Dexamethasone and hydrocortisone enhance the in vitro migration of prethymic stem cells to thymus supernatant.

Abstract

The migration of prethymic stem cells from the bone marrow to thymus supernatant was examined in a blind well migration assay following treatment with glucocorticoids (GCS). To study the in vivo effects of GCS, time release pellets containing dexamethasone (DEX) were implanted subcutaneously in young adult CBA/J mice for 7, 14 and 21 days. After seven and 21 days of DEX treatment, enhanced migration of bone marrow lymphoid cells to thymus supernatant occurred. To study the in vitro effects of GCS on prethymic stem cell migration, bone marrow cells were incubated for one or six hours in media containing dexamethasone (DEX), hydrocortisone (HCS), or medium alone. After a six-hour incubation with GCS, significantly more bone marrow cells migrated toward thymus supernatant in vitro than bone marrow cells incubated in medium alone. The enhanced migration of cells to thymus supernatant seen in this assay may reflect a feedback mechanism whereby bone marrow cell migration is enhanced to restore the thymic lymphocyte reserves depleted following treatment with GCS.