Rate of chondroitin sulfate formation in wound healing

Early Outcome of a Single Peri-Tendinous Hyaluronic Acid Injection for Mid-Portion Non-Insertional Achilles Tendinopathy - A Pilot Study

AIM

The aim of this study was to evaluate the efficacy and safety of a single, peri-tendinous injection of hyaluronic acid for mid-portion, non-insertional Achilles tendinopathy.

MATERIALS AND METHODS

A prospective, open labelled, single center, pilot study was conducted. All patients enrolled received a single peri-tendinous injection of Ostenil Tendon™ (40 mg/2 ml 2% HA with 0.5% mannitol). Outcome measures were Visual Analogue Scale (VAS) pain score and Manchester-Oxford Foot Questionnaire (MOxFQ) scores at 2 weeks and at final follow at 12 weeks. Any major and minor adverse effects were recorded. To assess change in VAS and MOxFQ scores, t test and Wilcoxon signed rank test were employed.

RESULTS

Seventeen patients were enrolled in this study with a mean follow-up of 12 weeks. Mean pre-injection VAS score was 9.38 cm (9-9.8), which significantly reduced post-injection to a mean score of 4.09 cm (2-8) at week-2 stage, and further improved to 3.01 cm (2-3.9) at the final follow-up (p < 0.0001). MOxFQ score showed a significant improvement from pre-injection value of 67.77 (63.03-72.55) to 31.18 (13-60) at week-2 stage, and further improved to 24.20 (15.73-32.67) at the final follow-up (p < 0.0001). The mean improvement from pre-injection to the final follow up was 43.57 (34.25-52.90). No adverse effects for injections were recorded.

CONCLUSION

This small series suggests an encouraging response of a single injection of HA as an effective and safe option for non-insertional Achilles tendinopathy.

Connective tissue response to fractionated thermo-ablative Erbium: YAG skin laser treatment

Indications for and prevalence of laser therapies with a fractionated laser beam have risen significantly. However, as of yet, little is known about the underlying molecular changes, especially with respect to dermal extracellular-matrix remodelling, wound healing and inflammation. This study aimed at the investigation of the connective tissue response of sun-damaged skin following fractionated laser treatment. Seven patients received a laser therapy on the lateral side of the neck of wrinkles grade III-IV (Glogau scale) using a fractionated thermo-ablative erbium yttrium aluminium garnet (Er:YAG) laser (2940 nm, BURANE XL; Quantel Derma, Erlangen, Germany). Skin biopsies were taken at baseline from untreated skin, 1 and 6 weeks after laser intervention to investigate hyaluronan (HA), collagen-I (Coll-I) and collagen-III (Coll-III) remodelling as well as alteration of matrix metalloproteinase 1 expression (MMP-1). To address this issue, HA synthesizing (HA synthetases, HAS) and degrading (hyaluronidases, HYAL) enzymes were measured at mRNA-level using a real-time PCR. Furthermore, immunohistochemical staining for HA was performed by using the HA binding protein (HAbP) and for Coll-I, Coll-III and MMP-1 by using monoclonal antibodies. The degree of inflammation was correlated descriptively. Our findings were that at the two examined read out points, HAS and HYAL showed a slight response alluding to HA synthesis under minimal signs of inflammatory reaction. Concordantly, although to a varying degree, an increase in the HA content of the skin after laser treatment could be detected by immunhistochemistry. During remodelling, Coll-I, Coll-III and MMP-1 showed a cyclic course with a peak after 1 week. Conclusively, our results indicate a light alteration of the HA metabolism towards synthesis and a transient collagen neogenesis caused by a single fractionated thermo-ablative laser skin intervention. Clinical improvement might be attributed to synergistic effects between collagen neogenesis and the water binding capacities of HA and its influence on skin contraction and remodelling.

Effect of lyophilized amniotic membrane, hyaluronic acid, and their combination in preventing adhesion after tendon repair in New Zealand white rabbits

Background: Several promising methods to reduce the peritendinous adhesion after repair include amniotic membrane and hyaluronic acid application on the repaired tendon site. This study aimed to compare the effect of lyophilized amniotic membrane, application of hyaluronic acid, and their combination in preventing peritendinous adhesion after tendon repair in New Zealand white rabbits.Methods: 64 flexor digitorum fibularis tendon from 16 rabbits were cut and then repaired by modified Kessler technique. Samples were allocated into four test groups; group I as control had simple tendon repair, group II had amniotic membrane wrapping at repair site, group III had hyaluronic acid application at repair site, and group IV had combination of amniotic membrane wrapping and hyaluronic acid application. On 6th week, 8 tendon from each group underwent macroscopic and histologic evaluation of peritendon adhesion by Tang scoring system. The rest of samples were evaluated for tendon gliding at tenth week by measuring active and passive range of motion of metatarsophalangeal joint.Results: At 6th week, macroscopic and histologic evaluation showed that groups II, III, and IV had significantly lower peritendinous adhesion compared to control group (p < 0.05). However, there was no significant difference found among groups II, III, and IV (p > 0.05). Similar results were found in tendon gliding evaluation, groups II, III, and IV had significantly better range of motion compared to control group (p < 0.05), but there was no significant difference found between these groups (p > 0.05).Conclusion: The application of lyophilized amniotic membrane, hyaluronic acid, or their combination significantly reduce the formation of peritendinous adhesion in repaired flexor digitorum fibularis tendon in rabbit model.

Propolis induces chondroitin/dermatan sulphate and hyaluronic Acid accumulation in the skin of burned wound

Changes in extracellular matrix glycosaminoglycans during the wound repair allowed us to apply the burn model in which therapeutic efficacy of propolis and silver sulfadiazine was compared. Burns were inflicted on four pigs. Glycosaminoglycans isolated from healthy and burned skin were quantified using a hexuronic acid assay, electrophoretic fractionation, and densitometric analyses. Using the reverse-phase HPLC the profile of sulfated disaccharides released by chondroitinase ABC from chondroitin/dermatan sulfates was estimated. Chondroitin/dermatan sulfates and hyaluronic acid were found in all samples. Propolis stimulated significant changes in the content of particular glycosaminoglycan types during burn healing. Glycosaminoglycans alterations after silver sulfadiazine application were less expressed. Propolis maintained high contribution of 4-O-sulfated disaccharides to chondroitin/dermatan sulfates structure and low level of 6-O-sulfated ones throughout the observed period of healing. Propolis led to preservation of significant contribution of disulfated disaccharides especially 2,4-O-disulfated ones to chondroitin sulfates/dermatan sulfates structure throughout the observed period of healing. Our findings demonstrate that propolis accelerates the burned tissue repair by stimulation of the wound bed glycosaminoglycan accumulation needed for granulation, tissue growth, and wound closure. Moreover, propolis accelerates chondroitin/dermatan sulfates structure modification responsible for binding growth factors playing the crucial role in the tissue repair.

Accumulation of Glycosaminoglycans in Radiation-induced Muscular Fibrosis

The content and biosynthesis of glycosaminoglycans (GAGs) were studied in the pig thigh muscle after acute local gamma-irradiation. Seven months following irradiation, the muscular tissue next to the irradiation cone was replaced by severe mutilating fibrosis delimited by an intermediary perifbrotic zone. Fibrosis, perifibrotic tissue and normal muscle, were sampled and incubated with [3H]glucosamine and [35S]sulphate, and GAGs were isolated following pronase digestion. Results showed a parallel increase of collagen and GAG content in perifibrotic and fibrotic tissues. Sulphated GAGs, heparan sulphate and dermatan sulphate were preferentially accumulated in fibrotic tissue, while the hyaluronic acid content increased only slightly. Synthesis of sulphated GAGs was more elevated in fibrotic tissue than in perifibrotic zone as compared with normal muscle. Seven months after irradiation well-developed fibrotic tissue continued to synthesize and to accumulate extracellular matrix macromolecules, indicating the invasive aspect of post-irradiation fibrosis.

Hyaluronan in human acute and chronic dermal wounds

There is growing interest in the relationship of hyaluronan and inflammation in a number of physiologic processes including wound healing. The objective of this study was to make a quantitative comparison of inflammation and hyaluronan expression in human normal healing open wounds and in pressure ulcers. Using an open dermal wound model, myeloperoxidase activity was found to peak at day 3. Hyaluronan levels showed a bimodal distribution with transient peaks occurring on days 1 and 7. Mean levels of myeloperoxidase activity in pressure ulcers were significantly higher than at any time in the acute wounds, whereas hyaluronan levels were significantly lower than at any time in the acute wounds. Levels of hyaluronidase activity increased slightly in the postwound period. Hyaluronidase activity in pressure ulcers was significantly elevated compared with the acute wounds. These results suggest a role for increased enzymatic degradation of hyaluronan as a function of inflammation during wound repair. This is the first reported quantitative examination of hyaluronan expression in human acute dermal wounds and in chronic pressure ulcers.

Profiling of differentially expressed genes in wound margin biopsies of horses using suppression subtractive hybridization

Disturbed gene expression may disrupt the normal process of repair and lead to pathological situations resulting in excessive scarring. To prevent and treat impaired healing, it is necessary to first define baseline gene expression during normal repair. The objective of this study was to compare gene expression in normal intact skin (IS) and wound margin (WM) biopsies using suppression subtractive hybridization (SSH) to identify genes differentially expressed during wound repair in horses. Tissue samples included both normal IS and biopsies from 7-day-old wounds. IS cDNAs were subtracted from WM cDNAs to establish a subtracted (WM-IS) cDNA library; 226 nonredundant cDNAs were identified. Detection of genes previously shown to be expressed 7 days after trauma, including the pro-α2-chain of type 1 pro-collagen (COL1A2), annexin A2, the pro-α3-chain of type 6 pro-collagen, β-actin, fibroblast growth factor 7, laminin receptor 1, matrix metalloproteinase 1 (MMP1), secreted protein acidic cystein rich, and tissue inhibitor of metalloproteinase 2, supported the validity of the experimental design. A RT-PCR assay confirmed an increase or induction of the cDNAs of specific genes (COL1A2, MMP1, dermatan sulfate proteoglycan 2, cluster differentiation 68, cluster differentiation 163, and disintegrin and metalloproteinase domain 9) within wound biopsies. Among these, COL1A2 and MMP1 had previously been documented in horses; 68.8% of the cDNAs had not previously been attributed a role during wound repair, of which spermidine/spermine- N-acetyltransferase, serin proteinase inhibitor B10, and sorting nexin 9 were highly expressed and whose known functions in other processes made them potential candidates in regulating the proliferative response to wounding. In conclusion, we identified novel genes that are differentially expressed in equine wound biopsies and that may modulate repair. Future experiments must correlate changes in mRNA levels for precise molecules with spatiotemporal protein expression within tissues.

Fibroblast growth factor-2 regulates the synthesis of hyaluronan by human periodontal ligament cells

Basic fibroblast growth factor (FGF-2) can enhance biological potentials of periodontal ligament cells and its topical application induces considerable periodontal tissue regeneration in vivo. In this study, we examined the effect of FGF-2 on the production of hyaluronan (HA), an extracellular matrix playing important roles in homeostasis and inflammatory/wound healing responses, by human periodontal ligament (HPDL) cells. An inhibition binding-protein assay revealed that FGF-2 significantly increased HA production by HPDL cells in a dose dependent manner. Analysis by HPLC revealed that in conditioned medium of FGF-2-treated HPDL cells HA had a higher molecular mass, compared to that of untreated HPDL cells. RT-PCR analysis revealed the enhancement of mRNA expression of hyaluronan synthase (HAS) 1 and HAS 2, both of which contribute to the production of HA with a high molecular mass, but not HAS 3 in the FGF-2-treated HPDL cells. In contrast, three isoforms of hyaluronidase (HYAL) transcript were unchanged in the FGF-2-treated HPDL cells. These results provide new evidence for the possible involvement of FGF-2 in the regulation of HA production and its appreciable roles in not only homeostasis but also regeneration of periodontal tissues.

COX-2 inhibitors prolong trauma-induced elevations of iris hyaluronan

PURPOSE

To investigate whether and how treatment with COX-2 inhibitors influences hyaluronan responses to a standardized trauma, argon laser induced iritis, in rabbits.

METHODS

Two different COX-2 inhibitors were used, SC-236 and rofecoxib. The drugs were administered orally, 6 mg/kg/day and 1.5 mg/kg/day respectively. Iris and aqueous humor hyaluronan concentrations were measured with a radiometric assay at different time points after laser irradiation.

RESULTS

The hyaluronan concentration in the iris increased 3-4-fold with a peak concentration of 129.1 microg/g wet weight 2 days after laser irradiation. It then decreased to normal values after 1 week. In eyes treated with either of the COX-2 inhibitors, iris hyaluronan concentrations did not decrease as rapidly and were significantly higher at day 4 and 7 when compared to drug untreated eyes.

CONCLUSION

Treatment with COX-2 inhibitors prolongs trauma induced elevation of iris content of endogenous hyaluronan. This may be, at least partly, due to an inhibition of interstitial fluid pressure regulation.

Influence of laser irradiation on endogenous hyaluronan in rabbit iris and aqueous humor

PURPOSE

To monitor changes of endogenous hyaluronan in the iris tissue and aqueous humor after an isolated trauma to the iris by argon laser irradiation of the anterior surface of the iris.

METHODS

Iris and aqueous hyaluronan concentrations in rabbit were measured with a radiometric assay at different time points after laser irradiation.

RESULTS

Total hyaluronan content in iris tissue increased 3-fold to a peak concentration of 71-72 microg/g at 1 and 2 days after laser treatment. Aqueous hyaluronan increased to a maximum of about 1.6 microg/ml at 2 h and 12 h after laser irradiation of the iris.

CONCLUSIONS

The iris tissue responds with increased hyluronan synthesis to an isolated iris argon laser irradiation and it seems to be the most important source of aqueous hyaluronan.

Glycosaminoglycans in gingival crevicular fluid of patients with periodontal class II furcation involvement before and after guided tissue regeneration. A pilot study

BACKGROUND

The levels of glycosaminoglycans in gingival crevicular fluid (GCF) are good indicators of underlying tissue turnover. We hypothesize that connective tissue elements in GCF may be used as indicators of tissue maturation underneath barrier membranes. Therefore, we investigated the levels of sulfated glycosaminoglycans in GCF at sites before and after guided tissue regeneration (GTR).

METHODS

Six patients were selected on the basis of having at least one Class II buccal furcation involvement on a molar tooth. Each molar furcation was treated with the standard GTR surgical protocol using a non-resorbable expanded polytetrafluoroethylene membrane. Gingival crevicular fluid samples were taken at baseline (immediately prior to insertion of the membrane) and at 1, 2, 3, 4, 5, and 6 weeks (immediately prior to removal of the membrane). Glycosaminoglycan levels were determined using an Alcian blue dye detection system.

RESULTS

The mean levels of chondroitin sulfate and total sulfated glycosaminoglycans in GCF significantly decreased during the first 4 weeks after GTR surgery. By week 5, the levels began to rise, and by week 6 the levels had returned to baseline levels.

CONCLUSIONS

Sulfated glycosaminoglycans can be monitored in GCF at healing GTR sites. It is proposed that this is a useful means of monitoring the status of the regenerating tissues. However, further longitudinal studies are required to assess if the sulfated glycosaminoglycans can be used as indicators of tissue maturation under guided tissue membranes used to treat periodontal defects.

Chitosan and chitosan sulfate have opposing effects on collagen-fibroblast interactions

Soon after injury, hyaluronan is prominent in granulation tissue. As hyaluronan wanes, sulfated glycosaminoglycans predominate. The temporal relationship between the transition from unsulfated to sulfated glycosaminoglycans and the phenotypic changes in fibroblasts in the wound bed suggest that these two events are interrelated. This possibility was investigated using chitosan and its sulfated product as model compounds. The ability of cultured human foreskin fibroblasts to bind and to contract lattices of collagen, collagen-chitosan, and collagen-chitosan sulfate was determined. Fibroblast adherence to substrates after 24 hours was determined by the MTT assay at A570. Adherence to the collagen-chitosan substrate was markedly reduced (mean A570 +/- SD; 0.16 +/- 0.05, n = 6) (p < 0.01) compared to collagen alone (0.92 +/- 0.04) or to collagen-chitosan sulfate (0.84 +/- 0.05). Kinetics of contraction of lattices by enmeshed fibroblasts was determined by planimetric measurements, 0-48 hours after loosening the lattices. Contraction of the collagen-chitosan lattices (n = 5) was less at all time points than for the other two lattices. After 48 hours, the collagen- chitosan lattices contracted significantly (p < 0.01) less (30.0% +/- 4.4) compared to collagen alone (66.9% +/- 4.7) and collagen-chitosan sulfate (71.6% +/- 7.7). Scanning electron microscopy of the acellular lattices showed fibers of the collagen-chitosan mixture to be the thickest and with altered organization. These results show that chitosan sulfation markedly enhances fibroblast adhesion and promotes contraction of a collagen lattice compared to the unsulfated material. By analogy to the in vivo sequence of hyaluronan followed by sulfated glycosaminoglycans in wounds, the results suggest that glycosaminoglycan sulfation may be a contributing signal for phenotypic transformation during wound healing.

Autologous keratinocytes cultured on benzylester hyaluronic acid membranes in the treatment of chronic full-thickness ulcers

Keratinocytes were obtained from three patients with chronic full-thickness ulcers of different aetiologies. The cells were isolated, cultured and then seeded on to a membrane composed of benzylester hyaluronic acid. Once the keratinocytes had become subconfluent, the keratinocyte-containing matrix sheets were then applied as autologous grafts to the patients' ulcers. Results indicate that autologous grafting of keratinocytes cultured on benzylester hyaluronic acid membranes provides improved graft handling, reduces total time required for tissue cultivation and enhances cellular vitality because of the possibility of grafting at a subconfluent non-differentiated stage.

Changes in sulfated macromolecules produced in vivo during normal and indomethacin-delayed ulcer healing in rats

The aim of this study was to examine the synthesis of sulfated glycosaminoglycans during normal healing of experimental acetic acid-induced gastric ulcer in rats and to investigate the effect of indomethacin, a drug known to delay ulcer healing, on this synthesis using an in vivo labelling system. Analysis revealed the presence of two major sulfated species in control tissue; a population of sulfated mucins and glycosaminoglycans, predominantly galactosaminoglycans. The incorporation of [35S]sulfate label into glycosaminoglycans synthesized in the granulation tissue of healing ulcers increased significantly (P < 0.05) as compared to day 0 and control levels at day 14. Treatment of animals with indomethacin (1 mg/kg daily) resulted in a further significant (P < 0.01) rise in sulfated glycosaminoglycan synthesis in indomethacin-treated ulcer tissue compared to that found in healing ulcers at day 14. The increased glycosaminoglycan synthesis was due to increased levels of chondroitin sulfate and dermatan sulfate. Glycosaminoglycan synthesis is elevated at the ulcer site during healing of experimental gastric ulcers; however, indomethacin treatment, which delays ulcer healing, significantly increases the synthesis of glycosaminoglycans above that seen in healing ulcers. Changes in the sulfated glycosaminoglycan content of the ulcer may play a role in the healing process and may give further insight into the mechanisms by which indomethacin delays ulcer healing.

General principles of wound healing

Wound healing is a complex process involving different biologic and immunologic systems. Despite improvements in diagnostics and therapy, wound failures remain a clinical problem. The approach to a nonhealed wound is an interdisciplinary challenge that should not be underestimated. Better understanding of the complex wound-healing cascade helps our approach to wound healing and its possible failure. Manipulations of the involved immunologic features offer future therapeutic strategies.

Fibrotic healing of adult and late gestation fetal wounds correlates with increased hyaluronidase activity and removal of hyaluronan

The lack of scarring and fibrosis in healing fetal skin wounds may relate to a prolonged presence of hyaluronan (HA). It has been suggested that fetal wounds may lack hyaluronidase, but the hyaluronidase levels in fetal wounds remain unknown. The size of HA influences its biological action, especially in relation to angiogenesis, which is also reduced in fetal wound healing. The present study determined the levels and size of HA, as well as hyaluronidase levels, in fetal and adult lamb wounds. Wire mesh cylinders, or polyvinyl acetate sponges, were placed subcutaneously in fetal lambs at 75, 100 or 120 days gestation. Wound fluid and wound tissue were harvested 3, 7 or 14 days later. Samples were digested with papain and both HA and hyaluronidase activity were determined in a competitive ELISA assay. Size distribution of HA was estimated using a Sephacryl S1000 column and fractions were collected for HA determination. Adult wound fluid HA remained low (4-5 micrograms/ml) over the 14 days. Fetal fluids were similar on day 3, but increased to 15-25 micrograms/ml by day 7. In 75/100-day wounds, HA remained elevated at 14 days, but in 120-day fluids decreased to levels similar to adult fluid. The HA in all fluids was polydisperse with a main peak at 200 kDa. Hyaluronidase levels were detected in all samples, reaching a peak 7 days post-wounding. In adult wound fluids hyaluronidase was much higher than the fetal wound fluids. These data suggest that lower hyaluronidase levels in fetal wounds may underlie the different pattern of HA deposition seen in fetal wounds.

Histochemical identification of hyaluronan in the rabbit anterior segment during the healing period after extracapsular lens extraction

Extracapsular lens extractions were performed in rabbits. The eyes were examined at different time intervals after surgery with a histochemical method visualizing hyaluronan. There was positive staining for hyaluronan in the wound region from 2 to 90 days postoperatively. The staining was most intense and widespread between 7 and 14 days after surgery. A hyaluronan staining in the corneal stroma extended from the wound towards the central cornea 4 to 14 days postoperatively. The iris showed increased staining on the second postoperative day, but much less so at the other times studied. Cells on the posterior lens capsule were surrounded by hyaluronan from the seventh postoperative day throughout the observation time up to 90 days postoperatively. It is concluded that hyaluronan reacts during corneal wound healing.

Stimulation of sulfated glycosaminoglycan synthesis by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu2+

Glycyl-L-histidyl-L-lysine-copper (II) complex (GHK-Cu) is a naturally occurring tripeptide with potential healing properties. We studied the effect of GHK-Cu on the synthesis of glycosaminoglycans (GAGs) by normal human fibroblasts in culture. Cells were incubated with 3H glucosamine and 35S sulfate and the radioactivity of isolated GAGs was determined. GHK-Cu induced a dose-dependent increase of the synthesis of total GAGs secreted into the culture medium and those associated with the cell layer. The effect of GHK-Cu was biphasic with a maximal stimulation at 10(-9) to 10(-8) M. At higher concentrations, the rate of synthesis returned progressively to that of control cultures. Electrophoretic analysis of the different GAG populations showed that GHK-Cu preferentially stimulated the synthesis of extracellular dermatan sulfate and cell layer associated heparan sulfate. No influence of GHK-Cu on the synthesis of hyaluronic acid was observed. GHK-Cu stimulation of GAG synthesis may be one of the phenomenons implicated in the wound healing properties of the peptide.

Sodium hyaluronate increases vascular ingrowth in the rabbit ear chamber

The rabbit ear-chamber model was used to study the effect of sodium hyaluronate (NaHe, Healon) on the rate of ingrowth of vascular structures of healing granulation tissue. The chamber area covered by granulation tissue was determined by in-vivo microscopy at regular intervals during a period of 32 days. Daily injections of 1% NaHe into the ear chamber, 50 microliters from day 0 to day 7 and 25 microliters from day 8 to day 21, significantly inhibited ingrowth as observed between days 20 and 26, compared with buffer-injected controls. There was no difference between the latter and non-injected chambers. Intermittent injections of 1% NaHe, 50 microliters on days 1 and 5 and 25 microliters on days 9, 13 and 22 significantly increased the ingrowth as observed between days 6 and 18. It was noted that wound macrophages internalized fluorescein-labelled NaHe. The inhibitory effect of daily injections on angiogenesis was probably due to physical hindrance caused by the NaHe. The stimulatory effect of intermittent administration of NaHe on angiogenesis may have several explanations, including activation of macrophages and their release of angiogenetic factors.

A paradigm for restenosis based on cell biology: clues for the development of new preventive therapies

Angioplasty causes substantial injury to the coronary artery intima and media that is unrecognizable by angiography. On the basis of a substantial body of research in oncology and wound healing, it is hypothesized that restenosis is a manifestation of the general wound healing response expressed specifically in vascular tissue. The temporal response to injury occurs in three characteristic phases: inflammation, granulation and extracellular matrix remodeling. The specific expression of these phases in the coronary artery leads to intimal hyperplasia at 1 to 4 months. The major milestones in the temporal sequence of restenosis are platelet aggregation, inflammatory cell infiltration, release of growth factors, medial smooth muscle cell modulation and proliferation, proteoglycan deposition and extracellular matrix remodeling. Each step has potential inhibitors that could be used for preventive therapy. Resolution of restenosis, however, probably requires both creation of the largest possible residual lumen and substantial inhibition of intimal hyperplasia.

Binding of hyaluronic acid to mammalian fibrinogens

We have postulated that the interaction of hyaluronic acid (HA), an extracellular matrix glycosaminoglycan, with fibrin is important during the early stages of wound healing and inflammation (J. Theor. Biol. 119:219; 1986), and have demonstrated the specific binding of 125I-labeled HA to human fibrinogen (J. Biol. Chem. 261:12 586; 1986). To determine whether HA binding is limited to human fibrinogen, we tested the ability of fibrinogens from various mammalian species to bind 125I-HA using a dot-blot assay. Increasing amounts of fibrinogen were adsorbed to nitrocellulose, and incubated with 125I-HA in the presence or absence of a 100-fold excess of nonradiolabeled HA to assess specific binding. In three independent experiments, the amount of 125I-HA bound/mg fibrinogen was determined from the slope derived by linear regression analysis of specifically bound 125I-HA versus protein concentration. A Student's t-test was performed to determine whether the slopes were statistically greater than zero. HA binding was considered statistically significant when P less than 0.05 was obtained by this analysis. Rabbit and dog fibrinogens significantly bound HA in all three trials. Baboon fibrinogen demonstrated significant HA binding in two of three trials. Pig, sheep and goat fibrinogens bound HA significantly in only one of three trials, whereas horse, rat and cow fibrinogens did not bind HA significantly at all. We conclude that fibrinogen from mammalian species other than human can specifically bind HA. The ability of fibrinogen to bind HA appears to correlate with an evolutionary divergence that separated human, baboon, dog, rabbit and rat from cow, pig, horse, goat and sheep.

Expression of different glycosaminoglycan synthetic phenotypes by lapine dermal and dermal wound fibroblasts

Synthesis of extracellular matrix by dermal fibroblasts is an important component of cutaneous wound repair. Scar remodeling and maturation is generally seen as the result of a fibroblast-regulated equilibrium between production and degradation of specific matrix constituents. Fibroblasts from normal dermis, reparative granulation tissue and mature scars were compared in vitro in terms of their ability to produce extracellular glycosaminoglycans (GAGs). All cell lines secreted dermatan sulfate (DS) and chondroitin sulfate (CS) into the culture medium. Hyaluronate (HA) was detected in medium from mature granulation tissue and scar cells, but little or none was found in medium from early granulation tissue or skin cells. In medium from normal skin fibroblasts, an unusual GAG was identified as a potential variant of DS on the basis of co-migration with HA but susceptibility to digestion with chondroitinase ABC. Heparan sulfate (HS) was the major pericellular GAG of all cultures except the mature scar cells, which contained a predominance of DS. A second pericellular GAG was identified as CS in mature granulation tissue cells, scar cells and skin cells; while HA was identified in the pericellular matrix of early granulation tissue cells. In addition, fibroblasts from both skin and early granulation tissue contained a GAG believed to be a variant of CS. These differences in GAG synthesis/secretion between cells maintained under identical culturing conditions could indicate either that distinct fibroblastic substrains exist during different stages of healing or that influences present during the healing process induce stable phenotypic alterations that are maintained through explant culturing and subsequent subcultivation.

Wound healing for the dermatologic surgeon

An understanding of the basic science of cutaneous wound repair is essential to the dermatologic surgeon for the management of the postoperative wound. This review discusses the stages of wound healing and then applies these principles to the preoperative, intraoperative, and postoperative management of the surgical patient.

The effects of mechanical stability on the macromolecules of the connective tissue matrices produced during fracture healing. II. The glycosaminoglycans

The glycosaminoglycans secreted into the matrices associated with fractures of the rabbit tibia healing under stable and unstable mechanical conditions have been characterized histochemically using the dye Alcian Blue at pH 5.7 in the presence of increasing concentrations of magnesium chloride, and after enzymatic extractions. These results are compared with those of immunohistochemical experiments using monoclonal antibodies which recognize epitopes specific to various glycosaminoglycans. The results indicate that the fibrous tissues, including those of the cavities of the cancellous bone and periosteum, possess hyaluronate and chondroitin sulphate, but the amounts present are small. The glycosaminoglycans detected in the cortical bone are located mainly around the osteocyte lacunae where chondroitin and keratan sulphates are found. The developing trabeculae of cancellous bone in the callus contain chondroitin and keratan sulphates, but as the trabeculae mature, these glycosaminoglycans are no longer present throughout the matrix; they are found particularly around the osteocyte lacunae. The cartilage in the callus of mechanically unstable fractures contains chondroitin, chondroitin-4- and 6-sulphates and keratan sulphate, through their distribution is variable. The small, transient areas of cartilage in the callus of mechanically stable fractures also contain those glycosaminoglycans, but they appear to be less highly sulphated. The mechanical stability of the fractures appears to affect the amount and degree of sulphation of the glycosaminoglycans, rather than the types of glycosaminoglycan produced. The glycosaminoglycans produced during fracture healing are compared with those produced during embryonic development and other healing processes.

A model for the role of hyaluronic acid and fibrin in the early events during the inflammatory response and wound healing

A model is presented outlining the molecular and cellular events that occur during the early stages of the wound healing process. The underlying theme is that there is a specific binding interaction between fibrin, the major clot protein, and hyaluronic acid (HA), a constituent of the wound extracellular matrix. This binding interaction, which could also be stabilized by other cross-linking components, provides the driving force to organize a three-dimensional HA matrix attached to and interdigitated with the initial fibrin matrix. The HA-fibrin matrix plays a major role in the subsequent tissue reconstruction processes. We suggest that HA and fibrin have both structural and regulatory functions at different times during the wound healing process. The concentration of HA in blood and in the initial clot is very low. This is consistent with the proposed interaction between HA and fibrin(ogen), which could interfere with either fibrinogen activation or fibrin assembly and cross-linking. We propose that an activator (e.g. derived from a plasma precursor, platelets or surrounding cells) is produced during the clotting reaction and then stimulates one or more blood cell types to synthesize and secrete HA into the fibrin matrix of the clot. We predict that HA controls the stability of the matrix by regulating the degradation of fibrin. The new HA-fibrin matrix increases or stabilizes the volume and porosity of the clot and then serves as a physical support, a scaffold through which cells trapped in the clot or cells infiltrating from the peripheral edge of the wound can migrate. The HA-fibrin matrix also actively stimulates or induces cell motility and activates and regulates many functions of blood cells, which are involved in the inflammatory response, including phagocytosis and chemotaxis. The secondary HA-fibrin matrix itself is then modified as cells continue to migrate into the wound, secreting hyaluronidase and plasminogen activator to degrade the HA and fibrin. At the same time these cells secrete collagen and glycosaminoglycans to make a more differentiated matrix. The degradation products derived from both fibrin and HA are, in turn, important regulatory molecules which control cellular functions involved in the inflammatory response and new blood vessel formation in the healing wound. The proposed model generates a number of testable experimental predictions.

Cutaneous tissue repair: basic biologic considerations. I

Wound repair of the integument is reviewed in the context of new developments in cell biology and biochemistry. Injury of the skin and concomitant blood vessel disruption lead to extravasation of blood constituents, followed by platelet aggregation and blood clotting. These events initiate inflammation and set the stage for repair processes. The macrophage plays a pivotal role in the transition between wound inflammation and repair (granulation tissue formation), since this cell both scavenges tissue debris and releases a plethora of biologically active substances that include growth factors. Although concrete evidence is lacking, growth factors are probably at least partially responsible for the angiogenesis and fibroplasia (granulation tissue) that gradually fill the wound void. If the epidermal barrier is disrupted during injury, reepithelialization begins within 24 hours and proceeds first over the margin of residual dermis and subsequently over granulation tissue. The signals for angiogenesis, fibroplasia, neomatrix formation, and reepithelialization in wound repair are not known, but a number of possibilities are discussed. Matrix remodeling is the last stage of wound repair and gradually increases the scar tensile strength to 70% to 80% of normal skin.

Ibuprofen inhibition of postsurgical adhesion formation: a time and dose response biochemical evaluation in rabbits

Recently, a reduction in postoperative adhesion formation in rabbits which received high-dose ibuprofen (280 mg/kg/day) treatment in the perioperative interval was reported. Because these results could have resulted from a nonspecific effect of ibuprofen, the effects of ibuprofen on peritoneal injury in a time and dose response fashion was evaluated. Seventy rabbits were assigned to seven groups. All rabbits received a dose of ibuprofen 1 hr prior to surgery. The time of the second dose was either 8 or 12 hr after the surgical procedure; 8 hr for groups A, C, and E; 12 hr for groups B, D, and F (A, B: 70 mg/kg; C, D: 35 mg/kg; E, F: 17.5 mg/kg, respectively). Thereafter, rabbits received further dosing every 6 hr to complete a total 10-dose regimen. Group G served as a nontreatment control. Surgical injury was induced by either abrasion or ischemia of the right uterine horn. Immediately after closing the incision, 10 muCi of 14C-labeled glucosamine and 10 muCi of 14C-labeled proline were injected into each rabbit. All rabbits underwent a second laparotomy on the fifth postoperative day for evaluation of adhesion formation. Uterine tissue adjacent to the site of uterine healing was excised for determination of glycosaminoglycan and collagen concentration. In the nontreatment control group G, 5 of the 10 rabbits had severe grade 2 adhesions at the time of second laparotomy, 3 had grade 1 filmy adhesions, and 2 had no adhesions. This is in marked contrast (P less than 0.025) to the group that received ibuprofen at 70 mg/kg/day with the first postoperative dose 8 hr after surgery (group A). In this group, no rabbits had severe grade 2 adhesions, 3 rabbits had filmy grade 1 adhesions, and 7 rabbits were free of pelvic adhesions. A gradual tendency towards more adhesions and more severe adhesions was apparent in groups B-F as the dose of ibuprofen was decreased and the time of first postoperative injection was prolonged. The recovery of 14C-labeled glucosamine from the glycosaminoglycan extraction demonstrated a positive correlation between the cpm recovered and the severity of adhesions formed. Groups A and B had, overall, the lowest ratios of glucosamine (1.47 +/- 0.08 and 1.56 +/- 0.09, respectively) which were statistically different from the nontreatment control group G (1.76 +/- 0.11, P less than 0.05). There was also a positive correlation between the formation of severe adhesions and the ratio of 14C-labeled proline recovered by collagen extraction.(ABSTRACT TRUNCATED AT 400 WORDS)

Healing of hyaluronic acid-enriched wounds: histological observations

The influence of an exogenous supply of Na hyaluronate (HA) on the healing of superficial skin wounds in healthy and alloxan-induced diabetic rats was histologically assessed. Rats were treated by topical application on the wound site of a 2% Na hyaluronate solution. A facilitating effect of the HA-enrichment on wound repair processes (particularly epithelial migration and differentiation) was markedly evident in wounded diabetic rats. This result is discussed in terms of a possible favorable influence of an HA-enriched wound environment on cell migratory processes occurring during wound healing.

Current concepts in soft connective tissue wound healing

The strength and integrity of intact soft connective tissues are related to the forces which exist between collagen fibrils and these in turn appear to depend on collagen fibril size, density and architecture en masse. The genetic type of collagen, enzymic modifications to the collagen monomer and the proteoglycan environment all affect fibril size. Current evidence suggests that the restoration of tissue continuity and the early redevelopment of tissue strength following wounding are initially achieved by the formation of a myofibroblast-reticulin network which eventually disappears as the healing wound ages. The extent of this network defines the area in which repair tissue will be laid down and the network is equipped with the sensory apparatus to monitor the physical and chemical environment where healing is taking place and thus to direct the various facets of connective tissue synthesis outlined above. The maturation of the scar connective tissue matrix and the development of attachment between new and original connective tissues are simultaneous, related but independent processes. It takes some time before the weld is achieved by the same forces that hold connective tissue fibres together in intact tissues and the myofibroblast-reticulin network is replaced.

Biochemical evaluation of postsurgical wound repair: prevention of intraperitoneal adhesion formation with ibuprofen

Proteins central to normal wound repair, including collagen and proteoglycans, were extracted during postoperative mesothelial regeneration, then the quantitation was correlated to macroscopic observations of normal peritoneal reepithelialization and/or postoperative adhesion formation. Sixty-three New Zealand white female rabbits of reproductive age were prospectively assigned to either Group A, untreated control; Group B, which received intramuscular injections of ibuprofen, 70 mg/kg per injection (immediately and 6 hr after surgery); or Group C, which received 5 intramuscular injections of ibuprofen (4 hr before surgery, and immediately, 6, 12, and 18 hr after surgery). The right uterine horn underwent one of three standardized surgical traumas: (1) abrasion of the peritoneal surface with a scalpel until punctate bleeding developed, (2) ischemia of the uterine horn by removal of the collateral blood supply (devascularization), (3) crushing of the uterine horn by cross clamping for 3 min with a Kelley hemostat. Thereafter, 10 microCi of C-14-labeled glucosamine and 10 microCi of C-14-labeled proline were injected into the marginal ear vein of each rabbit. All rabbits underwent a laparotomy on the fifth postoperative day for evaluation of adhesion formation and tissue biopsy for protein extraction. No reduction in adhesion formation was found using a 2-dose postoperative treatment regimen. However, using a 70 mg/kg X 5-doses regimen in the immediate perioperative interval, a significant reduction in both adhesion formation and severe adhesion formation (both P less than 0.025) were found following standardized surgical injury. The extent of adhesion formation was correlated with the extractable glycosaminoglycan and collagen concentrations. As determined by recovered glucosamine and proline, a positive correlation was apparent between the severity of adhesion grade and formation of new glycosaminoglycans or collagens. Thus, ibuprofen appears to inhibit adhesion formation through suppression of fibroproliferative inflammation.

Identification, characterization, and partial purification of mammalian skin wound hyaluronidase

A recently described mammalian wound hyaluronidase is successfully characterized and partially purified in the current study. Peak enzyme activity occurred on postwound day 7, pH optimum 4.5. Both crude and purified wound enzyme exhibited endoglycosidic activity against hyaluronate and chondroitin-4-sulfate but not against chondroitin-6-sulfate or dermatan sulfate. A 5.3-fold increase in activity was obtained by the DEAE-Sephadex purification technique described. Polyacrylamide gel electrophoresis yielded a single major band near the gel's midrange and one minor band of lesser electrophoretic mobility. These enzyme characteristics support a biochemical analogy between tissue repair in skin and numerous developmental systems and may also provide a simple means for enzymatic differentiation among chondroitin sulfate isomers.

Effect of fixation upon the histochemistry of glycosaminoglycans (mucopolysaccharides) in intraoral wounds

Intraoral wounds and biochemical films were examined to determine the best method of fixation for glycosaminoglycans. Tissues fixed in 1% cetyl pyridinium chloride-10% formalin stained intensely with preparations of Alcian blue. When these tissues were treated with Streptomyces hyaluronidase and bacterial chondroitinases, staining was comparable to untreated tissues fixed in only 10% formalin. The addition of cetyl pyridinium chloride to formalin fixatives was a requirement for glycosaminoglycan histochemistry in open wounds, and presumably in other tissues that contain these complex sugars.