In vitro effect of carboplatin, cytarabine, paclitaxel, vincristine, and low-power laser irradiation on murine mesenchymal stem cells.

BACKGROUND AND OBJECTIVES: Mesenchymal stem cells (MSCs) are promising for use in regenerative medicine. Cytostatics can decrease, but low-power laser irradiation (LPLI) can increase the growth of MSCs. The interaction of LPLI, MSCs and cytostatics is not known. This study investigated the effect of four cytostatics (carboplatin, cytarabine, paclitaxel, vincristine), LPLI, and combination of a cytostatic drug and LPLI on murine MSCs (mMSCs). STUDY DESIGN/MATERIALS AND METHODS: MMSCs were exposed to LPLI (660 nm diode laser; 60 mW output power; range of power density: 76-156 mW/cm(2); range of energy density: 1.9-11.7 J/cm(2)) and/or a cytostatic drug (carboplatin: 2, 10, 50; cytarabine: 0.4, 10, 50; paclitaxel: 0.4, 2, 10; vincristine: 0.02, 0.1, 0.5 microg/ml, respectively). Cell proliferation was measured after 24, 48, or 72 hours incubation. RESULTS: LPLI at 1.9 J/cm(2) dose increased the proliferation rate with 41% after 48 hours. However, 11.7 J/cm(2) LPLI caused 42% inhibition and cytostasis was still detectable after 72 hours. LPLI caused equivalent stimulation in single or in divided doses (3.8 vs. double 1.9 J/cm(2) in a 24-hour period). The cytotoxicity of 50 microg/ml carboplatin was eliminated, the inhibitory power of 0.1 microg/ml vincristine was attenuated by 1.9 J/cm(2) LPLI even 3 days post-treatment (attenuation >10%). The 11.7 J/cm(2) LPLI enhanced the cytotoxicity of 50 microg/ml cytarabine (from 48% to 73%) and 10 microg/ml paclitaxel (from 37% to 78%). Combination of the ineffective 0.4 microg/ml cytarabine or paclitaxel with the inhibitory 11.7 J/cm(2) LPLI exhibited stronger inhibition than the 11.7 J/cm(2) LPLI alone (69% and 69% vs. 42%). CONCLUSIONS: Low energy density of LPLI increases and high energy density of LPLI decreases the proliferation of mMSCs. Furthermore, LPLI can prevent or attenuate some drug's cytotoxicity and amplify others'. The result depends on the applied energy density, on the type and concentration of the cytostatics.

In vitro expansion of long-term repopulating hematopoietic stem cells in the presence of immobilized Jagged-1 and early acting cytokines.

There is an increasing body of evidence that suggests that genes involved in cell fate decisions and pattern formation during development also play a key role in the continuous cell fate decisions made by adult tissue stem cells. Here we show that prolonged in vitro culture (14 days) of murine bone marrow lineage negative cells in medium supplemented with three early acting cytokines (stem cell factor, Flk-2/Flt-3 ligand, thrombopoietin) and with immobilized Notch ligand, Jagged-1, resulted in robust expansion of serially transplantable hematopoietic stem cells with long-term repopulating ability. We found that the absolute number of marrow cells was increased approximately 8 to 14-fold in all cultures containing recombinant growth factors. However, the frequency of high quality stem cells was markedly reduced at the same time, except in cultures containing growth factors and Jagged-1-coated Sepharose-4B beads. The absolute number of hematopoietic cells with long-term repopulating ability was increased approximately 10 to 20-fold in the presence of multivalent Notch ligand. These results support a role for combinatorial effects by Notch and cytokine-induced signaling pathways in regulating hematopoietic stem cell fate and to a potential role for Notch ligand in increasing cell numbers in clinical stem cell transplantation.