The dermis is the mesenchymal component of the skin, separated from the epidermis by the basement membrane. The dermis comprises two structurally different layers named the papillary and reticular layer.
The papillary layer contains nerve endings and microvascular vessels, necessary for nourishment and innervation. The papillary dermis has got a higher density of cells, a higher content of proteoglycans, and a weaker alignment of collagen fibres. The extracellular matrix (ECM) of the reticular dermis has a more pronounced structure: collagen bundles are organized into dense fibres, which, together with elastin strands, create an ordered network. Fibroblasts (FBs) are the most abundant cells in the dermis. s. A characteristic feature of these cells is the ability to synthesize and remodel ECM.
FBs of the papillary layer retain increased proliferative and synthetic activity in culture. It has been shown that they synthesize more proteoglycans, but less collagen when compared with FBs of the reticular layer.
The FBs of the reticular layer are usually strongly spread out over the substrate and have a stellate shape. Studies have shown that this cell population has an increased expression of genes responsible for cell mobility and contraction.
Wound healing in the skin depends on the coordinated collective activity of several cell types. FBs play a pivotal role in wound healing, mediate fibrosis, participate in inflammatory networks, synthesize matrix, and modulate immune cell functions. Shortly after wounding, the wound is populated with FBs from the reticular dermis and cells from the hypodermis.
Scars differ from normal skin aesthetically, functionally, and morphologically. The scar is comprised of poorly structured and densely packed collagen fibres while the hair and glands are missing. Keloids are abnormal scars caused by disturbances of skin wound healing characterized by excessive ECM production and are prone to form in areas of the body with increased skin tension or stiffness. It is known that keloids do not have a malignant potential, but they cause physical ailments and affect the life quality of patients.
Alexandra L. Rippa and Coll published this scientific article about the different steps of the wound healing and which cells are involved in the healing process.
Many studies indicate a special role of papillary fibroblasts in the favourable outcome of wound healing and epithelial-mesenchyme interactions. Neofolliculogenesis can substantially reduce scarring. The role of hair follicle mesenchyme cells in skin repair and possible therapeutic applications is discussed. Dermal white adipose tissue involvement in wound healing is also overviewed. Characteristics of myofibroblasts and their activity in scar formation are extensively discussed. Tissue tension to the scar formation as well was discussed as the criteria and effectiveness of skin substitutes in skin reconstruction.
Authors: Alexandra L. Rippa, Ekaterina P. Kalabusheva and Ekaterina A. Vorotelyak
Newspaper: Cells. 2019 Jun; 8(6): 607.