The freezing responses of hematopoietic progenitor cells isolated from normal donors and from donors with mucopolysaccharidosis type 1 (MPS 1) were determined using cryomicroscopy and analyzed using theoretical models for water transport and intracellular ice formation. The cells from donors with MPS 1 used in this investigation were cultured and transduced with a retroviral vector for the α-L-iduronidase (IDUA) enzyme in preclinical studies for human gene therapy. The water transport and intracellular ice formation (IIF) characteristics were determined at different time points in the culture and transduction process for hematopoietic progenitor cells expressing CD34 antigen from donors with MPS 1 and from normal donors. There were statistically significant changes in water transport, osmotically inactive cell volume fraction, and permeability between cells from different sources (normal donors vs donors with MPS1) and different culture conditions (freshly isolated vs cultured and transduced). Specifically, L(pg) and E(a) increased after ex vivo culture of the cells and the changes in permeability parameters were observed alter as little as 3 days in culture. Similarly, the IIF characteristics of hematopoietic progenitor cells can also be influenced by the culture and transduction process. The IIF characteristics of freshly isolated cells from donors with MPS 1 were statistically distinct from those of cultured and transduced cells from the same donor. The ability to cryopreserve cells which are cultured ex vivo for therapeutic purposes will require an understanding of the biophysical changes resulting from the culture conditions and the manner in which these changes influence viability.
Bibliographical noteFunding Information:
This work was partially supported by NIH Grant P01-HD32652 and the Minnesota Medical Foundation. Thanks to John Bischof for the use of inverse fitting programs for water transport. We also thank Greg Herr for his statistical analysis.
- Gene therapy
- Hematopoietic stem cells
- Water transport