Skin, a brief description of wound healing

The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals, except that it is not protected by a pelt. Though nearly all human skin is covered with hair follicles, it can appear hairless. There are two general types of skin, hairy and glabrous skin.

Because it interfaces with the environment, skin plays a key role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B folates. Severely damaged skin will try to heal by forming scar tissue. This is often discolored and depigmented.
In humans, skin pigmentation varies among populations, and skin type can range from dry to oily. Such skin variety provides a rich and diverse habitat for bacteria which number roughly at 1000 species.
The skin contains DNA-repair enzymes that help reverse UV damage, and people who lack the genes for these enzymes suffer high rates of skin cancer. One form predominantly produced by UV light, malignant melanoma, is particularly invasive, causing it to spread quickly, and can often be deadly. Human skin pigmentation varies among populations in a striking manner. This has led to the classification of people on the basis of skin color.

As well as protection from the environment, the skin is a biological heat regulator. It contains a blood supply far greater than its requirements which allows precise control of energy loss by radiation, convection and conduction. Dilated blood vessels increase perfusion and heat loss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat.
Sweat glands in the skin release more sweat. This evaporates,further removing heat energy from the skin. And Muscles contract rapidly as we shiver. These contractions need energy from respiration, and some of this is released as heat.

Wound healing, or cicatrisation, is an intricate process in which the skin (or another organ-tissue) repairs itself after injury. In normal skin, the epidermis (outermost layer) and dermis (inner or deeper layer) exists in a steady-state equilibrium, forming a protective barrier against the external environment. Once the protective barrier is broken, the normal (physiologic) process of wound healing is immediately set in motion. The classic model of wound healing is divided into three or four sequential, yet overlapping, phases.
Hemostasis occurs when blood is present outside of the body or blood vessels. It is the instinctive response for the body to stop bleeding and loss of blood. During Hemostasis three steps occur in a rapid sequence. Vascular spasm is the first response as the blood vessels constrict to allow less blood to be lost.
In the second step, platelet plug formation, platelets stick together to form a temporary seal to cover the break in the vessel wall. The third and last step is called coagulation or blood clotting. Coagulation reinforces the platelet plug with fibrin threads that act as a “molecular glue”.
Platelets are a large factor in the hemostatic process. They allow for the creation the “platelet plug” that forms almost directly after a blood vessel has been ruptured. Within seconds of a blood vessel’s epithelial wall being disrupted platelets begin to adhere to the sub-endothelium surface. It takes approximately sixty seconds until the first fibrin strands begin to intersperse among the wound. After several minutes the platelet plug is completely formed by fibrin.
Fibrin mesh is then produced all around the platelet plug, which helps hold the fibrin in place. Once this begins, red and white blood cells caught up in the fibrin mesh which causes the clot to become even stronger There is currently a lot of research being conducted on hemostasis.
Negative Pressure Wound Therapy (NPWT) or Wound Suction, promotes healing for wounds that are difficult to treat with conventional wound dressings. The negative pressure pump acts like a vacuum and the dressings create a tight seal against the skin. The pump creates just enough of a vacuum on the wound bed that the negative pressure helps draw out the unwanted fluids in order to promote healing. NPWT appears to be useful for diabetic ulcers and management of the open abdomen (laparostomy) but further research is required for other wound type.Depending on the type of wound being treated and the clinical objectives. Typically, the dressing is changed two to three times per week. While reports of complications can occur if dressings are not changed properly by unskilled staff.
New research in the emerging field of nanodermatology is setting the stage for the more efficient use of nitric oxide to treat infections. Nitric oxide (NO) is known for its antimicrobial activity, but it is difficult to channel this highly reactive gas into a convenient tool for clinical use.
Nanotechnology allows researchers to create a vehicle for the controlled release of NO, study co-author Dr. Adam Friedman of Montefiore Medical Center in Bronx, NY, explained in an interview. Tiny NO nanoparticles can penetrate the skin's surface and deliver the goods to deep tissue infections, overcoming the biological barriers that block the use of other therapeutic agents, he said
"In this study [in rats], we demonstrated that both topical and intralesional injection of the nitric oxide nanoparticles were more effective in clearing MRSA muscle abscesses than vancomycin, a common first line systemic antibiotic for deep skin and soft tissue infections," said Dr. Friedman. "When the infected muscle tissue was examined under the microscope, samples from the nanoparticle-treated groups showed both decreased inflammation and destruction to normal tissue, likely owing to the swift and potent antibacterial impact of nitric oxide."

While Professor Russell Morris, from the University of St Andrews, has used an exciting development in chemical technology metal-organic frameworks (MOFs) – to apply small, beneficial amounts of the gas, nitric oxide, to wounds safely in order speed up healing.
When a wound occurs in normal skin the body produces nitric oxide to fight infection through its antibacterial properties and then to signal the production of new blood vessels to increase blood flow to the damaged area. Unfortunately people who suffer from diabetes, or those who are elderly or obese often don’t produce enough nitric oxide naturally which can lead to poor wound healing. In bad cases, such as chronic wounds which do not heal, the affected limbs may need to be amputated. Professor Morris and his team are developing non toxic MOFs to be incorporated into wound dressings which deliver nitric oxide slowly and at levels which do not cause any toxic or inflammatory effects but show beneficial effect of improved wound healing.

Ultimately an immediate option could be Spray-on skin, a patented skin culturing treatment for burns victims, developed by scientist Marie Stoner and plastic surgeon Dr Fiona Wood of Perth, Western Australia. Wood's treatment is under ongoing development. Where previous techniques of skin culturing required 21 days to produce enough cells to cover major burns, Wood has reduced the period to five days. Through research, she found that scarring is greatly reduced if replacement skin could be provided within 10 days. Dr Wood's reported goal is "scarless woundless healing".
The procedure is performed on site, utilizes a patented and proprietary 'spray-on' application technique, takes approximately 30 minutes to complete and does not require laboratory facilities.
Clinical trials with the process involved burn patients and showed extremely promising results. Not only did the cells promote growth in the wounds, the recovery time was similar to skin grafting, the standard approach to burn repairs, but without the complications or aesthetic scarring involved.
The Future of medicine may not be distant  possibility, while common problems particular in skin repair are being solved. Its is likely that further development could help surgical matters or non skilled treatment in isolated areas. The possibility of avoiding scars and painful stitches could one day be a reality...