Local Injection of Pulp Cells Enhances Wound Healing during the Initial Proliferative Phase through the Stimulation of Host Angiogenesis

Challenges and tissue engineering strategies of periodontal guided tissue regeneration

Periodontitis is a chronic infectious oral disease with a high prevalence rate in the world, and is a major cause of tooth loss. Nowadays, people have realized that the local microenvironment that includes proteins, cytokines, and extracellular matrix has a key influence on the functions of host immune cells and periodontal ligament stem cells during a chronic infectious disease such as periodontitis. The above pathological process of periodontitis will lead to a defect of periodontal tissues. Through the application of biomaterials, biological agents, and stem cells therapy, guided tissue regeneration (GTR) makes it possible to reconstruct healthy periodontal ligament tissue after local inflammation control. To date, substantial advances have been made in periodontal guided tissue regeneration. However, the process of periodontal remodeling experiences complex microenvironment changes, and currently periodontium regeneration still remains to be a challenging feat. In this review, we summarized the main challenges in each stage of periodontal regeneration, and try to put forward appropriate biomaterial treatment mechanisms or potential tissue engineering strategies that provide a theoretical basis for periodontal tissue engineering regeneration research.

Dental Pulp Stem Cells Derived From Adult Human Third Molar Tooth: A Brief Review

The fields of regenerative medicine and stem cell-based tissue engineering have the potential of treating numerous tissue and organ defects. The use of adult stem cells is of particular interest when it comes to dynamic applications in translational medicine. Recently, dental pulp stem cells (DPSCs) have been traced in third molars of adult humans. DPSCs have been isolated and characterized by several groups. DPSCs have promising characteristics including self-renewal capacity, rapid proliferation, colony formation, multi-lineage differentiation, and pluripotent gene expression profile. Nevertheless, genotypic, and phenotypic heterogeneities have been reported for DPSCs subpopulations which may influence their therapeutic potentials. The underlying causes of DPSCs’ heterogeneity remain poorly understood; however, their heterogeneity emerges as a consequence of an interplay between intrinsic and extrinsic cellular factors. The main objective of the manuscript is to review the current literature related to the human DPSCs derived from the third molar, with a focus on their physiological properties, isolation procedures, culture conditions, self-renewal, proliferation, lineage differentiation capacities and their prospective advances use in pre-clinical and clinical applications.

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

OBJECTIVES

To enhance myogenic differentiation in pulp cells isolated from extracted premolars by epigenetic modification using a DNA demethylation agent, 5-aza-2'-deoxycytidine (5-Aza), and to evaluate the potent stimulatory effect of 5-Aza-treated pulp cell injection for craniofacial muscle regeneration in vivo.

SETTING AND SAMPLE POPULATION

Pulp cells were isolated from premolars extracted for orthodontic purposes from four adults (age range, 18-22.1 years).

MATERIAL AND METHODS

Levels of myogenic differentiation and functional contraction response in vitro were compared between pulp cells with or without pre-treatment of 5-Aza. Changes in muscle regeneration in response to green fluorescent protein (GFP)-labelled myogenic pulp cell injection in vivo were evaluated using a cardiotoxin (CTX)-induced muscle injury model of the gastrocnemius as well as the masseter muscle in mice.

RESULTS

Pre-treatment of 5-Aza in pulp cells stimulated myotube formation, myogenic differentiation in terms of desmin and myogenin expression, and the level of collagen gel contraction. The local injection of 5-Aza pre-treated myogenic pulp cells was engrafted into the host tissue and indicated signs of enhanced muscle regeneration in both the gastrocnemius and the masseter muscles.

CONCLUSION

The epigenetic modification of pulp cells from extracted premolars and the local injection of myogenic pulp cells may stimulate craniofacial muscles regeneration in vivo.

Exosomes with Highly Angiogenic Potential for Possible Use in Pulp Regeneration

INTRODUCTION

Angiogenesis is critical for pulp regeneration. Exosomes, a key component of paracrine secretion, have emerged as important players in the modulation of angiogenesis. The role of dental pulp cell-derived exosomes (DPC-Exos) in angiogenesis has rarely been reported. The proangiogenic properties of DPC-Exos in human umbilical vein endothelial cells (HUVECs) are investigated in the current study.

METHODS

Exosomes were isolated from dental pulp cell (DPC) culture supernatants by ultracentrifugation and were characterized by transmission electron microscopy, Western blotting, and nanoparticle tracking analysis. Their roles in HUVEC proliferation, proangiogenic factor expression, and tube formation were examined in vitro.

RESULTS

We isolated and characterized exosomes from DPCs and showed that DPC-Exos promoted HUVEC proliferation, proangiogenic factor expression, and tube formation. Furthermore, we found that p38 mitogen-activated protein kinase (MAPK) signaling inhibition enhances DPC-Exos-induced tube formation.

CONCLUSIONS

Taken together, these results suggest that DPC-Exos have vital roles in angiogenesis, and p38 MAPK signaling inhibition enhances tubular morphogenesis.

Angiogenic and osteogenic potentials of dental stem cells in bone tissue engineering

Manipulation of dental stem cells (DSCs) using current technologies in tissue engineering unveil promising prospect in regenerative medicine. DSCs have shown to possess angiogenic and osteogenic potential in both in vivo and in vitro. Neural crest derived DSCs can successfully be isolated from various dental tissues, exploiting their intrinsic great differentiation potential. In this article, researcher team intent to review the characteristics of DSCs, with focus on their angiogenic and osteogenic differentiation lineage. Clinical data on DSCs are still lacking to prove their restorative abilities despite extensive contemporary literature, warranting research to further validate their application for bone tissue engineering.

Immune Tolerance of Human Dental Pulp-Derived Mesenchymal Stem Cells Mediated by CD4⁺CD25⁺FoxP3⁺ Regulatory T-Cells and Induced by TGF-β1 and IL-10

PURPOSE

Most studies on immune tolerance of mesenchymal stem cells (MSCs) have been performed using MSCs derived from bone marrow, cord blood, or adipose tissue. MSCs also exist in the craniofacial area, specifically in teeth. The purpose of this study was to evaluate the mechanisms of immune tolerance of dental pulp-derived MSC (DP-MSC) in vitro and in vivo.

MATERIALS AND METHODS

We isolated DP-MSCs from human dental pulp and co-cultured them with CD4⁺ T-cells. To evaluate the role of cytokines, we blocked TGF-β and IL-10, separately and together, in co-cultured DP-MSCs and CD4⁺ T-cells. We analyzed CD25 and FoxP3 to identify regulatory T-cells (Tregs) by fluorescence-activated cell sorting (FACS) and real-time PCR. We performed alloskin grafts with and without DP-MSC injection in mice. We performed mixed lymphocyte reactions (MLRs) to check immune tolerance.

RESULTS

Co-culture of CD4⁺ T-cells with DP-MSCs increased the number of CD4⁺CD25⁺FoxP3⁺ Tregs (p<0.01). TGF-β or/and IL-10 blocking suppressed Treg induction in co-cultured cells (p<0.05). TGF-β1 mRNA levels were higher in co-cultured DP-MSCs and in co-cultured CD4⁺ T-cells than in the respective monocultured cells. However, IL-10 mRNA levels were not different. There was no difference in alloskin graft survival rate and area between the DP-MSC injection group and the non-injection group. Nonetheless, MLR was reduced in the DP-MSC injected group (p<0.05).

CONCLUSION

DP-MSCs can modulate immune tolerance by increasing CD4⁺CD25⁺FoxP3⁺ Tregs. TGF-β1 and IL-10 are factors in the immune-tolerance mechanism. Pure DP-MSC therapy may not be an effective treatment for rejection, although it may module immune tolerance in vivo.

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.

In vitro characterization of human dental pulp stem cells isolated by three different methods

OBJECTIVES

In this study, we characterized human dental pulp cells (HDPCs) obtained by different culture methods to establish the most suitable methodology for dental tissue engineering and regenerative endodontic applications.

MATERIALS AND METHODS

HDPCs were isolated by the outgrowth method (HDPCs-OG), the enzymatic digestion method (collagenase/dispase/trypsin, HDPCs-ED), or the combination of both methods (HDPCs-Combined). The expression of mesenchymal stem cell markers (CD105, CD90, and CD73) was investigated. In vitro differentiation capacities of HDPCs into adipogenic, osteogenic, and chondrogenic lineages were compared. Differentiation markers were analyzed by quantitative reverse-transcription polymerase chain reaction (RT-PCR) and western blotting.

RESULTS

Our data indicated that whole HDPCs-ED, HPDCs-OG, and HDPCs-Combined could be differentiated into adipogenic, chrondrogenic, and osteogenic cell types. However, we found that the methods for isolating and culturing HDPCs influence the differentiation capacities of cells. HDPCs-OG and HDPCs-ED were preferably differentiated into adipogenic and osteogenic cells, respectively. Differentiation markers shown by RT-PCR and western blotting analysis were mostly upregulated in the treated groups compared with the control groups.

CONCLUSIONS

Our findings confirmed that cell populations formed by two different culture methods and the combined culture method exhibited different properties. The results of this study could provide an insight into regenerative endodontic treatment using HDPCs.

Generation and characterization of a human nanobody against VEGFR-2

AIM

Nanobody is an antibody fragment consisting of a single monomeric variable antibody domain, which can be used for a variety of biotechnological and therapeutic purposes. The aim of this work was to isolate and characterize a human signal domain antibody against VEGFR-2 domain3 (VEGFR D3) from a phage display library.

METHODS

To produce antigen-specific recombinant nanobodies with high affinity to VEGFR2 D3, a liquid phase panning strategy was used for all rounds of panning. For nanobody expression and purification, four VEGFR2 D3-blocking clones were subcloned into a pETduet-biotin-MBP expression vector. The recombinant proteins carried an MBP tag to facilitate purification by affinity chromatography. Recombinant NTV(1-4) was obtained after an additional gel filtration chromatography step. The interactions between VEGFR2 D3 and NTV(1-4) were assessed with luminescence-based AlphaScreen assay and SPR assay. Anti-angiogenesis effects were examined in human umbilical vein endothelial cells (HUVECs).

RESULTS

In the AlphaScreen assay, NTV1 (100 and 200 nmol/L) elicited the highest binding signal with VEGFR2 D3; NTV2 showed moderate interactions with VEGFR2 D3; NTV3 and NTV4 exhibited little or no interaction with VEGFR2 D3. In the SPR assay, NTV1 displayed a high affinity for VEGFR2 D3 with an equilibrium dissociation constant (KD) of 49±1.8 nmol/L. NTV1 (1-1000 nmol/L) dose-dependently inhibited the proliferation of HUVECs and the endothelial tube formation by the HUVECs.

CONCLUSION

The nanobody NTV1 is a potential therapeutic candidate for blocking VEGFR2. This study provides a novel and promising strategy for development of VEGFR2-targeted nanobody-based cancer therapeutics.

Angiogenesis in glaucoma filtration surgery and neovascular glaucoma: A review

Angiogenesis may pose a clinical challenge in glaucoma, for example, during the wound healing phase after glaucoma filtration surgery and in the severe secondary glaucoma called neovascular glaucoma (NVG). Upregulation of vascular endothelial growth factor (VEGF), a key mediator of angiogenesis, occurs in eyes that have undergone glaucoma filtration surgery, as well as those with NVG. This has led investigation of the ability of anti-vascular endothelial growth factor therapy to improve outcomes, and we examine the findings with respect to the safety and efficacy of anti-vascular endothelial growth factor agents, mainly bevacizumab and ranibizumab, in eyes that have undergone glaucoma filtration surgery or have NVG. Combining conventional therapies-such as antimetabolites after filtration surgery and panretinal photocoagulation in NVG-and anti-vascular endothelial growth factor drugs may produce a synergetic effect, although further studies are required to evaluate the long-term efficacy of combination treatments.

Local application of periodontal ligament stromal cells promotes soft tissue regeneration

OBJECTIVES

To test the potential stimulatory effect of local application of periodontal ligament (PDL) stromal cells on soft tissue regeneration.

MATERIALS AND METHODS

Fluorescently labeled PDL cells outgrown from extracted human premolars or phosphate-buffered saline were locally injected to the cutaneous wounds created on mice. Soft tissue regeneration was evaluated for 14 days using photographs and histomorphometry. PDL cell engraftment was tracked with confocal microscopy. To detect the paracrine effect of the PDL cells on soft tissue regeneration, PDL cell-conditioned medium (CM) was evaluated for the concentration of secretory factors, transforming growth factor-beta 1 (TGFβ1). The effect of PDL CM on the proliferation and migration of dermal fibroblast and keratinocyte was tested using MTT assay and migration assay.

RESULTS

The application of PDL cells significantly promoted soft tissue regeneration compared with the application of PBS. Self-replicating PDL cells were engrafted into the hair follicles of the host tissue. Dermal fibroblast proliferation and keratinocyte migration were significantly enhanced by the treatment with PDL CM. Physiologically significant amount of TGFβ1 was secreted from PDL cells into the CM.

CONCLUSION

Local injection of PDL cells promoted soft tissue regeneration in part by the enhancement of fibroblast proliferation and keratinocyte migration through a paracrine mechanism.