Skeletal myogenic differentiation of human periodontal ligament stromal cells isolated from orthodontically extracted premolars

Comparative analysis of proliferative and multilineage differentiation potential of human periodontal ligament stem cells from maxillary and mandibular molars

BACKGROUND

Clinical experience indicates that wounds in alveolar bone and periodontal tissue heal faster and more efficiently in the maxilla compared with the mandible. Since stem cells are known to have a decisive influence on wound healing and tissue regeneration, the aim of this study was to determine whether differences in proliferation and differentiation of periodontal ligament stem cells (PDLSC) from upper (u-PDLSC) and lower jaw (l-PDLSC) contribute to the enhanced wound healing in the maxilla.

METHODS

u-PDLSC and l-PDLSC from the same donor were harvested from the periodontal ligament of extracted human maxillary and mandibular third molars. Cell differentiation potential was assessed by analyzing stem cell markers, proliferation rate, and multilineage differentiation among each other and bone marrow-derived mesenchymal stem cells (MSC). Successful differentiation of PDLSC and MSC toward osteoblasts, adipocytes, and chondrocytes was analyzed via reverse transcriptase-quantitative polymerase chain reaction and histochemical staining (Alizarin Red, Oil Red O, Toluidine Blue).

RESULTS

u-PDLSC and l-PDLSC expressed the MSC-markers CD73+ , CD90+ , and CD105+ and lacked expression of CD34- and CD45- . Proliferation was significantly higher in u-PDLSC than in l-PDLSC, regardless of the culture conditions. Osteogenic (ALP, RunX2, and osteocalcin) and chondrogenic (SOX9 and ACAN) related gene expression as well as staining intensities were significantly higher in u-PDLSC than in l-PDLSC. No difference in adipogenic differentiation was observed.

CONCLUSION

u-PDLSC showed a significantly higher proliferative and differentiation potential than l-PDLSC, offering a possible cell-based explanation for the differences in periodontal wound healing efficacy between maxilla and mandible.

Transforming Growth Factor-β3/Recombinant Human-like Collagen/Chitosan Freeze-Dried Sponge Primed With Human Periodontal Ligament Stem Cells Promotes Bone Regeneration in Calvarial Defect Rats

Patients with a skull defect are at risk of developing cerebrospinal fluid leakage and ascending bacterial meningitis at >10% per year. However, treatment with stem cells has brought great hope to large-area cranial defects. Having found that transforming growth factor (TGF)-β3 can promote the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs), we designed a hybrid TGF-β3/recombinant human-like collagen recombinant human collagen/chitosan (CS) freeze-dried sponge (TRFS) loading hPDLSCs (TRFS-h) to repair skull defects in rats. CFS with 2% CS was selected based on the swelling degree, water absorption, and moisture retention. The CS freeze-dried sponge (CFS) formed a porous three-dimensional structure, as observed by scanning electron microscopy. In addition, cytotoxicity experiments and calcein-AM/PI staining showed that TRFS had a good cellular compatibility and could be degraded completely at 90 days in the implantation site. Furthermore, bone healing was evaluated using micro-computed tomography in rat skull defect models. The bone volume and bone volume fraction were higher in TRFS loaded with hPDLSCs (TRFS-h) group than in the controls (p < 0.01, vs. CFS or TRFS alone). The immunohistochemical results indicated that the expression of Runx2, BMP-2, and collagen-1 (COL Ⅰ) in cells surrounding bone defects in the experimental group was higher than those in the other groups (p < 0.01, vs. CFS or TRFS alone). Taken together, hPDLSCs could proliferate and undergo osteogenic differentiation in TRFS (p < 0.05), and TRFS-h accelerated bone repair in calvarial defect rats. Our research revealed that hPDLSCs could function as seeded cells for skull injury, and their osteogenic differentiation could be accelerated by TGF-β3. This represents an effective therapeutic strategy for restoring traumatic defects of the skull.

Comparative study of hyperpure chlorine dioxide with two other irrigants regarding the viability of periodontal ligament stem cells

Objectives

Periodontal ligament stem cells (PDLSCs) have an underlined significance as their high proliferative capacity and multipotent differentiation provide an important therapeutic potential. The integrity of these cells is frequently disturbed by the routinely used irrigative compounds applied as periodontal or endodontic disinfectants (e.g., hydrogen peroxide (H₂O₂) and chlorhexidine (CHX)). Our objectives were (i) to monitor the cytotoxic effect of a novel dental irrigative compound, chlorine dioxide (ClO₂), compared to two traditional agents (H₂O₂, CHX) on PDLSCs and (ii) to test whether the aging factor of PDLSC cultures determines cellular responsiveness to the chemicals tested.

Methods

Impedimetry (concentration-response study), WST-1 assays (WST = water soluble tetrazolium salt), and morphology analysis were performed to measure changes in cell viability induced by the 3 disinfectants; immunocytochemistry of stem cell markers (STRO-1, CD90, and CD105) measured the induced mesenchymal characteristics.

Results

Cell viability experiments demonstrated that the application of ClO₂ does not lead to a significant decrease in viability of PLDSCs in concentrations used to kill microbes. On the contrary, traditional irrigants, H₂O₂, and CHX are highly toxic on PDLSCs. Aging of PLDSC cultures (passages 3 vs. 7) has characteristic effects on their responsiveness to these agents as the increased expression of mesenchymal stem cell markers turns to decreased.

Conclusions and clinical relevance

While the active ingredients of mouthwash (H₂O₂, CHX) applied in endodontic or periodontitis management have a serious toxic effect on PDLSCs, the novel hyperpure ClO₂ is less toxic providing an environment favoring dental structure regenerations during disinfectant interventions.

Electronic supplementary material

The online version of this article (10.1007/s00784-020-03618-5) contains supplementary material, which is available to authorized users.

Mass acquisition of human periodontal ligament stem cells

The periodontal ligament (PDL) is an essential fibrous tissue for tooth retention in the alveolar bone socket. PDL tissue further functions to cushion occlusal force, maintain alveolar bone height, allow orthodontic tooth movement, and connect tooth roots with bone. Severe periodontitis, deep caries, and trauma cause irreversible damage to this tissue, eventually leading to tooth loss through the destruction of tooth retention. Many patients suffer from these diseases worldwide, and its prevalence increases with age. To address this issue, regenerative medicine for damaged PDL tissue as well as the surrounding tissues has been extensively investigated regarding the potential and effectiveness of stem cells, scaffolds, and cytokines as well as their combined applications. In particular, PDL stem cells (PDLSCs) have been well studied. In this review, I discuss comprehensive studies on PDLSCs performed in vivo and contemporary reports focusing on the acquisition of large numbers of PDLSCs for therapeutic applications because of the very small number of PDLSCs available in vivo.

A compound of concentrated growth factor and periodontal ligament stem cell-derived conditioned medium

The aim of this study was to determine the in vitro effect of a compound of concentrated growth factor (CGF) and periodontal ligament stem cell-derived conditioned medium (PDLSCs-CM) as a potential product for future applications in periodontal tissue regeneration. Isolated PDLSCs were characterized using flow cytometry and differentiation into osteoblasts and adipocytes cells. PDLSCs-CM and CGF were prepared and lyophilized. To determine the optimal concentration of the CGF-CM compound, the proliferation of PDLSCs after exposure to a wide range of different concentrations of CGF, CM, or their combination (CGF + CM) was investigated by methyl thiazol tetrazolium assay. Successful isolation of PDLSCs was confirmed by high expression of mesenchymal surface markers and differentiation into osteoblasts and adipocytes. PDLSCs showed higher proliferation in the 6.25 mg/mL concentration of CM and 94 μg/mL concentration of CGF. High concentrations of CGF and CM markedly inhibited the proliferation of PDLCs (p < 0.05). The exposure of PDLSCs to the compound of 10% CM + 90% CGF significantly increased the cell proliferation (p < 0.05). The results showed that CGF, CM, or their combination exert a proliferative effect on cells at a certain concentration. Further investigation on the synergistic effect of this compound may approve its application for periodontal regeneration.

Lapine periodontal ligament stem cells for musculoskeletal research in preclinical animal trials

Background

Human periodontal ligament stem cells (hPDLSCs) have been shown to be a reliable source of mesenchymal stem cells (MSCs). On the other hand, rabbits have been commonly used in preclinical trials for musculoskeletal research. However, there is a lack of sufficient data on using rabbit periodontal ligament stem cells (rPDLSCs) for regenerative dentistry. This study, for the first time, comprehensively compared rPDLSCs against hPDLSCs in terms of clonogenicity, growth potential, multi-differential capacity and surface antigens.

Methods

Periodontal ligament (PDL) was obtained from the rabbit and human teeth. rPDL and hPDL cells were isolated from PDL using enzymatic digestion method. After culturing for 2 weeks, the cells were first analyzed microscopically. STRO-1⁺CD146⁺ PDLSCs were then sorted from PDL cells by fluorescence-activated cell sorting (FACS) followed by examination of CD34, CD45, CD90, vimentin and desmin markers. The cells were also evaluated by immunohistocytochemical and multi-differentiation potential tests. The clonogenicity and growth of PDL cells were analyzed by Independent T test and 2-way repeated measures ANOVA respectively.

Results

rPDL cells were broader and less elongated as compared to hPDL cells. STRO-1⁺CD146⁺ hPDLSCs were isolated from hPDL cells but not from the rPDL cells. Therefore, heterogeneous population of rabbit and human PDL cells were subsequently used for latter comparative studies. FACS analysis and immunohistocytochemistry revealed that rPDL cells were partially positive for STRO-1 as compared to hPDL cells. Furthermore, both rPDL cells and hPDL cells were positive for CD146, CD90, vimentin, and desmin, while negative for CD34 and CD45. No difference in clonogenicity between rPDL and hPDL cells was found (p > 0.05). The proliferative potential of rPDL cells displayed significantly slower growth as compared to hPDL cells (p < 0.05). Osteogenic, adipogenic, and chondrogenic differentiation potential was comparatively less in rPDL cells than that of hPDL cells, but the neurogenic differential potential was similar.

Conclusion

Although rPDL cells manifested variable differences in expression of stem cell markers and multi-differential potential as compared to hPDL cells, they demonstrated the attributes of stemness. Further studies are also required to validate if the regenerative potential of rPDL cells is similar to rPDLSCs.

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.

Postnatal periodontal ligament as a novel adult stem cell source for regenerative corneal cell therapy

Corneal opacities are a leading cause of global blindness. They are conventionally treated by the transplantation of donor corneal tissue, which is, restricted by a worldwide donor material shortage and allograft rejection. Autologous adult stem cells with a potential to differentiate into corneal stromal keratocytes (CSKs) could offer a suitable choice of cells for regenerative cell therapy. Postnatal periodontal ligament (PDL) contains a population of adult stem cells, which has a similar embryological origin as CSK, that is cranial neural crest. We harvested PDL cells from young adult teeth extracted because of non-functional or orthodontic reason and differentiated them towards CSK phenotype using a two-step protocol with spheroid formation followed by growth factor and cytokine induction in a stromal environment (human amnion stroma and porcine corneal stroma). Our results showed that the PDL-differentiated CSK-like cells expressed CSK markers (CD34, ALDH3A1, keratocan, lumican, CHST6, B3GNT7 and Col8A2) and had minimal expression of genes related to fibrosis and other lineages (vasculogenesis, adipogenesis, myogenesis, epitheliogenesis, neurogenesis and hematogenesis). Introduction of PDL spheroids into the stroma of porcine corneas resulted in extensive migration of cells inside the host stroma after 14-day organ culture. Their quiescent nature and uniform cell distribution resembled to that of mature CSKs inside the native stroma. Our results demonstrated the potential translation of PDL cells for regenerative corneal cell therapy for corneal opacities.

Dental stem cells: a future asset of ocular cell therapy

Regenerative medicine using patient's own stem cells (SCs) to repair dysfunctional tissues is an attractive approach to complement surgical and pharmacological treatments for aging and degenerative disorders. Recently, dental SCs have drawn much attention owing to their accessibility, plasticity and applicability for regenerative use not only for dental, but also other body tissues. In ophthalmology, there has been increasing interest to differentiate dental pulp SC and periodontal ligament SC (PDLSC) towards ocular lineage. Both can commit to retinal fate expressing eye field transcription factors and generate rhodopsin-positive photoreceptor-like cells. This proposes a novel therapeutic alternative for retinal degeneration diseases. Moreover, as PDLSC shares similar cranial neural crest origin and proteoglycan secretion with corneal stromal keratoctyes and corneal endothelial cells, this offers the possibility of differentiating PDLSC to these corneal cell types. The advance could lead to a shift in the medical management of corneal opacities and endothelial disorders from highly invasive corneal transplantation using limited donor tissue to cell therapy utilizing autologous cells. This article provides an overview of dental SC research and the perspective of utilizing dental SCs for ocular regenerative medicine.

Increased CCL19 and CCL21 levels promote fibroblast ossification in ankylosing spondylitis hip ligament tissue

Background

It is well-documented that both chemokine (C-C motif) ligand 19 (CCL19) and 21 (CCL21) mediate cell migration and angiogenesis in many diseases. However, these ligands’ precise pathological role in ankylosing spondylitis (AS) has not been elucidated. The objective of this study was to examine the expression of CCL19 and CCL21 (CCL19/CCL21) in AS hip ligament tissue (LT) and determine their pathological functions.

Methods

The expression levels of CCL19, CCL21 and their receptor CCR7 in AS (n = 31) and osteoarthritis (OA, n = 21) LT were analyzed via real-time polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). The expression of CCL19, CCL21 and CCR7 in AS ligament fibroblasts was also detected. The proliferation of ligament fibroblasts was measured via a cell counting kit-8 (CCK8) assay after exogenous CCL19/CCL21 treatment. Additionally, the role of CCL19/CCL21 in osteogenesis was evaluated via RT-PCR and enzyme-linked immunosorbent assay (ELISA) in individual AS fibroblast cultures. Furthermore, the expression of the bone markers alkaline phosphatase (ALP), osteocalcin (OCN), collagenase I (COL1), integrin-binding sialoprotein (IBSP) and the key regulators runt-related transcription factor-2 (Runx-2) and osterix were investigated. Moreover, the CCL19/CCL21 levels in serum and LT were measured via ELISA.

Results

The mRNA levels of CCL19/CCL21 in AS hip LT were significantly higher than that in OA LT, and IHC analysis revealed a similar result. Exogenous CCL19/CCL21 treatment did not affect the proliferation of ligament fibroblasts but significantly up-regulated the expression of bone markers, including ALP and OCN, and the key regulators Runx-2 and osterix. In addition, the serum levels of CCL19/CCL21 were apparently elevated in AS patients compared to healthy controls (HC), and the expression of the two chemokines correlated significantly in AS patients.

Conclusions

CCL19 and CCL21, two chemokines displaying significantly associated expression in serum, indicating a synergistic effect on AS pathogenesis, may function as promoters of ligament ossification in AS patients.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-316) contains supplementary material, which is available to authorized users.

Systemic treatment with strontium ranelate accelerates the filling of a bone defect and improves the material level properties of the healing bone

Rapid bone defect filling with normal bone is a challenge in orthopaedics and dentistry. Strontium ranelate (SrRan) has been shown to in vitro decrease bone resorption and increase bone formation, and represents a potential agent with the capacity to accelerate bone defect filling. In this study, bone tibial defects of 2.5 mm in diameter were created in 6-month-old female rats orally fed SrRan (625 mg/kg/d; 5/7 days) or vehicle for 4, 8, or 12 weeks (10 rats per group per time point) from the time of surgery. Tibias were removed. Micro-architecture was determined by micro-computed tomography (µCT) and material level properties by nanoindentation analysis. µCT analysis showed that SrRan administration significantly improved microarchitecture of trabecular bone growing into the defect after 8 and 12 weeks of treatment compared to vehicle. SrRan treatment also accelerated the growth of cortical bone over the defect, but with different kinetics compared to trabecular bone, as the effects were already significant after 4 weeks. Nanoindentation analysis demonstrated that SrRan treatment significantly increased material level properties of both trabecular bone and cortical bone filling the defect compared to vehicle. SrRan accelerates the filling of bone defect by improving cortical and trabecular bone microarchitecture both quantitatively and qualitatively.

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.