High magnification in situ viewing of wound healing in oral mucosa

Involvement of neural crest and paraxial mesoderm in oral mucosal development and healing

Tissue engineering therapies using adult stem cells derived from neural crest have sought accessible tissue sources of these cells because of their potential pluripotency. In this study, the gingiva and oral mucosa and their associated stem cells were investigated. Biopsies of these tissues produce neither scarring nor functional problems and are relatively painless, and fresh tissue can be obtained readily during different chairside dental procedures. However, the embryonic origin of these cells needs to be clarified, as does their evolution from the perinatal period to adulthood. In this study, the embryonic origin of gingival fibroblasts were determined, including gingival stem cells. To do this, transgenic mouse models were used to track neural crest derivatives as well as cells derived from paraxial mesoderm, spanning from embryogenesis to adulthood. These cells were compared with ones derived from abdominal dermis and facial dermis. Our results showed that gingival fibroblasts are derived from neural crest, and that paraxial mesoderm is involved in the vasculogenesis of oral tissues during development. Our in vitro studies revealed that the neuroectodermal origin of gingival fibroblasts (or gingival stem cells) endows them with multipotential properties as well as a specific migratory and contractile phenotype which may participate to the scar-free properties of the oral mucosa. Together, these results illustrate the high regenerative potential of neural crest-derived stem cells of the oral mucosa, including the gingiva, and strongly support their use in cell therapy to regenerate tissues with impaired healing.

Effectiveness of laser adjunctive therapy for surgical treatment of gingival recession with flap graft techniques: a systematic review and meta-analysis

Various flap graft techniques in the treatment of gingival recession have already been reported in the literatures for root coverage. Laser therapy has effects of ablative, hemostatic, and decontamination. Therefore, we performed a meta-analysis of randomized controlled trials (RCTs) to compare the efficacy of flap surgery combined with laser with surgery alone for treating gingival recession. The studies were searched from PubMed, Embase, Web of science, and the Cochrane Central Register of Controlled Trials by two reviewers up to August 2017. The quality of RCTs was assessed by Cochrane Handbook. Data were extracted from studies and analyzed by Review Manager 5.3. 95% confidence interval (CI) and risk ratio (RR) were calculated for dichotomous data. Seven RCTs with 173 patients and 296 teeth were included in the meta-analysis. We found no statistically significant differences between two groups in GRD (gingival recession depth) (P = 0.21), GRW (gingival recession width) (P = 0.92), RES (root esthetic score) (P = 0.21), and CRC (complete root coverage) (P = 0.09). Statistically significant differences were found between two groups in the WKT (width of keratinized tissue) (P < 0.0001) and 1-year follow-up of PD (probing depth) (P = 0.03) and CAL (clinical attachment level) (P < 0.00001). The meta-analysis found that surgery with laser therapy provided clinical advantages in terms of WKT and 1-year follow-up of PD and CAL. However, flap graft associated with laser did not offer additional benefit to root coverage and esthetics in treating gingival recession. More long-term studies are required to assess these parameters.

Flap Designs for Implant-Related Surgical Procedures: A Review

PURPOSE

The objective of this study was to compare the reliability and results of 2 flap techniques, flapless (FL) and full-thickness (FT) flap, during implant placement.

MATERIALS AND METHODS

Online and hand searches of the literature published were conducted to identify studies examining different flap techniques on clinical and histological outcomes. The search terms used, alone or in combination, were "flapless," "full-thickness flap," "crestal bone resorption," "gingival blood circulation," and "biological width."

RESULTS

Fifty studies were selected for comparison and to address the points highlighted in this study. Fourteen articles and 1 book were not directly related to flap design but were included for understanding the process of soft tissue healing. Five articles discussed the principles of oral surgery and flap design.

CONCLUSION

This review revealed that the FL technique might be more appropriate in immediate implant loading cases. This specific technique results in shallower biological width, reduced inflammation, less morbidity with guided implant placement, and better esthetics in comparison with the FT technique. The implant survival rates are not significantly different between the 2 flap techniques. With respect to crestal bone resorption in FL and FT, it is inconclusive, depending on the study type (human or animal).

iPS Cells-The Triumphs and Tribulations

The year 2006 will be remembered monumentally in science, particularly in the stem cell biology field, for the first instance of generation of induced pluripotent stem cells (iPSCs) from mouse embryonic/adult fibroblasts being reported by Takahashi and Yamanaka. A year later, human iPSCs (hiPSCs) were generated from adult human skin fibroblasts by using quartet of genes, Oct4, Sox2, Klf4, and c-Myc. This revolutionary technology won Yamanaka Nobel Prize in Physiology and Medicine in 2012. Like human embryonic stem cells (hESCs), iPSCs are pluripotent and have the capability for self-renewal. Moreover, complications of immune rejection for therapeutic applications would be greatly eliminated by generating iPSCs from individual patients. This has enabled their use for drug screening/discovery and disease modelling in vitro; and for immunotherapy and regenerative cellular therapies in vivo, paving paths for new therapeutics. Although this breakthrough technology has a huge potential, generation of these unusual cells is still slow, ineffectual, fraught with pitfalls, and unsafe for human use. In this review, I describe how iPSCs are being triumphantly used to lay foundation for a fully functional discipline of regenerative dentistry and medicine, alongside discussing the challenges of translating therapies into clinics. I also discuss their future implications in regenerative dentistry field.

Intrinsic differences between oral and skin keratinocytes

Keratinocytes cover both the skin and some oral mucosa, but the morphology of each tissue and the behavior of the keratinocytes from these two sites are different. One significant dissimilarity between the two sites is the response to injury. Oral mucosal wounds heal faster and with less inflammation than equivalent cutaneous wounds. We hypothesized that oral and skin keratinocytes might have intrinsic differences at baseline as well as in the response to injury, and that such differences would be reflected in gene expression profiles.

Effect of transforming growth factor Beta 1 on wound healing in induced diabetic rats

OBJECTIVE

Delayed wound healing is one of the complications of diabetes mellitus, exhibited by profound inflammation and decreased granulation tissues. The current study was carried out to evaluate wound healing in both normal and diabetic rats. In addition, it evaluated the potential protective effect of transforming growth factor β1 (TGF β1), that has the broadest spectrum of actions, affecting all cell types that are involved in all stages of wound healing to accelerate wound healing in normal & diabetic rats.

METHODS

: The present study was performed on 40 male albino rats. Each 10 rats were designed as a group. Group I saved as control. They received incisional wound in their tongues 1 cm length and 1/2 cm depth. Group II received 500 ng/kg of TGF β1 5 minutes before wounding. Group III diabetes was induced then rats were treated as second group. At the 14(th) day post wounding, sections of tongues were taken for hematoxylin and eosin and Masson's trichome staining to examine the histological changes. The intracellular actions of TGF β1 were studied by TEM.

RESULTS

A higher cell proliferation rate and a denser and more organized new extracellular matrix and complete wound closure was detected at the 14(th) days in the TGF β1 treated wound in comparison with the 14(th) days for the untreated, control groups. There were delayed wound healing in diabetic rats, decreased re-epithelialization, granulation tissue thickness, matrix density, number of infiltrated cells, and number of capillaries. In TGF β1 treated diabetic rats, showed significant healing improvement was obvious as compared with diabetic rats.

CONCLUSIONS

A single intravenous injection of TGF β1 was sufficient to enhance wound healing in rat's tongue. This approach represents a new strategy that may be applied to the treatment of incisional wounds in human diabetic patients.

Chaperonin containing T-complex polypeptide (CCT) subunit expression in oral mucosal wounds and fibroblasts

Mucosal wound healing in adults has been reported to feature diminished scar formation compared to healing skin wounds. We sought to determine if the expression pattern of chaperonin containing T-complex polypeptide (CCT) subunits in mucosal wounds and fibroblasts is different from that observed in skin wounds and fibroblasts. We found that CCT-beta is the only subunit message to be reduced in wounded mucosa versus unwounded control, and this reduction was confirmed at the protein level. In contrast, mRNA levels of CCT-zeta, -delta, -eta, and -epsilon were significantly increased in mucosal wounds. The increase in CCT-eta was also confirmed at the protein level. Expression levels of CCT-alpha, -beta, -delta; -epsilon, and -theta mRNAs were significantly increased in adult mucosal fibroblasts in culture compared to skin-derived fibroblasts. Western blot analyses confirmed a modest increase in CCT-beta in adult mucosal fibroblasts relative to skin fibroblasts, but CCT-eta protein was unaffected. These differences may contribute to the reported difference in healing outcomes between these two tissue types.

The influence of zoledronic acid and cyclophosphamide on microcirculation regeneration in healing oral mucosal flaps

The use of intravenous nitrogenous bisphosphonates and antineoplastic agents as postoperative adjuvant cancer management strategies may influence the course of oral wound healing by altering tissue vascularisation kinetics. The aim of this study was to investigate if single or combined zoledronic acid (ZOL) and cyclophosphamide (CTX) would influence microcirculation regeneration in healing oral mucosal flaps. Twenty female specific-pathogen free New Zealand white rabbits were randomised into four groups. In all animals a mucosal flap was raised; three groups were treated each separately with intravenous infusions of 0.14mg/kg ZOL, 100mg/kg CTX, or both, respectively. The fourth group was used as a control. Capillary density measurements, expressed as the mean number of capillaries±SD per mm(2) (cpll/mm(2)), was performed preoperatively using sidestream dark-field (SDF) imaging and repeated immediately postoperatively and on days 2, 4, 7, 9, 11, 14, and 21. Whole blood count and body weight was assessed in each group to monitor pharmacotherapeutic responses. Preoperative mean capillary density was 74±8cpll/mm(2) and 40±11cpll/mm(2) directly after surgery (P<0.0001). Post hoc comparisons of follow-up SDF measurements on days 9-21 between control and ZOL vs. CTX and ZOL+CTX were statistically significant (P<0.05). The present study demonstrates that ZOL did not alter capillary regeneration in healing mucosal flaps. However, although the early healing phase is generally characterised by rapid progression of capillary regeneration, interventions with CTX and ZOL+CTX significantly altered capillary regeneration and persisted beyond the third postoperative week.

Gingival fibroblasts as a promising source of induced pluripotent stem cells

Background

Induced pluripotent stem (iPS) cells efficiently generated from accessible tissues have the potential for clinical applications. Oral gingiva, which is often resected during general dental treatments and treated as biomedical waste, is an easily obtainable tissue, and cells can be isolated from patients with minimal discomfort.

Methodology/Principal Findings

We herein demonstrate iPS cell generation from adult wild-type mouse gingival fibroblasts (GFs) via introduction of four factors (Oct3/4, Sox2, Klf4 and c-Myc; GF-iPS-4F cells) or three factors (the same as GF-iPS-4F cells, but without the c-Myc oncogene; GF-iPS-3F cells) without drug selection. iPS cells were also generated from primary human gingival fibroblasts via four-factor transduction. These cells exhibited the morphology and growth properties of embryonic stem (ES) cells and expressed ES cell marker genes, with a decreased CpG methylation ratio in promoter regions of Nanog and Oct3/4. Additionally, teratoma formation assays showed ES cell-like derivation of cells and tissues representative of all three germ layers. In comparison to mouse GF-iPS-4F cells, GF-iPS-3F cells showed consistently more ES cell-like characteristics in terms of DNA methylation status and gene expression, although the reprogramming process was substantially delayed and the overall efficiency was also reduced. When transplanted into blastocysts, GF-iPS-3F cells gave rise to chimeras and contributed to the development of the germline. Notably, the four-factor reprogramming efficiency of mouse GFs was more than 7-fold higher than that of fibroblasts from tail-tips, possibly because of their high proliferative capacity.

Conclusions/Significance

These results suggest that GFs from the easily obtainable gingival tissues can be readily reprogrammed into iPS cells, thus making them a promising cell source for investigating the basis of cellular reprogramming and pluripotency for future clinical applications. In addition, high-quality iPS cells were generated from mouse GFs without Myc transduction or a specific system for reprogrammed cell selection.

Small cytoskeleton-associated molecule, fibroblast growth factor receptor 1 oncogene partner 2/wound inducible transcript-3.0 (FGFR1OP2/wit3.0), facilitates fibroblast-driven wound closure

Wounds created in the oral cavity heal rapidly and leave minimal scarring. We have examined a role of a previously isolated cDNA from oral wounds encoding wound inducible transcript-3.0 (wit3.0), also known as fibroblast growth factor receptor 1 oncogene partner 2 (FGFR1OP2). FGFR1OP2/wit3.0 was highly expressed in oral wound fibroblasts without noticeable up-regulation of alpha-smooth muscle actin. In silico analyses, denaturing and nondenaturing gel Western blot, and immunocytology together demonstrated that FGFR1OP2/wit3.0 were able to dimerize and oligomerize through coiled-coil structures and appeared to associate with cytoskeleton networks in oral wound fibroblasts. Overexpression of FGFR1OP2/wit3.0 increased the floating collagen gel contraction of naïve oral fibroblasts to the level of oral wound fibroblasts, which was in turn attenuated by small-interfering RNA knockdown. The FGFR1OP2/wit3.0 synthesis did not affect the expression of collagen I as well as procontractile peptides such as alpha-smooth muscle actin, and transforming growth factor-beta1 had no effect on FGFR1OP2/wit3.0 expression. Fibroblastic cells derived from embryonic stem cells carrying FGFR1OP2/wit3.0 (+/-) mutation showed significant retardation in cell migration. Thus, we postulate that FGFR1OP2/wit3.0 may regulate cell motility and stimulate wound closure. FGFR1OP2/wit3.0 was not up-regulated during skin wound healing; however, when treated with FGFR1OP2/wit3.0 -expression vector, the skin wound closure was significantly accelerated, resulting in the limited granulation tissue formation. Our data suggest that FGFR1OP2/wit3.0 may possess a therapeutic potential for wound management.

Role of secreted frizzled-related protein 1 (SFRP1) in wound healing

Wound healing is a complex cascade of events, which diminishes the size of the wound and reestablishes tissue integrity. Secreted frizzled-related protein 1 (SFRP1) contributes to the inhibition of apoptosis in fibroblast populations. We investigated the role of SFRP1 in a mouse wound-healing model; 2.0-mm excisional wounds were created in the scalp and hard palate. Healing responses were measured by histomorphometric analysis, apoptosis assay, and immunohistochemistry. Dermal wounds did not harbor SFRP1, but healed faster than palatal wounds which expressed significant levels of SFRP1. Antibody experiments aimed at blocking SFRP1 in palatal wounds resulted in promotion of wound closure, enhancement of new tissue formation, decrease of inflammatory cell infiltrate, and increase of apoptotic fibroblasts. Analysis of the present data suggests that SFRP1 may be partly responsible for the poorer healing performance of the palatal wounds compared with dermal wounds. Blocking SFRP1 results in improvement of palatal healing outcomes.

Oral fibroblast expression of wound-inducible transcript 3.0 (wit3.0) accelerates the collagen gel contraction in vitro

Wounds of the oral mucosa show faster closure with less scar formation than skin wounds in other areas. A differentially expressed cDNA, wound-inducible transcript 3.0 (wit3.0), was isolated from oral mucosal wound in rats (Sukotjo, C., Abanmy, A. A., Ogawa, T., and Nishimura, I. (2002) J. Dent. Res. 81, 229-235). The purpose of this study was to characterize the wit3.0 gene structure and the function of its deduced peptide. Human and rat genome databases revealed that the gene for wit3.0 was located in human chromosome 12p11.23 and rat chromosome 4q44. Its human and rat gene structures were well conserved, composed of 7 exons spread over 20 kb. Exon 5 was alternatively spliced generating two transcripts encoding deduced peptides of 215 and 253 amino acids (wit3.0 alpha and wit3.0 beta, respectively). The protein families data base of alignments (Pfam) analysis suggested the wit3.0 peptide sequence shared similarity with a portion of the myosin II coiled-coil domain consensus sequence. Fibroblasts isolated from the rat oral wound up-regulated wit3.0 expression and exhibited greater ability to contract collagen gel in vitro than fibroblasts isolated from untreated oral mucosa/gingiva. NIH3T3 and rat oral fibroblasts transfected with expression vector containing the coding sequences of wit3.0 alpha or wit3.0 beta increased in vitro collagen gel contraction. When treated with TGF beta-1, NIH3T3 fibroblast expression of wit3.0 showed no significant change, whereas alpha smooth muscle actin was increased in a dose-dependent manner. These data suggest that there may be a novel wound healing pathway involving wit3.0 underlying the favorable early wound closure characteristics of oral mucosa.

Differential injury responses in oral mucosal and cutaneous wounds

Oral mucosa heals faster than does skin, yet few studies have compared the repair at oral mucosal and cutaneous sites. To determine whether the privileged healing of oral injuries involves a differential inflammatory phase, we compared the inflammatory cell infiltrate and cytokine production in wounds of equivalent size in oral mucosa and skin. Significantly lower levels of macrophage, neutrophil, and T-cell infiltration were observed in oral vs. dermal wounds. RT-PCR analysis of inflammatory cytokine production demonstrated that oral wounds contained significantly less IL-6 and KC than did skin wounds. Similarly, the level of the pro-fibrotic cytokine TGF-b1 was lower in mucosal than in skin wounds. No significant differences between skin and mucosal wounds were observed for the expression of the anti-inflammatory cytokine IL-10 and the TGF-beta1 modulators, fibromodulin and LTBP-1. These findings demonstrate that diminished inflammation is a key feature of the privileged repair of oral mucosa.

The effect of thrombocytopenia on dermal wound healing

The immediate appearance of platelets in wounds and the ability of platelets to release growth factors suggest that platelets are an important trigger of the tissue repair process. To examine the effect of systemic thrombocytopenia on both the inflammatory and proliferative aspects of wound healing, adult mice were rendered thrombocytopenic by intraperitoneal administration of a rabbit antimouse platelet serum. Full-thickness excisional dermal wounds were prepared and analyzed for inflammatory cell content, growth factor production, reepithelialization, collagen synthesis, and angiogenesis at multiple time points after injury. Compared to control mice, thrombocytopenic mice exhibited significantly altered wound inflammation. Wounds of thrombocytopenic mice contained significantly more macrophages and T cells, yet exhibited neutrophil content similar to wounds from control mice. Surprisingly, thrombocytopenic mice exhibited no delay in the reparative aspects of wound healing. The rate of wound reepithelialization, collagen synthesis, and angiogenesis was nearly identical for thrombocytopenic and control mice. Analysis of vascular endothelial growth factor, fibroblast growth factor 2, transforming growth factor beta1, keratinocyte growth factor, and epidermal growth factor revealed no difference in the levels of these growth factors in the wounds of control and thrombocytopenic mice. Taken together, the results suggest that the presence of platelets may influence wound inflammation, but that platelets do not significantly affect the proliferative aspects of repair, including wound closure, angiogenesis, and collagen synthesis.

Clinical comparison between conventional suture and vaporization with carbon dioxide laser in rat's skin

OBJECTIVE

This study compares wound healing efficiency on a rat's skin when the incision was closed with a conventional suture versus vaporized with a CO2 laser.

MATERIALS AND METHODS

In this study, 24 rats were used, and two longitudinal incisions were made with a conventional scalpel in the dorsum of each rat. The left incision was sutured with nylon thread, and the right incision was closed by vaporization with a defocused CO2 laser in continuous mode with an 8-watt power density. Clinical photographs were taken immediately after the procedure, 24 h later, and after 3, 7, 14, and 21 days, documenting the healing of the incision.

RESULTS

The results showed that there was an initial delay in wound repair in the vaporized incision as compared to the scalpel incision, but after 21 days, both incisions showed the same clinical characteristics. However, the vaporized incision showed no trauma of the tissue, as opposed to the sutured incision, and no hemorrhagic complications.

CONCLUSION

These results suggest that the CO2 laser can eventually replace the use of sutures.

The use of magnification in general dental practice in Scotland--a survey report

OBJECTIVES

This study had two aims, first, to quantify the level of the use of magnification in general dental practice in Scotland and second, to determine the current and potential areas of clinical use of magnification by general dental practitioners.

METHODS

A questionnaire was sent to all general dental practitioners in Scotland with a Health Board list number (n = 1790). The questionnaire asked the practitioners about their experience of magnification and their opinions on possible areas for clinical use. An information sheet and a prepaid envelope were included with the questionnaire.

RESULTS

One thousand two hundred and eighty (72%) of the dentists replied to the questionnaire. Nine percent of the respondents routinely used magnification. The level of routine use of magnification by practitioners increased with time since qualification. The suggested areas of clinical use of magnification by all the respondents were crown and bridge work, diagnosis and radiography. The routine users of magnification had a more positive view of magnification than non-users.

CONCLUSIONS

Routine use of magnification was associated with the length of time the practitioner had been qualified and the attendance at a course at which magnification was discussed. The perceived uses of magnification depended on the experience of the practitioner with magnification. It was considered suitable for all clinical procedures except orthodontics and prosthodontics.