Three-Dimensional Model of Dorsal Root Ganglion Explant as a Method of Studying Neurotrophic Factors in Regenerative Medicine

Abstract

Neurotrophic factors play a key role in the development, differentiation, and survival of neurons and nerve regeneration. In the present study, we evaluated the effect of certain neurotrophic factors (NGF, BDNF, and GDNF) on axon growth and migration of Nestin-green fluorescent protein (GFP)-positive cells using a 3D model of dorsal root ganglion (DRG) explant culture in Matrigel. Our method generally represents a convenient model for assessing the effects of soluble factors and therapeutic agents on axon growth and nerve regeneration in R&D studies. By analyzing the DRG explants in ex vivo culture for 21 days, one can evaluate the parameters of neurite outgrowth and the rate of cell migration from the DRG explants into the Matrigel. For the current study, we used Nestin-GFP-expressing mice in which neural precursors express Nestin and the green fluorescent protein (GFP) under the same promoter. We revealed that GDNF significantly (two fold) stimulated axon outgrowth (p < 0.05), but not BDNF or NGF. It is well-known that axon growth can be stimulated by activated glial cells that fulfill a trophic function for regenerating nerves. For this reason, we evaluated the number of Nestin-GFP-positive cells that migrated from the DRG into the Matrigel in our 3D ex vivo explant model. We found that NGF and GDNF, but not BDNF, stimulated the migration of Nestin-GFP cells compared to the control (p < 0.05). On the basis of the aforementioned finding, we concluded that GDNF had the greatest stimulating potential for axon regeneration, as it stimulated not only the axon outgrowth, but also glial cell migration. Although NGF significantly stimulated glial cell migration, its effect on axon growth was insufficient for axon regeneration.Biomedicines 2020, 8, 49 2 of 13 (ECM) that surrounds the cells and creates the microenvironment in vivo [6,8]. The lack of the proper cell-cell and cell-matrix contacts results in change of gene and protein expression profiles [9]. These can adversely affect cell morphology, cell cycle progression, cell survival, and intracellular signaling, potentially resulting in false positive or false negative data acquisition [8,10].In 2D culturing systems, the bioavailability of substances is difficult to evaluate [11]. All cells in a monolayer in 2D culturing conditions simultaneously receive the same dose of a tested agent, whereas in vivo there is a gradient of a tested agent that penetrates the matrix and several layers of cells in a tissue [12]. 3D cultures allow for the assessment of the parameters of a gradual diffusion of tested agents through the gel [6,11].Primary neural cell cultures represent a modern challenge in cell biology, as mature neurons do not undergo cell division in vitro, making it complicated to obtain a sufficient number of cells for experiments [13]. Cell survival is usually low, and neural cell cultures from DRG can be maintained for only 5-7 days, provided that soluble factors that increase survival are added [14]. This is one of the complications in result interpretation when...

Synergistic effect of CNTF and GDNF on directed neurite growth in chick embryo dorsal root ganglia

“…More specifically, it induced the increase in both neurite length and their number without significantly affecting the direction of their growth. These observations corroborate previously published studies that established beneficial effects of this neurotrophic factor on neuronal survival and axonal outgrowth [ 2 , 21 , 23 , 26 ].…”

“…Chick and mammalian DRGs have been extensively used as a convenient model to study the effect of different extrinsic treatments on neurite outgrowth, as they can be easily manipulated and easily subjected to quantification, provide consistent and reproducible results, retain the relevant tissue structure allowing proper interactions between neurons and glia and thus generally show better cell viability in vitro than pure cultures of dissociated neurons [1,3,22,23].…”

Engineering a multicompartment in vitro model for dorsal root ganglia phenotypic assessment

“…Maximum neurite length of the three longest neurites per DRG was 1239 ± 291 μm for control hydrogel 1 and 1318 ± 323 μm for control hydrogel 2 (Figure 5B). Importantly, a previous study culturing mouse DRG explants in a 3D Matrigel 85 showed robust neurite outgrowth comparable to this culture platform, suggesting this platform parallels previous literature. In addition, the maximum neurite length for DRGs embedded in MC devices within hydrogel 2 was 1062 ± 185 μm, suggesting the presence of the MC device did not inhibit neurite growth (Figure 5B).…”

New Frontiers in Peripheral Nerve Regeneration: Concerns and Remedies

“…Several papers reported that the sustained delivery of GDNF, rather than NGF, to the site of nerve injury enabled efficient in vivo regeneration of both sensory and motor axons [47]. Using an ex vivo three-dimensional model of mouse DRG explants, we have shown that GDNF delivery exerts a more pronounced stimulatory effect on axonal growth and regeneration as compared to BDNF or NGF, as well as promotes glial cell migration [37,48].…”