Salivary EGF regulates eosinophil-derived TGF-alpha expression in hamster oral wounds

Cell type-specific transforming growth factor-β (TGF-β) signaling in the regulation of salivary gland fibrosis and regeneration

Salivary gland damage and hypofunction result from various disorders, including autoimmune Sjögren's disease (SjD) and IgG4-related disease (IgG4-RD), as well as a side effect of radiotherapy for treating head and neck cancers. There are no therapeutic strategies to prevent the loss of salivary gland function in these disorders nor facilitate functional salivary gland regeneration. However, ongoing aquaporin-1 gene therapy trials to restore saliva flow show promise. To identify and develop novel therapeutic targets, we must better understand the cell-specific signaling processes involved in salivary gland regeneration. Transforming growth factor-β (TGF-β) signaling is essential to tissue fibrosis, a major endpoint in salivary gland degeneration, which develops in the salivary glands of patients with SjD, IgG4-RD, and radiation-induced damage. Though the deposition and remodeling of extracellular matrix proteins are essential to repair salivary gland damage, pathological fibrosis results in tissue hardening and chronic salivary gland dysfunction orchestrated by multiple cell types, including fibroblasts, myofibroblasts, endothelial cells, stromal cells, and lymphocytes, macrophages, and other immune cell populations. This review is focused on the role of TGF-β signaling in the development of salivary gland fibrosis and the potential for targeting TGF-β as a novel therapeutic approach to regenerate functional salivary glands. The studies presented highlight the divergent roles of TGF-β signaling in salivary gland development and dysfunction and illuminate specific cell populations in damaged or diseased salivary glands that mediate the effects of TGF-β. Overall, these studies strongly support the premise that blocking TGF-β signaling holds promise for the regeneration of functional salivary glands.

Comprehensive characterization of myeloid cells during wound healing in healthy and healing-impaired diabetic mice

Wound healing involves the concerted action of various lymphoid and in particular myeloid cell populations. To characterize and quantitate different types of myeloid cells and to obtain information on their kinetics during wound healing, we performed multiparametric flow cytometry analysis. In healthy mice, neutrophil numbers increased early after injury and returned to near basal levels after completion of healing. Macrophages, monocyte‐derived dendritic cells (DCs), and eosinophils were abundant throughout the healing phase, in particular in early wounds, and Langerhans cells increased after wounding and remained elevated after epithelial closure. Major differences in healing‐impaired diabetic mice were a much higher percentage of immune cells in late wounds, mainly as a result of neutrophil, macrophage, and monocyte persistence; reduced numbers and percentages of macrophages and monocyte‐derived DCs in early wounds; and of Langerhans cells, conventional DCs, and eosinophils throughout the healing process. Finally, unbiased cluster analysis (PhenoGraph) identified a large number of different clusters of myeloid cells in skin wounds. These results provide insight into myeloid cell diversity and dynamics during wound repair and highlight the abnormal inflammatory response associated with impaired healing.

Fibronectin synthesis, but not α-smooth muscle expression, is regulated by periostin in gingival healing through FAK/JNK signaling

During skin healing, periostin facilitates myofibroblast differentiation through a β1 integrin/FAK dependent mechanism and continued expression is associated with scarring. In contrast to skin, gingival tissue does not typically scar upon injury, but the role of periostin in gingival healing has never been investigated. Using a rat gingivectomy model, we show that the gingival architecture is re-established within 14 days of wounding. Periostin mRNA levels peak at day 7 post-wounding, with persistence of periostin protein in the connective tissue through day 14. Collagen type I and lysyl oxidase mRNA levels peak at day 7 post wounding, which corresponded with the peak of fibroblast proliferation. Although α-smooth muscle actin mRNA levels increased 200-fold in the tissue, no myofibroblasts were detected in the regenerating tissue. In vitro, human gingival fibroblast adhesion on periostin, but not collagen, was inhibited by blocking β1 integrins. Fibroblasts cultured on periostin exhibited similar rates of proliferation and myofibroblast differentiation to cells cultured on collagen only. However, human gingival fibroblasts cultured in the presence of periostin exhibited significantly increased fibronectin and collagen mRNA levels. Increases in fibronectin production were attenuated by pharmacological inhibition of FAK and JNK signaling in human gingival fibroblasts. In vivo, mRNA levels for fibronectin peaked at day 3 and 7 post wounding, with protein immunoreactivity highest at day 7, suggesting periostin is a modulator of fibronectin production during gingival healing.

Bombesin improves adaptive immunity of the salivary gland during parenteral nutrition

BACKGROUND

The parotid and submandibular salivary glands are gut-associated lymphoid tissues (GALTs) that secrete immune compounds into the oral cavity. Parenteral nutrition (PN) without enteral stimulation decreases GALT function, including intestinal lymphocyte counts and secretory immunoglobulin A (sIgA) levels. Since the neuropeptide bombesin (BBS), a gastrin-releasing peptide analogue, stimulates intestinal function and restores GALT parameters, we hypothesized that PN + BBS would stimulate parotid and salivary gland IgA levels, T lymphocytes, and IgA plasma cell counts compared with PN alone.

METHODS

Male (Institute of Cancer Research) ICR mice received intravenous catheters and were randomized to chow with saline, PN, or PN + BBS (15 µg/tid/mouse) for 5 days (8/group), 2 days after cannulation. Salivary glands were weighed and either frozen for IgA and amylase analysis or fixed for histological analysis of acinar cells, IgA+ plasma cells, and T lymphocytes. Small intestinal wash fluid was collected for IgA regression analysis with salivary glands.

RESULTS

PN reduced organ weight, acinar cell size, and amylase activity compared with chow; BBS had no significant effects on these parameters. Compared with chow, PN significantly reduced salivary gland IgA levels, IgA+ plasma cells, and T lymphocytes. PN + BBS significantly elevated IgA and restored cellularity compared with PN. Salivary gland tissue homogenate IgA levels significantly correlated with intestinal fluid IgA levels.

CONCLUSIONS

Compared with chow, PN results in atrophy of the salivary glands characterized by reduced amylase, IgA, and immune cellularity. BBS has no effect on acinar cells or amylase activity compared with PN but maintains tissue IgA and plasma cells and T-lymphocyte numbers compared with chow.

Wound closure and wound management: A new therapeutic molecular target

Wound closure and infection control are the primary goal of wound management. A variety of disinfectants and antimicrobial agents are widely available today and routinely achieve infection control. On the contrary, wound closure still remains a challenging goal. Cell adhesion, migration and contraction play significant roles in creating contractile force of patent wound margins and in contributing to wound closure. Modulations of these cellular behaviors have been investigated in the context of wound contraction; however, therapeutic strategy to achieve wound closure has not been established. Recently, we have reported that a previously unknown cytoskeleton molecule, wound inducible transcript-3.0 (wit3.0) also known as fibroblast growth factor receptor 1 oncogene partner 2 (FGFR1OP2), can significantly modulate fibroblast-driven wound closure in vitro and in vivo. The dynamic role of cytoskeleton in different experimental models may provide a novel platform for designing the therapeutic target of wound management.

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.

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.