Inseparable iduronic acid-containing proteoglycan PG(IdoA) preparations of human skin and post-burn scar tissues: evidence for elevated levels of PG(IdoA)-I in hypertrophic scar by N-terminal sequencing

Mechanical evaluation of the resistance and elastance of post-burn scars after topical treatment with tretinoin

OBJECTIVE

After burn injuries, scarred skin lacks elasticity, especially in hypertrophic scars. Topical treatment with tretinoin can improve the appearance and quality of the skin (i.e., texture, distensibility, color, and hydration). The objective of this prospective study was to examine the effects of treatment with 0.05% tretinoin for one year on the biomechanical behavior and histological changes undergone by facial skin with post-burn scarring.

SETTING

Tertiary, Institutional.

METHOD

Fifteen female patients who had suffered partial thickness burns with more than two years of evolution were selected. Skin biopsies were obtained initially and after one year of treatment. The resistance and elastance of these skin biopsies were measured using a mechanical oscillation analysis system. The density of collagen fibers, elastic fibers, and versican were determined using immunohistochemical analysis.

RESULTS

Tretinoin treatment significantly lowered skin resistance and elastance, which is a result that indicates higher distensibility of the skin. However, tretinoin treatment did not significantly affect the density of collagen fibers, elastic fibers, or versican.

CONCLUSION

Topical tretinoin treatment alters the mechanical behavior of post-burn scarred skin by improving its distensibility and thus leads to improved quality of life for patients.

Pentoxifylline modifies three-dimensional collagen lattice model contraction and expression of collagen types I and III by human fibroblasts derived from post-burn hypertrophic scars and from normal skin

Fibroblasts are thought to be partially responsible for the persisting contractile forces that result in burn contractures. Using a monolayer cell culture and fibroblast populated collagen lattice (FPCL) three-dimensional model we subjected hypertrophic scar and non-cicatricial fibroblasts to the antifibrogenic agent pentoxifylline (PTF - 1mg/mL) in order to reduce proliferation, collagen types I and III synthesis and model contraction. Fibroblasts were isolated from post-burn hypertrophic scars (HSHF) and non-scarred skin (NHF). Cells were grown in monolayers or incorporated into FPCL's and exposed to PTF. In monolayer, cell number proliferation was reduced (46.35% in HSHF group and 37.73% in NHF group, p<0.0001). PTF selectively inhibited collagen III synthesis in the HSHF group while inhibition was more evident to type I collagen synthesis in the NHF group. PTF also reduced contraction in both (HSHF and NHF) FPCL.

A role for decorin in cutaneous wound healing and angiogenesis

Decorin is known to influence tissue tensile strength and cellular phenotype. Therefore, decorin is likely to have an impact on tissue repair, including cutaneous wound healing. In this study, cutaneous healing of both excisional and incisional full-thickness dermal wounds was studied in decorin-deficient (Dcn(-/-)) animals. A statistically significant delay in excisional wound healing in the Dcn(-/-) mice occurred at 4 and 10 days postwounding and, in incisional wounds at 4, 10, and 18 days when compared with wild-type (Dcn(-/-)) controls. Fibrovascular invasion into polyvinylalcohol sponges was significantly increased by day 18 in Dcn(-/-) mice relative to Dcn(+/+) mice. The 18-day sponge implants in the Dcn(-/-) mice showed a marked accumulation of biglycan when compared with the corresponding implants in Dcn(+/+) mice. Thus, regulated production of decorin may serve as an excellent therapeutic approach for modifying impaired wound healing and harmful foreign body reactions.

Combined tretinoin and glycolic acid treatment improves mouth opening for postburn patients

Postburn tissue repair progresses late, with changes in the skin's physical properties. Clinically, the skin appears dry, scaly, and dyschromic, with diminished elasticity, particularly in the presence of hypertrophic scars. Improvement of postburn skin can be obtained by using topical agents normally used in pathologies such as acne and photoaging. This study analyzed 77 patients, ages 6 to 46 years, with late perioral burn sequelae. The resulting integument was classified as grafted or restored when it epithelialized spontaneously. Topical treatment consisted of tretinoin (0.01-0.05%) and glycolic acid (5-7%) over a 3-month period. With the mouth opened maximally, the interdental (D) and interlabial (L) distances were measured using a digital caliper. Significant increases in D and L distances were observed after treatment, as compared with controls (p < 0.01). These results were similar in the restored and skin-grafted groups.

Hypertrophic Response and Keloid Diathesis: Two Very Different Forms of Scar

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Have a greater appreciation of the extent of differences and similarities between keloid and hypertrophic scarring. 2. Have a greater appreciation of the significance of the stage of maturation of a keloid or hypertrophic scar with regard to its morphologic, biochemical, and molecular profile. 3. More critically review basic science research that is based on poorly characterized scar tissue. 4. More critically review clinical studies that are based on poorly characterized scar tissue.

BACKGROUND

Hypertrophic and keloid scars remain extremely challenging, particularly in their variable response to treatment. The understanding of hypertrophic and keloid scarring is evolving from a position where they were regarded as different stages of the same process to the contemporary perspective of two separate entities. This article reviews the differences in the two forms of scarring and discusses the implications for future research.

METHODS

The authors conducted a MEDLINE search of all English language reviews linking key words "hypertrophic," "keloid," and "scarring."

RESULTS

Over the past four decades, there has been considerable clinical and experimental research looking at the biological nature and therapeutic response of keloid and hypertrophic scarring. As more differences are emerging regarding the fundamental biology of the scars, investigators are giving more detailed characterization of their source material. It is evident that even within the broad categories of hypertrophic and keloid scarring there is a heterogenous distribution of pathologic connective tissue matrix biology.

CONCLUSION

Considerable advances have been made in our understanding of the fundamental biology of scarring. As research methodology becomes even more sophisticated, it will be even more crucial to extensively characterize source material, recognizing major differences not only between keloid and hypertrophic scar but also between scars of varying stages of maturation and histomorphological, biochemical, and molecular variations within individual scars.

Midmembranous vocal fold lamina propria proteoglycans across selected species

OBJECTIVES

We examined the proteoglycan (PG) and associated sulfated glycosaminoglycan (GAG) content of the midmembranous vocal fold lamina propria (LP) of humans, dogs, pigs, and ferrets.

METHODS

The LP PG levels were assessed indirectly by quantifying the associated sulfated GAGs, and immunohistochemical analyses of specific PGs and/or GAGs (PGs/GAGs) were conducted.

RESULTS

Sulfated GAGs constituted approximately (average +/- SEM) 14.7 +/- 2.1 microg per milligram of tissue total protein in the human LP--similar to levels in canine, porcine, and ferret LPs (p > .05). Immunohistochemical analysis identified versican, chondroitin 4- and 6-sulfate, and heparan sulfate in the LP extracellular matrix--PGs/GAGs previously believed to be localized only intracellularly and in the basement membrane. Observations of PG/GAG staining patterns resulted in identification of microstructurally based subdivisions of canine, porcine, and ferret LPs.

CONCLUSIONS

The sulfated GAG concentration in human LP was similar to that of dermis. In contrast to the interspecies similarity in LP sulfated GAG levels, immunohistochemical analysis indicated notable interspecies differences in specific PG/GAG distributions. Moreover, spatial variations in the presence of several PGs/GAGs were observed--variations that may be integral in maintaining normal LP physiology. Finally, the noted canine, porcine, and ferret LP subdivisions may yield insight into the adaptation of LP microstructure to the phonatory needs of each species.

Advances in the Modulation of Cutaneous Wound Healing and Scarring

Cutaneous wounds inevitably heal with scars, which can be disfiguring and compromise function. In general, the greater the insult, the worse the scarring, although genetic make up, regional variations and age can influence the final result. Excessive scarring manifests as hypertrophic and keloid scars. At the other end of the spectrum are poorly healing chronic wounds, such as foot ulcers in diabetic patients and pressure sores. Current therapies to minimize scarring and accelerate wound healing rely on the optimization of systemic conditions, early wound coverage and closure of lacerations, and surgical incisions with minimal trauma to the surrounding skin. The possible benefits of topical therapies have also been assessed. Further major improvements in wound healing and scarring require an understanding of the molecular basis of this process. Promising strategies for modulating healing include the local administration of platelet derived growth factor (PDGF)-BB to accelerate the healing of chronic ulcers, and increasing the relative ratio of transforming growth factor (TGF)beta-3 to TGFbeta-1 and TGFbeta-2 in order to minimize scarring.

Extracellular matrix signaling through growth factor receptors during wound healing

Recently, extracellular matrix components have been shown to contain domains that can interact with and activate receptors with intrinsic tyrosine kinase activity. These receptor tyrosine kinases are strong mediators of the cell responses of proliferation, migration, differentiation, and dedifferentiation. However, an interesting question is raised as to why cells would present growth factor receptor ligands in such a manner, as the majority of growth factors are small, soluble, or only transiently tethered ligands. With the exception of the discoidin domain receptors that bind collagen, the other described domains interact with a receptor that binds ubiquitous soluble peptide growth factors, the epidermal growth factor receptor. Unlike traditional growth factors, these individual "matrikine" domains within tenascin-C, laminin, collagen, and decorin possess relatively low binding affinity (high nanomolar or micromolar) and are often presented in multiple valency. The presentation of ligands within the extracellular matrix in this fashion might allow for unique biochemical and physiological outcomes. This new class of "matrikine" ligand may be critical for wound healing, as the majority of known extracellular matrix components possessing matrikines play a strong role, or are presented uniquely, during skin repair. Tenascin-C expression, for instance, is uniquely regulated spatially and has been proposed to present pro-migratory tracks during skin repair through its epidermal growth factor-like repeats. The epidermal growth factor-like repeats of laminin-5 act as cryptic ligands revealed upon matrix metalloproteinase-2 degradation of the surrounding extracellular matrix. The deletion of the discoidin domain receptors 1 and 2 for collagen have negative consequences on the role of fibroblasts and epithelial cells for matrix metalloproteinase production, migration, proliferation, and extracellular matrix turnover. Finally, decorin can bind to, inhibit, and down-regulate epidermal growth factor receptor levels and signaling, suggesting a tonic role of the epidermal growth factor binding domain of decorin in the resolution of wound healing. We provide a model framework for further studies into this emerging class of signals.

Fibrillin-1 and elastin are differentially expressed in hypertrophic scars and keloids

Hypertrophic scars and keloids are two forms of excessive cutaneous scarring. Considering the importance of extracellular matrix elements in tissue repair, a morphological and quantitative analysis of the elastic system components (fibrillin-1 and elastin) was performed in normal skin, normal scars, hypertrophic scars, and keloids. In superficial and deep dermis, fibrillin-1 volume density was significantly higher in normal skin compared with normal scars, hypertrophic scars, and keloids. The fibrillin-1 volume density did not show differences between hypertrophic scars and keloids in superficial or deep dermis. In superficial dermis, elastin volume density was higher in normal skin compared with normal scars, hypertrophic scars, and keloids. In deep dermis, the elastin volume density was higher in keloids compared with normal skins, normal scars, and hypertrophic scars. We showed that the distribution of fibrillin-1 and elastin is disrupted in all kinds of scars analyzed, but there are two patterns: one for normal scars and another for excessive scars.

Vocal fold proteoglycans and their influence on biomechanics

OBJECTIVE/HYPOTHESIS

To examine the interstitial proteins of the vocal fold and their influence on the biomechanical properties of that tissue.

STUDY DESIGN

Anatomic study of the lamina propria of human cadaveric vocal folds combined with some viscosity testing.

METHODS

Identification of proteoglycans is performed with histochemical staining. Quantitative analysis is performed using an image analysis system. A rheometer is used for viscosity testing. Three-dimensional rendering program is used for the computer images.

RESULTS

Proteoglycans play an important role in tissue biomechanics. Hyaluronic acid is a key molecule that affects viscosity.

DISCUSSION

The proteoglycans of the lamina propria have important biological and biomechanical effects. The role of hyaluronic acid in determining tissue viscosity is emphasized. Viscosity, its effect on phonatory threshold pressure and energy expended due to phonation is discussed.

CONCLUSION

Proteoglycans, particularly hyaluronic acid, play important roles in determining biomechanical properties of tissue oscillation. Future research will likely make these proteins of important therapeutic interest.