Myofibroblasts in Palatal Wound Healing: Prospects for the Reduction of Wound Contraction after Cleft Palate Repair

A Novel Rat Model for Muscle Regeneration and Fibrosis Studies in Surgical Lip Repair

OBJECTIVE

Lip muscle undergoes suboptimal regeneration after surgical repair, but the mechanism underlying this observation remains obscure. This study provided a rat model to investigate lip muscle regeneration after surgical intervention.

DESIGN

This work provided a detailed description of the rat orbicularis oris muscle anatomy, and a surgically injured model was established based on the muscle anatomy.

MAIN OUTCOME MEASURES

Morphological and histological features of the rat orbicularis oris muscle were characterized. The processes of myogenesis and fibrogenesis were examined between the untreated and surgically injured groups.

RESULTS

Rat orbicularis oris muscle is encapsulated by the vermilion and oral mucosa. Although it remains a thin layer of flat muscle with tight myocutaneous and myomucosal junctions, if accessed properly, the rat orbicularis oris muscle could be isolated as a cylindrical muscle bundle with considerable size, facilitating further surgical manipulations of the muscle fibers. Muscles in steady state and after surgical intervention demonstrated distinct molecular features in the myogenesis and fibrogenesis processes, which were quantifiable in tissue section analysis.

CONCLUSION

The orbicularis oris muscle dissection procedures and injury model provided in this work clarify the rat lip muscle anatomy. The injury model offered a platform to analyze the effects of surgical interventions commonly used in lip repair on orbicularis oris muscle regeneration.

Green Synthesis of Gold Nanoparticles with Curcumin or Açai in the Tissue Repair of Palatal Wounds

This study aimed to evaluate and compare the effects of treatment with gold nanoparticles (GNPs) reduced with Curcumin (Curcuma longa L.) or Açai (Euterpe oleracea) to a standard commercial treatment of the pharmacological type (Omcilon®) and an electrophysical agent (photobiomodulation) in the palatal wounds of rats. As for the in vitro assay, a cell viability test was performed to assess the toxicity of the synthesized nanoparticles. In vivo assay: 60 Wistar rats were divided into five groups (n = 12): I. Palatal Wound (PW); II. PW + Photobiomodulation (PBM); III. PW + Omcilon®; IV. PW + GNPs-Cur (0.025 mg/mL); V. PW + GNPs-Açai (0.025 mg/mL). Animals were first anesthetized, and circular lesions in the palatine mucosa were induced using a 4 mm-diameter punch. The first treatment session started 24 h after the injury and occurred daily for 5 days. The animals were euthanized, and the palatal mucosa tissue was removed for histological, biochemical, and molecular analysis. GNPs-Açai were able to significantly reduce pro-inflammatory cytokines and increase anti-inflammatory ones, reduce oxidant markers, and reduce inflammatory infiltrate while increasing the collagen area and contraction rate of the wound, along with an improved visual qualification. The present study demonstrated that the proposed therapies of GNPs synthesized greenly, thus associating their effects with those of plants, favor the tissue repair process in palatal wounds.

The Impact of Corticosteroid Administration at Different Time Points on Mucosal Wound Healing in Rats: An Experimental Pilot In Vivo Study

Simple Summary

The objective of this pilot study was to evaluate the impact of corticosteroid (CS) administration at different time points on palatal wound healing in rats. Thirty-six young male rats were divided into three groups. The test groups were treated by CS in the early (1–4 days) and late (5–9 days) stages after palatal wounding, while the control group was left for spontaneous healing. Our findings do not support the positive impact of CS administration on palatal wound healing. While microscopically, we found no difference between the CS and control groups, CS exposure was associated with a macroscopically larger final wound area, reflecting a possible harmful effect of CS.

Abstract

Background: Conflicting results were found regarding the effect of corticosteroid (CS) administration upon wound healing. The objective of this pilot study was to evaluate the impact of CS administration at different time points on palatal wound healing in rats. Methods: A 4.2 mm diameter punch created a secondary healing excisional palatal defect in thirty-six (36) Wistar-derived, two-month-old male rats weighing 250–270 g. We evaluated the effect of CS by comparing wound healing between three equal groups: 12 rats who were not exposed to CS and two additional groups in which 1 mg/kg dexamethasone (1 mg/kg) was administered daily, early (1–4 days) and late (5–9 days) after injury. The dynamics of the healing process were evaluated weekly in 4 sacrificed rats from each group for three weeks. The wound area was assessed both macroscopically and microscopically; the inflammation score was assessed microscopically. Results: The initial wound area in all the rats was 13.85 mm². At the end of the study, it decreased to 4.11 ± 0.88 mm², 7.32 ± 2.11 mm², and 8.87 ± 3.01 mm² in control, early, and late CS administration groups, respectively (p = 0.075). Inflammation scores showed a tendency to decrease in the third week in all groups, with no statistical differences. Conclusions: Our findings do not support the positive impact of CS administration on palatal wound healing. While microscopically, we found no difference between the CS and control groups, CS exposure was associated with a macroscopically larger final wound area, reflecting a possible harmful effect of CS.

Silk protein/polyvinylpyrrolidone nanofiber membranes loaded with puerarin accelerate wound healing in mice by reducing the inflammatory response

In modern clinical applications, wound healing remains a considerable challenge. Excessive inflammatory response is associated with delayed wound healing. In this study, we prepared composite nanofibrous membranes by mixing the Chinese herbal extract puerarin (PUE) with natural silk protein (SF) and synthetic polymer polyvinylpyrrolidone (PVP) using electrostatic spinning technique, and conducted a series of studies on the structural and biological properties of the fibrous membranes. The results showed that the loading of PUE increased the diameter, porosity and hydrophilicity of nanofibers, which were more favorable for cell adhesion and proliferation. ABTS radical scavenging assay also showed that the loading of PUE enhanced the antioxidant properties of the fibrous membranes. In addition, SF/PVP/PUE nanofibers are non-toxic and can be used as wound dressings. In vitro experiments showed that SF/PVP/PUE nanofibers could effectively alleviate lipopolysaccharide (LPS)-induced inflammation in Immortalized human keratinocytes (HaCaT) cells and down-regulate pro-inflammatory cytokine expression in cells. In vivo studies further showed that the SF/PVP/PUE nanofibers could effectively accelerate wound repair. The mechanism is that SF/PVP/PUE nanofibers can inhibit the activation and transduction of toll-like receptor 4/myeloid differentiation factor88/nuclear factor kappa B (TLR4/MyD88/NF-κB) and phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathways, thereby reducing the inflammatory response and achieving wound healing.

β-Elemene induces apoptosis by activating the P53 pathway in human hypertrophic scar fibroblasts

BACKGROUND

Hypertrophic scar (HS) is a condition characterized by excessive synthesis and deposition of collagen. There are many clinical methods to alleviate HS, but most of them are accompanied by many complications.

AIM OF THE STUDY

To investigate the effects of β-Elemene, extracted from the ginger family plant Wenyujin, on Human hypertrophic scar fibroblast.

MATERIALS AND METHODS

Cultured human hypertrophic scar fibroblast (hHSFs) and human normal fibroblasts (HF), and observed the effect of β-Elemene on apoptosis、extracellular matrix and endoplasmic reticulum stress by Western blot、RT-PCR and flow cytometry.

RESULTS

Based on our findings, it is clear that β-Elemene could inhibit the expression of α-SMA、collagen I and Fibronectin, reduced collagen deposition. Further studies had found that β-Elemene could increase the expression of endoplasmic reticulum stress (ERS)-related proteins CHOP and Calnexin in a dose-dependent manner, thereby promoting the aggregation of cleaved-caspase-3 and inducing hHSFs to undergo apoptosis. This process may depend on the regulation of P53.

CONCLUSIONS

The results of our study indicates that β-Elemene induced hHSFs to undergo apoptosis though ERS pathway in a P53-dependent manner, which means that our research provided a new strategy for the development of drugs for the treatment of HS. This article is protected by copyright. All rights reserved.

Osteopontin-derived synthetic peptide SVVYGLR upregulates functional regeneration of oral and maxillofacial soft-tissue injury

Wound healing in the oral and maxillofacial region is a complicated and interactive process. Severe mucosal or skeletal muscle injury by trauma or surgery induces worse healing conditions, including delayed wound closure and repair with excessive scar tissue. These complications lead to persistent functional impairment, such as digestive behavior or suppression of maxillofacial growth in infancy. Osteopontin (OPN), expressed in a variety of cells, is multifunctional and comprises a number of functional domains. Seven amino acids sequence, SVVYGLR (SV peptide), exposed by thrombin cleavage of OPN, has angiogenic activity and promotes fibroblast differentiation into myofibroblasts and increased expression of collagen type III. Additionally, synthetic SV peptide shows faster dermal and oral mucosal wound closure by facilitating cell motility and migratory activities in dermal- or mucosal-derived keratinocytes and fibroblasts. Moreover, cell motility and differentiation in myogenic cell populations are accelerated by SV peptide, which contributes to the facilitation of matured myofibers and scarless healing and favorable functional regeneration after skeletal muscle injury. SV peptide has high affinity with TGF-β, with potential involvement of the TGF-β/Smad signaling pathway. Clinical application of single-dose SV peptide could be a powerful alternative treatment option for excessive oral and maxillofacial wound care to prevent disadvantageous events.

A Living Cell Repository of the Cranio-/Orofacial Region to Advance Research and Promote Personalized Medicine

The prevalence of congenital anomalies in newborns is estimated to be as high as 6%, many of which involving the cranio-/orofacial region. Such malformations, including several syndromes, are usually identified prenatally, at birth, or rarely later in life. The lack of clinically relevant human cell models of these often very rare conditions, the societal pressure to avoid the use of animal models and the fact that the biological mechanisms between rodents and human are not necessarily identical, makes studying cranio-/orofacial anomalies challenging. To overcome these limitations, we are developing a living cell repository of healthy and diseased cells derived from the cranio-/orofacial region. Ultimately, we aim to make patient-derived cells, which retain the molecular and genetic characteristics of the original anomaly or disease in vitro, available for the scientific community. We report our efforts in establishing a human living cell bank derived from the cranio-/orofacial region of otherwise discarded tissue samples, detail our strategy, processes and quality checks. Such specific cell models have a great potential for discovery and translational research and might lead to a better understanding and management of craniofacial anomalies for the benefit of all affected individuals.

Multi-functional effects of a nitric oxide-conjugated copolymer for accelerating palatal wound healing

The damaged site of a palatal wound is difficult to repair and often remains unclosed due to failure of the healing process, which occurs in inadequate environments of the oral cavity. Nitric oxide (NO) has effective functions in repairing damaged tissues, but it has a limitation due to short lifetime and rapid diffusion. Here, we synthesize a donor to deliver exogenous NO gas and verify its therapeutic effect for the palatal wound healing, which is known to take longer for healing due to the poor environment of warm saliva containing millions of microbes. NO was incorporated into the synthetic polymer and the NO-donors were characterized based upon their ability to release NO. The NO donor not only reduced cytotoxicity but also increased migration and proliferation in gingival fibroblasts. Moreover, the angiogenic capacity was improved by NO-donor treatment. In the palatal wound model, the NO-treatment was involved in enhancing the biological responses associated with wound healing. This strategy suggests that treatment involving controlled NO release may have beneficial effects on palatal wound healing.

Synthetic peptide SVVYGLR upregulates cell motility and facilitates oral mucosal wound healing

Osteopontin-derived SVVYGLR (SV) 7-amino-acid sequence is a multifunctional and synthetic SV peptide implicated in angiogenesis, production of collagen III, and fibroblast differentiation into myofibroblasts. This study investigated the effect of the SV peptide on mucosal wound healing activity. Normal human-derived gingival fibroblasts (NHGF) and human oral mucosa keratinocytes (HOMK) were used for in vitro experiments. In addition, an oral punch wound was prepared at the buccal mucosa in male rats aged 11 weeks, and we evaluated the effect of local injection of SV peptide on wound healing. The synthetic SV peptide showed no influence on the proliferation and adhesion properties of NHGF and HOMK, but it enhanced the cell motility and migration activities. TGF-β1 receptor inhibitor, SB431542 or SB505124, substantially suppressed the SV peptide-induced migration activity, suggesting an involvement of TGF-β1 receptor activation. Furthermore, SV peptide accelerated the healing process of an in vivo oral wound model, compared with control groups. Further immunohistological staining of wound tissue revealed that an increase in capillary growth and the greater number of fibroblasts and myofibroblasts that migrated into the wound area might contribute to the facilitation of the healing process produced by the SV peptide. The SV peptide has beneficial effects on oral wound healing through enhancement of the earlier phase consisting of angiogenesis and remodeling with granulation tissue. The synthetic SV peptide can be a useful treatment option, particularly for intractable mucosal wounds caused by trauma or surgery for progressive lesions such as oral cancer.

New Progress of Adipose-derived Stem Cells in the Therapy of Hypertrophic Scars

Burns are a global public health issue of great concern. The formation of scars after burns and physical dysfunction of patients remain major challenges in the treatment of scars. Regenerative medicine based on cell therapy has become a hot topic in this century. Adipose-derived stem cells (ADSCs) play an important role in cellular therapy and have become a promising source of regenerative medicine and wound repair transplantation. However, the anti-scarring mechanism of ADSCs is still unclear yet. With the widespread application of ADSCs in medical, we firmly believe that it will bring great benefits to patients with hypertrophic scars.

Formulation and Evaluation of <i>Binahong </i>Leaves Extract Gel on Wound Healing of the Palatal Mucosa

Wound healing is a complex and integrated process that requires the collective roles of various cells and tissues of the palatal mucosa. During the proliferation phase, the sum of fibroblasts increases in response to damaged oral tissues. Thus, the number of fibroblast cells in the palatal mucosa is a substantial indicator of wound healing. Binahong leaves possess the potential to accelerate wound healing by stimulating fibroblast proliferation. This study aimed to formulate and evaluate the effect of Binahong leaves extract (BLE) gel on wound healing of the palatal mucosa by investigating the fibroblast cell count in Wistar rats. This experimental study was carried out in several stages which included the collection and processing of fresh Binahong leaves followed by extraction with 70% ethanol using maceration method. The extract was formulated to be a gel product with a concentration of 3%, 5%, and 7%. BLE gel was administered to Wistar rats which were deliberately injured at the palatal mucosa by excision. Wound healing was assessed using hematoxylin-eosin staining and the number of fibroblast cells was counted. The result of fibroblast proliferation was analyzed by One Way ANOVA followed by Bonferroni’s test with a significance level of 95%. There were significant differences in fibroblast cell proliferation between all test groups except between base gel and Aloclair® gel, base gel and BLE gel 7%, Aloclair® gel and BLE gel 7%, BLE gel 3% and BLE gel 5%. Application of BLE gel 3% promotes better wound healing of the palatal mucosa of Wistar rats.

A Novel Van der Woude Syndrome-Causing IRF6 Variant Is Subject to Incomplete Non-sense-Mediated mRNA Decay Affecting the Phenotype of Keratinocytes

Van der Woude syndrome (VWS) is a genetic syndrome that leads to typical phenotypic traits, including lower lip pits and cleft lip/palate (CLP). The majority of VWS-affected patients harbor a pathogenic variant in the gene encoding for the transcription factor interferon regulatory factor 6 (IRF6), a crucial regulator of orofacial development, epidermal differentiation and tissue repair. However, most of the underlying mechanisms leading from pathogenic IRF6 gene variants to phenotypes observed in VWS remain poorly understood and elusive. The availability of one VWS individual within our cohort of CLP patients allowed us to identify a novel VWS-causing IRF6 variant and to functionally characterize it. Using VWS patient-derived keratinocytes, we reveal that most of the mutated IRF6_VWS transcripts are subject to a non-sense-mediated mRNA decay mechanism, resulting in IRF6 haploinsufficiency. While moderate levels of IRF6_VWS remain detectable in the VWS keratinocytes, our data illustrate that the IRF6_VWS protein, which lacks part of its protein-binding domain and its whole C-terminus, is noticeably less stable than its wild-type counterpart. Still, it maintains transcription factor function. As we report and characterize a so far undescribed VWS-causing IRF6 variant, our results shed light on the physiological as well as pathological role of IRF6 in keratinocytes. This acquired knowledge is essential for a better understanding of the molecular mechanisms leading to VWS and CLP.

Use of Mechanical Stretching to Treat Skin Graft Contracture

After transplantation, skin grafts contract to different degrees, thus affecting the appearance and function of the skin graft sites. The exact mechanism of contracture after skin grafting remains unclear, and reliable treatment measures are lacking; therefore, new treatment methods must be identified. Many types of centripetal contraction forces affect skin graft operation, thus leading to centripetal contracture. Therefore, antagonizing the centripetal contraction of skin grafts may be a feasible method to intervene in skin contracture. Here, the authors propose the first reported mechanical stretching method to address contracture after skin grafting. A full-thickness skin graft model was established on the backs of SD rats. The skin in the experimental group was stretched unilaterally or bidirectionally with a self-made elastic stretching device, whereas the skin was non-stretched in the control group. The rats were sacrificed 2 weeks after stretching. The area, length, and width of the skin were measured. The grafts were cut and fixed with formalin. Routine paraffin sections were stained with hematoxylin-eosin, picric acid-Sirius red, Victoria blue, and anti-alpha-smooth muscle actin (SMA). Mechanical stretching made the graft lengthen in the direction of the stress and had an important influence on collagen deposition and alpha-SMA expression in the graft. This method warrants further in-depth study to provide a basis for clinical application.

Comparison of three surgical models of bone tissue defects in cleft palate in rabbits

OBJECTIVE

Cleft palate is one of the most common craniofacial birth defects in the maxillofacial region. There is an urgent need in tissue regeneration research to establish animal models that faithfully mimic human diseases. Here, we compared three surgical models of bone tissue defects in cleft palate in rabbits in order to screen for the biomaterials that induced optimal bone regeneration.

DESIGN

Rabbits were used to establish the models of hard palate cleft, alveolar cleft, and alveolar process cleft. Eight weeks following surgery, bone tissue self-healing capacity was estimated by macroscopic appearance and calculating the area of defective bone tissue. The dimensions of the upper jaw in left and right sides were measured at zero and eight weeks.

RESULTS

Bone defects in three types of cleft palate models were made at the positions of the hard palate, alveoli and alveolar process. After 8 weeks, when the hard palate was partially excised, it underwent self-healing. When the hard palate was completely excised, it underwent partial self-healing. However, in the models of alveolar cleft and alveolar process cleft, there was no significant self-healing in the bone tissues. The dimensions of the upper jaw in left and right sides were no significant differences in three types of cleft palate models.

CONCLUSIONS

Bone defects in the alveolar and alveolar process clefts exhibit a diminished capability for self-healing. This study may provide valuable information for the screening of materials that induce bone regeneration.

Regeneration of injured skin and peripheral nerves requires control of wound contraction, not scar formation

We review the mounting evidence that regeneration is induced in wounds in skin and peripheral nerves by a simple modification of the wound healing process. Here, the process of induced regeneration is compared to the other two well-known processes by which wounds close, i.e., contraction and scar formation. Direct evidence supports the hypothesis that the mechanical force of contraction (planar in skin wounds, circumferential in nerve wounds) is the driver guiding the orientation of assemblies of myofibroblasts (MFB) and collagen fibers during scar formation in untreated wounds. We conclude that scar formation depends critically on wound contraction and is, therefore, a healing process secondary to contraction. Wound contraction and regeneration did not coincide during healing in a number of experimental models of spontaneous (untreated) regeneration described in the literature. Furthermore, in other studies in which an efficient contraction-blocker, a collagen scaffold named dermis regeneration template (DRT), and variants of it, were grafted on skin wounds or peripheral nerve wounds, regeneration was systematically observed in the absence of contraction. We conclude that contraction and regeneration are mutually antagonistic processes. A dramatic change in the phenotype of MFB was observed when the contraction-blocking scaffold DRT was used to treat wounds in skin and peripheral nerves. The phenotype change was directly observed as drastic reduction in MFB density, dispersion of MFB assemblies and loss of alignment of the long MFB axes. These observations were explained by the evidence of a surface-biological interaction of MFB with the scaffold, specifically involving binding of MFB integrins α1 β1 and α2 β1 to ligands GFOGER and GLOGER naturally present on the surface of the collagen scaffold. In summary, we show that regeneration of wounded skin and peripheral nerves in the adult mammal can be induced simply by appropriate control of wound contraction, rather than of scar formation.

Myofibroblasts: Master of disguise

Myofibroblasts are the unique population of smooth muscle-like fibroblasts. These cells have a role in growth factors secretion, matrix deposition and degradation. Thereby, myofibroblast contributes in both human physiology and pathology. This review explains the myofibroblastic lesions, imperative role of myofibroblasts in organogenesis, repair, regeneration, inflammation and tumorigenesis.

Mechanical Stress Changes the Complex Interplay Between HO-1, Inflammation and Fibrosis, During Excisional Wound Repair

Mechanical stress following surgery or injury can promote pathological wound healing and fibrosis, and lead to functional loss and esthetic problems. Splinted excisional wounds can be used as a model for inducing mechanical stress. The cytoprotective enzyme heme oxygenase-1 (HO-1) is thought to orchestrate the defense against inflammatory and oxidative insults that drive fibrosis. Here, we investigated the activation of the HO-1 system in a splinted and non-splinted full-thickness excisional wound model using HO-1-luc transgenic mice. Effects of splinting on wound closure, HO-1 promoter activity, and markers of inflammation and fibrosis were assessed. After seven days, splinted wounds were more than three times larger than non-splinted wounds, demonstrating a delay in wound closure. HO-1 promoter activity rapidly decreased following removal of the (epi)dermis, but was induced in both splinted and non-splinted wounds during skin repair. Splinting induced more HO-1 gene expression in 7-day wounds; however, HO-1 protein expression remained lower in the epidermis, likely due to lower numbers of keratinocytes in the re-epithelialization tissue. Higher numbers of F4/80-positive macrophages, αSMA-positive myofibroblasts, and increased levels of the inflammatory genes IL-1β, TNF-α, and COX-2 were present in 7-day splinted wounds. Surprisingly, mRNA expression of newly formed collagen (type III) was lower in 7-day wounds after splinting, whereas, VEGF and MMP-9 were increased. In summary, these data demonstrate that splinting delays cutaneous wound closure and HO-1 protein induction. The pro-inflammatory environment following splinting may facilitate higher myofibroblast numbers and increase the risk of fibrosis and scar formation. Therefore, inducing HO-1 activity against mechanical stress-induced inflammation and fibrosis may be an interesting strategy to prevent negative effects of surgery on growth and function in patients with orofacial clefts or in patients with burns.

Disrupting the intrinsic growth potential of a suture contributes to midfacial hypoplasia

Children with unoperated cleft palates have nearly normal growth of their faces whereas patients who have had early surgical repair often exhibit midfacial hypoplasia. Surgical repair is responsible for the underlying bone growth arrest but the mechanisms responsible for these surgical sequelae are poorly understood. We simulated the effect of cleft palate repair by raising a mucoperiosteal flap in the murine palate. Three-dimensional micro-CT reconstructions of the palate along with histomorphometric measurements, finite element (FE) modeling, immunohistochemical analyses, and quantitative RT-PCR were employed to follow the skeletal healing process. Inflammatory bone resorption was observed during the first few days after denudation, which destroyed the midpalatal suture complex. FE modeling was used to predict and map the distribution of strains and their associated stresses in the area of denudation and the magnitude and location of hydrostatic and distortional strains corresponded to sites of skeletal tissue destruction. Once re-epithelialization was complete and wound contracture subsided, the midpalatal suture complex reformed. Despite this, growth at the midpalatal suture was reduced, which led to palatal constriction and a narrowing of the dental arch. Thus the simple act of raising a flap, here mimicked by denuding the mucoperiosteum, was sufficient to cause significant destruction to the midpalatal suture complex. Although the bone and cartilage growth plates were re-established, mediolateral skeletal growth was nonetheless compromised and the injured palate never reached its full growth potential. These data strongly suggest that disruption of suture complexes, which have intrinsic growth potential, should be avoided during surgical correction of congenital anomalies.

Accelerated wound closure in vitro by fibroblasts from a subgroup of cleft lip/palate patients: role of transforming growth factor-α

In a fraction of patients surgically treated for cleft lip/palate, excessive scarring disturbs maxillary growth and dento-alveolar development. Since certain genes are involved in craniofacial morphogenesis as well as tissue repair, a primary defect causing cleft lip/palate could lead to altered wound healing. We performed in vitro wound healing assays with primary lip fibroblasts from 16 cleft lip/palate patients. Nine foreskin fibroblast strains were included for comparison. Cells were grown to confluency and scratch wounds were applied; wound closure was monitored morphometrically over time. Wound closure rate showed highly significant differences between fibroblast strains. Statistically, fibroblast strains from the 25 individuals could be divided into three migratory groups, namely “fast”, “intermediate”, and “slow”. Most cleft lip/palate fibroblasts were distributed between the “fast” (5 strains) and the “intermediate” group (10 strains). These phenotypes were stable over different cell passages from the same individual. Expression of genes involved in cleft lip/palate and wound repair was determined by quantitative PCR. Transforming growth factor-α mRNA was significantly up-regulated in the “fast” group. 5 ng/ml transforming growth factor-α added to the culture medium increased the wound closure rate of cleft lip/palate strains from the “intermediate” migratory group to the level of the “fast”, but had no effect on the latter group. Conversely, antibody to transforming growth factor-α or a specific inhibitor of its receptor most effectively reduced the wound closure rate of “fast” cleft lip/palate strains. Thus, fibroblasts from a distinct subgroup of cleft lip/palate patients exhibit an increased migration rate into wounds in vitro, which is linked to higher transforming growth factor-α expression and attenuated by interfering with its signaling.

Molecular mechanisms underlying skeletal growth arrest by cutaneous scarring

In pediatric surgeries, cutaneous scarring is frequently accompanied by an arrest in skeletal growth. The molecular mechanisms responsible for this effect are not understood. Here, we investigated the relationship between scar contracture and osteogenesis. An excisional cutaneous wound was made on the tail of neonatal mice. Finite element (FE) modeling of the wound site was used to predict the distribution and magnitude of contractile forces within soft and hard tissues. Morphogenesis of the bony vertebrae was monitored by micro-CT analyses, and vertebral growth plates were interrogated throughout the healing period using assays for cell proliferation, death, differentiation, as well as matrix deposition and remodeling. Wound contracture was grossly evident on post-injury day 7 and accompanying it was a significant shortening in the tail. FE modeling indicated high compressive strains localized to the dorsal portions of the vertebral growth plates and intervertebral disks. These predicted strain distributions corresponded to sites of increased cell death, a cessation in cell proliferation, and a loss in mineralization within the growth plates and IVD. Although cutaneous contracture resolved and skeletal growth rates returned to normal, vertebrae under the cutaneous wound remained significantly shorter than controls. Thus, localized contractile forces generated by scarring led to spatial alterations in cell proliferation, death, and differentiation that inhibited bone growth in a location-dependent manner. Resolution of cutaneous scarring was not accompanied by compensatory bone growth, which left the bony elements permanently truncated. Therefore, targeting early scar reduction is critical to preserving pediatric bone growth after surgery.

MiR-21 expression in the tumor stroma of oral squamous cell carcinoma: an independent biomarker of disease free survival

Oral squamous cell carcinoma (OSCC) patients have a high mortality rate; thus, new clinical biomarkers and therapeutic options are needed. MicroRNAs (miRNAs) are short noncoding RNAs that regulate posttranscriptional gene expression and are commonly deregulated in OSCC and other cancers. MicroRNA-21 (miR-21) is the most consistently overexpressed miRNA in several types of cancer, and it might be a useful clinical biomarker and therapeutic target. To better understand the role of miR-21 in OSCC, paraffin-embedded tumor tissue samples from 86 patients with primary OSCC were analyzed by in situ hybridization. We found that miR-21 was primarily expressed in the tumor stroma and in some tumor-associated blood vessels with no expression in the adjacent normal epithelia or stroma. Using image analysis, we quantitatively estimated miR-21 expression levels specifically in the stroma of a cohort of OSCC samples. These miR-21 levels significantly correlated with disease free survival with the highest levels being located in the stroma. Stromal miR-21 expression was independently associated with a poorer prognosis, even after adjusting for clinical parameters (perineural invasion and N-stage) in a multivariate analysis. In summary, we have shown that miR-21 is located in the carcinoma cells, stroma and blood vessels of tumors, and its expression specifically in the stromal compartment has a negative prognostic value in OSCC.

Real-time quantification of proteins secreted by artificial connective tissue made from uni- or multidirectional collagen I scaffolds and oral mucosa fibroblasts

Previously, we found that oral autologous artificial connective tissue (AACT) had a different protein secretion profile to that of clot-embedded AACT. Other oral mucosa substitutes, having different cell types and scaffolds, had dissimilar secretion profiles of proteins (including that for AACT) that influence healing outcome; thus, to ascertain the profiles of factors secreted by artificial tissue and whether they are influenced by their microstructure might help in understanding their bioactivity. An important component of tissue microstructure is the fiber orientation of the scaffold used for manufacturing it. This work developed a surface plasmon resonance (SPR) methodology to quantify factors secreted by oral artificial connective tissue (ACT) in culture medium, and a method to manufacture unidirectional laminar collagen I scaffolds. The SPR methodology was used for assessing differences in the protein secretion profile of ACT made with collagen scaffolds having different fiber orientation (unidirectional vs multidirectional). Oral fibroblasts seeded onto unidirectional scaffolds increased the secretion of six factors involved in modulating healing compared to those seeded onto multidirectional scaffolds. Histological analysis of uni- and multidirectional ACT showed that cells differ in their alignment and morphology. This SPR-methodology led to nanoscale detection of paracrine factors and might be useful to study biomarkers of three-dimensional cell growth, cell differentiation, and wound-healing progression.

Down-regulation of Smad3 Accelerates Palatal Wound Repair

Smad3-deficient mice exhibit accelerated re-epithelialization and tissue remodeling during palatal wound repair. In addition, transforming growth factor beta 1 (TGF-β1) and other inflammatory factors are down-regulated compared with those in wild-type mice. The aim of this study was to examine whether targeting of Smad3 with small interfering RNA (siRNA) accelerates wound-healing and inhibits wound contraction in palatal mucoperiosteal wounds. An initial histological examination of wound closure in mouse palates treated with Smad3-targeted siRNA vs. a scrambled siRNA found that wound-healing was accelerated when levels of Smad3 were decreased. Furthermore, with real-time PCR, mRNA levels of Smad3, TGF-β1, monocyte chemotactic protein-1 ( MCP-1), and macrophage inflammatory protein-1α ( MIP-1α) were found to be significantly down-regulated in palatal tissue treated with Smad3–targeted siRNA vs. a control siRNA. Protein and mRNA levels of α-smooth-muscle actin (α-SMA), type I collagen, and fibronectin were also lower in palates treated with Smad3-targeted siRNA vs. control siRNA. Taken together, these results indicate that down-regulation of Smad3 expression by siRNA can accelerate wound-healing and may inhibit wound contraction. Therefore, siRNA-targeted inhibition of Smad3 may represent a valuable therapeutic tool for palatal mucoperiosteal wound-healing.

Carcinoma-associated fibroblasts, its implication in head and neck squamous cell carcinoma: a mini review

The communication between tumor stromal and parenchymal cells provides an insight to tumor progression. One of the main elements of the stroma, a major contributor to the extracellular environment of tumors, is carcinoma-associated fibroblasts. They can originate from either normal fibroblasts in the immediate vicinity of the tumor or from circulating bone marrow-derived mesenchymal stem cells. These myofibroblasts can arise locally from an endothelial-mesenchymal transformation at the invasive edge of the cancer and are physically associated with carcinoma cells, that is, in the development of high-grade malignancies and poor prognosis. These carcinoma-associated fibroblasts feed the epithelial tumor cells in a host-parasite relationship establishing its role in head and neck squamous cell carcinoma progression.

Two distinct processes of bone-like tissue formation by dental pulp cells after tooth transplantation

Dental pulp is involved in the formation of bone-like tissue in response to external stimuli. However, the origin of osteoblast-like cells constructing this tissue and the mechanism of their induction remain unknown. We therefore evaluated pulp mineralization induced by transplantation of a green fluorescent protein (GFP)-labeled tooth into a GFP-negative hypodermis of host rats. Five days after the transplantation, the upper pulp cavity became necrotic; however, cell-rich hard tissue was observed adjacent to dentin at the root apex. At 10 days, woven bone-like tissue was formed apart from the dentin in the upper pulp. After 20 days, these hard tissues expanded and became histologically similar to bone. GFP immunoreactivity was detected in the hard tissue-forming cells within the root apex as well as in the upper pulp. Furthermore, immunohistochemical observation of α-smooth muscle actin, a marker for undifferentiated cells, showed a positive reaction in cells surrounding this bone-like tissue within the upper pulp but not in those within the root apex. Immunoreactivities of Smad4, Runx2, and Osterix were detected in the hard tissue-forming cells within both areas. These results collectively suggest that the dental pulp contains various types of osteoblast progenitors and that these cells might thus induce bone-like tissue in severely injured pulp.

Oxidative damage in human gingival fibroblasts exposed to cigarette smoke

Cigarette smoke, a complex mixture of over 7000 chemicals, contains many components capable of eliciting oxidative stress, which may induce smoking-related disorders, including oral cavity diseases. In this study, we investigated the effects of whole (mainstream) cigarette smoke on human gingival fibroblasts (HGFs). Cells were exposed to various puffs (0.5-12) of whole cigarette smoke and oxidative stress was assessed by 2',7'-dichlorofluorescein fluorescence. The extent of protein carbonylation was determined by use of 2,4-dinitrophenylhydrazine with both immunocytochemical and Western immunoblotting assays. Cigarette smoke-induced protein carbonylation exhibited a puff-dependent increase. The main carbonylated proteins were identified by means of two-dimensional electrophoresis and MALDI-TOF mass spectrometry (redox proteomics). We demonstrated that exposure of HGFs to cigarette smoke decreased cellular protein thiols and rapidly depleted intracellular glutathione (GSH), with a minimal increase in the intracellular levels of glutathione disulfide and S-glutathionylated proteins, as well as total glutathione levels. Mass spectrometric analyses showed that total GSH consumption is due to the export by the cells of GSH-acrolein and GSH-crotonaldehyde adducts. GSH depletion could be a mechanism for cigarette smoke-induced cytotoxicity and could be correlated with the reduced reparative and regenerative activity of gingival and periodontal tissues previously reported in smokers.

Preferential recruitment of bone marrow-derived cells to rat palatal wounds but not to skin wounds

OBJECTIVE

To investigate the contribution of bone marrow-derived cells to oral mucosa wounds and skin wounds.

BACKGROUND

Bone marrow-derived cells are known to contribute to wound healing, and are able to differentiate in many different tissue-specific cell types. As wound healing in oral mucosa generally proceeds faster and with less scarring than in skin, we compared the bone marrow contribution in these two tissues.

DESIGN

Bone marrow cells from GFP-transgenic rats were transplanted to irradiated wild-type rats. After recovery, 4-mm wounds were made in the mucoperiosteum or the skin. Two weeks later, wound tissue with adjacent normal tissue was stained for GFP-positive cells, myofibroblasts (a-smooth muscle actin), activated fibroblasts (HSP47), and myeloid cells (CD68).

RESULTS

The fraction of GFP-positive cells in unwounded skin (19%) was larger than in unwounded mucoperiosteum (0.7%). Upon wounding, the fraction of GFP-positive cells in mucoperiosteum increased (8.1%), whilst it was unchanged in skin. About 7% of the myofibroblasts in both wounds were GFP-positive, 10% of the activated fibroblasts, and 25% of the myeloid cells.

CONCLUSIONS

The results indicate that bone marrow-derived cells are preferentially recruited to wounded oral mucosa but not to wounded skin. This might be related to the larger healing potential of oral mucosa.

Bone marrow-derived cells in palatal wound healing

OBJECTIVE

Myofibroblasts are responsible for contraction and scarring after cleft palate repair. This leads to growth disturbances in the upper jaw. We hypothesized that cells from the bone marrow are recruited to palatal wounds and differentiate into myofibroblasts.

METHODS

We transplanted bone marrow from green fluorescent protein (GFP)-transgenic rats into lethally irradiated wild-type rats. After recovery, experimental wounds were made in the palatal mucoperiosteum, and harvested 2 weeks later. GFP-expressing cells were identified using immunostaining. Myofibroblasts, activated fibroblasts, endothelial cells, and myeloid cells were quantified with specific markers.

RESULTS

After transplantation, 89 ± 8.9% of mononuclear cells in the blood expressed the GFP and about 50% of adherent cells in the bone marrow. Tissue obtained during initial wounding contained only minor numbers of GFP-positive cells, like adjacent control tissue. Following wound healing, 8.1 ± 5.1% of all cells in the wound area were positive, and 5.0 ± 4.0% of the myofibroblasts, which was significantly higher than in adjacent tissue. Similar percentages were found for activated fibroblasts and endothelial cells, but for myeloid cells it was considerably higher (22 ± 9%).

CONCLUSIONS

Bone marrow-derived cells contribute to palatal wound healing, but are not the main source of myofibroblasts. In small wounds, the local precursor cells are probably sufficient to replenish the defect.

Skeletal muscle fibrosis: the effect of stromal-derived factor-1&#x03B1;-loaded collagen scaffolds

AIM

To develop a model for muscle fibrosis based on full-thickness muscle defects, and to evaluate the effects of implanted stromal-derived factor (SDF)-1α-loaded collagen scaffolds.

METHODS

Full-thickness defects 2 mm in diameter were made in the musculus soleus of 48 rats and either left alone or filled with SDF-1α-loaded collagen scaffolds. At 3, 10, 28 and 56 days postsurgery, muscles were analyzed for collagen deposition, satellite cells, myofibroblasts and macrophages.

RESULTS

A significant amount of collagen-rich fibrotic tissue was formed, which persisted over time. Increased numbers of satellite cells were present around, but not within, the wounds. Satellite cells were further upregulated in regenerating tissue when SDF-1α-loaded collagen scaffolds were implanted. The scaffolds also attracted macrophages, but collagen deposition and myofibroblast numbers were not affected.

CONCLUSION

Persistent muscle fibrosis is induced by full-thickness defects 2 mm in diameter. SDF-1α-loaded collagen scaffolds accelerated muscle regeneration around the wounds, but did not reduce muscle fibrosis.

Collagen-based films containing liposome-loaded usnic acid as dressing for dermal burn healing

The aim of this study was assess the effect of collagen-based films containing usnic acid as a wound dressing for dermal burn healing. Second-degree burn wounds were performed in forty-five Wistar rats, assigned into nine groups: COL-animals treated with collagen-based films; PHO-animals treated with collagen films containing empty liposomes; UAL-animals treated with collagen-based films containing usnic acid incorporated into liposomes. After 7, 14, and 21 days the animals were euthanized. On 7th day there was a moderate infiltration of neutrophils, in UAL, distributed throughout the burn wounds, whereas in COL and PHO, the severity of the reaction was slighter and still limited to the margins of the burn wounds. On the 14th day, the inflammatory reaction was less intense in UAL, with remarkable plasma cells infiltration. On the 21st day, there was reduction of the inflammation, which was predominantly composed of plasma cells in all groups, particularly in UAL. The use of the usnic acid provided more rapid substitution of type-III for type-I collagen on the 14th day, and improved the collagenization density on the 21st day. It was concluded that the use of reconstituted bovine type-I collagen-based films containing usnic acid improved burn healing process in rats.

Effects of whole cigarette smoke on human gingival fibroblast adhesion, growth, and migration

The aim of this study was to investigate the effects of a single exposure to whole cigarette smoke on human gingival fibroblast behavior. Normal oral mucosa fibroblasts were exposed once to whole cigarette smoke for 5, 15, or 30 min, and then were used to analyze cell adhesion, β1-integrin expression, cell growth and viability, cell capacity to contract collagen gel, and cell migration following wound infliction. Our findings showed that when gingival fibroblasts were exposed once to whole cigarette smoke, this resulted in a significant inhibition of cell adhesion, a decrease in the number of β1-integrin-positive cells, increased LDH activity in the target cells, and reduced growth. The smoke-exposed fibroblasts were also not able to contract collagen gel matrix and migrate following insult. Overall results demonstrate that a single exposure to whole cigarette smoke produced significant morphological and functional deregulation in gingival fibroblasts. This may explain the higher predisposition of tobacco users to oral infections and diseases such as cancer.

Orthodontic mechanical tension effects on the myofibroblast expression of alpha-smooth muscle actin

OBJECTIVE

To detect myofibroblast formation on the tension side during orthodontic tooth movement in vivo and myofibroblast expression of alpha-smooth muscle actin (alpha-SMA) induced by tension both in vivo and in vitro.

MATERIALS AND METHODS

Fifty 6-week male rats were used in this in vivo study, and the right maxillary first molar was moved mesially, which served as the experimental group, and the left maxillary first molar served as the control. Rats were sacrificed at days 0, 3, 5, 7, and 14 after force loading. Myofibroblasts, identified with alpha-SMA, were examined through immunohistochemistry. For the in vitro study, human periodontal ligament (PDL) fibroblasts were obtained. Cyclic mechanical tension was applied to the fibroblasts for 0, 1, 3, 6, and 12 hours. Transmission electron microscopy was used to detect the ultrastructure of myofibroblasts. alpha-SMA mRNA gene expression was quantified by real-time quantitative PCR. The expression of alpha-SMA was detected by immunofluorescence and quantified by Western blotting.

RESULTS

In vivo, the myofibroblasts expressing alpha-SMA were identified both in the experimental group and in the control group. The expressions of alpha-SMA were increased in the tension areas of the experimental group over time, and reached the maximum in day 14. In vitro, fibronexus junctions and actin microfilaments in the cells could be found with transmission electron microscopy. Cyclic mechanical tension could significantly induce alpha-SMA expression at 12 hours (P < .01) than the controls.

CONCLUSIONS

Myofibroblasts existed in the PDL. The expressions of alpha-SMA in the myofibroblasts were significantly up regulated under tension both in vivo and in vitro.

Scarless healing of oral mucosa is characterized by faster resolution of inflammation and control of myofibroblast action compared to skin wounds in the red Duroc pig model

BACKGROUND

Scar formation following skin trauma can have devastating consequences causing physiological and psychosocial concerns. Currently, there are no accepted predictable treatments to prevent scarring which emphasizes a need for a better understanding of the wound healing and scar formation process.

OBJECTIVES

Previously it was shown that healing of small experimental wounds in the oral mucosa of red Duroc pigs results in significantly reduced scar formation as compared with equivalent full-thickness skin wounds. In the present study, scar formation was assessed in 17 times larger experimental wounds in both oral mucosa and skin of the red Duroc pigs.

METHODS

Equivalent experimental wounds were created in the oral mucosa and dorsal skin of red Duroc pigs, and scar formation, localization and abundance of key wound healing cells, transforming growth factor-beta (TGF-beta) and phosphorylated Smad3 (pSmad3) were assessed.

RESULTS

Oral mucosal wounds displayed significantly less clinical and histological scar formation than did the corresponding skin wounds. The number of macrophages, mast cells, TGF-beta and pSmad3 immunopositive cells was significantly reduced in the oral mucosal wounds as compared with skin wounds during the maturation stage of the healing process. Although the number of myofibroblasts was significantly elevated, the oral mucosal wounds showed significantly less contraction than did the skin wounds over time.

CONCLUSIONS

Earlier resolution of the inflammatory reaction and reduced wound contraction may promote scarless oral mucosal wound healing. In addition, scar formation likely depends not only on the number of myofibroblasts but also on the extracellular environment which regulates their function.

Recombinant human decorin inhibits TGF-beta1-induced contraction of collagen lattice by hypertrophic scar fibroblasts

Decorin was reported to bind transforming growth factor-beta (TGF-beta(1)) and neutralise some of its activity as a key regulator of wound contraction and hypertrophic scar formation. In this study, we investigated whether recombinant human decorin affected TGF-beta(1)-induced fibroblast contractile activity, by using fibroblast-populated collagen lattice with decorin added to the collagen gel. Hypertrophic scar fibroblasts showed greater basal contraction of collagen gels than normal fibroblasts, and the addition of TGF-beta(1) significantly enhanced this. Decorin inhibited both the basal and TGF-beta(1)-enhanced contraction of collagen gel by both normal and hypertrophic scar fibroblasts. Decorin also inhibited TGF-beta(1)-induced alpha-smooth muscle actin (alpha-SMA), plasminogen activator inhibitor-1 (PAI-1) protein and mRNA expressions in normal and hypertrophic scar fibroblasts. These results suggest that decorin may have therapeutic potential for excessive skin contraction as observed in hypertrophic scarring.

Matrix metalloproteinase inhibitors reduce collagen gel contraction and alpha-smooth muscle actin expression by periodontal ligament cells

BACKGROUND AND OBJECTIVE

Orthodontic tooth movement requires remodeling of the periodontal tissues. The matrix metalloproteinases (MMPs) degrade the extracellular matrix components of the periodontal ligament, while the tissue inhibitors of metalloproteinases (TIMPs) control their activity. Synthetic MMP inhibitors have been developed to inhibit MMP activity. In this study, periodontal ligament cells in contracting collagen gels served as a model for enhanced periodontal remodeling. The effect of MMP inhibitors on gel contraction and on MMP and TIMP expression was analyzed.

MATERIAL AND METHODS

Human periodontal ligament cells were cultured in three-dimensional collagen gels and incubated with the MMP inhibitors BB94, CMT-3, doxycycline and Ilomastat. Gel contraction was determined using consecutive photographs. The relative amounts of MMPs and TIMPs were analyzed using substrate zymography and mRNA expression using quantitative polyermase chain reaction.

RESULTS

All MMP inhibitors reduced MMP activity to about 20% of the control activity. They all reduced contraction, but CMT-3 and doxycycline had the strongest effect. These inhibitors also reduced MMP-2, MMP-3 and alpha-smooth muscle actin mRNA expression. The expression of MMP-1 mRNA seemed to be increased by CMT-3. No effects were found on the amounts of MMPs and TIMPs.

CONCLUSION

Synthetic MMP inhibitors strongly reduced gel contraction by periodontal ligament cells. This was primarily caused by an inhibitory effect on MMP activity, which reduces matrix remodeling. In addition, alpha-smooth muscle actin expression was reduced by CMT-3 and doxycycline, which limits the contractile activity of the fibroblasts.

Collagen scaffolds implanted in the palatal mucosa

Scar formation after repair of the cleft palate leads to growth impairment of the upper jaw and midface. The implantation of a suitable scaffold during surgery may reduce this adverse effect. However, little is known about tissue reactions to scaffolds implanted in the oral cavity. Our goal was to analyze the tissue reactions to cross-linked type I collagen scaffolds after submucoperiosteal implantation in the palate of rats. Collagen type I scaffolds were implanted in the palate of 25 male Wistar rats. Groups of 5 rats were killed consecutively after 1, 2, 4, 8, and 16 weeks and were processed for histologic and immunohistochemical analyses. After 1 and 2 weeks, 3 rats from the sham group were also killed. On hematoxylin and eosin-stained sections, the cell density and the number of giant cells were determined. Blood vessels, inflammation, and the presence of myofibroblasts were detected by immunohistochemistry. An influx of inflammatory cells started after 1 week but had completely subsided after 8 weeks. Myofibroblasts were observed within the scaffolds only in the first 2 weeks. Angiogenesis already started after 1 week and showed a peak after 4 weeks, slowly declining afterward. The scaffolds were gradually integrated within the host tissue and only elicited a mild and transient inflammatory response. The scaffolds were biocompatible and seemed to be promising for future applications in cleft palate surgery.

Immunohistochemical study of hard tissue formation in the rat pulp cavity after tooth replantation

While mineralized tissue is formed in the pulp cavity after tooth replantation or transplantation, little is known of this hard tissue formation. Therefore, we conducted histological and immunohistochemical evaluations of hard tissue formed in the pulp of rat maxillary molars after tooth replantation. At 5 days after replantation, degenerated odontoblasts were lining the pulp cavity. At 14 days, dentin- or bone-like tissue was present in the pulp cavity. Immunoreactivity for osteopontin (OPN) and bone sialoprotein (BSP) was strong in the bone-like tissue, but weak in the dentin-like tissue. Conversely, dentin sialoprotein (DSP) was localized in the dentin-like tissue, but not in the bone-like tissue. Cells positive for BMP4, Smad4, Runx2, and Osterix were found around the blood vessels of the root apex at 5 days. At 14 days, these cells were also localized around the bone-like tissue. Cells expressing alpha-smooth muscle actin (SMA) were seen around the newly formed bone-like tissue, whereas no such cells were found around the newly formed dentin-like tissue. In an experiment involving the transplantation of a green fluorescent protein (GFP)-transgenic rat tooth into a wild-type rat tooth socket, GFP-positive cells were detected on the surface of the bone-like tissue and over all dentin-like tissue. These results indicate that the original pulp cells had the ability to differentiate into osteoblast-like cells as well as into odontoblast-like cells.