Thymalin: Activation of Differentiation of Human Hematopoietic Stem Cells

This experimental study investigated the effects of Thymalin on the differentiation of human hematopoietic stem cells in vitro, using cell cultures and immunocytochemical analysis of surface markers. Researchers from the St. Petersburg Institute of Bioregulation and Gerontology evaluated the expression of stem cell markers and mature T lymphocyte markers after treatment with the peptide.

The results revealed that Thymalin exerted significant effects on cell differentiation: there was a 2-3 fold reduction in the expression of stem cell markers CD44 and CD117 (c-Kit), indicating that cells were exiting the undifferentiated state. Simultaneously, the expression of CD28 — a marker of functional mature T lymphocytes — increased 6.8-fold, demonstrating directed differentiation toward the T cell lineage.

• The effect was dose-dependent and most pronounced after 72 hours of incubation
• Thymalin did not affect cell viability, indicating absence of cytotoxicity
• Differentiation was specifically directed toward T lymphocytes, not other lineages
• The findings were consistent with the physiological role of thymic peptides in thymopoiesis

These results provide a molecular mechanism for the immunostimulatory effects clinically observed with Thymalin, particularly in elderly individuals with thymic involution. The ability to promote stem cell differentiation into mature T lymphocytes explains, at least partially, the immune recovery observed in previous clinical studies.