Regeneration in humans

Regeneration in humans is the regrowth of lost tissues or organs in response to injury. This is in contrast to wound healing, which involves closing up the injury site with a scar. Some tissues such as skin and large organs including the liver regrow quite readily, while others have been thought to have little or no capacity for regeneration. However ongoing research, particularly in the heart and lungs, suggests that there is hope for a variety of tissues and organs to eventually become regeneration-capable. Regeneration in humans is the regrowth of lost tissues or organs in response to injury. This is in contrast to wound healing, which involves closing up the injury site with a scar. Some tissues such as skin and large organs including the liver regrow quite readily, while others have been thought to have little or no capacity for regeneration. However ongoing research, particularly in the heart and lungs, suggests that there is hope for a variety of tissues and organs to eventually become regeneration-capable. In humans with non-injured tissues, the tissue is naturally regenerated over time; by default these tissues have new cells available to replace expended cells. For example, the body regenerates a full bone within 10 years, while non-injured skin tissue is regenerated within two weeks. With injured tissue, the body usually has a different response – this emergency response usually involves building a degree of scar tissue over a time period longer than a regenerative response, as has been proven clinically and via observation. There are many more historical and nuanced understandings about regeneration processes. In full thickness wounds that are under 2mm, regeneration generally occurs before scarring. In 2008, in full thickness wounds over 3mm, it was found that a wound needed a material inserted in order to induce full tissue regeneration. There are some human organs and tissues that regenerate rather than simply scar, as a result of injury. These include the liver, fingertips, and endometrium. More information is now known regarding the passive replacement of tissues in the human body, as well as the mechanics of stem cells. Advances in research have enabled the induced regeneration of many more tissues and organs than previously thought possible. The aim for these techniques is to use these techniques in the near future for the purpose of regenerating any tissue type in the human body. By 2016, regeneration had been operationalised and induced by four main techniques: regeneration by instrument; regeneration by materials; regeneration by 3d printing; and regeneration by drugs. By 2016, regeneration by instrument, regeneration by materials and by regeneration drugs had been generally operationalised in vivo (inside living tissues). Whilst by 2016, regeneration by 3d printing had been generally operationalised by in vitro (inside the lab) in order to be build and prepare tissue for transplantation. A cut by a knife or a scalpel generally scars though a piercing by a needle does not scar. In 1976, a 3 by 3cm scar on a non-diabetic was regenerated by insulin injections and the researchers, highlighting earlier research, argued that the insulin was regenerating the tissue. The anecdotal evidence also highlighted that a syringe was one of two variables that helped bring regeneration of the arm scar. The syringe was injected into the four quadrants three times a day for eighty-two days. After eighty-two days, after many consecutive injections, the scar was resolved and it was noted no scar was observable by the human eye. After seven months the area was checked again and it was once again noted that no scar could be seen. In 1997, it was proven that wounds created with an instrument that are under 2mm can heal scar free, but larger wounds that are larger than 2mm healed with a scar. In 2013 it was proven in pig tissue that full thickness micro columns of tissue, less than 0.5mm in diameter could be removed and that the replacement tissue, was regenerative tissue, not scar. The tissue was removed in a fractional pattern, with over 40% of a square area removed; and all of the fractional full thickness holes in the square area healed without scarring. In 2016 this fractional pattern technique was also proven in human tissue. Generally humans, in vivo, can regenerate injured tissues for limited distances of up to 2mm. The further the wound distance is from 2mm the more the wound regeneration will need inducement. By 2009, via the use of materials, a max induced regeneration could be achieved inside a 1 cm tissue rupture. Bridging the wound, the material allowed cells to cross the wound gap; the material then degraded. This technology was first used inside a broken urethra in 1996. In 2012, using materials, a full urethra was restored in vivo. In 2009, the regeneration of hollow organs and tissues with a long diffusion distance, was a little more challenging. Therefore, to regenerate hollow organs and tissues with a long diffusion distance, the tissue had to be regenerated inside the lab, via the use of a 3D printer.