Review Article
Volume 2 Issue 5 - 2015
Self-Assembling Peptide Nano fibrous Hydrogel Scaffold (PuramatrixTM) in Regenerative Endodontics
Constanza L Jiménez1, Mira S Haidar2 and Ziyad S Haidar1,3,4*
1BioMAT’X, Facultad de Odontología, Universidad de Los Andes, Santiago de Chile
2Programa de Diplomado en Endodoncia, Facultad de Odontología, Universidad de Los Andes, Santiago de Chile
3Plan de Mejoramiento Institucional (PMI) en Innovación I+D+i, Universidad de Los Andes, Santiago de Chile
4Centro de Investigación Biomédica, Facultad de Medicina, Universidad de Los Andes, Santiago de Chile
*Corresponding Author: Prof. Dr. Ziyad S Haidar, Professor and Scientific Director, Facultad de Odontología, Universidad de los Andes, Mons. Álvaro del Portillo 12.455 - Las Condes, Santiago, Chile. Founder and Head of BioMAT’X (Biomaterials, Pharmaceutical Delivery and Cranio-Maxillo-Facial Tissue Engineering Laboratory and Research Group), Biomedical Research Center (CIB), PMI I+D+i, Department for Research, Development and Innovation, Universidad de los Andes, Mons. Álvaro del Portillo 12.455 - Las Condes, Santiago, Chile.
Received: October 02, 2015; Published: October 19, 2015
Citation: Ziyad S Haidar., et al. “Self-Assembling Peptide Nano fibrous Hydrogel Scaffold (PuramatrixTM) in Regenerative Endodontics”. EC Dental Science 2.5 (2015): 394-402.
Abstract
Regenerative Endodontics is a novel discipline within Dentistry that aims to treat necrotized and infected teeth through regeneration, repair and restoration of the dentin-pulp complex. PuraMatrix™ is a commercially-available self-assembling peptide nano fibrous scaffold with appealing properties for dental pulp regeneration. This review provides an up-to-date overview of the prospective use of PuraMatrix™ for dentin-pulp regeneration.
Although the number of studies identified can be considered a limitation, available/accruing evidence suggests that self-assembling peptide PuraMatrix™ is a promising nano fibrous hydrogel scaffold for stem cell-based engineering and regeneration of functional dental pulp tissues. Additional studies are deemed necessary to assess safety, efficacy, impact potential and cost-effectiveness of this new technology on the future of Regenerative Endodontics and beyond.
A structured and systematic literature search and analysis was performed. PuraMatrix™ supports survival, proliferation and migration of hDPSC/hSHED without interference with odonto-/osteo-genic differentiation. Culture of stem cell/PuraMatrix™ constructs supplemented with induction media resulted in increased ALP activity and formation of calcium salt deposits. Same constructs in normal medium co-cultured with tooth slices or root segments showed increased expression of odontoblastic markers (DSPP, DMP-1, MEPE). In animal studies, hDPSC/PuraMatrix™ hydrogel constructs subcutaneously implanted in SCID mice produced highly-vascular mineralized tissues with strong osteogenic marker expression (Parathyroid Hormone receptor, Osteopontin, Osteocalcin, Osteonectin). Same constructs inserted into root segment implants formed vascularized pulp-like tissues which occupied the whole extension of the root canal and produced new dentin.
Keywords: Dental Pulp; Hydrogel; Nano fiber; PuraMatrix; Regenerative Endodontics; Stem Cells; Tissue Engineering
Abbreviations: MTA: Mineral Trioxide Aggregate; hSCAP: Human Apical Papillae Stem Cell; hDPSC: Human Dental Pulp Stem Cell; hSHED: Human Exfoliated Deciduous Teeth Stem Cell; HUVEC: Human Umbilical Vein Cord Cell; DSPP: Dentin Sialo-Phosphoprotein; DMP-1: Dentin Matrix Protein-1
Introduction
Caries, dental trauma and forceful orthodontic treatments which intrude or extrude teeth may result in dental pulp necrosis. In young teeth, necrosis interrupts root development leading to incomplete dentinogenesis, narrow dentin walls and large pulp chambers which increase the risk of fracture upon trauma and reduce survival rate of the affected teeth [1]. While traditional endodontic treatment for such cases (usually by means of multiple visit apexification using calcium hydroxide and other materials) allows control of the infection with reasonable success rates in terms of periapical healing; it does not provide the necessary stimulus to regenerate the dentin-pulp complex, resume root development or strengthen root structure; reason for which long-term structural integrity of these teeth remains compromised [1,2].
Recent advances in stem cell biology, genetics and tissue engineering gave raise to “Regenerative Endodontics”; a novel field within dentistry which aims to treat (repair, restore and regenerate) necrotized and infected immature teeth via the regeneration of the dentin-pulp complex. The original concept dates back to 1932, when stomatologist G.L. Feldman first proposed the use dentine fillings in order to stimulate remaining viable dental pulp cells within root canals to proliferate and regenerate continuing interrupted root development [2]. Since then, numerous regenerative approaches have been developed and tested including root canal revascularization, post-natal stem cell therapy, scaffold implantation, pulp implantation, 3D cell printing and gene therapy [2]. It is noteworthy that Root canal revascularization is the only aforementioned method currently approved for routine clinical application. Treatment is based upon the principle that under ideal circumstances [i.e. tight coronal tooth seal, absence of bacteria and necrotic tissues within root canal system, presence of an adequate intra-canal blood-derived scaffold, etc …], viable progenitor cells from the surrounding peri-apical tissues may re-populate root canal space differentiating into primary odontoblasts which re-establish the dentin-pulp complex for resuming normal root development [1]. Retrospective outcome studies of this approach demonstrate that root canal revascularization successfully increases both, tooth length and dentin wall thickness; with treated teeth exhibiting significantly higher survival rates and radiographic healing (of periapical lesions) when compared to the previous calcium hydroxide apexification or MTA apical plug approaches/strategies. Nonetheless, similar studies have reported several un-favorable outcomes including: (a) higher risk of tooth discoloration (derived from the use of minocycline as a root canal antibiotic), (b)unpredictable root development in long-term pulp necrosis cases (> 6 months, presumably due to absence of viable periapical progenitor cells) and (c) empty root canal spaces (presumably due to lack of tissue regeneration) [1]. Additionally, accumulating evidence obtained from pre-clinical and animal/in vivo studies shows that root canal revascularization is not predictable in terms of which type of tissue is formed within the root canal space. Indeed, studies often report the presence of cementum-like, bone-like and periodontal ligament-like tissues instead of dentin-pulp complex structures [3-5]. Similar results (Table 1) have been reported in limited human case reports [6-8], suggesting that the foreseen biological outcomes of root canal revascularization are not predictable and may not allow for true dentin-pulp regeneration to happen [1,3-5].
  Re-vascularization Stem Cell/PuraMatrix™
Application Clinical Research
Colonizing cells Random progenitor cells from periapical tissues (probably hSCAP) [1]. Customized according needs (i.e. hDPSC, hSHED or HUVEC).
Dental-pulp regeneration Unpredictable (formation of cementoid, osteoid and periodontal ligament-like tissues) (3–5) Osteoid and Dentin pulp-like tissues [14-16].
Dentin formation Yes [1]. Yes [16].
Root length Increased [1]. Not reported.
Root wall thickness Increased [1]. Increased [16].
Tooth survival Increased [1]. Unknown.
Disadvantages Risk of tooth discoloration (derived from antibiotic use) [1]. Unpredictable results in long-term pulp necrosis cases (> 6 months) [1]. Empty root canals [1]. Higher cost of implementation.
Table 1: Re-vascularization vs. Stem Cell/PuraMatrix™ Dental Pulp Regeneration.
Furthermore, the regeneration of cementoid, osteoid and periodontal ligament tissues within root canals treated with re-vascularization approaches may relate to the peri-apical origin of colonizing progenitor cells which are theorized to be “Apical Papillae Stem Cells” or SCAP. SCAP are highly un-differentiated/multi potent stem cells responsible for radicular pulp and root-complex formation. As such, they are capable to differentiate intodentin-pulp, cement, alveolar bone and periodontal ligament structures [9]. Absence of specific differentiation cues within the re-vascularized root canals may induce SCAP to indiscriminately differentiate into peri-apical tissues instead of dentin-pulp structures; resulting in failed endodontic regeneration. In this context, the use of alternative progenitor cell lines with preference for dentin-pulp structure formation may be a solution. Within the oral mesenchymal stem cells, Dental Pulp Mesenchymal Stem Cells (DPSC) and Exfoliated Deciduous Teeth Stem Cells (SHED) show this quality and potential. Both (Table 2) have been reported to contain specific sub-populations capable to differentiate into odontoblasts, neurons and endothelial cells [9], all crucial for the successful regeneration of functional dental pulp with appropriate immune responsiveness, vitality and sensibility [1]. However, one of the main challenges for the clinical application of DPSC and SHED continues to be the need for an appropriate scaffold or delivery system; which allows both, release and support of cells within root canals. From a clinical stand point, an ideal scaffold can be expected to: (a) Adapt and model root canal anatomy, (b) Setin a reasonable clinical time, and; (c) Orient DPSC and SHED towards odontoblast differentiation. Thus, the commercially-available peptide nano fibrous hydrogel scaffold known as PuraMatrix™ (BD Bioscience, Bedford, MA) seems to be a naturally-appealing solution and strategy for dental pulp regeneration (Figure 1). Briefly, the material is characterized by: (a) Liquid/solution and may be easily and directly injected into the pulp chamber and the root canals [10], (b) Self-polymerizes rapidly under physiological conditions, forming a solid 3-Dhydrogel which also encapsulates cells (allowing adequate delivery into target structures) and supports their survival and proliferation [11,12], (c) May be customized at the molecular level according to special or individual needs [13]. Hence, the purpose of this review is to provide an up-to-date overview on the use and regenerative potential of the PuraMatrix™ in Regenerative Endodontics.
  hDPSC hSHED hSCAP
Origin Dental pulp of permanent teeth. Dental pulp of temporal teeth. Apical Papillae.
Most common method for isolation Enzymatic digestion. Enzymatic digestion. Enzymatic digestion or explants culture.
Proliferation Velocity Intermediate. Fast. Fast.
Superficial markers (+): CD13, CD29, CD44, CD59, CD73, CD90, CD105, CD146, STRO-1. (-): CD14, CD19, CD24, CD34, CD45 HLA-DR. (+) Oct14, CD13, CD29, CD44, CD73, CD90, CD105, CD146, CD166. (-): CD14, CD34, CD45. (+): CD13, CD24, CD29, CD44, CD73, CD90, CD105, CD106, CD146. (-): CD18, CD34, CD38, CD45, CD150.
Differentiation Potential in vitro Odontoblasts, Osteoblasts, Condrocytes, Adipocytes, Miocytes, Neurons, Endothelial Cells, Corneal Epithelial Cells and Melanocytes. Odontoblasts, Osteoblasts, Chondrocytes, Adipocytes, Neurons, endothelial cells. Odontoblasts, Osteoblasts, Condrocytes, Adipocytes.
Dentin-Pulp DifferentiationPotential in vivo. Formed functional dentin-like structures with dentin/pulp complexes. Formed dentin-like tissues but fail regenerating dentin/pulp complexes. Induced whole root formation.
Table 2: hDPSC, hSHED and hSCAP characterization [9,18].
Figure 1: Electron Micrograph of PuraMatrixTM Peptide Hydrogel and Flow Chart of followed Strategy/Results in this Systematic Literature Review.
Materials and Methods
A structured literature search (Figure 1) was performed on PUBMED (May - July 2015) using the search terms “PuraMatrix” and “Dentistry” according to the following search strategy: “PuraMatrix [all fields] AND Dentistry [all fields]”. Results were limited by: language (English) and full text availability. A total of 9 articles were found. Focus was centered on the use/application of self-assembling peptide hydrogel PuraMatrix™ in Regenerative Endodontics; reason why a total of 5 articles (related to bone regeneration) were excluded from this review. Data from the remaining studies was abstracted and compiled in tables and latter appraised by the authors. It is noteworthy that an additional manual search on PuraMatrix™’s official web-page (www.puramatrix.com) was performed to fetch for published or unpublished articles; however none in regenerative endodontic were found.
Results and Discussion
A total of 9 articles dealing with the potential use and application of PuraMatrix™ in Dentistry were found. Only 4 articles explored the prospective application of the material to regenerate the dental-pulp complex [10,14-16]. All studies were published recently (2011, 2013 and 2015) indicating that this particular topic and biomaterial is a novel field of research and development within contemporary Regenerative Endodontics. As a synthetic self-assembling peptide extracellular matrix, PuraMatrix™’s application requires combination with cells in order to promote tissue regeneration. Main cellular lines reviewed in the studies corresponded to: (a) Human Dental Pulp Stem Cells (hDPSC, 3/4 studies) [10,14,15], (b) Human Exfoliated Deciduous Teeth Stem Cells (hSHED, 1/4 studies) [16] and (c) Human Umbilical Cord Vein Cells (HUVEC, 1/4 studies) [14]. Most cell lines were tested in mono-cultures, except for hDPSC and HUVEC which were also co-cultured in one study [14]. Overall, the tested PuraMatrix™ concentrations ranged from 0.05% to 0.25%, (with 0.15% and 0.2% being the most recurrent for in vivo investigation).Regarding in vitro models, cell/biomaterial constructs were tested either alone (15,16) and/or combined with: (a) tooth slices (onto which constructs were seeded) [10] or (b) human root canals (into which constructs were injected) [14,16]. Pre-clinical testing models employed SCID mice and investigated the subcutaneous implantation of: (a) cell/biomaterial gel constructs [15] and (b) roots with injected cell/biomaterial constructs [14,16]. For the benefit of the reader, consult: Figure 1 and Table 3.
REF Design PuraMatrix™ Cells Main Outcomes
[10] in vitro 0.05% – 0.25% co-cultured with tooth slices. hDPSC (4th to 8th passage) ↑ Survival, proliferation and expression of odontoblastic markers (DSPP and DMP-1).
[16] in vivo (subcutaneous implantation in SCID mice) 0.2% injected into root segments. hSHED (3rd to 8th passage) ↑ Survival, proliferation and expression of odontoblastic markers (DSPP, DMP-1 and MEPE). In vivo formation of vascular-rich pulp-like tissues within root canals, dentin neo-formation.
[14] in vivo (subcutaneous implant in SCID mice) 0.5%, 0.15%, 0.25% injected into root segments. hDPSC +/- HUVEC (3rd to 6th passage) ↑ Survival, proliferation, VEGF production and differentiation / mineralization (measured by ALP activity and Von Kossa staining). In vivo formation of vascular-rich pulp-like tissues within root canals [Combination with HUVEC enhanced outcomes and promoted fast vessel network development (24 hours in vitro)].
[15] in vivo (subcutaneous implant in SCID mice) 0.5 % hDPSC (2nd passage) ↑ Survival, proliferation, differentiation (measured by Alizarin Red staining). In vivo formation of highly vascularized / mineralized tissues, increased expression of osteogenic markers (Paratyroid hormone receptor, osteonectin, osteocalcin, osteopontin). No adverse or inflammatory reactions were reported.
Table 3: PuraMatrix™ in Dental Pulp Regeneration.
PuraMatrix™ supports in vitro survival, proliferation and migration of hDPSC and hSHED
hDPSC: Available in vitro evidence from mono-culture hDPSCs seeded in PuraMatrix™ show that cells survive and successfully proliferate in spite of the concentration of the biomaterial (which ranged from 0.05% to 0.25% in reviewed studies) [10,14]. Findings are as remarkable as previous studies with other primary cell lines reporting that variations in PuraMatrix™’s density often altered cell growth (i.e. 0.15% PuraMatrix™ is the optimal concentration for HUVEC cell viability compared to 0.5% and 0.25% concentrations) [10,14]. Initially (first 24 hours), encapsulated hDPSC appeared as “tiny round peas” evenly dispersed within the hydrogel [15]. At this stage, some cells seemed to develop primitive “cell processes” which oriented and extended towards nearby cell-clusters. After 3 days of culture, hDPSC within PuraMatrix™ resumed former “spindle-like” appearance while cell extensions appeared more mature into what the authors described as “cytoplasmic elongations” [10]. By 2 weeks of culture, individual hDPSC could not be identified using contrast light microscopy. According to authors, this is mainly due to increased cell cluttering and extracellular matrix build-up resulting from extensive proliferation [15]. Using laser confocal images, the researchers reported that hDPSC no longer distributed homogenously within the PuraMatrix™. Instead, cells aligned and connected forming thread-like structures highly interwoven into PuraMatrix™’s 3D configuration [15]. By the fourth week of culture, hDPSC began spreading outside the biomaterial forming large colonies of adherent cells onto the culture-ware. Interestingly significant mineralized deposits nearby these colonies, which resulted to be calcium depositions according to Alizarin Red Staining, were reported [15]. Together, these observations support the potential application of PuraMatrix™ in dental pulp regeneration, where it seems that the biomaterial serves as a functional and cytocompatible nano fibrous hydrogel scaffold/carrier, without interfering with hDPSC growth.
hSHED: Mono-cultured hSHED in 0.2% PuraMatrix™ reported similar results to those of hDPSC. It was demonstrated that cells remained viable and actively proliferating, reaching a 4-fold increase in cell number after 7 culture days [16]. Seeded hSHED initially exhibited a round shape with cluster organization (24 hours), yet, as time progressed (7 days), the cells changed their phenotype into a characteristic spindle-like form [16].
PuraMatrix™ supports in vitro odontoblastic differentiation of DPSC and hSHED
hDPSC: According to reviewed studies, mono-cultured hDPSC embedded in PuraMatrix™ exhibited positive ALP activity [14] and the presence of mineralized depositions after four weeks of culture in PuraMatrix™ [15]. Alizarin Red and Von Kossa staining of these nodules, in separate studies, indicated the presence of calcium salt depositions, suggesting that PuraMatrix™ allows for the osteogenic/odontogenic differentiation of the hDPSC (reader must be aware that both studies supplemented cell cultures with osteogenic induction medium thus findings should be attributed to the innate differentiation potential of hDPSC rather than the PuraMatrix™ itself/alone) [14,15]. To further characterize and understand the differentiation potential of PuraMatrix™, Calvancanti et al. recently performed RT-PCR on hDPSC samples seeded in 0.2% PuraMatrix™/tooth slice models, in normal medium conditions [10]. After 21 days, expression of the putative odontoblastic markers DSPP and DMP-1 (dentin Sialo-Phosphoprotein and dentin matrix protein-1respectively) was recorded. The control group in the same study (hDPSC seeded in PuraMatrix™ in absence of tooth slices) failed to express the aforementioned markers [10]. Considering that previous studies have reported that dentin-derived factors are considered crucial for hDPSC differentiation [10], results from this study may be attributed to: (a) the tooth slide model (which acts as natural source of soluble dentin-derived factors which stimulate the differentiation) and (b) PuraMatrix™ acting like a free- diffusion delivery system for these factors (and not as a inductive material). Based on these observations it may be concluded that the role of the PuraMatrix™ in hDPSC odontoblastic differentiation is supportive rather than stimulating. From a clinical standpoint, the potential of PuraMatrix™ to function as a delivery system for soluble proteins is highly appealing; especially for application in Regenerative Endodontics, as: (a) Necrotized teeth lack vascularization and (b) Usually have small apex openings which prevent the development of a new vascular supply from peri-apical tissues [14]. Thus, since rapid vascularization is necessary for successful tissue regeneration, root canal filling with PuraMatrix™ may provide enough oxygen and nutrients (via free diffusion) for hDPSC to proliferate and differentiate into endothelial cells; ensuring cell survival while the new micro-vascular system is developed.
hSHED: Regarding odontoblastic differentiation of hSHED, limited evidence obtained from Rosa et al. [16] where similar results to those of hDPSC were reported Re-suspended hSHED/0.2% PuraMatrix™ constructs injected into human root canals exhibited an increased expression of the odontoblastic markers DSPP, DMP-1 and MEPE after 21 days of culture [16]. PuraMatrix™ by itself (without injection into human roots) was not able to induce the expression of any of the aforementioned markers [16], suggesting, once again, that dentin-derived growth factors are vital or key for odontoblastic differentiation of oral mesenchymal stem cells.
PuraMatrix™ generates in vivo dentin-pulp-like structures
hDPSC: Chan et al. [15] constructed hDPSC/0.5% PuraMatrix™ hydrogel for subcutaneous insertion into immuno-compromised nude mice. Complete transformation into solid chunks or pieces of viable tissue resulted after 4 weeks of implantation [15]. This contrasted with plain-gel PuraMatrix™ controls (no cells) which could not be found/located for retrieval; suggesting complete resorption of the biomaterial without new tissue formation. 2D-Radiografic analyses of the constructs revealed the presence of multiple mineralization foci which (according to light microscopy analysis) coincided with regions of nuclear sparse extracellular matrix of lobular appearance. Further, higher magnification revealed rich vascularization and distinct outline of each lobule; while gaps in-between lobules were filled with tissue of higher nuclei density [15]. While circumferential apposition of cells contouring each lobule was noticed, no inflammatory infiltrate or adverse reactions to the implant were reported. Further immunohistochemical analyses of same samples revealed the presence of large portions of in-between-lobule tissues stained positive for parathyroid hormone receptor (which is responsible for bone matrix formation), while osteopontin, osteocalcin and osteonectin expression was limited to the lobules themselves [15]. Aforementioned ostegenic markers were not equally expressed among the lobules; as follows: (a) Osteocalcin was the most widely distributed (mainly in large and medium-size lobules and occasionally in smaller ones), (b) Osteonectin was limited to the core of large lobules and (c) Osteopontin was found in smaller lobules [15]. Altogether, these results not only indicate that hDPSC/PuraMatrix™ gel constructs possess in vivo osteogenic capacity, yet also suggests that a specific pattern for lobule formation exists, characterized by: (a) initial formation of small osteopontin packed lobules, (b) progressive increasing in size with replacement of osteopontin for osteocalcin and (c) final replacement of osteocalcin for osteonectin and collagen type I in larger lobules [15]. A main critic for this study is the absence of a control hDPSC group without PuraMatrix™ to which one can compare the degree of differentiation/mineralization of treated tissues. As mentioned previously, in vitro evidence suggests that the role of PuraMatrix™ within odonto-/osteo-genic differentiation is supportive rather than inductive; hence it would have been interesting to evaluate pre-clinically/in vivo whether the incorporation of PuraMatrix™ clinically enhances differentiation. This is the subject of continuing trials within our BioMAT’X research group.
Dissanayaka., et al. [14] investigated hDPSC/PuraMatrix™ roots (main difference with previous hDPSC study which inserted the hydrogel freely) implanted subcutaneously in SCID mice. Vascularized pulp-like tissues resulted [14]. Antibody-staining against human mitochondria confirmed hDPSC as the main source of regenerated structures. On the contrary, PuraMatrix™ alone (without cells) root segments failed to produce tissues at all. Results indicate that PuraMatrix™ does not possess intrinsic ability to attract endogenous cells to populate the scaffold within root canals. An interesting observation was that the hDPSC/PuraMatrix™ constructs near the coronal aspect of the roots (which were sealed) did not survive, therefore dental pulp-like structures only formed up to the middle (5mm) or lower third (3.3mm) of the root canals [14]. Furthermore, in open apex teeth, host tissue in-growths tended to occur, pushing constructs further into the coronal aspects of the tested root canals [14]. From a clinical stand-point, both observations are interesting as: (a) immature open apex teeth are the primary target of Regenerative Endodontic procedures and (b) coronal root sealing is a requirement for endodontic treatment. Combined, this may challenge the clinical application of hDPSC/PuraMatrix™ constructs in Regenerative Endodontics; hence, is to be addressed in future investigations.
hSHED: Subcutaneous implantation of human premolar roots loaded with hSHED/0.2% PuraMatrix™ constructs in SCID mice resulted in the formation of new vascularized connective-like tissues, close to pre-dentin (whereas PuraMatrix™ alone formed minimal and poorly organized tissues).PuraMatrix™ engineered pulps occupied the whole extension of the root canal and had similar (a) cell proliferation (b) number of cells close to pre-dentin, (c) vessel density and (d) occurrence of cell apoptosis, to human dental pulp controls [16]. From a functional standpoint, tetracycline staining revealed that engineered structures generated new dentin throughout root canal walls. Together with immunohistochemistry confirmation that newly formed tissues are primarily populated by hSHED [16]; PuraMatrix™ seems to be a proper delivery vehicle for hSHED in Regenerative Endodontics favoring cell differentiation into dental pulp-like structures within dental root canal.
Comments on the application of PuraMatrix™ in Regenerative Endodontics
Optimal Biomaterial Concentration: The concentration of PuraMatrix™ has no significant effect or influence on cell growth and proliferation [10,14]. Hence, the selection of the ideal concentration for endodontic applicationswill relies on other considerations. According to Calvancanti et al. [10], the 0.2% concentration is optimal for regenerative endodontic applications as it increases the rigidity of the biomaterial resulting in a more suitable or appropriate gel for root canal injection and manipulation [10]. Similar observations were made by Dissanayaka et al. [14], were they warned against using PuraMatrix™ in concentrations < 0.15%, as it increases fragility, rendering it difficult to handle and inject into the root canals.
Optimal model for in vitro and in vivo testing: As mentioned previously, present evidence suggests that the dentin-derived molecules are crucial for hDPSC and hSHED odontoblastic differentiation. Pre-clinical studies suggest that the residual dentin within tooth slices and root canals serve as a reservoir and source for these molecules, under experimental conditions [10]. Considering that root canal segments provide a much more similar environment than that of clinical endo-treated teeth (with sealed coronal aspect and narrow apical opening) [14]; this might be the ideal model for in vitro and in vivo investigation of PuraMatrix™/cell constructs. Also, root canal anatomy of segments allows testing the capacity of the engineered constructs to model the root anatomy in a reasonable clinical time; a crucial aspect for bench-top to chair-side translation of this technology.
hDPSC or hSHED mono-cultured vs. co-cultured with Human Umbilical Vein Cord Cells (HUVEC): Basic surgical and tissue engineering concepts state that vascularization is a key factor in tissue repair and regeneration. Rapid in vivo vascularization via intrinsic capillary formation of grafts and alternative bio-engineered implants (i.e. cell/PuraMatrix™ constructs) is critical for successful clinical outcomes. A major limiting/challenging factor in clinical application of endodontic regeneration procedures is the small diameter of the apical foramen, hindering the development and re-establishment of an adequate vascular supply during dental pulp regeneration. According to in vivo evidence discussed in this review, PuraMatrix™ scaffolds within root canals are poorly colonized by host cells; meaning that intrinsic vascularization depends almost exclusively on the seeded hDPSC or hSHED (which are capable to differentiate into endothelial cells). This phenomenon however, takes time and may be too slow for a successful clinical application. In order to promote and accelerate vascularization of hDPSC/PuraMatrix™ constructs, Dissanayaka and colleagues added commercial Human Umbilical Cord Vein Endothelial Cells (HUVEC, ScienCell Research Laboratories, San Diego, CA) to their preparations [14]. This unique approach proved to enhance (a) cell survival, (b) angiogenic factor production (VEGF), (c) vascular structure formation, (d) odonto-/osteo-genic differentiation and (e) extracellular matrix formation and collagen deposition, when compared to conventional hDPSC/PuraMatrix™ constructs. Excitingly, the vessels formed within the hDPSC/HUVEC/PuraMatrix™ constructs were 3D-organized and presented with larger lumen than that of the tubular structures within the HUVEC mono-cultures or HUVEC/hDPSC co-cultures. Moreover, the vascular structures appeared within only 24hours of in vitro incubation, suggesting that it may be possible to pre-vascularize the PuraMatrix™/cell constructs before clinical implantation [14]. Despite such promising results, for a successful clinical application of this strategy, the following are to be considered:
  1. Pre-clinical (in vitro) survival and proliferation of HUVEC in PuraMatrix™ depends on the biomaterial concentration. Using 0.15% PuraMatrix™ seems to be the “optimal” concentration for these cells.
  2. HUVEC survived up to two weeks in mono-culture whereas co-cultured cells with hDPSC lasted longer. This indicates that HUVEC are extremely delicate and need the support from hDPSC in order to survive within the PuraMatrix™. Studies to identify the optimal hDPSC numbers for in vitro and in vivo support of HUVEC should be performed prior to clinical application.
  3. Observed partial pulp regeneration (where dental pulp-like tissues formed up to first 3.3 mm-5 mm of the root canal and host-tissue invasion and coronal migration of the implant occurred in open apex teeth) indicates that both, critical size defect and critical apical opening size for pulp regeneration must be defined in order to assure a successful clinical application in the future [14].        
Conclusions
PuraMatrix™ is a synthetic, injectable and self-assembling peptide nano fibrous hydrogel scaffold recently introduced into the emerging field of Regenerative Endodontics. The material is a promising scaffold alternative for dental pulp tissue engineering. PuraMatrix™ supports hDPSC and hSHED viability, proliferation and migration without interfering with cell odonto-/osteo-genic differentiation [suggesting that the main stimulus for differentiation originates from the hDPSC/hSHED themselves as well as the host tissues (especially dentin)]. Under in vivo experimental conditions, stem cell/PuraMatrix™ constructs seem to generate highly-vascularized dental pulp-like structures with mineralization potential. These engineered pulp-like structures contain functional odontoblasts capable to generate appositional dentin within root canal walls. Although the number of studies analyzed in this review is limiting, results suggest that the biomaterial might be of great potential when used of applied for stem-cell delivery and dental pulp regeneration within necrotized root canals. Future studies will explore the use, application and potential of PuraMatrix™ and further assess clinical safety, efficacy, significance, impact and cost-effectiveness of this biomaterial/strategy in dental pulp regeneration, and beyond.
Acknowledgements
This work was supported by generous funding and operating grants provided to the BioMAT’X Research Group, partner of CIBRO (Centro Investigación en Biología y Regeneración Oral) and part of CIB (Centro de Investigación Biomédica), through the Faculty of Dentistry and PMI (Plan de Mejoramiento Institucional en Innovación I+D+i), Department for Research, Development and Innovation, Universidad de Los Andes, Santiago de Chile. Dr. Mira S. Haidar is a dentist and post-graduate trainee finalizing her endodontic studies within the Programa de Diplomado en Endodoncia, Facultad de Odontología, Universidad de Los Andes, Santiago de Chile.
Conflict of Interest
Authors of this article declare having no conflict of interest.
Bibliography
  1. Nosrat A., et al. “Tissue Engineering Considerations in Dental Pulp Regeneration”. Iranian Endodontic Journal 9.1 (2014): 30-39.
  2. Bansal R., et al. “Current overview on challenges in regenerative endodontics”. Journal of Conservative Dentistry 18.1 (2015): 1-6.
  3. Da Silva LAB., et al. “Revascularization and periapical repair after endodontic treatment using apical negative pressure irrigation versus conventional irrigation plus triantibiotic intracanal dressing in dogs’ teeth with apical periodontitis”. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology 109.5 (2010): 779-787.
  4. Thibodeau B., et al.“Pulp revascularization of immature dog teeth with apical periodontitis”. Journal of Endodontics 33.6 (2007): 680-689.
  5. Wang X., et al.“Histologic characterization of regenerated tissues in canal space after the revitalization/revascularization procedure of immature dog teeth with apical periodontitis”. Journal of Endodontics 36.1 (2010): 56-63.
  6. Torabinejad M., et al. “A clinical and histological report of a tooth with an open apex treated with regenerative endodontics using platelet-rich plasma”. Journal of Endodontics 38.6 (2012): 864-868.
  7. Shimizu E., et al. “Histologic observation of a human immature permanent tooth with irreversible pulpitis after revascularization/regeneration procedure”. Journal of Endodontics 38.9 (2012): 1293-1297.
  8. Martin G., et al. “Histological findings of revascularized/revitalized immature permanent molar with apical periodontitis using platelet-rich plasma”. Journal of Endodontics 39.1 (2013): 138-144.
  9. Sanz A., et al. “Mesenchymal stem cells from the oral cavity and their potential value in tissue engineering”. Periodontology 2000 67.1 (2015): 251-267.
  10.  Cavalcanti BN. et al. “A hydrogel scaffold that maintains viability and supports differentiation of dental pulp stem cells”. Dental Material 29.1 (2013): 97-102.
  11. Censi R., et al. “Hydrogels for protein delivery in tissue engineering”. Journal of Controlled Release161.2 (2012): 680-692.
  12. Moradi F., et al. “BD PuraMatrix peptide hydrogel as a culture system for human fetal Schwann cells in spinal cord regeneration”. Journal of Neuroscience Research 90.12 (2012): 2335-2348.
  13. Lampe KJ., et al. “Building stem cell niches from the molecule up through engineered peptide materials”. Neuroscience Letters 519.2 (2012): 138-146.
  14. Dissanayaka WL., et al. “The interplay of dental pulp stem cells and endothelial cells in an injectable peptide hydrogel on angiogenesis and pulp regeneration in vivo”. Tissue Engineering Part A 21.3-4 (2015): 550-563.
  15. Chan B., et al.In vivo production of mineralized tissue pieces for clinical use: a qualitative pilot study using human dental pulp cell”. International Journal of Oral and Maxillofacial Surgery 40.6 (2011): 612-620.
  16. Rosa V., et al. “Dental Pulp Tissue Engineering in Full-length Human Root Canals”. Journal of Dental Research 92.11 (2013): 970-975.
  17. Biosciences BD. “BDTM PuraMatrixTM Peptide Hydrogel”.
  18. Estrela C., et al. “Mesenchymal stem cells in the dental tissues: perspectives for tissue regeneration”. Brazilian Dental Journal 22.2 (2011):91-98.
Copyright: © 2015 Ziyad S Haidar., et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

PubMed Indexed Article


EC Pharmacology and Toxicology
LC-UV-MS and MS/MS Characterize Glutathione Reactivity with Different Isomers (2,2' and 2,4' vs. 4,4') of Methylene Diphenyl-Diisocyanate.

PMID: 31143884 [PubMed]

PMCID: PMC6536005


EC Pharmacology and Toxicology
Alzheimer's Pathogenesis, Metal-Mediated Redox Stress, and Potential Nanotheranostics.

PMID: 31565701 [PubMed]

PMCID: PMC6764777


EC Neurology
Differences in Rate of Cognitive Decline and Caregiver Burden between Alzheimer's Disease and Vascular Dementia: a Retrospective Study.

PMID: 27747317 [PubMed]

PMCID: PMC5065347


EC Pharmacology and Toxicology
Will Blockchain Technology Transform Healthcare and Biomedical Sciences?

PMID: 31460519 [PubMed]

PMCID: PMC6711478


EC Pharmacology and Toxicology
Is it a Prime Time for AI-powered Virtual Drug Screening?

PMID: 30215059 [PubMed]

PMCID: PMC6133253


EC Psychology and Psychiatry
Analysis of Evidence for the Combination of Pro-dopamine Regulator (KB220PAM) and Naltrexone to Prevent Opioid Use Disorder Relapse.

PMID: 30417173 [PubMed]

PMCID: PMC6226033


EC Anaesthesia
Arrest Under Anesthesia - What was the Culprit? A Case Report.

PMID: 30264037 [PubMed]

PMCID: PMC6155992


EC Orthopaedics
Distraction Implantation. A New Technique in Total Joint Arthroplasty and Direct Skeletal Attachment.

PMID: 30198026 [PubMed]

PMCID: PMC6124505


EC Pulmonology and Respiratory Medicine
Prevalence and factors associated with self-reported chronic obstructive pulmonary disease among adults aged 40-79: the National Health and Nutrition Examination Survey (NHANES) 2007-2012.

PMID: 30294723 [PubMed]

PMCID: PMC6169793


EC Dental Science
Important Dental Fiber-Reinforced Composite Molding Compound Breakthroughs

PMID: 29285526 [PubMed]

PMCID: PMC5743211


EC Microbiology
Prevalence of Intestinal Parasites Among HIV Infected and HIV Uninfected Patients Treated at the 1o De Maio Health Centre in Maputo, Mozambique

PMID: 29911204 [PubMed]

PMCID: PMC5999047


EC Microbiology
Macrophages and the Viral Dissemination Super Highway

PMID: 26949751 [PubMed]

PMCID: PMC4774560


EC Microbiology
The Microbiome, Antibiotics, and Health of the Pediatric Population.

PMID: 27390782 [PubMed]

PMCID: PMC4933318


EC Microbiology
Reactive Oxygen Species in HIV Infection

PMID: 28580453 [PubMed]

PMCID: PMC5450819


EC Microbiology
A Review of the CD4 T Cell Contribution to Lung Infection, Inflammation and Repair with a Focus on Wheeze and Asthma in the Pediatric Population

PMID: 26280024 [PubMed]

PMCID: PMC4533840


EC Neurology
Identifying Key Symptoms Differentiating Myalgic Encephalomyelitis and Chronic Fatigue Syndrome from Multiple Sclerosis

PMID: 28066845 [PubMed]

PMCID: PMC5214344


EC Pharmacology and Toxicology
Paradigm Shift is the Normal State of Pharmacology

PMID: 28936490 [PubMed]

PMCID: PMC5604476


EC Neurology
Examining those Meeting IOM Criteria Versus IOM Plus Fibromyalgia

PMID: 28713879 [PubMed]

PMCID: PMC5510658


EC Neurology
Unilateral Frontosphenoid Craniosynostosis: Case Report and a Review of the Literature

PMID: 28133641 [PubMed]

PMCID: PMC5267489


EC Ophthalmology
OCT-Angiography for Non-Invasive Monitoring of Neuronal and Vascular Structure in Mouse Retina: Implication for Characterization of Retinal Neurovascular Coupling

PMID: 29333536 [PubMed]

PMCID: PMC5766278


EC Neurology
Longer Duration of Downslope Treadmill Walking Induces Depression of H-Reflexes Measured during Standing and Walking.

PMID: 31032493 [PubMed]

PMCID: PMC6483108


EC Microbiology
Onchocerciasis in Mozambique: An Unknown Condition for Health Professionals.

PMID: 30957099 [PubMed]

PMCID: PMC6448571


EC Nutrition
Food Insecurity among Households with and without Podoconiosis in East and West Gojjam, Ethiopia.

PMID: 30101228 [PubMed]

PMCID: PMC6086333


EC Ophthalmology
REVIEW. +2 to +3 D. Reading Glasses to Prevent Myopia.

PMID: 31080964 [PubMed]

PMCID: PMC6508883


EC Gynaecology
Biomechanical Mapping of the Female Pelvic Floor: Uterine Prolapse Versus Normal Conditions.

PMID: 31093608 [PubMed]

PMCID: PMC6513001


EC Dental Science
Fiber-Reinforced Composites: A Breakthrough in Practical Clinical Applications with Advanced Wear Resistance for Dental Materials.

PMID: 31552397 [PubMed]

PMCID: PMC6758937


EC Microbiology
Neurocysticercosis in Child Bearing Women: An Overlooked Condition in Mozambique and a Potentially Missed Diagnosis in Women Presenting with Eclampsia.

PMID: 31681909 [PubMed]

PMCID: PMC6824723


EC Microbiology
Molecular Detection of Leptospira spp. in Rodents Trapped in the Mozambique Island City, Nampula Province, Mozambique.

PMID: 31681910 [PubMed]

PMCID: PMC6824726


EC Neurology
Endoplasmic Reticulum-Mitochondrial Cross-Talk in Neurodegenerative and Eye Diseases.

PMID: 31528859 [PubMed]

PMCID: PMC6746603


EC Psychology and Psychiatry
Can Chronic Consumption of Caffeine by Increasing D2/D3 Receptors Offer Benefit to Carriers of the DRD2 A1 Allele in Cocaine Abuse?

PMID: 31276119 [PubMed]

PMCID: PMC6604646


EC Anaesthesia
Real Time Locating Systems and sustainability of Perioperative Efficiency of Anesthesiologists.

PMID: 31406965 [PubMed]

PMCID: PMC6690616


EC Pharmacology and Toxicology
A Pilot STEM Curriculum Designed to Teach High School Students Concepts in Biochemical Engineering and Pharmacology.

PMID: 31517314 [PubMed]

PMCID: PMC6741290


EC Pharmacology and Toxicology
Toxic Mechanisms Underlying Motor Activity Changes Induced by a Mixture of Lead, Arsenic and Manganese.

PMID: 31633124 [PubMed]

PMCID: PMC6800226


EC Neurology
Research Volunteers' Attitudes Toward Chronic Fatigue Syndrome and Myalgic Encephalomyelitis.

PMID: 29662969 [PubMed]

PMCID: PMC5898812


EC Pharmacology and Toxicology
Hyperbaric Oxygen Therapy for Alzheimer's Disease.

PMID: 30215058 [PubMed]

PMCID: PMC6133268


News and Events


August Issue Release

We always feel pleasure to share our updates with you all. Here, notifying you that we have successfully released the August issue of respective journals and can be viewed in the current issue pages.

Submission Deadline for September Issue

Ecronicon delightfully welcomes all the authors around the globe for effective collaboration with an article submission for the September issue of respective journals. Submissions are accepted on/before August 21, 2020.

Certificate of Publication

Ecronicon honors with a "Publication Certificate" to the corresponding author by including the names of co-authors as a token of appreciation for publishing the work with our respective journals.

Best Article of the Issue

Editors of respective journals will always be very much interested in electing one Best Article after each issue release. The authors of the selected article will be honored with a "Best Article of the Issue" certificate.

Certifying for Review

Ecronicon certifies the Editors for their first review done towards the assigned article of the respective journals.

Latest Articles

The latest articles will be updated immediately on the articles in press page of the respective journals.

Immediate Assistance

The prime motto of this team is to clarify all the queries without any delay or hesitation to avoid the inconvenience. For immediate assistance on your queries please don't hesitate to drop an email to editor@ecronicon.uk