Local myogenic pulp-derived cell injection enhances craniofacial muscle regeneration in vivo

Novel Strategies for Orofacial Soft Tissue Regeneration

Significance: Orofacial structures are indispensable for speech and eating, and impairment disrupts whole-body health through malnutrition and poor quality of life. However, due to the unique and highly specialized cell populations, tissue architecture, and healing microenvironments, regeneration in this region is challenging and inadequately addressed to date. Recent Advances: With increasing understanding of the nuanced physiology and cellular responses of orofacial soft tissue, novel scaffolds, seeded cells, and bioactive molecules were developed in the past 5 years to specifically target orofacial soft tissue regeneration, particularly for tissues primarily found within the orofacial region such as oral mucosa, taste buds, salivary glands, and masseter muscles. Critical Issues: Due to the tightly packed and complex anatomy, orofacial soft tissue injury commonly implicates multiple tissue types, and thus functional unit reconstruction in the orofacial region is more important than single tissue regeneration. Future Directions: This article reviews the up-to-date knowledge in this highly translational topic, which provides insights into novel biologically inspired and engineered strategies for regenerating orofacial component tissues and functional units.

Skeletal Muscle Regeneration in Cardiotoxin-Induced Muscle Injury Models

Skeletal muscle injuries occur frequently in daily life and exercise. Understanding the mechanisms of regeneration is critical for accelerating the repair and regeneration of muscle. Therefore, this article reviews knowledge on the mechanisms of skeletal muscle regeneration after cardiotoxin-induced injury. The process of regeneration is similar in different mouse strains and is inhibited by aging, obesity, and diabetes. Exercise, microcurrent electrical neuromuscular stimulation, and mechanical loading improve regeneration. The mechanisms of regeneration are complex and strain-dependent, and changes in functional proteins involved in the processes of necrotic fiber debris clearance, M1 to M2 macrophage conversion, SC activation, myoblast proliferation, differentiation and fusion, and fibrosis and calcification influence the final outcome of the regenerative activity.

Epigenetic Regulation of Methylation in Determining the Fate of Dental Mesenchymal Stem Cells

Dental mesenchymal stem cells (DMSCs) are crucial in tooth development and periodontal health, and their multipotential differentiation and self-renewal ability play a critical role in tissue engineering and regenerative medicine. Methylation modifications could promote the appropriate biological behavior by postsynthetic modification of DNA or protein and make the organism adapt to developmental and environmental prompts by regulating gene expression without changing the DNA sequence. Methylation modifications involved in DMSC fate include DNA methylation, RNA methylation, and histone modifications, which have been proven to exert a significant effect on the regulation of the fate of DMSCs, such as proliferation, self-renewal, and differentiation potential. Understanding the regulation of methylation modifications on the behavior and the immunoinflammatory responses involved in DMSCs contributes to further study of the mechanism of methylation on tissue regeneration and inflammation. In this review, we briefly summarize the key functions of histone methylation, RNA methylation, and DNA methylation in the differentiation potential and self-renewal of DMSCs as well as the opportunities and challenges for their application in tissue regeneration and disease therapy.

DNA Methylation and Histone Modification in Dental-derived Mesenchymal Stem Cells

Epigenetic regulation, mainly involving DNA methylation, histone modification, and noncoding RNAs (ncRNAs), is essential for the regulation of multiple cellular processes. Dental-derived mesenchymal stem cells (DMSCs), a kind of multipotent cells derived from dental tissues, are impactful in regenerative medicine. Recent studies have shown that epigenetic regulation plays a major role in DMSCs. Therefore, exploring how epigenetic regulation is involved in DMSCs may be of guiding significance for tissue repair and regeneration or for exploring more effective treatments. A number of research of ncRNAs in DMSCs have been reported. However, little is known about the roles of DNA methylation and histone modifications in DMSCs. In this review, we summarize the important roles of DNA methylation and histone modifications of the fate of DMSCs.

Epigenetic regulation of dental pulp stem cells and its potential in regenerative endodontics

Regenerative endodontics (RE) therapy means physiologically replacing damaged pulp tissue and regaining functional dentin–pulp complex. Current clinical RE procedures recruit endogenous stem cells from the apical papilla, periodontal tissue, bone marrow and peripheral blood, with or without application of scaffolds and growth factors in the root canal space, resulting in cementum-like and bone-like tissue formation. Without the involvement of dental pulp stem cells (DPSCs), it is unlikely that functional pulp regeneration can be achieved, even though acceptable repair can be acquired. DPSCs, due to their specific odontogenic potential, high proliferation, neurovascular property, and easy accessibility, are considered as the most eligible cell source for dentin–pulp regeneration. The regenerative potential of DPSCs has been demonstrated by recent clinical progress. DPSC transplantation following pulpectomy has successfully reconstructed neurovascularized pulp that simulates the physiological structure of natural pulp. The self-renewal, proliferation, and odontogenic differentiation of DPSCs are under the control of a cascade of transcription factors. Over recent decades, epigenetic modulations implicating histone modifications, DNA methylation, and noncoding (nc)RNAs have manifested as a new layer of gene regulation. These modulations exhibit a profound effect on the cellular activities of DPSCs. In this review, we offer an overview about epigenetic regulation of the fate of DPSCs; in particular, on the proliferation, odontogenic differentiation, angiogenesis, and neurogenesis. We emphasize recent discoveries of epigenetic molecules that can alter DPSC status and promote pulp regeneration through manipulation over epigenetic profiles.

Recent update on craniofacial tissue engineering

The craniofacial region consists of several different tissue types. These tissues are quite commonly affected by traumatic/pathologic tissue loss which has so far been traditionally treated by grafting procedures. With the complications and drawbacks of grafting procedures, the emerging field of regenerative medicine has proved potential. Tissue engineering advancements and the application in the craniofacial region is quickly gaining momentum although most research is still at early in vitro/in vivo stages. We aim to provide an overview on where research stands now in tissue engineering of craniofacial tissue; namely bone, cartilage muscle, skin, periodontal ligament, and mucosa. Abstracts and full-text English articles discussing techniques used for tissue engineering/regeneration of these tissue types were summarized in this article. The future perspectives and how current technological advancements and different material applications are enhancing tissue engineering procedures are also highlighted. Clinically, patients with craniofacial defects need hybrid reconstruction techniques to overcome the complexity of these defects. Cost-effectiveness and cost-efficiency are also required in such defects. The results of the studies covered in this review confirm the potential of craniofacial tissue engineering strategies as an alternative to avoid the problems of currently employed techniques. Furthermore, 3D printing advances may allow for fabrication of patient-specific tissue engineered constructs which should improve post-operative esthetic results of reconstruction. There are on the other hand still many challenges that clearly require further research in order to catch up with engineering of other parts of the human body.

Epigenetic Regulation of Dental Pulp Stem Cell Fate

Epigenetic regulation, mainly involving DNA methylation, histone modification, and noncoding RNAs, affects gene expression without modifying the primary DNA sequence and modulates cell fate. Mesenchymal stem cells derived from dental pulp, also called dental pulp stem cells (DPSCs), exhibit multipotent differentiation capacity and can promote various biological processes, including odontogenesis, osteogenesis, angiogenesis, myogenesis, and chondrogenesis. Over the past decades, increased attention has been attracted by the use of DPSCs in the field of regenerative medicine. According to a series of studies, epigenetic regulation is essential for DPSCs to differentiate into specialized cells. In this review, we summarize the mechanisms involved in the epigenetic regulation of the fate of DPSCs.

The Role of Skeletal Stem Cells in the Reconstruction of Bone Defects

Craniofacial surgery, since its inauguration, has been the culmination of collaborative efforts to solve complex congenital, dysplastic, oncological, and traumatic cranial bone defects. Now, 50 years on from the first craniofacial meeting, the collaborative efforts between surgeons, scientists, and bioengineers are further advancing craniofacial surgery with new discoveries in tissue regeneration. Recent advances in regenerative medicine and stem cell biology have transformed the authors' understanding of bone healing, the role of stem cells governing bone healing, and the effects of the niche environment and extracellular matrix on stem cell fate. This review aims at summarizing the advances within each of these fields.

Local Injection of Hyaluronic Acid Filler Improves Open Gingival Embrasure: Validation Through a Rat Model

BACKGROUND

The open gingival embrasure, the so-called black triangle, is one of the unsolved dilemmas in adult dentistry. Although various techniques have been introduced to improve black triangles, the lack of reproducible experimental models has prevented development of successful protocols to regenerate or to compensate loss of the interdental papilla. Therefore, the objective of this study is first to develop a reliable animal model of open gingival embrasure and then to validate a minimally invasive injection technique using hyaluronic acid (HA) filler to augment the interdental papilla.

METHODS

To reproduce open gingival embrasure in rats, rapid space opening was induced between the mandibular incisors by attachment of a compression spring. Loss of interdental papilla height was morphologically evaluated and calculated using standardized serial photographs, microcomputed tomography, and histologic sections. Afterward, HA fillers or phosphate-buffered saline (PBS) was locally injected, and changes in the interdental papilla were evaluated.

RESULTS

After 7 days of space opening, the margin of the interdental papilla between the mandibular incisors gradually became irregular and flat, indicating a condition similar to the open gingival embrasure (P <0.05). Local injection of HA filler induced an augmentation effect of the interdental papilla compared with injection of PBS (P <0.05). Interdental papilla became convex, and inner granules containing HA were detected within the submucosal layer after its injection.

CONCLUSIONS

Open gingival embrasure was reproduced reliably in vivo. Local injection of HA filler was validated as a meaningful minimally invasive procedure to improve open gingival embrasure.