Mesenchymal stromal cell remodeling of a gelatin hydrogel microenvironment defines an artificial hematopoietic stem cell niche

Abstract

We identify a combination of an initially low-diffusivity (autocrine dominated) hydrogel and a 1:1 HSCP:MSC seeding ratio as conducive to enhanced HSC population maintenance. Further, gene expression and serial mechanical testing data suggests that MSC-mediated matrix remodeling is significant for the long-term HSC culture, reducing HSC autocrine feedback and potentially enhancing MSC-mediated paracrine signaling over 7-day culture in vitro. This work demonstrates the design of an HSC culture system that couples initial hydrogel properties, MSC co-culture, and concepts of dynamic reciprocity mediated by MSC remodeling to achieve enhanced HSC maintenance.

Deciphering the Molecular Mechanism of Water Interaction with Gelatin Methacryloyl Hydrogels: Role of Ionic Strength, pH, Drug Loading and Hydrogel Network Characteristics

“…The hydrogel mesh size is derived from the equilibrium swelling ratio (See Materials and Methods section and Figure 5 and Figure S6) and was most significantly impacted by the ionic strength of the swelling media at low GelMA concentrations of 5%, compared to 10% and 15%, but overall followed a decreasing trend with increasing ionic strength (Figure 5). These were expected results and have previously been reported for hydrogels in other studies [64,73]. Across all GelMA concentrations, the mesh size varied from 23 to 4 and 61.6 to 8.7 nm.…”

“…Thirdly, the Flory-Rehner Equation (5), used for polymers crosslinked in solvents [56,62,63], was used to calculate the molecular weight between crosslinks M c (g/mol). The following polymer properties were used for the calculation: the specific volume of the polymer v = 0.7407 mL/g [64]; the molar volume of the solvent V 1 = 18.01 mL/mol for water; the polymer-solvent interaction X 1 = 0.497 (also known as the Flory's Chi parameter) [65]; and the number average molecular weight before crosslinking M n = 63,565 g/mol [66].…”

“…Finally, the mesh size ξ (nm) was calculated using Equation (6). M r = 91.19, the molecular weight of the repeat unit, was taken as the average molecular weight of the amino acid composition [64]. The amino acid bond length l = 4.28…”

Gelatin Methacryloyl Hydrogels for the Localized Delivery of Cefazolin

“…Mesh size was calculated using the molecular weight of the repeating unit M r (averaged molecular weight of the amino acid composition, M r = 91.19 g/mol) [26], the amino acid bond length l = 4.28…”

“…A [27], the Flory's characteristic ratio C n for GelMA was taken as 8.8785 [26], and the molecular weight between crosslinks M c was calculated using Equation (5).…”