Dermal equivalent. The history and results of clinical trials

In the late eighties, a liquid form of bovine collagen was developed at Stanford University, which at the body temperature was transformed into a soft elastic substrate. The drug was registered and approved for use in several European countries as an implantable drug called Zyderm Collagen Implantant. This drug was the first implant. Later, other agents for contour plasty appeared, such as restylane, perlene, pharmacrylic gel, artekol, biopolymer gel, and others. These drugs began to be used not only for contour modeling and correction of age-related changes in the skin, but also for treatment, or rather, for equalizing the relief of scars. All of them were injected into the bottom of the rumen.

The search for better methods of treatment of hypotrophic scars led us to the idea of using for this purpose an artificially created skin analogue - the "dermal equivalent" (DE), in which liquid collagen was also used. There were many options for artificial skin substitutes, but the idea is to create a tissue similar to skin from the structural components of the dermis, which would not be rejected in the case of transplantation and would be a good substrate for germination by the own components of the dermis and epidermis. It is known that the basic structural components of the dermis are cellular, fibrous elements and interstitial substance. Fibrous elements are mainly collagen and elastin fibers, interstitial substance - glycoproteins, proteoglycans and glycosaminoglycans. The main functional cellular element of the dermis is fibroblast, the cellular population of fibroblasts is the source of almost all structural components of the dermis. Therefore, when creating a "skin substitute", most scientists use a collagen substrate mixed with fibroblasts and glycosaminoglycans. Above, in one form or another, a layer of keratinocytes is superimposed to create a full-layer skin and a more rapid recovery of the vitality of the transplanted skin equivalent, facilitated by numerous keratinocyte-derived growth factors. One of the first variants of the "living equivalent of the skin" was proposed in 1983 by E.Bell and co-authors. Skin fibroblasts were mixed with collagen, plasma and growth medium, which led to the formation of a gel on the surface of which keratinocytes were grown. All this was cultivated for 1 -2 weeks in vilro, after which the dermal equivalent was considered mature and was a viable tissue in the form of a translucent elastic mass. The authors proposed to transfer the full-layer structure of the skin to the wound surfaces of burn patients. As a basis for the dermal equivalent, some authors used a collagen sponge or a collagen matrix coated with proteoglycans and colonized with fibroblasts, on top of which autologous keratinocytes were grown. As a result, the so-called three-dimensional skin model was created. For the cultivation of keratinocytes for the purpose of their subsequent transfer to the wound surfaces, some authors also used as an artificial matrix substrate from collagen, glycosaminoglycans and chitosan, cadaver skin, pig skin. 7-14 days after the start of the culture, a full-blown graft containing the dermis and epidermis was transplanted to the wounds of patients or animals.

The artificial skin substitute was used not only to restore the skin of burned, but also to test drugs for cytotoxicity, to study growth factors in vitro.

Insufficient, in our view, the effectiveness of operative dermabrasion of deep hypotrophic scars in combination with IPC transplantation gave an occasion to try to level the skin relief by inoculating into the deepening of the hypotrophic rumen analog of the dermal equivalent. The substratum for the creation of a dermal equivalent was liquid collagen, obtained by a laboratory route, where a suspension of fibroblasts was introduced. The dermal equivalent, as well as the IPC, was created in a specialized laboratory certified for this activity and on the day and hour of the operation it was delivered in a glass vial in an ice container to the clinic.

Surgical grinding of the scars was carried out according to the usual procedure after antiseptic treatment of the skin and local anesthesia with 2% lidocaine or novocaine or ultracaine. By grinding, the surface of the rumen was leveled and at the same time conditions were created for engrafting cultured cells or cell compositions. After that, the liquid collagen gel in the cooled state with fibroblasts inoculated into it was applied with a sterile spatula on the ground surface of the hypotrophic scars (into the indentation of the scar), where under the influence of the body temperature, its polymerization took place.

As a result, after 5-10 minutes, from the liquid state collagen with fibroblasts polymerized into a thick gel state. After thickening DE, a bandage with a suspension or IPC on the substrate was superimposed on top.

A multilayer sterile dressing was fixed as in the transplantation of the IPC. Depending on the surface of the scar, the wound covering, on which the keratinocytes were located and the type of grinding, the bandage was torn off within 7 to 12 days.

The method of combined treatment of hypotrophic scars with the help of operative dermabrasion with subsequent transplantation into the indentation of the scar of the dermal equivalent and keratinocytes in the form of a multilayered layer grown on special wound coatings or in the form of suspension allows to achieve significantly better, cosmetically acceptable results with reduction or complete disappearance -) cloth. The dermal equivalent forms its own tissue (dermis), the scar tissue remains below the newly formed tissue. IPC creates a normal thickness and functional activity of the epidermis, due to which the general appearance of the scar in a few months has a tendency to a significant improvement.

Such tactics of treatment of hypotrophic scars at present can be called optimal in solving this problem. However, the DE version used by us in the form of a collagen gel with fibroblasts inoculated into it is not very convenient in the work. DE for work with hypotrophic scars should initially be thicker, so that it can be placed in the deepening of the scar, distribute it. After which the top wound wound with keratinocytes. Thus, it can be said that this direction in the work with hypotrophic scars is only planned, but the forecasts for its further development and study are very optimistic.

Complexity and high cost of obtaining multilayered layers of keratinocytes, as a therapeutic material, stimulated the need to search for other variants of cellular compositions. The researchers are interested in the cultivation of fibroblasts, which, when transplanted to the wound surfaces, have an effect similar in many ways to the results of keratinocyte transplantation, but are much simpler and cheaper cellular material. In our studies, we conducted several patients with hypotrophic scars by mesotherapy using a suspension of fibroblasts for scarring.

Suspension of fibroblasts in a growth medium with 1.5-2 million cells per ml. Was administered under the scars by mesotherapy techniques (micropapulmonary, infiltrative). The number of treatment sessions from 4 to 10, depending on the limitation period of the rumen, the patient's age and the depth of the defect. The interval between sessions is 7-10 days. As a rule, the introduction of a suspension of autologous and allogeneic fibroblasts was accompanied by a slight, fast-flowing vascular reaction.

As a result of clinical studies, it was found that under the influence of transplanted IPC, the duration of the inflammatory reaction in the skin and scars after operative dermabrasion decreases and the epithelization of the wound surfaces accelerates on average by 3-4 days.

When working with normotrophic and hypertrophic scars, the acceleration of healing of postoperative erosions is of the greatest importance, since in this lies the possibility of obtaining the optimal therapeutic effect.

Transplantation of the dermal equivalent resulted in the filling of (-) tissue of hypotrophic scars, smoothing of their relief, smoothing out with the surrounding skin, which made the area of scars much smaller.

The introduction of a suspension of fibroblasts into hypotrophic scars also led to an equalization of the relief of the skin and a reduction in the area of the scars.

In all cases of transplantation of cellular material, the effect of aftereffect was noted, when for several months an improvement in the aesthetic appearance of the scars occurred, which tended to become a dermoid-like structure.

All the effects observed by us are related to the realization of the biostimulating potential by transplanted cells. Not the least role, it seems to us, is that the number of cell layers in transplants is usually 10-30% higher. Consequently, the total cellular potential per unit area is already 10-30% higher than normal. In addition, the best results in the transplantation of keratinocytes and fibroblasts were obtained by transplanting the cellular material from young healthy people. This fact, by the way, speaks in favor of the use of allogeneic culture obtained from young and healthy donors. The bioenergetic and informational potential of such a culture is transmitted to its own cells, sometimes very young recipients, which improves the "quality" of its own tissues and cells.

Thus, the application of the culture of keratinocytes and fibroblasts allows:

• Speed up epithelization of scars after dermabrasion.
• Reduce the appearance of scars, not only due to the alignment of their surface with the surface of the surrounding skin, but also due to the formation of a full epidermis over them.
• To improve the results of operative dermabrasion due to the effect of cytokines of transplanted cells on the scar, which ultimately tends to transform into a dermal-like structure.
• To obtain aesthetically much more acceptable results of treatment of patients with normotrophic, hypotrophic, hypertrophic, atrophic scars and striae.

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