Mesenchymal thymic niche cells enable regeneration of the adult thymus and T cell immunity.

A Postn+ mesenchymal cell subset is essential for T lymphopoiesis and thymus regeneration, and its transfer enhances T cell production and immune response.

• Why it matters: Thymic atrophy and immune decline are major health issues with no definitive treatment, especially as they worsen with age and immune injury. Understanding thymic niche components could enable therapeutic strategies to restore immune function.
• What they did: Single-cell analysis identified three mesenchymal cell subsets in human and mouse thymic stroma, with Postn+ cells being critical for T cell progenitor recruitment and thymus regeneration. These cells decline with age and after hematopoietic stem cell transplant conditioning. Isolated Postn+ cells, when adoptively transferred, engraft atrophic thymus tissue, recruit early T progenitors, and increase T cell neogenesis, while mesenchymal populations expressing Ccl19 produce similar effects.
• The result: Manipulating thymic mesenchymal niche cells, especially Postn+ cells, may offer a therapeutic approach to regenerate T lymphopoiesis and improve immune responses in aging and injury contexts.