Electrospun Fiber Alignment Guides Osteogenesis and Matrix Organization Differentially in Two Different Osteogenic Cell Types.

Robin M Delaine-Smith,Nicola H Green,Gwendolen Clair Reilly,Alice Jane Hann

doi:10.3389/fbioe.2021.672959

Robin M Delaine-Smith, Nicola H Green + Show 2 more

Open Access

https://doi.org/10.3389/fbioe.2021.672959

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Abstract

Biomimetic replication of the structural anisotropy of musculoskeletal tissues is important to restore proper tissue mechanics and function. Physical cues from the local micro-environment, such as matrix fiber orientation, may influence the differentiation and extracellular matrix (ECM) organization of osteogenic progenitor cells. This study investigates how scaffold fiber orientation affects the behavior of mature and progenitor osteogenic cells, the influence on secreted mineralized-collagenous matrix organization, and the resulting construct mechanical properties. Gelatin-coated electrospun poly(caprolactone) fibrous scaffolds were fabricated with either a low or a high degree of anisotropy and cultured with mature osteoblasts (MLO-A5s) or osteogenic mesenchymal progenitor cells (hES-MPs). For MLO-A5 cells, alkaline phosphatase (ALP) activity was highest, and more calcium-containing matrix was deposited onto aligned scaffolds. In contrast, hES-MPs, osteogenic mesenchymal progenitor cells, exhibited higher ALP activity, collagen, and calcium deposition on randomly orientated fibers compared with aligned counterparts. Deposited matrix was isotropic on random fibrous scaffolds, whereas a greater degree of anisotropy was observed in aligned fibrous constructs, as confirmed by second harmonic generation (SHG) and scanning electron microscope (SEM) imaging. This resulted in anisotropic mechanical properties on aligned constructs. This study indicates that mineralized-matrix deposition by osteoblasts can be controlled by scaffold alignment but that the early stages of osteogenesis may not benefit from culture on orientated scaffolds.

Highlights

Mature compact bone tissue has a well-organized, hierarchical structure, comprised mainly of collagen fibers and hydroxyapatite minerals (Weiner and Wagner, 1998; Summitt and Reisinger, 2003)
Young’s modulus, E, was 10- or 100-fold greater for aligned fibers stretched parallel to the strain direction compared with random fibers or aligned fibers stretched perpendicular to the strain direction
To develop tissue-engineered constructs that are suitable for implantation, both physiological function and tissue mechanical properties must be replicated

Summary

Introduction

Mature compact (cortical) bone tissue has a well-organized, hierarchical structure, comprised mainly of collagen fibers and hydroxyapatite minerals (Weiner and Wagner, 1998; Summitt and Reisinger, 2003). These collagen fibers resist tensile forces and are preferentially orientated within a bone lamella (layer), each of which has a different predominant orientation. During fetal bone growth or after a fracture, immature osseous tissue is initially formed of randomly organized coarse collagen fibers and is mechanically weak. This matrix is remodeled and replaced by organized lamellar bone. Despite the evident importance of collagen fiber alignment in enabling bone to resist fracture, the process of recreating the native anisotropy remains challenging

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