CXCL12-driven thymocyte migration is increased by thymic epithelial cells treated with prolactin in vitro

The prolactin hormone (PRL), in addition to its known effects on breast development and lactation, exerts effects on the immune system, including pleiotropic effects on the thymus. The aim of this study was to evaluate the influence of PRL on the epithelial compartment of the thymus. Thymic epithelial cells (TECs) (2BH4 cells) and fresh thymocytes were used. Immunofluorescence assay revealed that PRL treatment (10 ng/ mL) increases the deposition of laminin and expression of the chemokine CXCL12 in 2BH4 cells. However, no change was observed in the deposition of fibronectin. Moreover, PRL altered F-actin polymerisation, allowing the formation of focal adhesion complexes in treated cells. When 2BH4 cells were pre-treated with PRL, thymocyte adhesion was not altered. However, in the cell migration assay, pre-treatment with PRL potentiated the chemotactic effect of CXCL12 on the migration of total, double-positive, CD4-positive, and CD8-positive thymocytes. Together, the results of this study demonstrate the effect of PRL on thymic epithelial cells, particularly on CXCL12-driven thymocyte migration, confirming that this hormone is a regulator of thymic physiology.

Association between biomechanical alterations and migratory ability of semaphorin-3A-treated thymocytes

BACKGROUND

Class 3 semaphorins are soluble proteins involved in cell adhesion and migration. Semaphorin-3A (Sema3A) was initially shown to be involved in neuronal guidance, and it has also been reported to be associated with immune disorders. Both Sema3A and its receptors are expressed by most immune cells, including monocytes, macrophages, and lymphocytes, and these proteins regulate cell function. Here, we studied the correlation between Sema3A-induced changes in biophysical parameters of thymocytes, and the subsequent repercussions on cell function.

METHODS

Thymocytes from mice were treated in vitro with Sema3A for 30min. Scanning electron microscopy was performed to assess cell morphology. Atomic force microscopy was performed to further evaluate cell morphology, membrane roughness, and elasticity. Flow cytometry and/or fluorescence microscopy were performed to assess the F-actin cytoskeleton and ROCK2. Cell adhesion to a bovine serum albumin substrate and transwell migration assays were used to assess cell migration.

RESULTS

Sema3A induced filopodia formation in thymocytes, increased membrane stiffness and roughness, and caused a cortical distribution of the cytoskeleton without changes in F-actin levels. Sema3A-treated thymocytes showed reduced substrate adhesion and migratory ability, without changes in cell viability. In addition, Sema3A was able to down-regulate ROCK2.

CONCLUSIONS

Sema3A promotes cytoskeletal rearrangement, leading to membrane modifications, including increased stiffness and roughness. This effect in turn affects the adhesion and migration of thymocytes, possibly due to a reduction in ROCK2 expression.

GENERAL SIGNIFICANCE

Sema3A treatment impairs thymocyte migration due to biomechanical alterations in cell membranes.