Mimicking the Organic and Inorganic Composition of Anabolic Bone Enhances Human Mesenchymal Stem Cell Osteoinduction and Scaffold Mechanical Properties

Abstract

Engineered bone graft designs have been largely inspired by adult bone despite functionally significant differences from the composition of anabolic bone in both the mineralized and non-mineralized fractions. Specifically, anabolic bone contains hydroxyapatite with ionic substitutions that facilitate bone turnover and relatively rare collagens type VI and XII that are important for normal bone development. In this work, human mesenchymal stem cells (hMSCs) were cultured in lyophilized collagen type I scaffolds mineralized with hydroxyapatite containing Mg 2+ substitutions, then induced to deposit an extracellular matrix (ECM) containing collagens VI and XII by exposure to GW9662, a PPARγ inhibitor. Delivery of GW9662 was accomplished through either Supplemented Media or via composite microspheres embedded in the scaffolds for localized delivery. Furthermore, hMSCs and scaffolds were cultured in both static and perfuse conditions to investigate the interaction between GW9662 treatment and perfusion and their effects on ECM deposition trends. Perfusion culture enhanced cell infiltration into the scaffold, deposition of collagen VI and XII, as well as osteogenic differentiation, as determined by gene expression of osteopontin, BMP2, and ALP. Furthermore, scaffold mineral density and compressive modulus were increased in response to both GW9662 treatment and perfusion after 3 weeks of culture. Local delivery of GW9662 with drug-eluting microspheres had comparable effects to systemic delivery in the perfusate. Together, these results demonstrate a strategy to create a scaffold mimicking both organic and inorganic characteristics of anabolic bone and its potential as a bone graft.

Preparation and In Vitro Osteogenic Evaluation of Biomimetic Hybrid Nanocomposite Scaffolds Based on Gelatin/Plasma Rich in Growth Factors (PRGF) and Lithium-Doped 45s5 Bioactive Glass Nanoparticles

“…From a histological standpoint, bone tissue is a natural combination of bioceramic and polymer phases, principally apatite and collagen [ 70 ]. Therefore, nanocomposite polymer hybrid scaffolds have tremendous potential for bone tissue engineering [ 71 , 72 ]. Porous 3D polymeric Nanocomposite scaffolds have been repeatedly reported to provide a suitable matrix for connecting and expanding different cell types [ 73 ].…”

Studying Activated Fibroblast Phenotypes and Fibrosis‐Linked Mechanosensing Using 3D Biomimetic Models

“…[69] For this reason, we employed a freeze-drying technique while employing BDDGE as crosslinking strategy to produce bovine collagen type I-based interconnected porous structures with controlled and reproducible porosity and fiber organization, resulting in a tunable system for 3D mechanical studies. [50,70,71] In a native tissue context, cells are exposed to a variety of mechanical stimuli including hydrostatic pressure, shear, compression, and tensile force. [72] For this reason, soft biological tissues can be described as viscoelastic materials.…”

“…[ 69 ] For this reason, we employed a freeze‐drying technique while employing BDDGE as crosslinking strategy to produce bovine collagen type I‐based interconnected porous structures with controlled and reproducible porosity and fiber organization, resulting in a tunable system for 3D mechanical studies. [ 50,70,71 ]…”

Perfused Platforms to Mimic Bone Microenvironment at the Macro/Milli/Microscale: Pros and Cons

“…A few recent research works based on milliscale bioreactors have demonstrated that the combined effect of perfusion and anabolic drugs (e.g., 2-chloro-5-nitrobenzanilide, a PPARγ inhibitor (GW9662), hydrogen sulphide, parathyroid hormone) can enhance collagen deposition and bone mineralization ( Grant et al, 2016 ; Liu et al, 2018 ; Gambari et al, 2019 ; Mondragon et al, 2020 ; Liu et al, 2021 ). Mondragon et al showed that perfused cultures of MSCs on lyophilized bovine collagen type I scaffolds upon which Mg-doped HA nanocrystals nucleated during collagen fibrils self-assembly and treated with GW9662, led to an increased scaffold mineral density and compressive modulus ( Mondragon et al, 2020 ). Contrary to milliscale, at the microscale this topic is completely unexplored.…”