Cell-printing and transfer technology applications for bone defects in mice

Adipose-Derived Stromal Cells and Mineralized Extracellular Matrix Delivery by a Human Decellularized Amniotic Membrane in Periodontal Tissue Engineering

Periodontitis is a prevalent disease characterized by the loss of periodontal supporting tissues, bone, periodontal ligament, and cementum. The application of a bone tissue engineering strategy with Decellularized Human Amniotic Membrane (DAM) with adipose-derived stromal cells (ASCs) has shown to be convenient and valuable. This study aims to investigate the treatments of a rat periodontal furcation defect model with DAM, ASCs, and a mineralized extracellular matrix (ECM). Rat ASCs were expanded, cultivated on DAM, and with a bone differentiation medium for four weeks, deposited ECM on DAM. Periodontal healing for four weeks was evaluated by micro-computed tomography and histological analysis after treatments with DAM, ASCs, and ECM and compared to untreated defects on five consecutive horizontal levels, from gingival to apical. The results demonstrate that DAM preserves its structure during cultivation and healing periods, supporting cell attachment, permeation, bone deposition on DAM, and periodontal regeneration. DAM and DAM+ASCs enhance bone healing compared to the control on the gingival level. In conclusion, DAM with ASC or without cells and the ECM ensures bone tissue healing. The membrane supported neovascularization and promoted osteoconduction.

Applications of Human Amniotic Membrane for Tissue Engineering

An important component of tissue engineering (TE) is the supporting matrix upon which cells and tissues grow, also known as the scaffold. Scaffolds must easily integrate with host tissue and provide an excellent environment for cell growth and differentiation. Human amniotic membrane (hAM) is considered as a surgical waste without ethical issue, so it is a highly abundant, cost-effective, and readily available biomaterial. It has biocompatibility, low immunogenicity, adequate mechanical properties (permeability, stability, elasticity, flexibility, resorbability), and good cell adhesion. It exerts anti-inflammatory, antifibrotic, and antimutagenic properties and pain-relieving effects. It is also a source of growth factors, cytokines, and hAM cells with stem cell properties. This important source for scaffolding material has been widely studied and used in various areas of tissue repair: corneal repair, chronic wound treatment, genital reconstruction, tendon repair, microvascular reconstruction, nerve repair, and intraoral reconstruction. Depending on the targeted application, hAM has been used as a simple scaffold or seeded with various types of cells that are able to grow and differentiate. Thus, this natural biomaterial offers a wide range of applications in TE applications. Here, we review hAM properties as a biocompatible and degradable scaffold. Its use strategies (i.e., alone or combined with cells, cell seeding) and its degradation rate are also presented.

Angiogenic Effects of Secreted Factors from Periodontal Ligament Stem Cells

Periodontal disease is a chronic inflammation of tooth-supporting tissues, and the destruction of these tissues results in tooth loss. Regeneration of periodontal tissues is the ultimate goal of periodontal treatment. We previously reported that transplantation of conditioned medium (CM) of periodontal ligament stem cells (PDLSCs) demonstrated the enhancement of periodontal tissue regeneration, compared to CM from fibroblasts (Fibroblast-CM). We hypothesized that the angiogenic effects of PDLSC-CM might participate in the enhanced wound healing of periodontal tissues. The aim of this study was to investigate the effect of PDLSC-CM on the functions of endothelial cells. PDLSCs were cultured from periodontal ligament tissues obtained from healthy volunteers. Human gingival epithelial cells, dermal fibroblasts, osteoblasts, and umbilical vein endothelial cells (HUVECs) were purchased from commercial sources. The functions of endothelial cells were examined using immunostaining of Ki67, observation of nuclear fragmentation and condensation (apoptosis), and network formation on Matrigel. Vascular endothelial cell growth factor (VEGF) level was measured using an ELISA kit. HUVECs demonstrated higher cell viability in PDLSC-CM when compared with those in Fibroblast-CM. HUVECs demonstrated a higher number of Ki67-positive cells and lower apoptosis cells in PDLSC-CM, compared to Fibroblast-CM. Additionally, HUVECs formed more capillary-like structures in PDLSC-CM than Fibroblast-CM. PDLSC-CM contained higher levels of angiogenic growth factor, VEGF, than Fibroblast-CM. Our results showed that PDLSC-CM increased cell viability, proliferation, and capillary formation of HUVECs compared to Fibroblast-CM, suggesting the angiogenic effects of PDLSC-CM, and the effect is a potential regenerative mechanism of periodontal tissues by PDLSC-CM.

Use of Amniotic Membrane and Its Derived Products for Bone Regeneration: A Systematic Review

Thanks to their biological properties, amniotic membrane (AM), and its derivatives are considered as an attractive reservoir of stem cells and biological scaffolds for bone regenerative medicine. The objective of this systematic review was to assess the benefit of using AM and amniotic membrane-derived products for bone regeneration. An electronic search of the MEDLINE-Pubmed database and the Scopus database was carried out and the selection of articles was performed following PRISMA guidelines. This systematic review included 42 articles taking into consideration the studies in which AM, amniotic-derived epithelial cells (AECs), and amniotic mesenchymal stromal cells (AMSCs) show promising results for bone regeneration in animal models. Moreover, this review also presents some commercialized products derived from AM and discusses their application modalities. Finally, AM therapeutic benefit is highlighted in the reported clinical studies. This study is the first one to systematically review the therapeutic benefits of AM and amniotic membrane-derived products for bone defect healing. The AM is a promising alternative to the commercially available membranes used for guided bone regeneration. Additionally, AECs and AMSCs associated with an appropriate scaffold may also be ideal candidates for tissue engineering strategies applied to bone healing. Here, we summarized these findings and highlighted the relevance of these different products for bone regeneration.

Assessment of fresh and preserved amniotic membrane for guided bone regeneration in mice

Thanks to its biological properties, the human amniotic membrane (HAM) can be used as a barrier membrane for guided bone regeneration (GBR). However, no study has assessed the influence of the preservation method of HAM for this application. This study aimed to establish the most suitable preservation method of HAM for GBR. Fresh (F), cryopreserved (C) lyophilized (L), and decellularized and lyophilized (DL) HAM were compared. The impact of preservation methods on collagen and glycosaminoglycans (GAG) content was evaluated using Masson's trichrome and alcian blue staining. Their suture retention strengths were assessed. In vitro, the osteogenic potential of human bone marrow mesenchymal stromal cells (hBMSCs) cultured on the four HAMs was evaluated using alkaline phosphatase staining and alizarin red quantification assay. In vivo, the effectiveness of fresh and preserved HAMs for GBR was assessed in a mice diaphyseal bone defect after 1 week or 1 month healing. Micro-CT and histomorphometric analysis were performed. The major structural components of HAM (collagen and GAG) were preserved whatever the preservation method used. The tearing strength of DL-HAM was significantly higher. In vitro, hBMSCs seeded on DL-HAM displayed a stronger ALP staining, and alizarin red staining quantification was significantly higher at Day 14. In vivo, L-HAM and DL-HAM significantly enhanced early bone regeneration. One month after the surgery, only DL-HAM slightly promoted bone regeneration. Several preserving methods of HAM have been studied for bone regeneration. Here, we have demonstrated that DL-HAM achieved the most promising results for GBR.

Past, Present, and Future of Regeneration Therapy in Oral and Periodontal Tissue: A Review

Chronic periodontitis is the most common disease which induces oral tissue destruction. The goal of periodontal treatment is to reduce inflammation and regenerate the defects. As the structure of periodontium is composed of four types of different tissue (cementum, alveolar bone periodontal ligament, and gingiva), the regeneration should allow different cell proliferation in the separated spaces. Guided tissue regeneration (GTR) and guided bone regeneration (GBR) were introduced to prevent epithelial growth into the alveolar bone space. In the past, non-absorbable membranes with basic functions such as space maintenance were used with bone graft materials. Due to several limitations of the non-absorbable membranes, membranes of the second and third generation equipped with controlled absorbability, and a functional layer releasing growth factors or antimicrobials were introduced. Moreover, tissue engineering using biomaterials enabled faster and more stable tissue regeneration. The scaffold with three-dimensional structures manufactured by computer-aided design and manufacturing (CAD/CAM) showed high biocompatibility, and promoted cell infiltration and revascularization. In the future, using the cell sheath, pre-vascularizing and bioprinting techniques will be applied to the membrane to mimic the original tissue itself. The aim of the review was not only to understand the past and the present trends of GTR and GBR, but also to be used as a guide for a proper future of regeneration therapy in the oral region.

The Fate of Transplanted Periodontal Ligament Stem Cells in Surgically Created Periodontal Defects in Rats

Periodontal disease is chronic inflammation that leads to the destruction of tooth-supporting periodontal tissues. We devised a novel method (“cell transfer technology”) to transfer cells onto a scaffold surface and reported the potential of the technique for regenerative medicine. The aim of this study is to examine the efficacy of this technique in periodontal regeneration and the fate of transplanted cells. Human periodontal ligament stem cells (PDLSCs) were transferred to decellularized amniotic membrane and transplanted into periodontal defects in rats. Regeneration of tissues was examined by microcomputed tomography and histological observation. The fate of transplanted PDLSCs was traced using PKH26 and human Alu sequence detection by PCR. Imaging showed more bone in PDLSC-transplanted defects than those in control (amnion only). Histological examination confirmed the enhanced periodontal tissue formation in PDLSC defects. New formation of cementum, periodontal ligament, and bone were prominently observed in PDLSC defects. PKH26-labeled PDLSCs were found at limited areas in regenerated periodontal tissues. Human Alu sequence detection revealed that the level of Alu sequence was not increased, but rather decreased. This study describes a novel stem cell transplantation strategy for periodontal disease using the cell transfer technology and offers new insight for cell-based periodontal regeneration.

Human amniotic membrane for guided bone regeneration of calvarial defects in mice

Due to its biological properties, human amniotic membrane (hAM) is widely studied in the field of tissue engineering and regenerative medicine. hAM is already very attractive for wound healing and it may be helpful as a support for bone regeneration. However, few studies assessed its potential for guided bone regeneration (GBR). The purpose of the present study was to assess the potential of the hAM as a membrane for GBR. In vitro, cell viability in fresh and cryopreserved hAM was assessed. In vivo, we evaluated the impact of fresh versus cryopreserved hAM, using both the epithelial or the mesenchymal layer facing the defect, on bone regeneration in a critical calvarial bone defect in mice. Then, the efficacy of cryopreserved hAM associated with a bone substitute was compared to a collagen membrane currently used for GBR. In vitro, no statistical difference was observed between the conditions concerning cell viability. Without graft material, cryopreserved hAM induced more bone formation when the mesenchymal layer covered the defect compared to the defect left empty. When associated with a bone substitute, such improved bone repair was not observed. These preliminary results suggest that cryopreserved hAM has a limited potential for GBR.

What is the benefit of using amniotic membrane in oral surgery? A comprehensive review of clinical studies

OBJECTIVES

Since its first use for the reconstruction of tissue defects in the oral cavity in 1985, human amniotic membrane (hAM) has been widely studied in the field of oral surgery. Despite the growing number of publications in this field, there is no systematic review or meta-analysis concerning its clinical applications, outcome assessments, and relevance in oral surgery. The aim of this review is to provide a thorough understanding of the potential use of hAM for soft and hard tissue reconstruction in the oral cavity.

MATERIALS AND METHODS

A systematic electronic and a manual literature search of the MEDLINE-PubMed database and Scopus database was completed. Patient, Intervention, Comparison and Outcomes (PICO) technique was used to select the relevant articles to meet the objective. Studies using hAM for oral reconstruction, and conducted on human subjects, were included in this survey.

RESULTS

A total of 17 articles were analyzed. Five areas of interest were identified as potential clinical application: periodontal surgery, cleft palate and tumor reconstruction, prosthodontics and peri-implant surgery. Overall, periodontal surgery was the only discipline to assess the efficacy of hAM with randomized clinical trials. The wide variability of preservation methods of hAM and the lack of objective measurements were observed in this study.

CONCLUSION

hAM is already used in the field of oral surgery. Despite this, there is weak clinical evidence demonstrating convincingly the benefit of hAM in this area compared to standard surgery.

CLINICAL RELEVANCE

Several studies now suggest the interest of hAM for periodontal tissue repair. Due to its biological and mechanical properties, hAM seems to be a promising treatment for wound healing in various areas of oral reconstruction. However, further randomized clinical trials are needed to confirm these preliminary results.

Cell transfer technology for tissue engineering

We recently developed novel cell transplantation method “cell transfer technology” utilizing photolithography. Using this method, we can transfer ex vivo expanded cells onto scaffold material in desired patterns, like printing of pictures and letters on a paper. We have investigated the possibility of this novel method for cell-based therapy using several disease models. We first transferred endothelial cells in capillary-like patterns on amnion. The transplantation of the endothelial cell-transferred amnion enhanced the reperfusion in mouse ischemic limb model. The fusion of transplanted capillary with host vessel networks was also observed. The osteoblast- and periodontal ligament stem cell-transferred amnion were next transplanted in bone and periodontal defects models. After healing period, both transplantations improved the regeneration of bone and periodontal tissues, respectively. This method was further applicable to transfer of multiple cell types and the transplantation of osteoblasts and periodontal ligament stem cell-transferred amnion resulted in the improved bone regeneration compared with single cell type transplantation. These data suggested the therapeutic potential of the technology in cell-based therapies for reperfusion of ischemic limb and regeneration of bone and periodontal tissues. Cell transfer technology is applicable to wide range of regenerative medicine in the future.

The interfacial pH of acidic degradable polymeric biomaterials and its effects on osteoblast behavior

A weak alkaline environment is established to facilitate the growth of osteoblasts. Unfortunately, this is inconsistent with the application of biodegradable polymer in bone regeneration, as the degradation products are usually acidic. In this study, the variation of the interfacial pH of poly (D, L-lactide) and piperazine-based polyurethane ureas (P-PUUs), as the representations of acidic degradable materials, and the behavior of osteoblasts on these substrates with tunable interfacial pH were investigated in vitro. These results revealed that the release of degraded products caused a rapid decrease in the interfacial pH, and this could be relieved by the introduction of alkaline segments. On the contrary, when culturing with osteoblasts, the variation of the interfacial pH revealed an upward tendency, indicating that cell could construct the microenvironment by secreting cellular metabolites to satisfy its own survival. In addition, the behavior of osteoblasts on substrates exhibited that P-PUUs with the most PP units were better for cell growth and osteogenic differentiation of cells. This is due to the hydrophilic surface and the moderate N% in P-PUUs, key factors in the promotion of the early stages of cellular responses, and the interfacial pH contributing to the enhanced effect on osteogenic differentiation.

Double-layered cell transfer technology for bone regeneration

For cell-based medicine, to mimic in vivo cellular localization, various tissue engineering approaches have been studied to obtain a desirable arrangement of cells on scaffold materials. We have developed a novel method of cell manipulation called “cell transfer technology”, enabling the transfer of cultured cells onto scaffold materials, and controlling cell topology. Here we show that using this technique, two different cell types can be transferred onto a scaffold surface as stable double layers or in patterned arrangements. Various combinations of adherent cells were transferred to a scaffold, amniotic membrane, in overlapping bilayers (double-layered cell transfer), and transferred cells showed stability upon deformations of the material including folding and trimming. Transplantation of mesenchymal stem cells from periodontal ligaments (PDLSC) and osteoblasts, using double-layered cell transfer significantly enhanced bone formation, when compared to single cell type transplantation. Our findings suggest that this double-layer cell transfer is useful to produce a cell transplantation material that can bear two cell layers. Moreover, the transplantation of an amniotic membrane with PDLSCs/osteoblasts by cell transfer technology has therapeutic potential for bone defects. We conclude that cell transfer technology provides a novel and unique cell transplantation method for bone regeneration.

Periodontal regeneration using periodontal ligament stem cell-transferred amnion

Periodontal disease is characterized by the destruction of tooth supporting tissues. Regeneration of periodontal tissues using ex vivo expanded cells has been introduced and studied, although appropriate methodology has not yet been established. We developed a novel cell transplant method for periodontal regeneration using periodontal ligament stem cell (PDLSC)-transferred amniotic membrane (PDLSC-amnion). The aim of this study was to investigate the regenerative potential of PDLSC-amnion in a rat periodontal defect model. Cultured PDLSCs were transferred onto amniotic membranes using a glass substrate treated with polyethylene glycol and photolithography. The properties of PDLSCs were investigated by flow cytometry and in vitro differentiation. PDLSC-amnion was transplanted into surgically created periodontal defects in rat maxillary molars. Periodontal regeneration was evaluated by microcomputed tomography (micro-CT) and histological analysis. PDLSCs showed mesenchymal stem cell-like characteristics such as cell surface marker expression (CD90, CD44, CD73, CD105, CD146, and STRO-1) and trilineage differentiation ability (i.e., into osteoblasts, adipocytes, and chondrocytes). PDLSC-amnion exhibited a single layer of PDLSCs on the amniotic membrane and stability of the sheet even with movement and deformation caused by surgical instruments. We observed that the PDLSC-amnion enhanced periodontal tissue regeneration as determined by micro-CT and histology by 4 weeks after transplantation. These data suggest that PDLSC-amnion has therapeutic potential as a novel cell-based regenerative periodontal therapy.