A Wharton's Jelly Mesenchymal Stromal Cell Derived 3D Osteogenic Niche Allows for Cord Blood Stem Cell Attachment

Abstract

Abstract 4813 Background:Most of umbilical cord blood (UCB) stem cell ex vivo expansion methods have led to UCB stem cell differentiation instead of their self-renewal. Evidence suggests that bone osteoblastic cells are responsible, through physical contact with hematopoietic stem cells (HSCs), for the maintenance of long-term HSCs. Aims:To develop a 3 dimensional (3D) osteogenic structure that provides a niche for UCB stem cells and secondarily, assess the ability of this structure, in addition, to a cocktail of cytokines to expand UCB stem cells.> Methods:Mesenchymal stromal cells (MSCs) isolated form Wharton's Jelly (WJ) were seeded into biodegradable scaffolds followed by osteogenic differentiation induction using osteogenic differentiation media for up to 4 and 6 weeks to develop a 4-week and a 6-week osteogenic scaffolds, respectively. CD34+ selected UCB stem cells were expanded on a monolayer of WJMSCs using a cocktail of cytokines for one week, following which the monolayer and expanded CD34+ UCB stem cells were trypsinized and added to the 4-week and 6-week 3D osteogenic scaffolds (3D conditions), or plated again in culture flask (2D conditions). Pre- and post-expansion total nucleated cell counts were determined and flow cytometry was used to assess the phenotype of the expanded population. Results:Osteogenic differentiation was successfully induced in 3D scaffolds as evident by Alizarin-red staining, scanning electron microscopy (SEM) and molecular testing. UCB stem cell attachment to the osteogenic scaffold was verified by SEM. TNCs were expanded 10X in 2D and 200X in 3D conditions. However, the percentage of CD34+ cells was 5.31% and 4.91% in 2D, and 2.98% and 1.14% in 4-week and 6-week 3D conditions, respectively. Conclusion:Attachment of CD34+ UCB stem cells to 3D osteogenic scaffold allowed for their expansion, though the majority of the expanded cells lost their CD34 expression possibly secondary to their differentiation. Disclosures:No relevant conflicts of interest to declare.