-poly-D-lysine 3-dimensional hydrogel to mimic skin conditions. Fibroblasts from nonlymphedema skin were used as negative control and transforming growth factor β (TGF-β)-stimulated fibroblasts were used to recreate profibrotic myofibroblasts. Quantitative immunocytofluorescence confocal microscopy analysis and invasion functional assays were performed in all subpopulations and statistically compared.

RESULTS

In contrast to normal skin fibroblasts, LAFs exhibit α-smooth muscle actin-positive stress fibers and a reduced number of tight junctions in 3-dimensional hydrogel conditions. The switch from normal E-cadherin high phenotype to an N-cadherin high -E-cadherin low morphology suggests epithelial-to-mesenchymal transition for expansion and proliferation. This pathologic behavior of LAF was confirmed by live cell imaging analysis of invasion assays. The significant activation of markers of the TGF-β receptor 2-Smad pathway and collagen synthesis (HSP-47 [heat shock protein 47]) in LAFs supports epithelial-to-mesenchymal transition phenotypic changes and previous findings relating to TGF-β1 and fibrosis with lymphedema.

CONCLUSIONS

A characteristic SL myofibroblast subpopulation was identified and translationally related to fibrosis and TGF-β1-associated stage progression. This SL-related subpopulation was termed LAFs. A comprehensive stage-related characterization is required to validate LAFs as a reliable biomarker for SL disease progression.

CLINICAL RELEVANCE STATEMENT: The authors identify a cellular effector for fibrosis and stage progression of secondary lymphedema as a possible biomarker for surgical indication and therapy response.