Comparison of advanced therapy medicinal product gingiva and skin substitutes and their in vitro wound healing potentials

Spiroconjugated 1,2,3-triazolo[5,1-b]1,3,4-thiadiazine stimulates functional activity of fibroblasts under skin injury regeneration

Background and purpose

One of the most important mechanisms of tissue regeneration is the high functional activity of cells, including proliferation. Currently, there are practically no effective skin cell activators on the pharmaceutical market. The purpose of this work was to demonstrate the stimulating effect of spiroconjugated 1,2,3-triazolo[5,1-b]1,3,4-thiadiazine (STT) on the functional activity of fibroblasts.

Experimental approach

STT containing ointment for dermal application was made. To assess in vivo effect of the STT a linear wound model in rats was tested. A combination of histological techniques and mechanical testing was employed to estimate the stimulating effect of STT on the functional activity of fibroblasts.

Findings/Results

The STT significantly increased the number of fibroblasts as well as the density and order of produced collagen fibers in the dermis during the wound healing process. As a result, a tissue was formed at the site of damage with the structure corresponding to normal skin. In addition, skin functions were restored, in particular mechanically.

Conclusion and implications

The results suggested the stimulating effect of the STT on fibroblast activity and demonstrated its potential for skin regeneration.

A high-throughput, 28-day, microfluidic model of gingival tissue inflammation and recovery

Nearly half of American adults suffer from gum disease, including mild inflammation of gingival tissue, known as gingivitis. Currently, advances in therapeutic treatments are hampered by a lack of mechanistic understanding of disease progression in physiologically relevant vascularized tissues. To address this, we present a high-throughput microfluidic organ-on-chip model of human gingival tissue containing keratinocytes, fibroblast and endothelial cells. We show the triculture model exhibits physiological tissue structure, mucosal barrier formation, and protein biomarker expression and secretion over several weeks. Through inflammatory cytokine administration, we demonstrate the induction of inflammation measured by changes in barrier function and cytokine secretion. These states of inflammation are induced at various time points within a stable culture window, providing a robust platform for evaluation of therapeutic agents. These data reveal that the administration of specific small molecule inhibitors mitigates the inflammatory response and enables tissue recovery, providing an opportunity for identification of new therapeutic targets for gum disease with the potential to facilitate relevant preclinical drug efficacy and toxicity testing.

Amino Acid-Enriched Formula for the Post-Operative Care of Extraction Sockets Evaluated by 3-D Intraoral Scanning

Background: Hyaluronic acid and amino acids play an important role in the wound healing process, stimulating the development of the connective tissue and the activity and proliferation of fibroblasts. The aim of the present controlled clinical study was to evaluate the clinical efficacy of a topical gel formula containing hyaluronic acid and amino acids in terms of wound closure rate, painkiller intake, and patients’ reported pain and edema. Methods: This study included patients in need of a single tooth extraction. Patients were randomized into two groups with differing post-operative care regimens. Patients in the test group used the amino acid and hyaluronic acid-based gel, while the control group did not use any product. Each parameter was measured in both groups at different time points: immediately after surgery, and after 7, 14, 30, and 60 days. Results: A total of 40 patients (46.52 ± 9.84 years old) completed the observational period, and 40 extraction sockets were examined. After 7 days, the edema was significantly lower in the test group. The reported pain was lower in the test group without a significant difference, except for the first time point at 7 days. With the follow-up questionnaire, patients declared to have taken painkillers mainly during the first 7 days after surgery; however, the test group showed a lower need for painkillers than the control group. Conclusion: The post-operative and domiciliary use of an amino acid and hyaluronic acid-based gel for the management of soft tissue closure after tooth extraction is a valid coadjutant to reduce swelling, pain, and the need for painkillers. Additional studies are required to support the results of the present study.

FAK Shutdown: Consequences on Epithelial Morphogenesis and Biomarker Expression Involving an Innovative Biomaterial for Tissue Regeneration

By employing an innovative biohybrid membrane, the present study aimed at elucidating the mechanistic role of the focal adhesion kinase (FAK) in epithelial morphogenesis in vitro over 4, 7, and 10 days. The consequences of siRNA-mediated FAK knockdown on epithelial morphogenesis were monitored by quantifying cell layers and detecting the expression of biomarkers of epithelial differentiation and homeostasis. Histologic examination of FAK-depleted samples showed a significant increase in cell layers resembling epithelial hyperplasia. Semiquantitative fluorescence imaging (SQFI) revealed tissue homeostatic disturbances by significantly increased involucrin expression over time, persistence of yes-associated protein (YAP) and an increase of keratin (K) 1 at day 4. The dysbalanced involucrin pattern was underscored by ROCK-II^Ser1366 activity at day 7 and 10. SQFI data were confirmed by quantitative PCR and Western blot analysis, thereby corroborating the FAK shutdown-related expression changes. The artificial FAK shutdown was also associated with a significantly higher expression of filaggrin at day 10, sustained keratinocyte proliferation, and the dysregulated expression of K19 and vimentin. These siRNA-induced consequences indicate the mechanistic role of FAK in epithelial morphogenesis by simultaneously considering prospective biomaterial-based epithelial regenerative approaches.

The phenotype of gingival fibroblasts and their potential use in advanced therapies

Advanced therapies in medicine use stem cells, gene editing, and tissues to treat a wide range of conditions. One of their goals is to stimulate endogenous repair of tissues and organs by manipulating stem cells and their niche, as well as to optimize the intrinsic characteristics and plasticity of differentiated cells in adult tissues. In this context, fibroblasts emerge as an alternative source to stem cells because they share phenotypic and regenerative characteristics. Specifically, fibroblasts of the oral mucosae have been shown to have improved regenerative capacity compared to other fibroblast populations. Additionally, their easy access by means of minimally invasive procedures without generating aesthetic problems, with easy and rapid in vitro expansion and with great capacity to respond to extrinsic factors, make oral fibroblasts an attractive and interesting resource for regenerative medicine. This review summarizes current concepts regarding the phenotypic and functional aspects of human Gingival Fibroblasts and their niche, differentiating them from other fibroblast populations of oral-lining mucosa and skin fibroblasts. Furthermore, some applications are presented in regenerative medicine, emphasizing on the biological potential of human Gingival Fibroblasts.

Comparison of advanced therapy medicinal product gingiva and skin substitutes and their in vitro wound healing potentials

Skin and oral mucosa substitutes are a therapeutic option for closing hard‐to‐heal skin and oral wounds. Our aim was to develop bi‐layered skin and gingiva substitutes, from 3 mm diameter biopsies, cultured under identical conditions, which are compliant with current European regulations for advanced therapy medicinal products. We present in vitro mode of action methods to (i) determine viability: epithelial expansion, proliferation (Ki‐67), metabolic activity (MTT assay); (ii) characterize skin and gingiva substitutes: histology and immunohistochemistry; and (iii) determine potency: soluble wound healing mediator release (enzyme‐linked immunosorbent assay). Both skin and gingiva substitutes consist of metabolically active autologous reconstructed differentiated epithelium expanding from the original biopsy sheet on a fibroblast populated connective tissue matrix (donor dermis). Gingival epithelium expanded 1.7‐fold more than skin epithelium during the 3 week culture period. The percentage of proliferating Ki‐67‐positive cells located in the basal layer of the gingiva substitute was >1.5‐fold higher than in the skin substitute. Keratins 16 and 17, which are upregulated during normal wound healing, were expressed in both the skin and gingiva substitutes. Notably, the gingiva substitute secreted higher amounts of key cytokines involved in mitogenesis, motogenesis and chemotaxis (interleukin‐6 > 23‐fold, CXCL8 > 2.5‐fold) as well as higher amounts of the anti‐fibrotic growth factor, hepatocyte growth factor (>7‐fold), compared with the skin substitute. In conclusion, while addressing the viability, characterization and potency of the tissue substitutes, important intrinsic differences between skin and gingiva were discovered that may explain in part the superior quality of wound healing observed in the oral mucosa compared with skin.