BASIC BACKGROUND INFO Khan Academy explains the concept of stem cells. For more information on the Khan Academy, click here. Prof. Arnold Caplan explains the mode of action of Medicinal Signaling Cells (formerly known as Mesenchymal Stem Cells) For Dr. Caplan’s publications on PubMed, click here. The role of GHK-Cu (copper-bound tripeptide of amino acids glycyl-L, histidyl-L, and lysine) For unfiltered GHK-Cu information by its discoverer Dr. Loren Pickart, click here.