(678g) Tunable, Aligned Electrospun Nanofiber White Matter Mimetics for Investigating Tumor Cell Migration

Here, we present biomimetic materials mimicking specific features of brain white matter tracts to investigate the role of microenvironment on malignant brain tumors (i.e., glioblastoma multiforme, GBM), which have been observed to migrate most frequently along white matter tracts [1]. Specifically, we investigated the relative influences of chemistry, mechanics, and topography on glioblastoma multiforme (GBM) brain tumor migration using aligned electrospun nanofibers (ENFs) produced via core-shell electrospinning. These fibers mimic the topography of aligned white matter architectures found in the brain (e.g., diameters ~0.8-0.9 µm, similar to physiological reports of ~ 0.5-3 µm [2]), while possessing tunable mechanical and chemical features. One unique advantage of the ENF system is that, unlike hydrogel models, one feature can be varied while the others are held constant. For example, to modulate mechanical properties, different polymers (i.e., gelatin, polydimethylsiloxane (PDMS), and polyethersulfone (PES)) were used as a core material, while chemical continuity was provided by using polycaprolactone (PCL) as the shell and topographical features were fixed by the spinning parameters.

This was further corroborated with characterization. All ENFs examined displayed nearly the same micro-architectures, but differing mechanical properties. For example, gelatin-PCL showed a modulus of ~ 2.4 ± 0.5 MPa (wet state) approximately half the modulus of PCL (~ 4.1 ± 0.6 MPa), and PDMS-PCL and PES-PCL displayed moduli that were ~ 7 times higher than PCL (i.e., 33.3 ± 6.8 MPa, and 28.6 ± 6.6 MPa respectively). Similarly, chemical continuity was confirmed via contact angle measurements, with little to no variation seen between samples.

These materials were used to examine tumor cell migration behaviors ex vivo in a physiologically relevant setting as well as identify factors that strongly influence migration. Patient derived tumor cells displayed migration sensitivity to mechanics with the fastest migration observed on PCL (~ 11 µm/h), but slower migration on both higher and lower moduli fibers as quantified using time lapse confocal microscopy. Migration on the softest nanofiber examined (i.e., Gelatin-PCL) was also the slowest, correlating with significantly reduced expression of focal adhesion kinase (FAK)/myosin light chain kinase (MLCK) when compared to other core-shell nanofibers and a PCL control as examined using western blotting.

Further, to examine the influence of specific chemistries, Hyaluronic acid (HA), Collagen and Matrigel were spun as “shells” on PCL “core” nanofibers. We are currently examining the influence of such cues on GBM migratory potential. Ultimately, developing biomaterials that mimic specific highways for GBM migration and further identifying factors that strongly influence migration should allow identification of novel therapeutic targets.  Additionally, tunable ENFs, such as those described herein, could also be employed as ex vivo models to examine diseases of the white matter as well as neural regeneration.

References

[1] A.C. Bellail et al., Int J Biochem Cell Biol. 2004. 36 (6); 1046-1069.

[2] Benninger, Y., et al., Journal of Neuroscience, 2006. 26(29): 7665-7673.