Potential of electrospun cationic BSA fibers to guide osteogenic MSC differentiation via surface charge and fibrous topography

Annamarija Raic,Joerg Lahann,Frank Friedrich,Cornelia Lee-Thedieck,Karen Bieback,Domenic Kratzer

doi:10.1038/s41598-019-56508-6

Abstract

Large or complex bone fractures often need clinical treatments for sufficient bone repair. New treatment strategies have pursued the idea of using mesenchymal stromal cells (MSCs) in combination with osteoinductive materials to guide differentiation of MSCs into bone cells ensuring complete bone regeneration. To overcome the challenge of developing such materials, fundamental studies are needed to analyze and understand the MSC behavior on modified surfaces of applicable materials for bone healing. For this purpose, we developed a fibrous scaffold resembling the bone/bone marrow extracellular matrix (ECM) based on protein without addition of synthetic polymers. With this biomimetic in vitro model we identified the fibrous structure as well as the charge of the material to be responsible for its effects on MSC differentiation. Positive charge was introduced via cationization that additionally supported the stability of the scaffold in cell culture, and acted as nucleation point for mineralization during osteogenesis. Furthermore, we revealed enhanced focal adhesion formation and osteogenic differentiation of MSCs cultured on positively charged protein fibers. This pure protein-based and chemically modifiable, fibrous ECM model allows the investigation of MSC behavior on biomimetic materials to unfold new vistas how to direct cells’ differentiation for the development of new bone regenerating strategies.

Highlights

After bone fractures mesenchymal stromal cells (MSCs) take on a key role in the in vivo bone repair process[1]
The developed cationized bovine serum albumin (cBSA)-fibers showed a diameter of 1.53 ± 0.22 μm (±standard deviation (SD)) whereas the bovine serum albumin (BSA)-fibers had a diameter of 2.15 ± 0.61 μm (Fig. 1A)
The measurements revealed a mean surface roughness of 0.299 ± 0.048 nm (±SD) for cBSA-fibers and 0.209 ± 0.045 (±SD) nm for BSA-fibers showing that both fiber types possess a smooth surface structure (Fig. 1C, Table 1, detailed information on the Atomic force microscopy (AFM) measurements can be found in the supplementary information, Fig. S2)

Summary

Introduction

After bone fractures mesenchymal stromal cells (MSCs) take on a key role in the in vivo bone repair process[1]. It is important to understand how MSC differentiation into bone cells is controlled and how this process can be guided or improved by externally added factors. Addressing this issue can help to develop e.g. osteoinductive implants. Modification of in vitro model surfaces with the bone substrate hydroxyapatite shows a positive effect on MSC behavior regarding their osteogenic differentiation[10]. Our present study highlights the importance of the fibrous structure, the amination of BSA – leading to a positively charged cell culture substrate – and the calcifiability of the developed biomaterial for its effects on the osteogenic differentiation of MSCs

Methods

Results

Conclusion