Enhanced homing and engraftment of fresh but not ex vivo cultured murine marrow cells in submyeloablated hosts following CD26 inhibition by Diprotin A

Objective

We recently reported that murine marrow cultured ex vivo for γ-retrovirus transduction engrafts approximately 10-fold less well than fresh marrow upon transplantation into submyeloablated hosts. Here, we evaluated homing efficiency as a potential mechanism for this engraftment disparity, and whether CD26 inhibition with the tripeptide Diprotin A (DipA) would enhance engraftment of ex vivo cultured cells in submyeloablated hosts.

Materials and Methods

Homing and engraftment of fresh and ex vivo cultured lineage-negative (lin⁻) marrow cells in submyeloablated congenic hosts with and without DipA treatment was evaluated. Expression of CXCR4 and CD26 on fresh and cultured lin⁻ marrow cells was compared.

Results

Homing of lin⁻ cells cultured for γ-retrovirus transduction was at least threefold less than that of fresh lin⁻ cells 20 hours after transplantation into submyeloablated hosts. DipA treatment of fresh lin⁻ cells resulted in at least twofold increased homing and engraftment in submyeloablated hosts. DipA treatment, however, did not significantly improve homing or engraftment of cells undergoing a 3-day culture protocol for γ-retrovirus transduction in submyeloablated hosts. CXCR4 expression on lin⁻ cells was significantly decreased following 3 days of culture; CXCR4 expression was not significantly altered following overnight culture.

Conclusions

Ex vivo culture of lin⁻ cells for γ-retroviral transduction downregulates CXCR4 expression and markedly impairs homing and engraftment of murine lin⁻ marrow in submyeloablated hosts. While inhibition of CD26 activity with DipA increases homing and engraftment of fresh lin⁻ cells, DipA treatment does not improve homing and engraftment of cultured lin⁻ marrow cells in submyeloablated congenic hosts.