Fibroblasts in Focus

Exploring the dynamics of progenitor cells in the urethra after simulated birth trauma in mice

OBJECTIVE

To examine the alteration in the cellular dynamics of the urethral tissue after a simulated birth trauma in a mouse model.

MATERIALS AND METHODS

A total of 36 B6 mice received vaginal distention treatment, and four untreated mice were used as controls. Specimens were collected every 24 hours after the injury for 9 consecutive days and examined using immunofluorescent staining for cell markers including c-kit, smooth muscle actin (SMA), and vimentin. Confocal microscopy was used to localize the stained cells and determine the cell number.

RESULTS

The number of c-kit positive cells increased after the 1^st day and peaked on the 3^rd day. The amount of SMA positive cells rapidly reduced to its lowest count on the 1^st day and maintained a statistically significant low cell number than that at the basal level for 4 days after vaginal distension. The cell number finally returned to basal level on the 9^th day. The amount of vimentin positive cells increased dramatically after the 1^st day and plateaued from the 3^rd day to the 9^th day. The number of vimentin positive cells in the plateau phase was significantly higher than that of the control group.

CONCLUSION

Our study confirmed that the dynamic change in different cell types after the urethral injury was dependent on the nature and physiology of the wound repairing cells during the tissue healing process. It might be a simple animal model to study birth trauma repair; however, the varied progenitor cell activity in different species should also be considered.

Extracellular cysteine/cystine redox potential controls lung fibroblast proliferation and matrix expression through upregulation of transforming growth factor-beta

Oxidant stress has been implicated in the pathogenesis of chronic lung disorders like idiopathic pulmonary fibrosis. However, mechanisms that link oxidant stress to fibrogenesis remain partially elucidated. Emerging data suggest an important role for the extracellular thiol/disulfide redox environment. The cysteine (Cys)/cystine (CySS) redox couple represents the predominant low-molecular-weight thiol/disulfide pool found in plasma and is sensitive to aging, smoking, and other host factors. We hypothesized that an oxidized extracellular Cys/CySS redox potential (E(h) Cys/CySS) affects lung fibroblasts by inducing intracellular signals that stimulate proliferation and matrix expression. We tested this hypothesis in primary murine lung fibroblasts and found that an oxidized E(h) Cys/CySS (-46 mV) stimulated lung fibroblast proliferation. Furthermore, it stimulated their expression of fibronectin, a matrix glycoprotein highly expressed in fibrotic lung diseases and implicated in lung injury. This stimulatory effect was dependent on protein kinase C activation. Oxidant stress also increased the phosphorylation of cAMP response element binding protein, a transcription factor known for its ability to stimulate fibronectin expression, and increased the expression of mRNAs and proteins coding for the transcription factors nuclear factor (NF)-kappaB and mothers against decapentaplegic homolog 3. Fibroblasts cultured in normal (-80 mV) or reduced (-131 mV) E(h) Cys/CySS showed less induction. Furthermore, fibronectin expression in response to an oxidized E(h) Cys/CySS was associated with expression of transforming growth factor-beta1 (TGF-beta1) and was inhibited by an anti-TGF-beta1 antibody and SB-431542, a TGF-beta1 receptor inhibitor. These studies suggest that extracellular oxidant stress activates redox-sensitive pathways that stimulate lung fibroblast proliferation and matrix expression through upregulation of TGF-beta1.