Epithelium and connective tissue regeneration during palatal wound healing in desalivated rats--a comparative study

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.

Salivary gland function, development, and regeneration

Salivary glands produce and secrete saliva, which is essential for maintaining oral health and overall health. Understanding both the unique structure and physiological function of salivary glands, as well as how they are affected by disease and injury, will direct the development of therapy to repair and regenerate them. Significant recent advances, particularly in the OMICS field, increase our understanding of how salivary glands develop at the cellular, molecular, and genetic levels: the signaling pathways involved, the dynamics of progenitor cell lineages in development, homeostasis, and regeneration, and the role of the extracellular matrix microenvironment. These provide a template for cell and gene therapies as well as bioengineering approaches to repair or regenerate salivary function.

Age-Related Palatal Wound Healing: An Experimental In Vivo Study

We assessed age-related excisional palatal mucoperiosteal wound closure in rats. A 4.2 mm diameter punch was used to create a secondary healing defect in the palate of Wistar rats. Study group-21, 18-month-old vs. control 21, 2-month-old males. The 2-dimensional area, maximum length and width of the soft tissue defect served as clinical outcome parameters. The dynamics of the initial three healing weeks were assessed. Semi-quantitative histomorphometric analysis of inflammation and myofibroblasts served for the evaluation of the inflammatory and proliferative wound healing phases. Complete wound closure was faster in the old rats. A dimensional related wound closure was observed in the young rats versus a symmetrical wound closure in the old rats. Inflammatory response was significantly delayed and of lower intensity in the old rats. Myofibroblastic response, representing the proliferative stage, was delayed and of lower intensity in the old rats, albeit not statistically significant. Reduced initial tissue damage due to decreased and delayed inflammatory response in the old rats ultimately led to faster clinical wound healing compared to the young rats, despite a statistically non-significant lower proliferative response in the old rats.

Systematic review of natural and miscellaneous agents, for the management of oral mucositis in cancer patients and clinical practice guidelines - part 2: honey, herbal compounds, saliva stimulants, probiotics, and miscellaneous agents

OBJECTIVE

To update the clinical practice guidelines for the management of oral mucositis (OM) that were developed by the Multinational Association of Supportive Care in Cancer/International Society of Oral Oncology (MASCC/ISOO). This part focuses on honey, herbal compounds, saliva stimulants, probiotics, and miscellaneous agents.

METHODS

A systematic review was conducted by the Mucositis Study Group of MASCC/ISOO. The body of evidence for each intervention, in each clinical setting, was assigned an evidence level. The findings were added to the database used to develop the 2014 MASCC/ISOO clinical practice guidelines. Based on the evidence level, one of the following guidelines were determined: Recommendation, Suggestion, No Guideline Possible.

RESULTS

A total of 78 papers were identified within the scope of this section, of which 49 were included in this review and merged with nine publications that were reported in the previous guidelines update. A new Suggestion was made for honey (combined topical and systemic delivery) for the prevention of OM in head and neck cancer patients receiving radiotherapy with or without chemotherapy. A new Suggestion clarified that chewing gum is not effective for the prevention of OM in pediatric patients with hematological or solid cancer treated with chemotherapy. No guideline was possible for other interventions.

CONCLUSIONS

Numerous natural products and herbal remedies were studied for the management of OM. Of the agents reviewed in this systematic review, a guideline in favor was made for honey (combined topical and systemic), while a guideline against was made for chewing gum. Additional research is warranted to clarify the potential of other interventions.

Evaluating the Effects of a Topical Preparation with Dexpanthenol, Silbiol, Undecylenic Acid, and Lidocaine on Palatal Mucosa Wound Healing in a Rat Model

Background

Postoperative complications occur after periodontal plastic surgeries, but an ideal treatment to overcome them has not been found yet.

Aims

To evaluate the effects of topically applied Oral-norm gel on the healing of excisional wounds.

Study Design

Animal experiment.

Methods

Excisional wounds with a diameter of 3 mm were made in the center of the palatal mucosa of 63 Sprague Dawley rats. Seven animals were sacrificed at time 0. The remaining rats were divided into two groups: a test group in which the topical Oral-norm gel was applied three times a day and a control group in which nothing was applied. Seven animals in each group were sacrificed at 3, 7, 14, and 21 days. Mean wound surface area was measured photographically, while wound healing and width were evaluated microscopically.

Results

The mean wound surface area decreased significantly after 3 days in both groups (p<0.001). Between days 3 and 7, the mean wound surface area decreased from 6.62 (2.85) to 0.83 (1.62) mm² in the control group and 5.07 (0.88) to 1.42 (1.67) mm² in the test group. The wound width decreased significantly on day 7 in both groups (p<0.001), with no further changes by day 14. Both groups had a significant increase in inflammation and vascularization on day 3 (p<0.001), with a reduction thereafter. No significant differences in macroscopic and microscopic measurements were observed between the groups at any time point (p>0.05).

Conclusion

The Oral-norm gel has no positive healing effects in the palatal mucosa of rats.

Histatins, wound healing, and cell migration

Wounds in the oral mucosa heal faster and more efficiently than those in the skin, although the mechanisms underlying these differences are not completely clear. In the last 10 years, a group of salivary peptides, the histatins, has gained attention on behalf of their ability to improve several phases of the wound-healing process. In addition to their roles as anti-microbial agents and in enamel maintenance, histatins elicit other biological effects, namely by promoting the migration of different cell types contained in the oral mucosa and in non-oral tissues. Histatins, and specifically histatin-1, promote cell adhesion and migration in oral keratinocytes, gingival and dermal fibroblasts, non-oral epithelial cells, and endothelial cells. This is particularly relevant, as histatin-1 promotes the re-epithelialization phase and the angiogenic responses by increasing epithelial and endothelial cell migration. Although the molecular mechanisms associated with histatin-dependent cell migration remain poorly understood, recent studies have pointed to the control of signaling endosomes and the balance of small GTPases. This review aimed to update the literature on the effects of histatins in cell migration, with a focus on wound healing. We will also discuss the consequences that this increasing field will have in disease and therapy design.

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

The surgical closure of orofacial clefts is considered to impair maxillary growth and dento-alveolar development. Wound contraction and subsequent scar tissue formation, during healing of these surgical wounds, contribute largely to these growth disturbances. The potential to minimize wound contraction and subsequent scarring by clinical interventions depends on the surgeon’s knowledge of the events responsible for these phenomena. Fibroblasts initiate wound contraction, but proto-myofibroblasts and mature myofibroblasts are by far the most important cells in this process. Myofibroblasts are characterized by their cytoskeleton, which contains alpha-smooth-muscle actin. Additionally, their contractile apparatus contains bundles of actin microfilaments and associated contractile proteins, such as non-muscle myosin. This contractile apparatus is thought to be the major force-generating element involved in wound contraction. After closure of the wound, the myofibroblasts disappear by apoptosis, and a less cellular scar is formed. A reduction of contraction and scarring might be obtained by inhibition of myofibroblast differentiation, stimulation of their de-differentiation, stimulation of myofibroblast apoptosis, or impairment of myofibroblast function. In this review, we will discuss all of these possibilities, which ultimately may lead to a better outcome of cleft palate surgery.

Effects of topically applied agents on intra-oral wound healing in a rat model: a clinical and histomorphometric study

OBJECTIVES

Topically applied chlorhexidine and hyaluronan have many studies supporting their use to enhance oral wound healing. Allantoin is widely used topically to promote epithelial proliferation and wound healing, with very little scientific evidence to support such uses. This study investigated and compared the influence of these agents on the healing of intra-oral excisional wounds with large epithelial and connective tissue defects.

METHODS

Excisional wounds, 3 mm in diameter, were made at the centre of the palate of 125 Wistar male albino rats. Five animals constituted the baseline group at time 0. The remaining animals were divided into four experimental and one control groups, in which chlorhexidine digluconate gel 0.2% (Perio.Kin®), hyaluronan gel (Gengigel®), allantoin 0.5% in vehicle gel, vehicle gel alone and nothing were applied daily to the wounds. The wound areas were measured photographically and the epithelialization rates were determined histologically at 0, 3, 7, 14 and 21 days post-surgery.

RESULTS

The mean wound area and mean distance between the epithelial margins decreased significantly with time in all experimental and control groups (P < 0.05). A significant rate of wound area reduction was observed following the use of Perio.Kin® and Gengigel® at 7 and 14 days. Perio.Kin® showed a significant rate of wound epithelialization at 7 days. Allantoin did not positively or negatively affect wound healing.

CONCLUSIONS

None of the tested agents had a negative effect on the rate of wound healing when applied on an excisional wound with epithelial and connective tissue defect. Positive results were achieved with Perio.Kin® and Gengigel®.

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.

Effect of rat salivary glands extracts on the proliferation of cultured skin cells--a wound healing model

OBJECTIVE

Salivary gland secretions play an important role in promotion of wound healing. The healing of intra- or extra-oral wounds is delayed in desalivated rats. However, the specific role of each salivary gland in promoting wound healing is unknown. This study was aimed to investigate the effect of crude extracts of rat salivary glands on a simplified in vitro wound healing model.

DESIGN/METHODS

Cultured human keratinocytes (HaCat) and murine fibroblasts (3T3) were subjected to 48 h serum starvation, and were later activated by extracts of rat salivary glands, 1-10 mug protein/ml of each gland. The resultant cellular metabolic activity of the activated cells was determined 24 h later, measuring reduction of XTT by mitochondrial enzymes, and calculated relatively to positive controls [optimal supplementation of 10% fetal calf serum (FCS)], and negative controls (starved non-supplemented cells).

RESULTS

The relative stimulatory effect of parotid (P) extract on the cells was significantly lower than either submandibular (SM) or sublingual (SL) extracts. Under the assumption that physiologically, the cells are exposed to the combined effect of saliva secreted from all the glands, different combinations of the extracts were presented to the cells. The relative stimulation was maximal following treatment with the three glands extracts (P + SM + SL) and exceeded the effect of 10% FCS.

CONCLUSION

The results suggest that each salivary gland has a specific effect on wound healing and the combination of the three extracts has an additive effect but no the sum of all individual glands. This model might be useful to study the wound healing effect of salivary glands.