Your question is highly relevant, especially given the role of type I collagen as a hallmark of myofibroblast differentiation.

In short: Yes, the Human Pro-Collagen I ELISA kit can be used as a proxy for quantifying Collagen I production, especially in in vitro models like primary human cardiac fibroblasts. These kits typically detect the propeptide (e.g., PICP or PINP) cleaved during collagen I synthesis and secretion, which reflects newly synthesized collagen I.

However, keep in mind a few key points:

What the kit detects: Procollagen assays measure soluble pro-collagen peptides, not the mature, fibrillar collagen deposited in the extracellular matrix (ECM). For ECM collagen quantification, you'll need a separate method like:

• Sirius Red staining (for insoluble collagen),
• Western blot (targeting collagen I heavy chain),
• or hydroxyproline assay.

So, if your goal is to assess fibroblast activation and collagen synthesis, using this ELISA kit is acceptable and commonly done. If you want to validate ECM deposition, you’ll need complementary methods.

Hope this helps—and I’d be happy to share protocols if you're interested