Prolyl hydroxylase activity in human normal skins and post-burn scars

Modeling of Old Scars: Histopathological, Biochemical and Thermal Analysis of the Scar Tissue Maturation

Simple Summary

Severe skin scars (i.e., hypertrophic and keloid) induce physical and emotional discomfort and functional disorders such as contractures and body part deformations. Scar’s response to treatment depends on “maturity”, which increases with time but is not merely proportional to it. When “fresh”, scars are relatively more treatable by conservative methods, while the treatment is only partially efficient. In contrast, surgery is a preferred approach for the older scars, but it is associated with a risk of the scar regrowth and worsening after excision if unrecognized immature scar tissue remains in the operated lesion. Therefore, to develop better treatment and diagnostics of scars, understanding of the scar maturation is essential. This requires biologically accurate experimental models of skin scarring. The current models only mimic the early stages of skin scar development. They are useful for testing new scar-preventing approaches while not addressing the problem of the older scars that exist for years. In our study, we demonstrate a new rabbit model of “old” scars and explore what happens to the scar tissue during maturation. We define measurable signs to delineate the scar development stages and discuss how this knowledge can improve scar diagnostics and treatment.

Abstract

Mature hypertrophic scars (HSs) remain a challenging clinical problem, particularly due to the absence of biologically relevant experimental models as a standard rabbit ear HS model only reflects an early stage of scarring. The current study aims to adapt this animal model for simulation of mature HS by validating the time of the scar stabilization using qualitative and quantitative criteria. The full-thickness skin and perichondrium excision wounds were created on the ventral side of the rabbit ears. The tissue samples were studied on post-operation days (PODs) 30, 60, 90 and 120. The histopathological examination and morphometry were applied in parallel with biochemical analysis of protein and glycosaminoglycans (GAGs) content and amino acid composition. The supramolecular organization of collagen was explored by differential scanning calorimetry. Four stages of the rabbit ear HS maturation were delineated and attributed with the histolomorphometrical and physicochemical parameters of the tissue. The experimental scars formed in 30 days but stabilized structurally and biochemically only on POD 90–120. This evidence-based model can be used for the studies and testing of new treatments of the mature HSs.

Human prolyl hydroxylase. Purification, radioimmunoassay and clinical studies in liver diseases

Prolyl hydroxylase was purified from human placentae, specific antiserum against it was prepared, and a new radioimmunoassay system employing 125I-labelled enzyme preparation was established. The molecular weight of the placental enzyme was shown to be 320,000 by gel filtration. SDS-polyacrylamide gel electrophoresis showed two bands of unequal intensity having molecular weights of 60,000 and 130,000. Their amino acid compositions were identical to each other, suggesting the polypeptide with a molecular weight of 130,000 might be a dimer of the polypeptide with a molecular weight of 60,000. The new radioimmunoassay established had a sensitivity of the order of 10 ng/ml, indicating it was more sensitive than previous radioimmunoassay employing 3H-labelling method. Clinical studies on patients with liver diseases disclosed that the concentrations of serum immunoreactive prolyl hydroxylase were elevated both in cases of hepatocellular damage and in cases of cholestasis. In cases of hepatocellular damage the enzyme behaved like cytoplasmic enzymes such as glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and lactic dehydrogenase, but in cases of cholestasis it resembled biliary enzymes such as alkaline phosphatase and gamma-glutamyl transpeptidase. This result might be associated with the peculiar location of the enzyme within the cell, in the membrane of rough endoplasmic reticulum.

Enzymes of collagen biosynthesis in skin and serum in dermatological diseases. I. Enzymes of the skin

Immunoreactive prolyl hydroxylase protein, prolyl hydroxylase activity and galactosylhydroxylysyl glucosyltransferase activity were measured in skin biopsies from 54 patients with various dermatological disorders and compared with results from 15 control samples; The mean prolyl hydroxylase activity was significantly elevated in case of keloids (P less than 0.001) and lichen ruber planus (P less than 0.02) and the mean galactosylhydroxylysyl glucosyltransferase activity in keloids (P less than 0.005), lichen ruber planus (P less than 0.02) and psoriasis (P less than 0.05), and high activities of these two enzymes were also occasionally found in other skin diseases and active systemic connective tissue diseases. These two enzyme activities correlated highly significantly (P less than 0.001) with each other in the total disease material. Immunoreactive prolyl hydroxylase protein was significantly elevated in psoriasis (P less than 0.02) lichen ruber planus (P less than 0.005), but not in keloids, where very high activities of the corresponding enzyme were found. Active prolyl hydroxylase constituted about 1.3% of total immunoreactive prolyl hydroxylase protein in normal skin, but as much as 10% in cases of keloids.

Changes in type of collagen during the development of human post-burn hypertrophic scars

Neutral-salt soluble collagen was relatively abundant in young post-burn hypertrophic scars. The content of insoluble collagen was fairly low in granulation tissues, whereas it gradually increased over 2 years and reached a significantly higher value than that in normal skins. Interrupted gel electrophoresis was carried out to estimate the relative proportions of type III and type I collagens in the pepsin digests of human normal skins and post-burn scars. Granulation tissues showed an abnormally higher ratio of type III to type I (0.37--0.72) than the mean value of normal skins (0.17 +/- 0.04 (S.D.)). The ratio gradually decreased to the normal range after 2 years or so.