Fibroblast contraction of collagen matrices with and without covalently bound hyaluronan

Non-Surgical Touch-Up with Hyaluronic Acid Fillers Following Facial Reconstructive Surgery

The use of hyaluronic acid (HA) injectable fillers has become increasingly widespread in facial recontouring and rejuvenation. We report our experiences to emphasize the role of HA fillers as tools beyond aesthetic treatments in cases of post-surgical facial sequelae. HA fillers are generally used for aesthetic rejuvenation, but one potential new horizon could be their application in trauma, reconstructive, and craniofacial surgery. This study was conducted retrospectively, evaluating medical reports of patients treated at the Maxillofacial Surgery Unit, University of Campania “Luigi Vanvitelli”, Naples, for lip incompetence, trauma, oncological, reconstructive, and craniosynostosis surgery sequelae. Visual analog scale (VAS) evaluation was performed to assess patient satisfaction. No major complications (i.e., impending necrosis or visual loss) were reported. Bruising and swelling was reported for 48 h after lip injection. At the immediate VAS evaluation, 67% of the patients were “extremely satisfied” and 33% “satisfied”. In those 33%, VAS scores changed to “extremely satisfied” at 6–9 weeks and 3–6 months of VAS evaluation (contextually to improvement in tissue flexibility, elasticity, and aesthetic appearance). Results indicate that this minimally invasive approach achieves a high level of aesthetic enhancement, improving patient satisfaction. The concept of HA filler applications could be a frontier that may be applicable to other areas of reconstructive facial plastic surgery.

Hyaluronan Controls the Deposition of Fibronectin and Collagen and Modulates TGF-β1 Induction of Lung Myofibroblasts

The contribution of hyaluronan-dependent pericellular matrix to TGF-β1-driven induction and maintenance of myofibroblasts is not understood. Hyaluronan is an extracellular matrix (ECM) glycosaminoglycan important in cell adhesion, proliferation and migration, and is implicated in myofibroblast formation and maintenance. Reduced turnover of hyaluronan has been linked to differentiation of myofibroblasts and potentiation of lung fibrosis. Fibronectin is a fibril forming adhesive glycoprotein that is also upregulated following induction with TGF-β1. Although they are known to bind each other, the interplay between hyaluronan and fibronectin in the pericellular matrix during myofibroblast induction and matrix assembly is not clear. This study addresses the role of hyaluronan and its interaction with fibrillar matrix components during myofibroblast formation. Hyaluronan and fibronectin were increased and co-localized in the ECM following myofibroblast induction by TGF-β1. Inhibition of hyaluronan synthesis in TGF-β1-induced lung myofibroblasts over a 4day period with 4-methyl umbelliferone (4-MU) further enhanced myofibroblast morphology, caused increased deposition of fibronectin and type I collagen in the ECM, and increased expression of alpha-smooth muscle actin and hyaluronan synthase 2 (HAS2) mRNA. Hyaluronan oligosaccharides or hyaluronidase treatment, which more effectively disrupted the pericellular matrix, had similar effects. CD44 and β1 integrins co-localized in the cell membrane and along some stress fibers. However, CD44 and hyaluronan were specifically excluded from focal adhesions, and associated primarily with cortical actin. Time-lapse imaging of the immediate effects of hyaluronidase digestion showed that hyaluronan matrix primarily mediates attachment of membrane and cortical actin between focal contacts, suggesting that surface adhesion through hyaluronan and CD44 is distinct from focal adhesion through β1 integrins and fibronectin. Fluorescein-labeled hyaluronan bound regularly along fibronectin fibers and co-localized more with β1 integrin and less with CD44. Therefore, the hyaluronan matrix can interfere with the assembly of fibrillar ECM components, and this interplay regulates the degree of myofibroblast formation. These data also suggest that adhesion through hyaluronan matrix impacts cytoskeletal organization, and is potentially part of a clutch mechanism that regulates stick and slip of myofibroblasts by affecting the adhesion to and organization of fibronectin and collagen.

The structure of the basement membrane zone differs between keloids, hypertrophic scars and normal skin: a possible background to an impaired function

Scar tissues were collected from patients with keloids, hypertrophic scars and mature scars. Normal skin was obtained from healthy individuals. Clinical attributes were used to select which tissue to obtain but the distribution of the specific hyaluronan (HA) staining was then used for the definite classification of the various scar types. Light microscopic and ultrastructural analyses were performed with an HA-binding probe, antibodies for collagen I and III and staining for mast cells. Ultrastructural studies of keloids revealed an altered collagen structure in the dermal layers, with an abundance of collagen fibres of similar diameter in both the reticular dermis (RD) and the papillary dermis (PD) compared to normal skin. Furthermore, the keloids displayed epidermal changes, which involved the basement membrane (BM), with fewer hemidesmosomes and an altered shape of desmosomes in the entire enlarged spinous layer. The frequency of mast cells found in keloids was lower than in other scar tissues and normal skin. These alterations in epidermis could influence the hydrodynamic and cell regulatory properties of the wounded skin with impaired function and insufficient regulative capacity to hinder the ever-growing collagen tissue that is characteristic for keloids.

Systemic administration of high-molecular weight hyaluronan stimulates wound healing in genetically diabetic mice

Hyaluronic acid (HA), an essential component of the extracellular matrix, is an efficient space filler that maintains hydration, serves as a substrate for assembly of proteoglycans and is involved in wound healing. Although numerous pieces of evidence demonstrate beneficial effects in promoting wound healing in diabetes, a systemic approach has never been tested. We used an incisional wound healing model in genetically diabetic mice to test the effects of systemic injection of HA. Diabetic (n=56) and normoglycemic (n=56) mice were subjected to incision and randomized (8 groups of 7 animals each) to receive HA at different doses, 7.5, 15 and 30mg/kg/i.p., or vehicle (0.9% NaCl solution) for 12days. At the end of the experiment animals were sacrificed and skin wounds were excised for histological, biochemical and molecular analysis. Histology revealed that the most effective dose to improve wound repair and angiogenesis in diabetic mice was 30mg/kg. Furthermore HA injection (30mg/kg) improved the altered healing pattern in diabetic animals, increased skin remodeling proteins TGF-β and transglutaminase-II and restored the altered expression of cyclin B1/Cdc2 complex. Evaluation of skin from diabetic animals injected with HA revealed also an increase in HA content, suggesting that systemic injection may be able to restore the reduced intracellular HA pool of diabetic mice. Finally HA markedly improved skin mechanical properties. These promising results, if confirmed in a clinical setting, may improve the care and management of diabetic patients.

Hyaluronic acid: the scientific and clinical evidence

Hyaluronic acid is a naturally occurring biopolymer whose molecular structure is highly conserved between mammalian species. First described in 1934, it has since been used across a wide variety of medical fields as diverse as neurosurgery and cutaneous wound healing. Presently it has reached prominence in cosmetic practice where it is now the injectable dermal filler of choice for most surgeons. We used our experience of this technology with searches in the English language literature for the purpose of a systematic review. We present an overview, including the scientific evidence for its use in wound healing and, briefly, in other fields. We summarise the evidence for and against hyaluronic acid and provide a resumé of the current technologies available in fields such as skin regeneration and wound healing, in addition to cosmetic surgery. This overview is not intended to teach the reader about the various formulations currently on the market or how to use these materials clinically - rather to provide a solid scientific background enabling the reader to understand the attributes (and otherwise) of the material. We hope to allow clinicians to assess the evidence for a material now in common use in order that they may be fully aware of its properties.

The role of hyaluronic acid in wound healing: assessment of clinical evidence

Hyaluronic acid (hyaluronan), a naturally occurring polymer within the skin, has been extensively studied since its discovery in 1934. It has been used in a wide range of medical fields as diverse as orthopedics and cosmetic surgery, but it is in tissue engineering that it has been primarily advanced for treatment. The breakdown products of this large macromolecule have a range of properties that lend it specifically to this setting and also to the field of wound healing. It is non-antigenic and may be manufactured in a number of forms, ranging from gels to sheets of solid material through to lightly woven meshes. Epidermal engraftment is superior to most of the available biotechnologies and, as such, the material shows great promise in both animal and clinical studies of tissue engineering. Ongoing work centers around the ability of the molecule to enhance angiogenesis and the conversion of chronic wounds into acute wounds.

Prevention of pericardial adhesions with N-O carboxymethylchitosan in the rabbit model

The presence of mediastinal adhesions significantly increases the morbidity and mortality of reoperative cardiac surgical procedures. Previous investigations have reported on the therapeutic utility of topical hydrogels in reducing the formation of postsurgical adhesions. The goal of the present study is to evaluate the ability of N-O carboxymethylchitosan (a glycosaminoglycan hydrogel derivative) to reduce the formation ofpostsurgical pericardial adhesions in a large-animal model. Sixteen adult New Zealand white rabbits were randomly assigned to one of two treatment groups. Group 1 subjects (n = 8) had N-O carboxymethylchitosan directly applied to the heart and retrosternal surfaces after sternotomy was performed, while subjects in group 2 (n = 8) had saline applied to these areas. After a period of 14 days the animals were sacrificed under anesthesia, and independent observers, blinded to treatment, graded the formation of pericardial adhesions. The severity of adhesion formation was significantly less in the group treated with N-O carboxymethylchitosan (p < .01). This study demonstrates that N-O carboxymethylchitosan markedly decreases the formation of poststernotomy adhesions in a large-animal model without untoward cardiac side effects. This hydrogel derivative may prove to be of great therapeutic value when used prophylactically in the setting of cardiac surgery.

An inhibitor of cell proliferation associated with adhesion formation is suppressed by N,O-carboxymethyl chitosan

Surgical adhesions are a major cause of morbidity and mortality. The ideal barrier agent will both minimize adhesions and provide a milieu for the regeneration of the mesothelium lining of the abdominal and thoracic cavities. N,O-Carboxymethylchitosan (NOCC), a derivation of chitin that markedly reduces adhesions, may function to modulate intracellular signals such as growth factors and cytokines in the inflammatory exudate. Since transforming growth factor-beta is implicated in the fibrotic process, we investigated the possibility that NOCC's effects on adhesion formation reflects a modulation of TGF-beta activity. Using a biological assay for inhibition of cell proliferation to detect TGF-beta activity, we demonstrate that NOCC suppresses the levels of an inhibitor of cell proliferation released into serum and peritoneal exudates after cecal abrasion in the rat. However, this activity was distinct from known forms of TGF-beta as determined using both TGF-beta-neutralizing antisera and a TGF-beta-resistant cell proliferation assay. Thus at least one potential effect of NOCC involves a mechanism distinct from TGF-beta inhibition.