Assessment of the behavior of myofibroblasts on scalpel and CO(2) laser wounds: an immunohistochemical study in rats

CO2 Laser for Esthetic Healing of Injuries and Surgical Wounds with Small Parenchymal Defects in Oral Soft Tissues

A number of studies have recently demonstrated the effectiveness of CO2 laser irradiation for the repair and regeneration of scar tissue from injuries or surgical wounds. However, such studies of the oral mucosa are highly limited. Previous studies using CO2 laser irradiation have indicated that two factors contribute to esthetic healing, namely, artificial scabs, which are a coagulated and carbonized blood layer formed on the wound surface, and photobiomodulation therapy (PBMT) for suppressing wound scarring and promoting wound healing. This review outlines basic research and clinical studies of esthetic healing with the use of a CO2 laser for both artificial scab formation by high-intensity laser therapy and PBMT in the treatment of injuries and surgical wounds with small parenchymal defects in oral soft tissues. The results showed that the wound surface was covered by an artificial scab, enabling the accumulation of blood and the perfusion necessary for tissue regeneration and repair. Subsequent PBMT also downregulated the expression of transformation growth factor-b1, which is involved in tissue scarring, and decreased the appearance of myofibroblasts. Taken together, artificial scabs and PBMT using CO2 lasers contribute to the suppression of scarring in the tissue repair process, leading to favorable esthetic and functional outcomes of wound healing.

Space-making effect for new bone formation by suppressing scar contraction of mucosal epithelium of rat tooth extraction wound using diode laser and CO2 laser treatment

Background/purpose

As an extraction wound closes, the mucosal epithelium of the tooth extraction wound impedes the space for new bone formation by invading into the extraction socket. Thus, the height of the alveolar crest decreases, causing significant depression of the alveolar mucosa. In this study, we created a rat tooth extraction model and examined the effects of laser irradiation by CO₂ and diode on the dynamics of myofibroblast expression through α-SMA, and TGF-β1.

Materials and methods

After tooth extraction of five-week-old male Wistar rats, they were divided into two laser treatment groups (CO₂ laser or diode laser was irradiated into tooth extraction socket) and non-laser treatment group (control group). Surrounding tissues, including the extraction socket, were removed at 3, 5, 7, and 21 days after tooth extraction and the expression of α-SMA and TGF-β1 was verified using immunohistological techniques (6 animals in each group and each period, 72 animals in total).

Results

α-SMA-positive cells and TGF-β1-positive areas were significantly lower in the two laser treatment groups than in the control group. Particularly, the diode group almost had no TGF-β1-positive areas on the 21st day when healing after tooth extraction was deemed to be completed.

Conclusion

Both CO₂ and diode laser irradiation of tooth extraction wounds decreases α-SMA-positive cells and TGF-β1-positive areas. Further, it causes a decrease in myofibroblast expression and suppresses the invasion of mucosal epithelium into the extraction socket. Therefore, laser irradiation may exert a space-making effect for new bone formation and also contribute to socket preservation.

Utility of High-Intensity Laser Therapy Combined with Photobiomodulation Therapy for Socket Preservation After Tooth Extraction

Objective: High-intensity laser therapy (HILT) combined with photobiomodulation therapy (PBMT) using a diode or CO₂ laser was administered after extraction of the left first molar in rats. Effects on socket preservation (preservation of the alveolar bone and healing time after extraction) were evaluated histopathologically.

Background: Irradiation using a diode or CO₂ laser has been shown to hasten wound healing, but the effects remain controversial.

Methods: Five-week-old male Wistar rats that underwent extraction of the left maxillary first molar were divided into three groups: diode laser irradiation (diode group), CO₂ laser irradiation (CO₂ group), and no laser irradiation (control group). HILT (27 J) was performed immediately after tooth extraction to enhance blood coagulation, followed by PBMT (0.7 J) 1 day later to enhance healing. Tissues, including the extraction socket, were removed en bloc 3, 5, 7, 10, and 21 days postextraction to determine the morphological characteristics of wound healing and the distribution of myofibroblasts involved in scar formation.

Results: In the diode and CO₂ groups, new bone formation and cancellous bone maturation were observed at an early stage of wound healing. The number of myofibroblasts was significantly lower in the laser treatment groups than the control (p < 0.001), and both treatment groups had a significantly higher alveolar crest height (p < 0.01), with almost no concavity in the mucosa of the extraction wound.

Conclusions: Combined HILT and PBMT following tooth extraction hastened wound healing and preserved alveolar crest height, suggesting a role in socket preservation.

The advantages of carbon dioxide laser applications in paediatric oral surgery. A prospective cohort study

The aim of this study is to evaluate and demonstrate the advantages of the carbon dioxide laser in paediatric oral surgery patients in terms of less post-operative complications, healing without scaring, functional benefits, positive patient perception and acceptance of the treatment. One hundred fit and healthy paediatric patients (aged 4-15 years) were recruited to undergo laser surgery for different soft tissue conditions. The outcome of these laser treatments was examined. The Wong-Baker Faces Pain Rating Scale was employed to evaluate the pain before, immediately after laser treatment in the clinic and 1 day after post-operatively at home. Post-operative complications and patients' perception and satisfaction were self-reported during a review telephone call the day after treatment. The patients were reviewed 2 weeks after surgery. Laser parameter was 1.62 W, measured by power meter, continuous wave mode with 50 % emission cycle. The beam spot size at the target tissue was 0.8 mm. The pain score pre-operative, during and immediately after laser treatment was rated 0. Whilst the pain score 1 day after surgery was rated between 0 and 2, the healing time was measured over 2 weeks. None of the patients reported post-operative complications after surgery. Patients' perception and acceptance were rated very good. Laser dentistry is a promising field in modern minimally invasive dentistry, which enables provision of better care for children and adolescents. In this cohort study, the use of the carbon dioxide laser therapy offers a desirable, acceptable and minimally invasive technique in the surgical management of soft tissues in paediatric oral surgery with minimal post-operative complications.

Influence of carbon dioxide laser irradiation on the healing process of extraction sockets

OBJECTIVE

To clarify the healing-promoting effects of carbon dioxide laser irradiation in high and low reactive-level laser therapies (HLLT and LLLT, respectively) on extraction sockets after tooth extraction.

MATERIAL AND METHODS

Forty-two 5-week-old male Wistar rats were divided into laser irradiation and non-irradiation (control) groups and compared. The laser-irradiation group underwent HLLT immediately after tooth extraction and then LLLT 1 day post-extraction. Tissue was excised 6 h and 3, 7, or 21 days after extraction and histopathologically investigated. The alveolar crest height was measured osteomorphometrically 21 days post-extraction, and granulation tissue in the extraction socket surface layer was immunohistologically investigated using anti-α-smooth muscle actin (anti-α-SMA) antibody 3 and 7 days post-extraction.

RESULTS

Many osteoclasts appeared and active bone resorption was noted in the irradiation group 3 days after extraction compared to the controls. On Day 7, new bone formation started around the extraction socket in the control group, but from the superficial to over the middle layer of the socket in the irradiation group. On Day 21, a concavity existed in the alveolar crest region in the controls, whereas this region was flat, with no concavity, in the irradiation group. On osteomorphometry, the alveolar crest height was significantly higher in the irradiation (0.7791 ± 0.0122) than the control (0.6516 ± 0.0181) group (P < 0.05). On immunostaining, many α-SMA-positive cells were noted in the control group, but very few in the irradiation group.

CONCLUSION

Laser-irradiated extraction wound healing showed characteristics different from those of the normal healing process, suggesting a favorable healing-promoting effect.

Effects of a polarized light source (400-2000 nm) on Hep.2 and L929 cell lines: a spectroscopic in vitro study

OBJECTIVE

The aim of this study was to evaluate the effects on Hep.2 cells originating from laryngeal carcinomas, and L929 cells originating from a fibroblast line, subjected to polarized light at a wavelength of 400-2000 nm.

BACKGROUND DATA

Recently there has been increased interest in the propagation of polarized light in randomly scattering media such as biological tissues, because of its potential applications in medicine.

MATERIALS AND METHODS

Irradiation was performed at two time points: T0 (24 h after cell culture) and T48 (48 h after the first irradiation). Cellular viability was assessed using an MTT assay at the following times: T0 (first irradiation), T6 (6 h after the first irradiation), T12 (12 h after the first irradiation), T24 (24 h after the first irradiation), T48 (48 h after the first irradiation), and T72 (72 h after the first irradiation). The results were analyzed using Graphpad Prism software.

RESULTS

The results showed that time influenced the cellular viability of L929 cells of both control (p = 0.0014) and illuminated cultures (p = 0.0035). Significant differences between control cells (p = 0.0001) and illuminated Hep.2 cells (p = 0.0001) were observed. There was a significant difference between the proliferation of the two types of cells illuminated compared to their controls: Hep.2 (p = 0.0001) and L929 (p = 0.0002).

CONCLUSION

The use of polarized light on Hep.2 and L929 cells resulted in photobiological effects that need further investigation, as this is the first study using this methodology.

Pentadecapeptide BPC 157, in clinical trials as a therapy for inflammatory bowel disease (PL14736), is effective in the healing of colocutaneous fistulas in rats: role of the nitric oxide-system

We focused on the therapeutic effect of the stable gastric pentadecapeptide BPC 157 and how its action is related to nitric oxide (NO) in persistent colocutaneous fistula in rats (at 5 cm from anus, colon defect of 5 mm, skin defect of 5 mm); this peptide has been shown to be safe in clinical trials for inflammatory bowel disease (PL14736) and safe for intestinal anstomosis therapy. BPC 157 (10 microg/kg, 10 ng/kg) was applied i) in drinking water until the animals were sacrificed at post-operative day 1, 3, 5, 7, 14, 21, and 28; or ii) once daily intraperitoneally (first application 30 min following surgery, last 24 h before sacrifice) alone or with N(G)-nitro-L-arginine methyl ester (L-NAME) (5 mg/kg), L-arginine (200 mg/kg), and their combinations. Sulphasalazine (50 mg/kg) and 6-alpha-methylprednisolone (1 mg/kg) were given once daily intraperitoneally. BPC 157 accelerated parenterally or perorally the healing of colonic and skin defect, leading to the suitable closure of the fistula, macro/microscopically, biomechanically, and functionally (larger water volume sustained without fistula leaking). L-NAME aggravated the healing failure of colocutaneous fistulas, skin, and colon wounds (L-NAME groups). L-Arginine was effective only with blunted NO generation (L-NAME + L-arginine groups) but not without (L-arginine groups). All of the BPC 157 beneficial effects remained unchanged with blunted NO-generation (L-NAME + BPC 157 groups) and with NO substrate (L-arginine + BPC 157 groups) as well as L-NAME and L-arginine co-administration (L-NAME + L-arginine + BPC 157 groups). Sulphasalazine was only moderately effective, and corticosteroid even had an aggravating effect.

Use of the CO(2) laser on orthodontic patients suffering from gingival hyperplasia

OBJECTIVE

The present study aimed to assess the effect of the use of the CO(2) laser on the treatment of gingival hyperplasia in orthodontic patients wearing fixed appliances.

BACKGROUND DATA

Gingival hyperplasia is a condition very frequent in patients undergoing fixed orthodontic treatment. Amongst the treatments available for this is the use of surgical lasers.

METHODS

Ten patients entered this study and signed an informed consent. Seventy-five anterior teeth with gingival hyperplasia were selected for laser surgery. Prior to surgery, the length of the crowns were measured using a digital caliper, and depth of the pocket was probed. The hyperplasic gingival was removed with a CO(2) laser under local anesthesia. Immediately after surgery, measurement of the length of the crowns and probing were carried out and were repeated.

RESULTS

The results were statistically analyzed and significant differences were detected regarding the length of the crown (p = 0.000) and depth of the gingival sulcus (p = 0.000).

CONCLUSION

It is concluded that the use of the CO(2) laser was effective in the treatment of gingival hyperplasia.

Skin responses to fractional photothermolysis

BACKGROUND AND OBJECTIVE

Fractional photothermolysis (FP) is a new concept using arrays of microscopic thermal damage patterns to stimulate a therapeutic response. We analyzed epidermal and dermal response to FP with the aim of correlating histological and clinical response.

STUDY DESIGN/MATERIALS AND METHODS

Twelve subjects received a single treatment with a prototype diode laser emitting at a wavelength of 1,500 nm, delivering 5 mJ per microscopic treatment zone (MTZ), and a density of 1,600 MTZs/cm(2) on the forearm. Biopsies were procured over a period of 3 months. The biopsies were analyzed by two blinded dermatopathologists using hematoxylin and eosin (Hematoxylin and Eosin Stain), Elastica von Gieson, nitro-blue-tetrazolium-chloride (NBTC) viability, and immunohistochemistry stains. Furthermore, the treatment sites were evaluated in vivo by confocal microscopy.

RESULTS AND DISCUSSION

Twenty-four hours after fractional photothermolysis, the continuity of the epidermal basal cell layer is restored. Complete epidermal regeneration is obtained 7 days after the treatment. Microscopic epidermal necrotic debris (MENDs) are seen as early as 1 day after FP. MENDs contain melanin pigment, and are shed from the epidermis within 7 days. Evidence of increased collagen III production is shown with immunohistochemistry (IHC) staining 7 days after FP. IHC for heat shock protein 70 (HSP 70) shows the expression of HSP 1 day after FP, and IHC for alpha smooth muscle actin shows the presence of myofibroblasts 7 days after FP. These findings are concordant with the induction of a wound healing response by FP. There is no evidence of residual dermal fibrosis 3 months after treatment.

CONCLUSION

A single treatment with fractional photothermolysis induces a wound healing response in the dermis. A mechanism for the precise removal of epidermal melanin is described, in which MENDs act as a melanin shuttle.

Polarized Light (400–2000 nm) and Non-ablative Laser (685 nm): A Description of the Wound Healing Process Using Immunohistochemical Analysis

OBJECTIVE

This study aimed to describe, through morphologic and cytochemical analysis, the healing process of wounds submitted (or not) to laser therapy (lambda685 nm) or polarized light (lambda400-2000 nm).

BACKGROUND DATA

There are many reports on different effects of several types of phototherapies on the treatment of distinct conditions, amongst them, on wound healing. Laser therapy and the use of polarized light are still controversial despite successive reports on their positive effects on several biological processes.

METHODS

Thirty male Wistar rats, approximately 4 months old, were used, and standardized excisional wounds were created on their dorsum. The wounds were irradiated in four equidistant points with laser light or illuminated with polarized light, both with doses of 20 or 40 J/cm2. Group 1 acted as untreated controls. Animals were irradiated every 48 h during 7 days, starting immediately after surgery, and were humanely killed on the 8th post-operative day. Specimens were taken and routinely processed and stained with H&E, and for descriptive analysis of myofibroblasts and collagen fibers, the specimens were imunnomarked by smooth muscle alpha-actin and picrosirius stain.

RESULTS

Control specimens showed the presence of ulceration, hyperemia, discrete edema, intense, and diffuse inflammation, collagen deposition was irregular, and myofibroblasts were seen parallel to the wound margins. Wounds treated by laser therapy with a dose of 20 J/cm2 showed mild hyperemia, inflammation varied from moderate to intense, the number of fibroblasts was large, and the distribution of collagen fibers was more regular. Increasing the dose to 40 J/cm2 evidenced exuberant neovascularization, severe hyperemia, moderate to severe inflammation, large collagen deposition, and fewer myofibroblasts. On subjects illuminated with polarized light with a dose of 20 J/cm2, mild to moderate hyperemia was detectable, and collagen matrix was expressive and unevenly distributed; a larger number of myofibroblasts was present and no re-epithelialization was seen. Increasing the dose resulted in mild to moderate hyperemia, no re-epithelialization was seen, edema was discrete, and inflammation was moderate.

CONCLUSION

The use of 685-nm laser light or polarized light with a dose of 20 J/cm2 resulted in increased collagen deposition and better organization on healing wounds, and the number of myofibroblast was increased when polarized light is used.