Recently, it was reported that the use of mechanical force has a pivotal role in neuron development, as mechanical stretch can modulate several different cellular functions also in other tissues such as the electrical activity of cardiac muscle or osteogenesis.
The article that we are presenting herein, is about the investigation of a new methodology for stretching the axon shaft by developing a force similar or lower that those endogenously generated by the growth cone.
The proposed method is based on labelling the axon with magnetosomes and subsequent application of an external magnetic field to induce a force generation that stretches the axon.
The same research group has previously reported the use of superparemagnetic iron oxide nanoparticles of 75nm size for the same purpose and in this paper the advantages of the new proposal have been showed.
Magnetosomes are natural nano-size organelles enveloped by a biological membrane that enable magnetotactic bacteria to align along geomagnetic field lines.
They can be isolated from cells and purify, and they are stable and dispersible. In the present work magnetosomes were isolated with their intact biological membrane showing a particle size of around 40 nm. They were then tested on mouse hippocampal neurons excluding cytotoxicity and confirming that they can be administered to cells to the low concentration required for stretch-growth.
After plating cells with magnetosomes and exposing from day in vitro to the magnetic field, authors showed that there was a highly significant increase in axonal length in comparison to the control groups. Moreover, magnetosomes provided a statistically increase in the length of neurites compared to samples treated with magnetic nanoparticles. It was also found that magnetosomes are internalized by cells, they adhere to the cell membrane, localize as single particles within the axon and slowly degrade after few days from the internalization process. The smaller size of the inorganic core, the lower Fe concentration used for cell labelling and the strong ability to accumulate inside axons, are advantages of the use of bacterial magnetosomes for inducing stretch-growth of hippocampal neurons respect to the use of artificial magnetic iron oxide nanoparticles. The superior properties of magnetosomes are probably facilitated by their membranous structure and can be exploited for expanding the range of biotechnological applications to the neuroscience field.
To learn more, read the original article: “Induction of axonal outgrowth in mouse hippocampal neurons via bacterial magnetosomes”. S De Vincentiis et al, Int. J. Mol. Sci. 2021, 22, 4126.