The role of the alpha4 integrin-paxillin interaction in regulating leukocyte trafficking

The movement of leukocytes from the blood into peripheral tissues is a central feature of immune surveillance, but also contributes to the pathogenesis of inflammatory and autoimmune diseases. Integrins are a family of adhesion and signaling molecules made up of paired alpha and beta subunits, and the integrin alpha4beta1 plays a prominent role in the trafficking of mononuclear leukocytes. We have previously described the direct interaction of the signaling adaptor molecule paxillin with the cytoplasmic domain of the alpha4 integrin subunit. This interaction is critical for alpha4beta1 integrin dependent cell adhesion under shear flow conditions as it provides a needed connection to the actin cytoskeleton. Furthermore, the alpha4-paxillin interaction is required for effective alpha4beta1 dependent leukocyte migration and does so through the temporal and spatial regulation of the small GTPase Rac. These findings make the alpha4-paxillin interaction a potentially attractive therapeutic target in controlling leukocyte trafficking.

Stem Cells Expressing Homing Receptors Could be Expanded From Cryopreserved and Unselected Cord Blood

We assessed the cytokine combinations that are best for ex vivo expansion of cord blood (CB) and the increment for cell numbers of nucleated cells, as well as stem cells expressing homing receptors, by an ex vivo expansion of cryopreserved and unselected CB. Frozen leukocyte concentrates (LC) from CB were thawed and cultured at a concentration of 1x10(5)/mL in media supplemented with a combination of SCF (20 ng/mL)+TPO (50 ng/mL)+FL (50 ng/mL)+/-IL-6 (20 ng/mL)+/-G-CSF (20 ng/mL). After culturing for 14 days, the expansion folds of cell numbers were as follows: TNC 22.3+/-7.8~26.3+/-4.9, CFU-GM 4.7+/-5.1~11.7+/-2.6, CD34+CD38- cell 214.0+/-251.9~464.1+/-566.1, CD34+CXCR4+ cell 4384.5+/-1664.7~7087.2+/-4669.3, CD34+VLA4+ cell 1444.3+/-1264.0~2074.9+/-1537.0, CD34+VLA5+ cell 86.2+/-50.9~ 113.2+/-57.1. These results revealed that the number of stem cells expressing homing receptors could be increased by an ex vivo expansion of cryopreserved and unselected CB using 3 cytokines (SCF, TPO, FL) only. Further in vivo studies regarding the engraftment after expansion of the nucleated cells, as well as the stem cells expressing homing receptors will be required.