Heparan sulfate is essential for thymus growth

Area of Science:

• Immunology
• Developmental Biology
• Glycobiology

Background:

• Thymus organogenesis and T cell development rely on molecular interactions.
• Heparan sulfate (HS) proteoglycans shape signaling molecule gradients.
• The role of HS in thymic development is largely unknown.

Purpose of the Study:

• To investigate HS distribution within the thymus.
• To determine the impact of HS absence on thymus organogenesis.
• To analyze HS effects on T cell development and cell migration.

Main Methods:

• Examined HS distribution in thymic cells.
• Genetically disrupted Ext1 to eliminate HS in the thymus.
• Utilized fetal thymic organ cultures and in vivo mouse models.
• Assessed T cell production and development.
• Studied chemokine binding by thymic fibroblasts ex vivo.

Main Results:

• HS is abundant on thymic fibroblasts and present on other thymic cells.
• HS absence significantly reduced thymus size and T cell production.
• No specific blocks in T cell development stages were observed.
• HS facilitates binding of chemokines CCL19, CCL21, and CXCL12 by fibroblasts.
• HS degradation disrupted chemokine gradients and impaired dendritic cell migration.

Conclusions:

• HS is essential for thymus growth and T cell development.
• HS regulates interstitial cell migration by immobilizing chemokines.
• HS plays a critical role in establishing functional chemokine gradients within the thymus.