Fig. 6. Absence of PN-1 exacerbates the detrimental effects of thrombin on the ability of the DP cells to support keratinocytes. (A,B) Effect of DP cells on the growth and survival of keratinocytes. (A) Clusters formed after 8 days by YF29 keratinocytes plated at 15,000 cells/cm² on inactivated wild-type or PN-1^–/– DP feeder cells and visualized by Rhodamine B staining. (B) Capacity of DP cells to sustain cluster formation, quantified by counting clusters of different size ranges. ^***Significant difference from wild-type cells (P<0.001). (C) Immunoblot evaluation of Akt phosphorylation in keratinocyte to monitor the signaling triggered by DP cells secreted molecules. YF29 keratinocytes were maintained in minimal medium (control) or transferred for 30 min to minimal medium conditioned for 24 hours by untreated DP cells (WT, KO for PN-1^–/–) or by cells pretreated with thrombin at 1 U/ml (WT+, KO+).