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International Journal of Bioprinting 3D-bioprinted hydrogel for pulp regeneration

hDPSCs, but also boosted the capillary tube formation and According to recent studies, numerous strategies have been
neurogenesis. In vivo experiments confirmed the porous proposed to tune the stemness properties of stem cells, via
DPGC regenerated dental pulp with a dentin-like and the regulation of biomechanical/bioelectrical/biochemical
microvascular structure. factors. 63,64 For example, Kong et al. fabricated a ZnO
2+
GelMA is regarded as a good candidate for tissue nanorod array to sustain Zn release and synergistically
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engineering due to its similarity to natural ECM and promote cellular stemness with its nanotopography.
possession of tunable mechanical properties to mimic 3D However, extreme culture conditions (e.g., hypoxia and
microenvironment for regulating cell fates and steering low temperature) and biomaterial additives released
tissue regeneration. However, bulk GelMA hydrogels into surrounding tissues would heighten the risk of
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generally own dense structural networks that limit robust adverse side effects. To date, although the properties of
cytoskeleton extension and the diffusion of oxygen and promoted stemness commonly display desired outcomes
nutrients, leading to a relatively low survival of seed cells in vast biomedical applications (e.g., bone, nerve, and
following their engraftment into the host tissue. 11,57 To muscle), 66,67 the research in dental pulp regeneration is
address these restrictions, one strategy to improve cell still limited. In this study, the in situ-bioprinted DPGC
viability and therapeutic efficacy of tissue regeneration provided a favorable 3D microenvironment to promote
is to enhance the porosity of biomaterials. Microporous stemness properties and nuclear translocation of YAP
structures in hydrogels have been produced by various (Figure 3). We speculate that the stemness-promoting
techniques, which include freeze-drying, electrospinning, effect on DPGC might be attributed to the microporous
porogen leaching, and so on. 58,59 However, it is impossible structure. The microporous structure within DPGC could
to encapsulate any live cells during the manufacture of provide enough space to promote the metabolism of
scaffolds using these methods to generate porous structures. substances and improve the bioactivity of stem cells, thus
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In addition, after the accomplishment of porous scaffolds, enhancing the differentiation potentials of stem cells.
most cells are loaded on the surface of scaffolds, and a Furthermore, the nuclear transcriptional activity of YAP
precise 3D cell distribution within the construct can hardly relies on cell extension and spreading. Interconnected
be achieved. The water-in-water emulsion is composed of pores within DPGC offer adequate 3D space to promote
two aqueous phases, and the droplets of one aqueous phase DPSCs spreading in DPGC (Figure 6), which may
(dispersed phase) are dispersed into the other aqueous result in nuclear flattening and nuclear pores stretching,
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phase (continuous phase) to reach a thermodynamic facilitating YAP nuclear translocation. This process could
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equilibrium state. After the aqueous continuous phase be regulated by Rho GTPase and the tensile forces. In
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is polymerized around the dispersed droplets, the in situ this study, the YAP activity in DPGC may play a pivotal
pore-forming material is mildly produced following the role in the stemness maintenance of stem cells. Similarly,
removal of dispersed phase. Dextran is a biocompatible, Bhattacharya et al. also confirmed that undifferentiated
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biodegradable, and non-immunogenic biological limbal stem cells enhanced YAP nuclear translocation.
substance. In the present study, dextran was mixed with In contrast, a confining environment would lead to the
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GelMA solution to generate GelMA-Dextran emulsion inhibition of YAP activity within intestinal stem cells by
where dextran droplets were dispersed within GelMA, the reducing cellular tension, thus restricting further growth
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continuous phase (Figure 2A). In addition, as reported in and morphogenesis. Further in vitro odontogenic
our previous study, the microporous hydrogel constructs differentiation assays showed that nuclear accumulation of
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prepared by the GelMA-Dextran emulsion could enhance YAP proteins promoted ALP activity and the upregulation
the viability of chondrocytes and regulate cartilage tissue of odontogenesis-related genes when DPSCs were cultured
rebuilding. Hence, we hypothesize that the GelMA- in odontogenic differentiation medium, confirming the
Dextran emulsion is applicable as a bioink of DLP-based potential of DPSCs in dental pulp regeneration (Figure 4).
3D bioprinting, and in situ 3D-bioprinted DPGC can Promoting angiogenesis and neurogenesis remains
steer DPSCs fates and functions for enhanced dental a prime challenge in dental pulp regeneration.
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pulp regeneration. Angiogenesis could assist in the exchange of nutrition,
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Stemness maintenance is an indispensable factor for cell recruitment, and circulating factor delivery. In vitro
functional tissue regeneration essential in stem cell therapy. tube formation assay showed that DPGC significantly
Enhanced stemness properties of stem cells can promote promoted robust vessel formation (Figure 7). This is
the potential of these stem cells to replenish diverse types probably related to angiogenesis-related growth factors
of cells within injured sites and contribute pro-regenerative such as vascular endothelial growth factor (VEGF), which
paracrine factors. However, long-term 2D culture would is secreted by DPSCs encapsulated in DPGC. 70,71 In vitro
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result in alterations of phenotypes or even loss of stemness. experiments further verified that DPGC embedded with

Volume 10 Issue 3 (2024) 316 doi: 10.36922/ijb.1790