Can humans regrow fingers? by Julia Layton

When a hobby-store owner in Cincinnati sliced off his fingertip in 2005 while showing a customer why the motor on his model plane was dangerous, he went to the emergency room without the missing tip. He couldn’t find it anywhere. The doctor bandaged the wound and recommended a skin graft to cover the top of his right-middle stub for cosmetic purposes, since nothing could be done to rebuild the finger.

Months later, he had regrown it, tissue, nerves, skin, fingernail and all.

This particular hobbyist happened to have a brother in the tissue-regeneration business, who told him to forego the skin graft and instead apply a powdered extract taken from pig’s bladder to the raw finger tip. The extract, called extracellular matrix, lays the framework that cells use to generate any given body part. It’s like a cellular scaffolding, and all animals have it. It holds the signals that direct cells to divide, differentiate and build themselves into a specific form.

Extracellular matrix is a component of body tissue that functions outside of the body’s cells (thus the “extracellular” designation). It’s made up mostly of collagen, a type of protein. So extracellular matrix extracted from the bladder of a pig does not actually have any of the pig’s cells in it. ”

The article goes onto say:
Pig-extracted extracellular matrix is already used by veterinarians to help horses repair torn ligaments. In people, it’s used to treat ulcers, closing a hole in the tissue that lines the stomach. It employs an entirely different process than the typical mammalian healing mechanism. Let’s take the case of a person who loses the tip of a finger. When the finger is severed, the cells die, and their contents seep into the surrounding tissue. This alerts the immune system to a problem. The immune system’s response to cell death is inflammation and scar tissue. The formation of scar tissue prevents any future cellular development in the area. That’s why scars last — cells are prevented from doing a repair job on that skin.

But when extracellular matrix is applied to a wound, it doesn’t trigger an immune response. Instead, when it begins to break down into surrounding tissue, it causes the cells in that tissue to start repairing the damage the way they would in a developing fetus (or a salamander that loses a limb) — they divide and rebuild, creating new, normal tissue, not scar tissue.