Including Human-Computer Interaction (HCI) topics in courses of different levels may help students appreciate the importance of this field. Many didactic experiments have been previously described. These experiments are often related to the undergraduate or graduate levels, but some HCI topics should also be taught in middle-level professional education courses. However, students in this educational level have specific needs that should be considered for the effective teaching of HCI. In this article we present two didactic experiments that involve the direct and indirect application of HCI concepts in a professional education course. The lessons learned from these experiments led to the creation of a new discipline of HCI applied principles, whose structure is also presented.