A lab-centred approach for initiating early stage regeneration of dental pulp using specialised alginate biomimetic microenvironments

Abstract

A living, self-supporting pulp tissue replacement for patients remains a considerable bioengineering challenge. As yet there is no method for engineering a self-sustaining living pulp tissue that can be successfully transplanted into the patient and have any beneficial clinical outcomes. The main reason for this failure is the inability to reconstitute a functional blood vessel tubular network within the engineered pulp tissue. In addition, it has yet not been possible to engineer the various anatomically distinct structures and architectures of the healthy pulp tissue. The idea is that a bio-engineered pulp-like structure prior to transplantation will accelerate integration and reduce the potential for complications. Recently new strides are being taken to make a functioning living pulp tissue using the latest step by step enhancements that are occurring in biomimetic molecular engineering. The use of this basic tissue engineering processes of living organic matter in fabrication is ensuring that prospective lab-made tissue products are biologically compatible. Systems built into biomaterials involving self-assembly, feedback mechanisms will lead to realistic tissue replicates. The new methods include, fabricating biomimetic tissue frameworks with an array of keystone biochemical cues and structural cues. Alternatively others are suggesting that it is feasible to stimulate natural repair using small molecules and temporary frameworks together or independently. A typical tissue engineering strategy that also promises to work is to combine mixed cell populations and growth factors in a scaffold microenvironment. The hypothesis is that recreating an early stage tissue microenvironment-one that resembles the postnatal constitution that will initiate the autonomous reconstruction of native pulp tissue in vitro. As a result, a coherent self-sustaining and self-supporting tissue construct is prepared for rapid integration and remodeling. Our purpose, in this study is to create the formative elements for pulp tissue that go on to develop and regenerate into a functional living pulp tissue. The objective were firstly, to combine dental mesenchymal stem cells and human umbilical vein endothelial cells with limited key growth factors within a space filling the aalginate hydrogel. Secondly, to test the capacity of these encapsulated stem cells for proliferationon, and lastly, measure the capture level for soluble bio-chemicals and test the capacity of the system to release growth factors in a slow, continuous fashion. These are critical performance issues for building pulp de novo. There are more to be tackled in later stages of developing this technology. An alginate-RGD conjugated gel was used to encapsulate adult dental pulp mesenchymal stem cells and human umbilical vein endothelial cells (HUVEC) in the ratio of 1:1. It also served as a means for the targeted delivery of two key growth factors 〖VEGF〗^121 (Vascular endothelial growth factor) and FGF-2 (Fibroblastic growth factor) towards the population of cells. In the experiments we varied the combinations of these four components and results with SEM and confocal microscopy show uniform cell distribution and viable cells in all test and control groups. There were significant differences between the groups with no growth factors and groups in which growth factors were added.

Interestingly, combinations of VEGF and FGF synergize to up regulate cell proliferation with p value <0.05. The dental pulp and endothelial cells were compatible with the scaffold and were uniformly distributed from the coronal to apical end of the construct. To summarize, significant up-regulation in the proliferation with the addition of VEGF and FGF in 3:1 ratio was observed. Also the temporal release of growth factors from the construct could lead to new avenues in endodontic regeneration with diligent use and specialised tailoring of cellular microenvironments.