The influence of sustained dual-factor presentation on the expansion and differentiation of neural progenitors in affinity-binding alginate scaffolds

Abstract

Biomaterials capable of controlling the release of multiple growth factors (GFs) could potentially promote the integration of co-transplanted neural progenitor cells (NPCs) and stimulate the plasticity and regenerability of the lesioned spinal cord. As a first step towards the employment of such a vehicle for cell therapy, this study examined the capability of an alginate-sulphate/alginate scaffold, able to capture and rigorously control the release of GFs, to promote the expansion and lineage differentiation of NPCs in vitro. Epidermal growth factor (EGF) and fibroblast growth factor-2 (bFGF) were affinity-bound to alginate-sulphate (200 ng/scaffold) and the bioconjugates were mixed with partially calcium-crosslinked alginate. NPCs isolated from 18 day-old rat embryo brains and seeded into the scaffold during preparation were found to proliferate and differentiate within the vehicle. A continuous release of both bFGF and EGF was noted for a period of 21 days. The concentrations of released GFs were sufficient to promote extensive NPC proliferation at initial cultivation times; the number of neurospheres in the scaffold was twice the number found in the 2D cultures supplemented with 20 ng/ml each factor every 3 days. Between days 10-14, when the GF concentrations had substantially declined, extensive cell migration from the neurospheres as well as lineage differentiation were noted in the scaffold; immunocytochemical analyses confirmed the presence of neurons, astrocytes and oligodendrocytes.The scaffold has a potential to serve as cell delivery vehicle, with proven capability to promote cell retention and expansion, while enabling NPC lineage differentiation in situ.

Understanding Molecular Pathology along Injured Spinal Cord Axis: Moving Frontiers toward Effective Neuroprotection and Regeneration

“…Consequently, there was a decline in the growth factor concentrations; the cells migrated from the neurosphere and differentiated to neurons, astrocytes and oligodendrocytes. These results confirmed that the 3D alginate biomaterial, which gradually released growth factors, creates optimal conditions for long-term survival and differentiation of neural progenitors in vitro [82].…”

“…In this case, the equilibrium binding constant of the selected factors on alginate-sulfate plays an important role. The initial concentration of both bFGF and EGF factors (200 ng) was shown to be sufficient for their continuous release over 21-day incubation [82]. The concentration of growth factors released within the first week in vitro initiated cell proliferation and the formation of typical 3D neurospheres.…”

Delivery of Alginate Scaffold Releasing Two Trophic Factors for Spinal Cord Injury Repair

“…Bilateral delivery of i) saline, ii) ALG, or iii) ALG+GFs (2 injections of 2 μl/per injection/on left and 2 injections of 2 μl/per injection/on right side with delivery rate of 0.5 μl/min, loaded with 200 ng/ml of each GF) was performed. Based on our in vitro study results, an affinity-binding alginate scaffold loaded with 200 ng of bFGF/EGF confirmed long term release of GFs 25 . Each delivery was positioned 1 mm from the spinal cord midline and injected at the depth of 1.8–2 mm from the pial surface of the spinal cord.…”

“…Along these lines, we have recently reported that an affinity-binding alginate scaffold which sustains the release and presentation of both epidermal growth factor (EGF) and fibroblast growth factor-2 (bFGF) is capable of supporting the viability, expansion and lineage differentiation of neural progenitor cells (NPCs) in vitro 25 . Following these findings, our next goal was to test this scaffold with its affinity-bound growth factors (GFs) for treatment of spinal cord compression in rats.…”

Biomaterials for Sequestration of Growth Factors and Modulation of Cell Behavior

“…[50][51][52][53] Besides ECM molecules, other natural polymers widely researched in the field of tissue engineering have also been studied recently for GF delivery. Among these are alginate, a polysaccharide extracted from the cell wall of brown seaweed that grows in cold water regions, [54][55][56] chitosan, another polysaccharide, produced by controlled deacetylation of chitin, [57] and silk fibroin (SF), one of the two main constituent proteins in silk produced by certain arthropods. [58] Alginate exhibits excellent biocompatibility and biodegradability, as well as an ability to be readily processed for 3D scaffolding materials.…”