The plant mannose-binding lectin NTL preserves cord blood haematopoietic stem/progenitor cells in long-term culture and enhances their ex vivo expansion.

Ex vivo expansion of haematopoietic stem and progenitor cells in cytokine combinations is effective in promoting differentiation and proliferation of multilineage progenitor cells, but often results in reduction of self-renewable stem cells. This study investigated the effect of a mannose-binding lectin, NTL, purified from Narcissus tazetta var. chinensis, on prolonged maintenance and expansion of cord blood CD34+ cells. Our results showed that the presence of NTL or Flt-3 ligand (FL) significantly preserved a population of early stem/progenitor cells in a serum- and cytokine-free culture for 35 d. The effect of NTL on the ex vivo expansion of CD34+ cells in the presence of stem cell factor, thrombopoietin (TPO) and FL was also investigated. NTL-enhanced expansion of early progenitors (CD34+, CD34+CD38-, mixed colony-forming units and CFU-GEMM) and committed progenitor cells (granulocyte CFU, erythroid burst-forming units/CFU and megakayocyte CFU) after 8 and 12 d of culture. Six weeks after transplanting 12 d-expanded cells to non-obese diabetic severe combined immunodeficient mice, increased engraftment of human CD45+ cells was observed in the bone marrow of animals that received NTL-treated cells. The dual functions of NTL on long-term preservation and expansion of early stem/multilineage progenitor cells could be developed for applications in various cell therapy strategies, such as the clinical expansion of CD34+ cells for transplantation.