In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Blocking studies using receptor for AGE siRNA and a specific inhibitor of Smad3 ( SIS3 ) were performed in MMECs and in STZ - induced diabetic nephropathy in Tie2 - Cre ; Loxp - EGFP mice .
### Output Text:
Blocking studies using receptor for AGE siRNA and a specific inhibitor of Smad3 ( SIS3 ) were performed in MMECs and in <span class="chemical">STZ</span> - induced diabetic nephropathy in Tie2 - Cre ; Loxp - EGFP mice . 