Hyaluronan and wound healing: a new perspective

NexGen regen? Challenges and opportunities for growth factors and signaling agents in periodontal regeneration at intrabony defects

Regeneration of periodontal tissues that have been destroyed by inflammatory periodontitis involves the initiation of tissue engineering and wound healing of multiple tissues involved in the function of the teeth, including the periodontal ligament, cementum, and alveolar bone. Such regeneration is termed guided tissue regeneration and the unique challenges to reconstruct these tissues involve a complex interplay of cells, signaling molecules, and scaffolds. While traditional guided tissue regeneration treatments have involved cell occlusive membranes, bone replacement graft scaffolds, and endogenous multipotent mesenchymal stem cells, the use of adjunctive materials to enhance healing outcomes has been studied and many such adjunctive factors are in common current clinical use. This report will focus on the current and emerging adjunctive growth factors and signaling molecules that can be used to optimize periodontal regeneration in periodontal intrabony defects, their mechanisms of action, the challenges associated with periodontal regeneration, and future avenues for research.

Calreticulin: a multifunctional protein with potential therapeutic applications for chronic wounds

Calreticulin is recognized as a multifunctional protein that serves an essential role in diverse biological processes that include wound healing, modification and folding of proteins, regulation of the secretory pathway, cell motility, cellular metabolism, protein synthesis, regulation of gene expression, cell cycle regulation and apoptosis. Although the role of calreticulin as an endoplasmic reticulum-chaperone protein has been well described, several studies have demonstrated calreticulin to be a highly versatile protein with an essential role during wound healing. These features make it an ideal molecule for treating a complex, multifactorial diseases that require fine tuning, such as chronic wounds. Indeed, topical application of recombinant calreticulin to wounds in multiple models of wound healing has demonstrated remarkable pro-healing effects. Among them include enhanced keratinocyte and fibroblast migration and proliferation, induction of extracellular matrix proteins, recruitment of macrophages along with increased granulation tissue formation, all of which are important functions in promoting wound healing that are deregulated in chronic wounds. Given the high degree of diverse functions and pro-healing effects, application of exogenous calreticulin warrants further investigation as a potential novel therapeutic option for chronic wound patients. Here, we review and highlight the significant effects of topical application of calreticulin on enhancing wound healing and its potential as a novel therapeutic option to shift chronic wounds into healing, acute-like wounds.

Effectiveness of Sodium Hyaluronate and ADCON-T/N for the Prevention of Adhesions in Hand Flexor Tendon Surgery: A Systematic Review and Meta-Analysis

PURPOSE

A common complication after digital flexor tendon repair in the hand is postoperative adhesions that can cause loss of motion and compromise hand function. The aim of this review of relevant published literature was to assess the effectiveness of locally administered sodium hyaluronate or ADCON-T/N for the prevention of adhesions after hand flexor tendon repair.

METHODS

A literature search was conducted in June 2020 in multiple databases for randomized controlled trials . Our primary outcome was measurement of active finger motion. Follow-up was defined as short-term (< 12 weeks), mid-term (12 weeks to 6 months) and long-term (> 6 months). Mean differences (MD) and standardized mean differences (SMD) of total active motion (TAM) of the interphalangeal joints (IPJs) and active motion of the IPJs separately were calculated where results were meta-analyzed.

RESULTS

Six randomized controlled trials were included. For ADCON-T/N, no benefits were detected for TAM of the IPJs (MD 1.71 [-21.54, 24.96]) or active motion of the IPJs separately (proximal: MD 4.77 [-4.47, 14]; distal: MD 1.17 [-10.33, 12.66]) in the short-/mid-term. The mid-term benefit in TAM of sodium hyaluronate over standard care (placebo/no treatment) did not reach statistical significance (SMD 0.31 [0, 0.63]); however, a subgroup comparison of repeated administration of sodium hyaluronate versus standard care was both statistically and clinically significant (SMD 0.55 [0.11, 0.98]).

CONCLUSIONS

Repeated administration of sodium hyaluronate at the tendon repair site may be effective in improving postoperative active finger motion after primary hand flexor tendon repair in the mid-term.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic II.

The corticospinal tract structure of collagen/silk fibroin scaffold implants using 3D printing promotes functional recovery after complete spinal cord transection in rats

No effective treatment has been established for nerve dysfunction caused by spinal cord injury (SCI). Orderly axonal growth at the site of spinal cord transection and creation of an appropriate biological microenvironment are important for functional recovery. To axially guiding axonal growth, designing a collagen/silk fibroin scaffold fabricated with 3D printing technology (3D-C/SF) emulated the corticospinal tract. The normal collagen/silk fibroin scaffold with freeze-drying technology (C/SF) or 3D-C/SF scaffold were implanted into rats with completely transected SCI to evaluate its effect on nerve repair during an 8-week observation period. Electrophysiological analysis and locomotor performance showed that the 3D-C/SF implants contributed to significant improvements in the neurogolical function of rats compared to C/SF group. By magnetic resonance imaging, 3D-C/SF implants promoted a striking degree of axonal regeneration and connection between the proximal and distal SCI sites. Compared with C/SF group, rats with 3D-C/SF scaffold exhibited fewer lesions and disordered structures in histological analysis and more GAP43-positive profiles at the lesion site. The above results indicated that the corticospinal tract structure of 3D printing collagen/silk fibroin scaffold improved axonal regeneration and promoted orderly connections within the neural network, which could provided a promising and innovative approach for tissue repair after SCI.

The efficacy of hyaluronic acid for carpal tunnel syndrome: a randomized double-blind clinical trial

OBJECTIVES

To investigate the effect of hyaluronic acid (HA) in patients diagnosed with mild or moderate carpal tunnel syndrome (CTS).

DESIGN

A prospective randomized, double-blinded control study with 6 months of follow-up.

SETTING

Rehabilitation outpatient clinic of one single medical center.

SUBJECTS

Thirty-five participants with mild or moderate CTS.

METHODS

Participants were enrolled and randomly assigned to HA or control groups. The HA group received one ultrasound-guided perineural injection of 2.5 ml HA while the control group received 2.5 ml normal saline injection through in-plane, long-axis approach to separate the median nerve from the flexor retinaculum via nerve hydrodissection. Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) scores were the primary outcome, while secondary outcomes included the numeric rating scale (NRS), electrophysiological domains, and the cross-sectional area of the median nerve. The assessment was conducted prior to injection and during the second week and 1-, 3-, and 6-months post-injection.

RESULTS

Thirty-two patients (17 wrists in HA group and 15 wrists in control group) completed the study. Compared with the control group, the HA group did not show significantly superior outcomes, except in BCTQ and NRS at the second week post-injection (all p < 0.0125).

CONCLUSIONS

A single ultrasound guided perineural HA injection may have short-term therapeutic efficacy for mild or moderate CTS; however, the 2-weeks superior efficacy was not beneficial for chronic neuropathy. Further studies with larger sample sizes are required to verify its therapeutic efficacy.

Peripheral nerve injury, scarring, and recovery

Peripheral nerve injuries (PNI) resulting from trauma can be severe and permanently debilitating. Despite the armamentarium of meticulous microsurgical repair techniques that includes direct repair, grafting of defects with autograft nerve, and grafting with cadaveric allografts, approximately one-third of all PNI demonstrate incomplete recovery with poor restoration of function. This may include total loss or incomplete recovery of motor and/or sensory function, chronic pain, muscle atrophy, and profound weakness, which can result in lifelong morbidity. Much of this impaired nerve healing can be attributed to perineural scarring and fibrosis at the site of injury and repair. To date, this challenging clinical problem has not been adequately addressed. In this review, we summarize the existing literature surrounding biological aspects of perineural fibrosis following PNI, detail current strategies to limit nerve scarring, present our own work developing reliable nerve injury models in animal studies, and discuss potential future studies which may ultimately lead to new therapeutic strategies.

Cell Surface Access Is Modulated by Tethered Bottlebrush Proteoglycans

The hyaluronan-rich pericellular matrix (PCM) plays physical and chemical roles in biological processes ranging from brain plasticity, to adhesion-dependent phenomena such as cell migration, to the onset of cancer. This study investigates how the spatial distribution of the large negatively charged bottlebrush proteoglycan, aggrecan, impacts PCM morphology and cell surface access. The highly localized pericellular milieu limits transport of nanoparticles in a size-dependent fashion and sequesters positively charged molecules on the highly sulfated side chains of aggrecan. Both rat chondrocyte and human mesenchymal stem cell PCMs possess many unused binding sites for aggrecan, showing a 2.5x increase in PCM thickness from ∼7 to ∼18 μm when provided exogenous aggrecan. Yet, full extension of the PCM occurs well below aggrecan saturation. Hence, cells equipped with hyaluronan-rich PCM can in principle manipulate surface accessibility or sequestration of molecules by tuning the bottlebrush proteoglycan content to alter PCM porosity and the number of electrostatic binding sites.

A novel in situ silver/hyaluronan bio-nanocomposite fabrics for wound and chronic ulcer dressing: In vitro and in vivo evaluations

In-situ formed hyaluronan/silver (HA/Ag) nanoparticles (NPs) were used to prepare composite fibers/fabrics for the first time. Different concentrations of silver nitrate (1, 2mg/100ml) were added at ambient temperature to sodium hyaluronate solution (40mg/ml), then the pH was increased to 8 by adding sodium hydroxide. The in-situ formed HA/Ag-NPs were used to prepare fibers/nonwoven fabrics by wet-dry-spinning technique (WDST). UV/vis spectroscopy, SEM, TEM, DLS, XPS, XRD and TGA were employed to characterize the structure and composition of the nanocomposite, surface morphology of fiber/fabrics, particle size of Ag-NPs, chemical interactions of Ag⁰ and HA functional groups, crystallinity and thermal stability of the wound dressing, respectively. The resultant HA/Ag-NPs1 and HA/Ag-NPs2 composite showed uniformly dispersed throughout HA fiber/fabrics (SEM), an excellent distribution of Ag-NPs with 25±2, nm size (TEM, DLS) and acceptable mechanical properties. The XRD analysis showed that the in-situ preparation of Ag-NPs increased the crystallinity of the resultant fabrics as well as the thermal stability. The antibacterial performance of medical HA/Ag-NPs fabrics was evaluated against gram negative bacteria E. coli K12, exhibiting significant bactericidal activity. The fibers did not show any cytotoxicity against human keratinocyte cell line (HaCaT). In-vivo animal tests indicated that the prepared wound dressing has strong healing efficacy (non-diabetics/diabetics rat model) compared to the plain HA fabrics and greatly accelerated the healing process. Based on our results, the new HA/Ag-NPs-2mg nonwoven wound dressing fabrics can be used in treating wounds and chronic ulcers as well as cell carrier in different biological research and tissue engineering.

Surgical treatment of the neglected achilles tendon rupture with Hyalonect

BACKGROUND

The purpose of this study was to report the management and outcomes of ten patients with chronic Achilles tendon rupture treated with a turndown gastrocnemius-soleus fascial flap wrapped with a surgical mesh (Hyalonect).

METHODS

Ten men with neglected Achilles tendon rupture were treated with a centrally based turndown gastrocnemius fascial flap wrapped with Hyalonect. Hyalonect is a knitted mesh composed of HYAFF, a benzyl ester of hyaluronic acid. The Achilles tendon ruptures were diagnosed more than 1 month after injury. The mean patient age was 41 years. All of the patients had weakness of active plantarflexion. The mean preoperative American Orthopaedic Foot and Ankle Society score was 64.8.

RESULTS

The functional outcome was excellent. The mean American Orthopaedic Foot and Ankle Society score was 97.8 at the latest follow-up. There were significant differences between the preoperative and postoperative scores. Ankle range of motion was similar in both ankles. Neither rerupture nor major complication, particularly of wound healing, was observed.

CONCLUSIONS

For patients with chronic Achilles tendon rupture with a rupture gap of at least 5 cm, surgical repair using a single turndown fascial flap covered with Hyalonect achieved excellent outcomes.

Hyaluronic acid on collagen membranes: An experimental study in rats

OBJECTIVE

The aim of this study was to evaluate the effect of hyaluronic acid (HA) in the structure and degradation patterns of BioGide^® and OsseoGuard™ collagen membranes. HA mediates inflammation and acts in cell migration, adhesion, and differentiation, benefitting tissue remodeling and vascularization. These are desirable effects in guided regeneration procedures, but it is still unknown whether HA alters the barrier properties of absorbable membranes.

DESIGN

Bone defects were created in the calvaria of rats, which were treated with HA gel 1% (HA group) or simply filled with blood clot (control group), and covered with BioGide^® or OsseoGuard™. The animals were euthanized after 1, 30, and 60days, and their calvarias were processed for histological analysis.

RESULTS

BioGide^®, in both HA and control groups, showed vascularization, intense cell colonization, bone formation, and tissue integration at 30 and 60days. In contrast, Osseoguard™ presented minimal cellular colonization, and inflammatory reaction associated to foreign body reaction in both time points and groups. The HA group of BioGide^® showed higher cell colonization (574.9±137.6) than the control group (269.1±70.83) at 60days (p<0.05). Despite this finding, the structure and degradation pattern were similar for BioGide^® and Osseoguard™ in the HA and control groups.

CONCLUSION

The results suggest that HA did not interfere with tissue integration and structural degradation of BioGide^® and Osseoguard™ membranes.

Effects of hyaluronic acid and tacrolimus on the prevention of perineural scar formation and on nerve regeneration after sciatic nerve repair in a rabbit model

PURPOSE

Scar formation after injured peripheral nerve repair is a significant clinical problem because it prevents nerve regeneration. The aim of this study was to investigate and compare the effects of hyaluronic acid (HA) and tacrolimus (FK506) on peripheral nerve regeneration in rabbits after the drugs were topically applied at the site of nerve repair.

METHODS

Thirty adult male European rabbits (Oryctolagus cuniculus), ranging in weight from 2.5 to 3 kg, were randomly assigned to three groups: the HA and FK506 groups comprised the experimental groups, while the saline group served as the control. At week 12, macroscopic and microscopic evaluations were performed and analyzed.

RESULTS

In general, the macroscopic evaluations (skin and muscle fascia closure and nerve adherence), microscopic evaluations (cellular components, scar tissue formation index, and histomorphological organization), and measurements of nerve diameter and gastrocnemius muscle wet weight demonstrated the positive effects of topical application of these pharmacological agents (HA and FK506); HA and FK506 prevented scar formation and enhanced nerve regeneration. No significant differences in the parameters described above were observed between the HA and FK506 groups (P > 0.05). However, significant differences were observed between both the HA and FK506 groups and the saline group (P < 0.05).

CONCLUSION

Based on our findings, topical application of HA and FK506 exhibits equally positive effects, preventing perineural scar formation and enhancing nerve regeneration after peripheral nerve repair.

Effect of hyaluronic acid on bone formation in the expanded interpremaxillary suture in rats

OBJECTIVE

To evaluate the histomorphometric effects of different molecular weight hyaluronic acid on bone formation in rats after expansion of the interpremaxillary suture.

MATERIAL AND METHODS

Twenty-four male Sprague Dawley rats were divided into three groups. Each group was subjected to expansion for 5 days and retention for 10 days. Group 1 received 50 μl of high molecular weight hyaluronic acid (HMWHA), group 2 received 50 μl of low molecular weight hyaluronic acid (LMWHA), and the control group received same amount of saline solution to the interpremaxillary suture. Ten days after injection, the rats were killed and their maxillas dissected. For the histomorphometric evaluation, blocks were serially sectioned at 10-μm intervals. Sections were stained with hematoxylin-eosin (HE) and evaluated with image analysis software. Bone area (μm²) (BA), bone perimeter of suture borders (μm) (BP), and ratio of osteoblast cells and capillary cells to BA and BP parameters were evaluated.

RESULTS

HMWHA showed a statistically higher ratio of osteoblast and capillary cell scores compared with the LMWHA and control groups (p < 0.05). There were no statistically significant differences in between LMWHA and control groups (p > 0.05).

CONCLUSIONS

Local injection of HMWHA in the interpremaxillary suture after rapid maxillary expansion stimulated new bone formation, which may shorten the retention period and may reduce the risk of relapse. LMWHA has no effect on bone formation in interpremaxillary suture.

Scintigraphic evaluation of the osteoblastic activity of rabbit tibial defects after HYAFF11 membrane application

Background

An unfavorable condition for bone healing is the presence of bone defects. Under such conditions, a material can play a role to cover fractured or defective bone. Technological advances now allow for the use of such material. Hyalonect^® (Fidia Advanced Biopolymers SLR, Italy), a novel membrane comprising knitted fibers of esterified hyaluronan (HYAFF11) can be used to cover fractured or grafted bone and can also serve as a scaffold to keep osteoprogenitor cells in place. The aim of this study was to compare osteoblastic activity by the use of scintigraphic methods in defective rabbit tibias during early-phase bone healing with or without a hyaluronan-based mesh.

Methods

Two groups (A and B) of New Zealand albino rabbits were used; each group included 10 animals. Operations on all rabbits were performed under general anesthesia. We also resected 10-mm bone segments from each animal’s tibial diaphysis. After resection, tibias with defects were fixed using Kirschner wires. In group A, no hyaluronan-based mesh was used. In group B, tibial segmental defects were enclosed with a hyaluronan-based mesh. The rabbits were followed up for 4 weeks postoperatively, after which bone scintigraphic studies were performed on each animal to detect and compare osteoblastic activity.

Results

The mean count in the fracture side of the hyaluronan-based mesh group was significantly higher compared to that of the group A (p = 0.019). However, there was no significant difference between group B and control rabbits with respect to the mean count on the intact bone side (p = 0.437). The bone defect (fracture)/intact bone mean count ratio was significantly higher in group B compared to group A (p = 0.008).

Conclusions

A hyaluronan-based mesh plays a role in promoting osteoblastic activity. Hyalonect^® is suitable for restoring tissue continuity whenever the periosteal membrane is structurally impaired or inadequate. Our results demonstrated that, during early-phase bone healing, osteoblastic activity was increased in bone defect sites when a hyaluronan-based mesh was also used. The most important aspect of this study concerns its scintigraphy-based design. This study is the first to use a scintigraphic method to demonstrate the effectiveness of hyaluronic acid-based material for bone healing.

Hyaluronic Acid Improves Bone Formation in Extraction Sockets With Chronic Pathology: A Pilot Study in Dogs

BACKGROUND

Previous studies on ridge preservation focusing on fresh extraction sockets using graft materials for ridge preservation procedures have reported a delay in the tissue modeling and remodeling phases. The objective of this study is to evaluate the effect of hyaluronic acid (HA) on healing of infected sockets.

METHODS

Six beagle dogs were used in this study. Both mandibular third premolars were hemisected, and the distal roots were extracted. Subsequently, periodontal and endodontic lesions were induced at the remaining mesial root. After communication of the periodontal lesion, an endodontic periapical lesion was observed at 4 months, and the mesial roots of both the right and left sides were extracted. HA was applied into the socket of the test group, and no treatment was administered to the other group (control group). Three months after extraction of the mesial roots, the dogs were sacrificed, and histologic evaluations were performed.

RESULTS

The sockets were filled by mineralized bone (47.80% ± 6.60%) and bone marrow (50.47% ± 6.38%) in the control group, whereas corresponding values were 63.29% ± 9.78% and 34.73% ± 8.97% for the test group, respectively. There was a statistically significant difference between the groups. Reversal lines and a copious lineup of osteoblasts were observed in the middle and apical parts of the sockets in the test group.

CONCLUSION

An infected socket shows delayed healing of the socket wound, and HA, because of its osteoinductive, bacteriostatic, and anti-inflammatory properties, may improve bone formation and accelerate wound healing in infected sockets.

Roles of Proteoglycans and Glycosaminoglycans in Wound Healing and Fibrosis

A wound is a type of injury that damages living tissues. In this review, we will be referring mainly to healing responses in the organs including skin and the lungs. Fibrosis is a process of dysregulated extracellular matrix (ECM) production that leads to a dense and functionally abnormal connective tissue compartment (dermis). In tissues such as the skin, the repair of the dermis after wounding requires not only the fibroblasts that produce the ECM molecules, but also the overlying epithelial layer (keratinocytes), the endothelial cells, and smooth muscle cells of the blood vessel and white blood cells such as neutrophils and macrophages, which together orchestrate the cytokine-mediated signaling and paracrine interactions that are required to regulate the proper extent and timing of the repair process. This review will focus on the importance of extracellular molecules in the microenvironment, primarily the proteoglycans and glycosaminoglycan hyaluronan, and their roles in wound healing. First, we will briefly summarize the physiological, cellular, and biochemical elements of wound healing, including the importance of cytokine cross-talk between cell types. Second, we will discuss the role of proteoglycans and hyaluronan in regulating these processes. Finally, approaches that utilize these concepts as potential therapies for fibrosis are discussed.

More than just a filler - the role of hyaluronan for skin homeostasis

In recent years, hyaluronan (HA) has become an increasingly attractive substance as a non-immunogenic filler and scaffolding material in cosmetic dermatology. Despite its wide use for skin augmentation and rejuvenation, relatively little is known about the molecular structures and interacting proteins of HA in normal and diseased skin. However, a comprehensive understanding of cutaneous HA homeostasis is required for future the development of HA-based applications for skin regeneration. This review provides an update on HA-based structures, expression, metabolism and its regulation, function and pharmacological targeting of HA in skin.

Differential Apoptosis in Mucosal and Dermal Wound Healing

Objectives: Dermal and mucosal healing are mechanistically similar. However, scarring and closure rates are dramatically improved in mucosal healing, possibly due to differences in apoptosis. Apoptosis, nature's preprogrammed form of cell death, occurs via two major pathways, extrinsic and intrinsic, which intersect at caspase3 (Casp3) cleavage and activation. The purpose of this experiment was to identify the predominant pathways of apoptosis in mucosal and dermal wound healing. Approach: Wounds (1 mm biopsy punch) were made in the dorsal skin (n=3) or tongue (n=3) of female Balb/C mice aged 6 weeks. Wounds were harvested at 6 h, 24 h, day 3 (D3), D5, D7, and D10. RNA was isolated and analyzed using real time reverse transcriptase-polymerase chain reaction. Expression levels for genes in the intrinsic and extrinsic apoptotic pathways were compared in dermal and mucosal wounds. Results: Compared to mucosal healing, dermal wounds exhibited significantly higher expression of Casp3 (at D5; p<0.05), Casp7 (at D5; p<0.05), Trp53 (at 24 h and D5; p<0.05), Tnfrsf1b (at 24 h; p<0.05), FasR (at 24 h, D5, and D7; p<0.05), and Casp8 (at 24 h; p<0.05) and significantly lower gene expression of Tradd (at 24 h; p<0.05). Innovation: Our observations indicate differential execution of apoptosis in oral wound healing compared to skin. Conclusion: Expression patterns of key regulators of apoptosis in wound healing indicate that apoptosis occurs predominantly through the intrinsic pathway in the healing mucosa, but predominantly through the extrinsic pathway in the healing skin. The identification of differences in the apoptotic pathways in skin and mucosal wounds may allow the development of therapeutics to improve skin healing.

Application of topical pharmacological agents at the site of peripheral nerve injury and methods used for evaluating the success of the regenerative process

Traumatic injuries of the peripheral nerves are very common. Surgical repair of the damaged nerve is often complicated by scar tissue formation around the damaged nerve itself. The main objective of this study is to present the recent data from animal experimental studies where pharmacological topical agents are used at the site of peripheral nerve repair. Some of the most commonly topical agents used are tacrolimus (FK506), hyaluronic acid and its derivatives, and melatonin, whereas methylprednisolone and vitamin B12 have been used less. These studies have shown that the abovementioned substances have neuroprotective and neuroregenerative properties though different mechanisms. The successes of the regenerative process of the nerve repair in experimental research, using topical agents, can be evaluated using variety of methods such as morphological, electrophysiologic, and functional evaluation. However, most authors agree that despite good microsurgical repair and topical application of these substances, full regeneration and functional recovery of the nerve injured are almost never achieved.

Micheliolide, a new sesquiterpene lactone that inhibits intestinal inflammation and colitis-associated cancer

Inflammatory bowel diseases (IBD) are chronic inflammatory conditions of the gastrointestinal (GI) tract associated with an increased risk of colorectal cancer (CRC). Current treatments for both IBD and colitis-associated CRC suffer from numerous side effects. Parthenolide (PTL) is a sesquiterpene lactone with anti-inflammatory activity, and previous studies have demonstrated that PTL is a potent inhibitor of the NF-κB pathway. Micheliolide (MCL), substantially more stable than PTL in vivo, was recently developed, and this study aimed to decipher its suitability as therapeutic tool for IBD and IBD-associated diseases. Similar to PTL, MCL inhibited NF-κB activation and subsequent pro-inflammatory pathways activation in vitro. Pro-drug forms of both compounds inhibited the DSS-induced colitis when administrated intraperitoneally or encapsulated in a polysaccharide gel designed to release drugs in the colon. Interestingly, MCL was found to attenuate carcinogenesis in AOM/DSS-induced CRC, thus providing new candidate for the treatment of inflammatory bowel disease and CRC.

Detection of subtle neurological alterations by the Catwalk XT gait analysis system

BACKGROUND

A new version of the CatWalk XT system was evaluated as a tool for detecting very subtle alteration in gait based on higher speed sample rate; the system could also demonstrate minor changes in neurological function. In this study, we evaluated the neurological outcome of sciatic nerve injury intervened by local injection of hyaluronic acid. Using the CatWalk XT system, we looked for differences between treated and untreated groups and differences within the same group as a function of time so as to assess the power of the Catwalk XT system for detecting subtle neurological change.

METHODS

Peripheral nerve injury was induced in 36 Sprague-Dawley rats by crushing the left sciatic nerve using a vessel clamp. The animals were randomized into one of two groups: Group I: crush injury as the control; Group II: crush injury and local application with hyaluronic acid. These animals were subjected to neurobehavior assessment, histomorphology evaluation, and electrophysiology study periodically. These data were retrieved for statistical analysis.

RESULTS

The density of neurofilament and S-100 over the distal end of crushed nerve showed significant differences either in inter-group comparison at various time points or intra-group comparison from 7 to 28 days. Neuronal structure architecture, axon counts, intensity of myelination, electrophysiology, and collagen deposition demonstrate significant differences between the two groups. There was significant difference of SFI and angle of ankle in inter- group analysis from 7 to 28 days, but there were no significant differences in SFI and angle of ankle at time points of 7 and 14 days. In the Cat Walk XT analysis, the intensity, print area, stance duration, and swing duration all showed detectable differences at 7, 14, 21, and 28 days, whereas there were no significant difference at 7 and 14 days with CatWalk 7 testing. In addition, there were no significant differences of step sequence or regularity index between the two versions.

CONCLUSION

Hyaluronic acid augmented nerve regeneration as early as 7 days after crush injury. This subtle neurological alteration could be detected through the CatWalk XT gait analysis but not the SFI, angle of ankle, or CatWalk 7 methods.

Polymeric films loaded with vitamin E and aloe vera for topical application in the treatment of burn wounds

Burns are serious traumas related to skin damage, causing extreme pain and possibly death. Natural drugs such as Aloe vera and vitamin E have been demonstrated to be beneficial in formulations for wound healing. The aim of this work is to develop and evaluate polymeric films containing Aloe vera and vitamin E to treat wounds caused by burns. Polymeric films containing different quantities of sodium alginate and polyvinyl alcohol (PVA) were characterized for their mechanical properties and drug release. The polymeric films, which were produced, were thin, flexible, resistant, and suitable for application on damaged skin, such as in burn wounds. Around 30% of vitamin E acetate was released from the polymeric films within 12 hours. The in vivo experiments with tape stripping indicated an effective accumulation in the stratum corneum when compared to a commercial cream containing the same quantity of vitamin E acetate. Vitamin E acetate was found in higher quantities in the deep layers of the stratum corneum when the film formulation was applied. The results obtained show that the bioadhesive films containing vitamin E acetate and Aloe vera could be an innovative therapeutic system for the treatment of burns.

Effects of a cross-linked hyaluronic acid based gel on the healing of open wounds in dogs

OBJECTIVE

To compare effects of a cross-linked hyaluronic acid (HA) based gel (CMHA-S) to a standard wound management protocol on the healing of acute, full-thickness wounds in dogs.

STUDY DESIGN

A prospective, controlled, experimental study.

ANIMALS

Purpose-bred, adult, female beagles (n = 10).

METHODS

Two 2 × 2 cm wounds were surgically created bilaterally on the trunk of each dog and each side randomized to treatment (CMHA-S) or control (CON) groups. Total and open wound areas were measured with digital image planimetry at 15 time points. From these data, percent contraction and percent epithelialization were calculated. Tissue biopsies were obtained at 6 time points and histologic features were scored.

RESULTS

Total wound area was significantly larger and percent contraction was significantly less in CMHA-S compared to CON wounds at all data points between days 9 and 18. At day 25, and for the remainder of the study, CMHA-S wounds were smaller and contracted more than CON wounds, reaching significance at day 32. Percent epithelialization was significantly less in CMHA-S compared to CON wounds at all data points after day 11. Histologically, fibroblastic cellular infiltration was significantly higher in CMHA-S wounds at day 21.

CONCLUSIONS

CMHA-S wounds healed more slowly than CON wounds. This HA-based gel is not indicated in acute, full-thickness skin wounds in dogs as administered in this study. However, treatment may be beneficial in the mid-to-late repair stage of healing, or if scar minimization is desired. Further studies to evaluate the effects of the CMHA-S gel on canine wounds are indicated.

Molecular fabrications of smart nanobiomaterials and applications in personalized medicine

Recent advances in nanotechnology adequately address many of the current challenges in biomedicine. However, to advance medicine we need personalized treatments which require the combination of nanotechnological progress with genetics, molecular biology, gene sequencing, and computational design. This paper reviews the literature of nanoscale biomaterials described to be totally biocompatible, non-toxic, non-immunogenic, and biodegradable and furthermore, have been used or have the potential to be used in personalized biomedical applications such as drug delivery, tissue regeneration, and diagnostics. The nanobiomaterial architecture is discussed as basis for fabrication of novel integrated systems involving cells, growth factors, proteins, cytokines, drug molecules, and other biomolecules with the purpose of creating a universal, all purpose nanobiomedical device for personalized therapies. Nanofabrication strategies toward the development of a platform for the implementation of nanotechnology in personalized medicine are also presented. In addition, there is a discussion on the challenges faced for designing versatile, smart nanobiomaterials and the requirements for choosing a material with tailor made specifications to address the needs of a specific patient.

A rationale for delivery of osteoinductive proteins

Highly pure, recombinant human osteoinductive proteins make it possible to consider programmable osteoneogenesis. Until recently, it was believed that a bioresorbable excipient or physiologic solution would suffice to transport osteoinductive agents from source to wound. After considering surgical requirements, particular bone wound circumstances, scarcity of collateral circulation, phenotype plasticity of mesenchymal progenitor cells, and the morphogens' pleiotrophic effects, it becomes clear that the issue of controlled, programmable osteoneogenesis is a more complicated proposition than can be addressed solely by application of osteoinductive protein. The essential characteristics of a manufactured bone graft substitute (BGS) device are dictated by demands placed on such a device by the surgeons who will employ them and the cells that will occupy them. This review outlines a design process for BGS devices that (1) begins by surveying BGS requirements gathered from the literature from 1991 to 1995, (2) briefly reviews recent in vitro studies of rhBMP-2 and OP- 1, (3) describes commonly encountered circumstances of recipient wound beds, (4) describes behaviors of mesenchymal cells involved in connective tissue repair and regeneration, and (5) concludes with a rationale for design of an osteoinductive bone graft substitute. Emerging from this process is a composite device consisting of a bioresorbable structural polymer, a filamentous velour of hyaluronan (HY), and an osteoinductive protein. The structural polymer, D,D-L,L-polylactic acid, fabricated in the architecture of cancellous bone, is capable of maintaining its structural and architectural properties after being thoroughly saturated with water. Within its interstices is located a filamentous velour of hyaluronan which, when fully hydrated, becomes a viscoelastic gel. It is anticipated that the osteoinductive protein will either be carried on the dried hyaluronic acid velour or in solution via the viscoelastic HY gel.

Bioengineered scaffolds for spinal cord repair

Spinal cord injury can lead to devastating and permanent loss of neurological function, affecting all levels below the site of trauma. Unfortunately, the injured adult mammalian spinal cord displays little regenerative capacity and little functional recovery in large part due to a tissue environment that is nonpermissive for regenerative axon growth. Artificial tissue repair scaffolds may provide a physical guide to allow regenerative axon growth that bridges the lesion cavity and restores functional neural connectivity. By integrating different strategies, including the use of various biomaterials and microstructures as well as incorporation of bioactive molecules and living cells, combined or synergistic effects for spinal cord repair through regenerative axon growth may be achieved. This article briefly reviews the development of bioengineered scaffolds for spinal cord repair, focusing on spinal cord injury and the subsequent cellular response, scaffold materials, fabrication techniques, and current therapeutic strategies. Key issues and challenges are also identified and discussed along with recommendations for future research.

‘Young’ Oral Fibroblasts Are Geno/Phenotypically Distinct

Wound healing within the oral mucosa results in minimal scar formation compared with wounds within the skin. We have recently demonstrated distinct differences in the aging profiles of cells (oral mucosal and patient-matched skin fibroblasts) isolated from these tissues. We hypothesized that the increased replicative potential of oral mucosal fibroblasts may confer upon them preferential wound-healing capacities. Passage-matched early cultures of oral mucosal fibroblasts and skin fibroblasts demonstrated distinct gene expression profiles, with several genes linked to wound healing/tissue repair. This was related to an increased ability of the ‘replicatively younger’ oral mucosal fibroblasts to repopulate a wound space and reorganize their surrounding extracellular matrix environment, key activities during the wound-healing process. We conclude that oral mucosal fibroblasts exhibit a preferential healing response in vivo, due to their ‘replicatively younger’ phenotype when compared with that of patient-matched skin fibroblasts.

Drug-loaded nanoparticles targeted to the colon with polysaccharide hydrogel reduce colitis in a mouse model

BACKGROUND & AIMS

One of the challenges to treating inflammatory bowel disease (IBD) is to target the site of inflammation. We engineered nanoparticles (NPs) to deliver an anti-inflammatory tripeptide Lys-Pro-Val (KPV) to the colon and assessed its therapeutic efficacy in a mouse model of colitis.

METHODS

NPs were synthesized by double-emulsion/solvent evaporation. KPV was loaded into the NPs during the first emulsion of the synthesis process. To target KPV to the colon, loaded NPs (NP-KPV) were encapsulated into a polysaccharide gel containing 2 polymers: alginate and chitosan. The effect of KPV-loaded NPs on inflammatory parameters was determined in vitro as well as in the dextran sodium sulfate-induced colitis mouse model.

RESULTS

NPs (400 nm) did not affect cell viability or barrier functions. A swelling degree study showed that alginate-chitosan hydrogel containing dextran-fluorescein isothiocyanate-labeled NPs collapsed in the colon. Once delivered, NPs quickly released KPV on or within the closed area of colonocytes. The inflammatory responses to lipopolysaccharide were reduced in Caco2-BBE (brush border enterocyte) cells exposed to NP-KPV compared with those exposed to NPs alone, in a dose-dependent fashion. Mice given dextran sodium sulfate (DSS) followed by NP-KPV were protected against inflammatory and histologic parameters, compared with mice given only DSS.

CONCLUSIONS

Nanoparticles are a versatile drug delivery system that can overcome physiologic barriers and target anti-inflammatory agents such as the peptide KPV to inflamed areas. By using NPs, KPV can be delivered at a concentration that is 12,000-fold lower than that of KPV in free solution, but with similar therapeutic efficacy. Administration of encapsulated drug-loaded NPs is a novel therapeutic approach for IBD.

Increased Oral Fibroblast Lifespan Is Telomerase-independent

Oral mucosal wound-healing is characterized by rapid re-epithelialization and remodeling, with minimal scar formation. This may be attributed to the distinct phenotypic characteristics of the resident fibroblasts. To test this hypothesis, we investigated patient-matched oral mucosal and skin fibroblasts. Compared with skin fibroblasts, oral mucosal fibroblasts had longer proliferative lifespans, underwent more population doublings, and experienced senescence later, which was directly related to longer telomere lengths within oral mucosal fibroblasts. The presence of these longer telomeres was independent of telomerase expression, since both oral oral mucosal fibroblasts and skin fibroblasts were negative for active telomerase, as assessed according to the Telomeric Repeat Amplification Protocol. This study has demonstrated that, compared with skin fibroblasts, oral mucosal fibroblasts are ‘younger’, with a more embryonic/fetal-like phenotype that may provide a notable advantage for their ability to repair wounds in a scarless fashion.

Calreticulin enhances porcine wound repair by diverse biological effects

Extracellular functions of the endoplasmic reticulum chaperone protein calreticulin (CRT) are emerging. Here we show novel roles for exogenous CRT in both cutaneous wound healing and diverse processes associated with repair. Compared with platelet-derived growth factor-BB-treated controls, topical application of CRT to porcine excisional wounds enhanced the rate of wound re-epithelialization. In both normal and steroid-impaired pigs, CRT increased granulation tissue formation. Immunohistochemical analyses of the wounds 5 and 10 days after injury revealed marked up-regulation of transforming growth factor-beta3 (a key regulator of wound healing), a threefold increase in macrophage influx, and an increase in the cellular proliferation of basal keratinocytes of the new epidermis and of cells of the neodermis. In vitro studies confirmed that CRT induced a greater than twofold increase in the cellular proliferation of primary human keratinocytes, fibroblasts, and microvascular endothelial cells (with 100 pg/ml, 100 ng/ml, and 1.0 pg/ml, respectively). Moreover, using a scratch plate assay, CRT maximally induced the cellular migration of keratinocytes and fibroblasts (with 10 pg/ml and 1 ng/ml, respectively). In addition, CRT induced concentration-dependent migration of keratinocytes, fibroblasts macrophages, and monocytes in chamber assays. These in vitro bioactivities provide mechanistic support for the positive biological effects of CRT observed on both the epidermis and dermis of wounds in vivo, underscoring a significant role for CRT in the repair of cutaneous wounds.

Wound healing modulators in a tracheoplasty canine model

Postsurgical tracheal stenosis results from fibrosis formation due to ischemia. There are healing modulators, hyaluronic acid (HA) and collagen polyvinylpyrrolidone (CPVP), which reduce collagen fibers formation. Thus we can hypothesize that the topical application of one of these modulators can diminish postsurgical tracheal scarring and stenosis. The aim of this work was to evaluate the macroscopic, microscopic, and biochemical changes of tracheal healing after the application of HA or CPVP in a canine tracheoplasty model. The study design was prospective experimental investigation in a canine model. Eighteen mongrel dogs underwent three cervical tracheal rings resection and end-to-end anastomosis. They were randomized into three groups according to treatment: group I (control group) (n = 6), topical application of saline solution on tracheal anastomosis; group II (n = 6), topical application of 15 microg HA on tracheal anastomosis; and group III (n = 6), topical application of 2.5 mg CPVP on tracheal anastomosis. They were evaluated clinical, radiological and tracheoscopically during 4 weeks. They were euthanized at the end of the study time. Macroscopic, microscopic, and biochemical changes of tracheal anastomosis healing were analyzed. Collagen formation was quantified by the Woessner method. All the animals survived the surgical procedure and study period. Macroscopic, radiologic, and endoscopic studies showed that animals in group I developed tracheal stenosis, inflammation, and firm fibrous tissue formation, and histological studies also showed severe inflammatory reaction and fibrosis formation. Groups II (HA) and III (CPVP) showed well-organized thin collagen fibers with minimal inflammatory response. Biochemical evaluation revealed a higher collagen concentration in group I animals (analysis of variance [ANOVA] p < .05 and Tukey p < .01). Thus, hyaluronic acid or collagen polyvinylpyrrolidone administered after tracheal anastomosis diminished the degree of stenosis and inflammatory reaction. Both modulators improved tracheal healing.

An enzyme capture assay for analysis of active hyaluronan synthases

We describe a sensitive assay for detection of active hyaluronan synthases (HASs) capable of synthesizing hyaluronan (HA) without use of radioactive uridine 5'-diphosphate sugar precursors. The HAS capture assay is based on the binding of a biotinylated HA binding protein (bHABP) to HA chains that are associated with HAS and the subsequent capture of bHABP-HA-HAS complexes with streptavidin-agarose. Specific HAS proteins (e.g., HAS1, not HAS2 or HAS3) captured in this pull-down approach are readily immunodetected by Western blot analysis using appropriate antibodies. The assay was used to detect active HAS proteins in cell membranes, purified recombinant Streptococcus equisimilis HAS (SeHAS), and in vitro translated human HAS1 or SeHAS. The HAS capture assay was also used to assess the fraction of HAS molecules that were active, which cannot be done using standard assays for synthase activity. Assay sensitivity for detection of purified SeHAS is <1 pmol.

A comparative study of the cytotoxicity of silver-based dressings in monolayer cell, tissue explant, and animal models

Over the past decade, a variety of advanced silver-based dressings have been developed. There are considerable variations in the structure, composition, and silver content of these new preparations. In the present study, we examined five commercially available silver-based dressings (Acticoat, Aquacel Ag, Contreet Foam, PolyMem Silver, Urgotul SSD). We assessed their cytotoxicity in a monolayer cell culture, a tissue explant culture model, and a mouse excisional wound model. The results showed that Acticoat, Aquacel Ag, and Contreet Foam, when pretreated with specific solutes, were likely to produce the most significant cytotoxic effects on both cultured keratinocytes and fibroblasts, while PolyMem Silver and Urgotul SSD demonstrated the least cytotoxicity. The cytotoxicity correlated with the silver released from the dressings as measured by silver concentration in the culture medium. In the tissue explant culture model, in which the epidermal cell proliferation was evaluated, all silver dressings resulted in a significant delay of reepithelialization. In the mouse excisional wound model, Acticoat and Contreet Foam indicated a strong inhibition of wound reepithelialization on the postwounding-day 7. These findings may, in part, explain the clinical observations of delayed wound healing or inhibition of wound epithelialization after the use of certain topical silver dressings. Caution should be exercised in using silver-based dressings in clean superficial wounds such as donor sites and superficial burns and also when cultured cells are being applied to wounds.

Use of a new hemicellulose dressing (Veloderm) for the treatment of split-thickness skin graft donor sites A within-patient controlled study

A multi-centre, open, within-patient controlled study was performed on 23 adult burnt patients to investigate the effectiveness, safety and tolerability of Veloderm in comparison with Algisite M and Jaloskin in split-thickness skin graft donor site care. The areas dressed with Veloderm completely healed within 10-13 days in a significant higher proportion than the other two dressings (47.6% for Veloderm versus 26.3% for Algisite M and 10% for Jaloskin, P<0.03), showing during the whole study less incidence of exudates and of peri-lesional erythema. The aesthetic outcome of the treated lesions after healing was significantly better for Veloderm (P=0.0016). Veloderm) and Jaloskin required very few renewals of the medication during the first week of treatment, while Algisite M needed several multiple re-dressings. Veloderm was judged better than the other two treatments as far as the acceptability (P<0.001), ease of use (P<0.001) and efficacy (P<0.00001). Both pain during application or at removal of dressings and local infections were negligible with all treatments. No scars were formed in any skin donor site. In conclusion Veloderm is a safe and effective dressing for the re-epithelialization of the skin graft donor sites: it showed higher activity than the other two compared dressings.

Overview of the role for calreticulin in the enhancement of wound healing through multiple biological effects

Calreticulin (CRT), an intracellular chaperone protein crucial for the proper folding and transport of proteins through the endoplasmic reticulum, has more recent acclaim as a critical regulator of extracellular functions, particularly in mediating cellular migration and as a requirement for phagocytosis of apoptotic cells. Consistent with these functions, we show that the topical application of CRT has profound effects on the process of wound healing by causing a dose-dependent increase in epithelial migration and granulation tissue formation in both murine and porcine normal and impaired animal models of skin injury. These effects of CRTare substantiated, in vitro, as we show that CRT strongly induces cell migration/wound closure of human keratinocytes and fibroblasts, using a wound/scratch plate assay, and stimulates cellular proliferation of human keratinocytes, fibroblasts, and vascular endothelial cells, providing mechanistic insight into how CRT functions in repair. Similarly, in both animal models, the histology of the wounds show marked proliferation of basal keratinocytes and dermal fibroblasts, dense cellularity of the dermis with notably increased numbers of macrophages and well-organized collagen fibril deposition. Thus, CRT profoundly affects the wound healing process by recruiting cells essential for repair into the wound, stimulating cell growth, and increasing extracellular matrix production.

The effect of hyaluronic acid-supplemented bone graft in bone healing: experimental study in rabbits

Hyaluronic acid (HA) is one of the essential components of extracellular matrix, which plays a predominant role in tissue morphogenesis, cell migration, differentiation, and adhesion. Bone allografts are frequently used to repair and reconstruct bone defects. In this study, two cavities of 3 mm diameter and depth have been created in the right tibia of 30 mature rabbits in accordance with the principles of general surgery. One of the cavities in the tibia is filled with HA and bone graft and the other is filled with only spongiosal bone graft, for the purpose of control. On the 20th, 30th, and 40th days, rabbits have been sacrificed in equal numbers and defective regions have been extracted. The Kruskal-Wallis test was applied to the data obtained in the result of histopathologic survey of specimens. In conclusion, the cavities that have been filled with HA and bone graft have shown higher scores than the control group during every period of the study.

Construction of Chitosan— Gelatin—Hyaluronic Acid Artificial Skin In Vitro

To further enhance the properties of chitosan (Cs)-gelatin (Gel) scaffolds for skin tissue engineering, hyaluronic acid (HA) is introduced to the Cs—gel complex. Porous scaffolds composed of Cs, Gel, and HA are prepared using the freeze-drying method. The scaffold has an interconnected pore structure with two different pore size layers. The water uptake ability, flexibility, and biocompatibility of the scaffold are greatly increased with the incorporation of HA. To construct an artificial skin in vitro, fibroblasts and keratinocytes are co-cultured in Cs—Gel—HA scaffolds at an air—liquid interface. After 2 weeks of co-culture, the epithelial layer becomes progressively stratiform, including cubic perpendicularly oriented cells and a superficial layer of flattened cells. Immunohistochemical analyses confirmed the presence of laminin and type IV collagen, typical molecules of the basement membrane. The results of this study suggest that it is possible to construct a functional artificial skin in vitro and the Cs—Gel—HA scaffold is a promising matrix for skin tissue engineering.

Effect of human amniotic fluid on bone healing

BACKGROUND

Bone healing continues to pose challenges for researchers and clinicians working in the field of plastic surgery. Complete bone regeneration cannot be obtained in critical size osseous defects without the application of osteogenic or osteoinductive bone material. In this study, we hypothesized that because extracellular matrix components are known to play a major role in the first steps of healing during bone or injury healing and because hyaluronic acid as chondroitin sulfate is recognized as an osteogenic compound without osteoinductive activity, human amniotic fluid, which contains high concentrations of hyaluronic acid, gyaluronic acid -stimulating activator, and other factors, might accelerate bone healing when applied subperiosteally to rabbit calvarial defects.

MATERIALS AND METHODS

We created 20 calvarial defects in 10 12-week-old New Zealand white rabbits who were divided into 2 groups. Group 1 defects were instilled with human amniotic fluid, whereas the group with contralateral defects, i.e., group 2, were given with same amount of normal saline solution. We then measured the density of the bone that formed over the defects using computed tomography at the third, fourth, fifth, and sixth weeks postoperatively. After this period, the defects were harvested for histopathologic evaluation.

RESULTS

The defects from group 1, which were treated with human amniotic fluid, showed significantly higher ossification than the group 2 defects, which were instilled with saline solution. Histological examination at 6 weeks postoperatively revealed that the defects treated with human amniotic fluid (group 1) had superior ossification compared with the control group defects (group 2).

CONCLUSION

Because of its positive effects on bone healing and also because of its ability to be stored in deep freeze if made cell-free, human amniotic fluid would appear to be a useful adjunct in the treatment of bone healing.

Functional adaptation through changes in regional biochemical characteristics during maturation of equine superficial digital flexor tendons

OBJECTIVE

To quantify and compare biochemical characteristics of the extracellular matrix (ECM) of specimens harvested from tensional and compressive regions of the superficial digital flexor tendon (SDFT) of horses in age classes that include neonates to mature horses.

SAMPLE POPULATION

Tendon specimens were collected on postmortem examination from 40 juvenile horses (0, 5, 12, and 36 months old) without macroscopically visible signs of tendonitis.

PROCEDURE

Central core specimens of the SDFT were obtained with a 4-mm-diameter biopsy punch from 2 loaded sites, the central part of the mid-metacarpal region and the central part of the mid-sesamoid region. Biochemical characteristics of the collagenous ECM content (ie, collagen, hydroxylysylpyridinoline crosslink, and pentosidine crosslink concentrations and percentage of degraded collagen) and noncollagenous ECM content (percentage of water and glycosaminoglycans, DNA, and hyaluronic acid concentrations) were measured.

RESULTS

The biochemical composition of equine SDFT was not homogeneous at birth with respect to DNA, glycosaminoglycans, and pentosidine concentrations. For most biochemical variables, the amounts present at birth were dissimilar to those found in mature horses. Fast and substantial changes in all components of the matrix occurred in the period of growth and development after birth.

CONCLUSIONS AND CLINICAL RELEVANCE

Unlike cartilage, tendon tissue is not biochemically blank (ie, homogeneous) at birth. However, a process of functional adaptation occurs during maturation that changes the composition of equine SDFT from birth to maturity. Understanding of the maturation process of the juvenile equine SDFT may be useful in developing exercise programs that minimize tendon injuries later in life that result from overuse.

Effect of amniotic fluid on peri-implant capsular formation

Although commonly used biomaterials are physically and chemically stable, nonimmunogenic, and nontoxic, implanted and blood-contact biomaterials trigger a wide variety of unwanted responses, including inflammation, thrombosis, infection, and fibrosis. Peri-implant fibrosis is the response most commonly seen by plastic surgeons. In this study, the authors hypothesized that as hyaluronic acid (HA) reduces scar formation by inhibiting the activity of mononuclear phagocytes and lymphocytes, human amniotic fluid (HAF), which contains high concentrations of HA, HA-stimulating activator (HASA), and other factors, might prevent the formation of fibrous capsules and capsule contracture when applied intraluminally. Two 1 x 1-cm silicone blocks were placed dorsally into separate surgically created pockets underneath the panniculus carnosus muscle, distant from the incisions, in each of the 10 rats in the study. At the time of implant insertion, 2 ml of HAF was instilled into the cranially located pockets in group 1, whereas 2 ml of saline solution was instilled into the caudally located pockets in group 2. After 6 months, intracapsular static and dynamic pressure measurements were made, and then all the peri-implant capsules were excised and fixed in 10% neutral buffered formaldehyde. The thicknesses of the capsules were measured in three different areas of each section, and a mean was calculated. Capsular firmness, according to the static and dynamic pressure readings, was significantly greater in the control group, which had saline solution introduced into the pocket, than in the treatment group, which had HAF used in the same manner. The mean total thickness of the capsules surrounding the implants was 876.7 microm in the control group, as comparied with 466.8 microm in the HAF-treated group. This difference was statistically significant (p < 0.001). Because of its ability to reduce capsular thickness and firmness and also because it can be stored in a freezer if it is prepared in a cell-free manner, HAF would appear to be a useful adjunct in the prevention of capsular contracture formation.

Effects of human amniotic fluid on cartilage regeneration from free perichondrial grafts in rabbits

After the chondrogenic potential of free grafts of perichondrium was shown in several experimental studies, perichondrium has been used to reconstruct cartilage tissue in various clinical situations. This study investigates the effects of human amniotic fluid on neochondrogenesis from free perichondrial grafts in a rabbit model. Since this fluid contains high concentrations of hyaluronic acid, hyaluronic acid-stimulating activator, growth factors, and extracellular matrix precursors during the second trimester, it may have a stimulating effect on neochondrogenesis. Perichondrial grafts, measuring 20 x 20 mm2 were obtained from the ears of 144 New Zealand young rabbits and were sutured over the paravertebral muscles. The rabbits were randomly divided into three groups with 48 rabbits per group. In group 1, 0.3 ml human amniotic fluid, and in group 2, 0.3 ml saline were injected underneath the perichondrial grafts. Group 3 formed the control group in which no treatment was given. Histologically, neochondrogenesis was evaluated in terms of cellular form and graft thickness at 2, 4, 6, and 8 weeks after surgery. In group 1, the mature cartilage was generated quickly and the cartilage plate in this group was significantly thick and extensive when compared with groups 2 and 3 at 8 weeks ( p<0.05 ANOVA). In conclusion, our study shows that human amniotic fluid enhances neochondrogenesis from free perichondrial grafts. The rich content of hyaluronic acid and growth factors possibly participate in this result.

Effects of hyaluronic acid on peripheral nerve scarring and regeneration in rats

The purpose of this experimental study was to investigate the effects of topical applications of hyaluronic acid on peripheral nerve scarring and regeneration in an adult rat model. After the right sciatic nerves of 48 rats were transected and immediately repaired, nerves were randomly divided into two groups. Nerves to which were applied hyaluronic acid comprised the experimental group, and nerves to which were applied saline comprised the control group. Perineural scarring was evaluated at 4 and 12 weeks macroscopically and histologically. Nerves treated with hyaluronic acid demonstrated significant reduction in perineural scar thickness (P < 0.05, Student's t-test). Histomorphologic nerve analysis, electrophysiologic studies, muscle mass evaluation, and serial functional walking-track analysis were performed for evaluation of peripheral nerve regeneration at 12 weeks. The results showed better conduction velocities, increased axon-fiber diameter, and faster functional recovery in hyaluronic acid-treated nerves (P < 0.05, Student's t-test). In conclusion, hyaluronic acid appears to be effective in preventing perineural scar formation, resulting in enhancement of peripheral nerve regeneration.

A blocking antibody to the hyaluronan receptor for endocytosis (HARE) inhibits hyaluronan clearance by perfused liver

Hyaluronan (HA) and chondroitin sulfate clearance from lymph and blood is mediated by the hyaluronan receptor for endocytosis (HARE). The purification and molecular cloning (Zhou, B., Weigel, J. A., Saxena, A., and Weigel, P. H. (2002) Mol. Biol. Cell 13, 2853-2868) of this cell surface receptor were finally achieved after we developed monoclonal antibodies (mAbs) against HARE. There are actually two independent isoreceptors for HA, which in rat are designated the 175-kDa HARE and 300-kDa HARE. Only one mAb (number 174) effectively and completely blocked the specific uptake of 125I-HA at 37 degrees C by rat liver sinusoidal endothelial cells. 125I-HA binding to both the 175-kDa and 300-kDa HARE proteins in a ligand blot assay was almost completely inhibited by <1 microg/ml mAb-174, whereas mouse IgG had little or no effect. MAb-174 also performed very well in Western analysis, indirect fluorescence microscopy, and a variety of immuno-procedures. Immunohistochemistry using mAb-174 localized HARE to the sinusoidal cells of rat liver, spleen, and lymph node. Western analysis using mAb-174 revealed that the sizes of both HARE glycoproteins were the same in these three tissues. 125I-HA was taken up and degraded by excised rat livers that were continuously perfused ex vivo with a recirculating medium. This HA clearance and metabolism by liver, which is a physiological function of HARE, was very effectively blocked by mAb-174 but not by mouse IgG. The results indicate that mAb-174 will be a useful tool to study the functions of HARE and the physiological significance of HA clearance.

Effects of human amniotic fluid on peripheral nerve scarring and regeneration in rats

OBJECT

Peripheral nerve repair surgery is still replete with challenges. Despite technical improvements in microsurgery, classic methods of nerve repair have failed to provide satisfactory results. The purpose of this study was to investigate the effects of amniotic fluid from humans on peripheral nerve scarring and regeneration in rats.

METHODS

Forty adult Sprague-Dawley rats were used in this study. After the right sciatic nerve in each rat was transected and repaired using an epineural suture procedure, the nerves were divided into two groups according to the solution applied around the repair site: experimental group, 0.3 ml human amniotic fluid (HAF); and control group, 0.3 ml saline. Macroscopic and histological evaluations of peripheral nerve scarring were performed 4 weeks postsurgery. Nerves treated with HAF demonstrated a significant reduction in the amount of scar tissue surrounding the repair site (p < 0.05). No evidence of a reaction against HAF was noted. Functional nerve regeneration was measured once every 2 weeks by using a sciatic function index until 12 weeks postsurgery. Functional recovery in nerves treated with amniotic fluid occurred significantly faster than that in nerves treated with saline (p < 0.05). Peripheral nerve regeneration was evaluated histomorphologically at 12 weeks postsurgery. Nerves treated with amniotic fluid showed significant improvement with respect to the indices of fiber maturation (p < 0.05).

CONCLUSIONS

Preliminary data show that HAF enhances peripheral nerve regeneration. The preventive effect of HAF on epineural scarring and the rich content of neurotrophic and neurite-promoting factors possibly contribute to this result.