Engineered HA hydrogel for stem cell transplantation in the brain: Biocompatibility data using a design of experiment approach

Abstract

This article presents data related to the research article "Systematic optimization of an engineered hydrogel allows for selective control of human neural stem cell survival and differentiation after transplantation in the stroke brain" (P. Moshayedi, L.R. Nih, I.L. Llorente, A.R. Berg, J. Cinkornpumin, W.E. Lowry et al., 2016) [1] and focuses on the biocompatibility aspects of the hydrogel, including its stiffness and the inflammatory response of the transplanted organ. We have developed an injectable hyaluronic acid (HA)-based hydrogel for stem cell culture and transplantation, to promote brain tissue repair after stroke. This 3D biomaterial was engineered to bind bioactive signals such as adhesive motifs, as well as releasing growth factors while supporting cell growth and tissue infiltration. We used a Design of Experiment approach to create a complex matrix environment in vitro by keeping the hydrogel platform and cell type constant across conditions while systematically varying peptide motifs and growth factors. The optimized HA hydrogel promoted survival of encapsulated human induced pluripotent stem cell derived-neural progenitor cells (iPS-NPCs) after transplantation into the stroke cavity and differentially tuned transplanted cell fate through the promotion of glial, neuronal or immature/progenitor states. The highlights of this article include: (1) Data of cell and bioactive signals addition on the hydrogel mechanical properties and growth factor diffusion, (2) the use of a design of Experiment (DOE) approach (M.W. 2 Weible and T. Chan-Ling, 2007) [2] to select multi-factorial experimental conditions, and (3) Inflammatory response and cell survival after transplantation.

Keywords: Astrocytic scar; BDNF; BMP-4; Biocompatibility; Bone-morphogenic protein-4; Brain; Brain derived-neurotrophic factor; Brain repair; DOE; Design of experiment; Heparin; Hyaluronan; Hyaluronic acid; Hydrogel; IKVAV; Ischemia; NPC; Neural stem cell; RGD; Stem cell transplantation; Stroke; Toxicity; YIGSR.

Fig. 1

Mechanical and composition gel optimization in vitro. (A) Schematic illustration of the injectable hyaluronic acid (HA) composed of acrylated hyaluronic acid, MMP degradable or non-degradable motifs, adhesion peptides and heparin bound growth factors. (B) Rheology data evaluating the influence of heparin and adhesion motifs addition on HA gel stiffness. (C) Growth factor diffusion over time, after encapsulation in an HA-RGD gel. (D) DOE heat map showing the zones of cell survival on encapsulated iPS-NPCs in HA gel with the addition of soluble or heparin-bound BDNF and BMP-4 at day 7. (E) Heparin toxicity assay on 2D cell culture exposed to increasing concentrations of modified or non-modified heparin. (F) DOE data table showing the combination of heparin and growth factor leading to the most positive cell survival data in 3D at day 7. (G) Rheology data evaluating the influence of cell addition on gel stiffness. * indicates P<0.05.

Fig. 2

Biocompatibility data in vivo. (A) Schematic illustration of a brain coronal section after a cortical stroke and the transplanted hydrogel conditions. (B) Evaluation of the astrocytic scar density, (C) the microglial response and (D) the number of transplanted cells positive for the marker DCX, expressed in neuronal progenitors, 2 weeks after transplantation. (E) Evaluation of Sox2 expression, a stem cell marker, in transplanted cells, (F) quantification of vessel density in the stroke area and (G) Cell survival after gel transplantation at 6 weeks after stroke. * and ** indicate P<0.05 and P<0.01 respectively.