As with most things in life, Spider-Man predicted it first: scientists may soon be looking to reptiles for inspiration about how to regenerate human organs and even whole limbs. Salamanders are often referred to as having “perfect” regeneration, in that there seems to be almost no structure or cell type they cannot regenerate entirely. Thankfully, our efforts to replicate this are unlikely to involve injections of Doc Connor’s reptile DNA cocktail, as new research conducted into salamander regeneration suggests that we may already have the crucial cell types ourselves.Macrophages are a sort of all-purpose immune cell, huge actors that circulate through the blood both as passive guardians and targeted hunters. Their classical method of action is to wholly engulf unwelcome visitors, eat them whole, and digest them internally. Though the cells were once thought to be purely destructive, research has revealed that they can do much more than that. Now, Australian Regenerative Medicine Institute (ARMI) says they’ve found evidence that macrophages are a crucial component in salamanders’ famous ability to regenerate limbs.The study itself is fairly simple, just a yes-no experiment seeing what happened to the regenerative ability when macrophages were totally removed from the equation. When macrophages were removed, the result was a stump of scar tissue. When macrophages were allowed to participate, the salamanders could regenerate everything from a tail to a section of spinal cord. That’s what makes reptilian regeneration so important — we’re already on the path to growing organs via pathways of our own invention, but salamanders can regrow cell types that have long been thought of as impossible.This finding is not entirely unexpected. Macrophages have long been known for their involvement in regeneration of muscle tissue, among other types. When you work out hard enough to induce the “good” hurt of micro-torn muscle tissue, two waves of macrophages rush in to mediate regeneration and growth. The first wave gobbles up the products of the damage, clearing the area, while the second wave produces growth factors near regenerative fibers.Realistically, we probably won’t be regrowing a person’s arm or leg, if for no other reason than sheer size; regenerating a quarter-ounce salamander leg is a discreetly different sort of thing than regenerating a five-kilogram human leg. Though the Star Wars bacta tank might one day come to be, for now this research has profound implications for more specific tissue regrowth. Modern biochemistry won’t take long to track these new findings back to a gene or group of genes most responsible for this effect, and it’s at that point that we could start to ask how we might force our macrophages to function like a salamander’s.