How to handle HTML text format with VSTO powerpoint

Question

I am currently creating a powerpoint file in C# using VSTO. My problem is that I need to display HTML formated text in a textbox :

PowerPoint.Shape descriptionTitle = slide6.Shapes.AddTextbox(xxx);
descriptionTitle.TextFrame.TextRange.Text = "<b>html string</b>";

Is there any way to display my string?