1. Janahan Arulmoli, Medha M. Pathak, Lisa P. McDonnell, Jamison L. Nourse, Francesco Tombola, James C. Earthman, & Lisa A. Flanagan STATIC STRETCH AFFECTS NEURAL STEM CELL DIFFERENTIATION IN AN EXTRACELLULAR MATRIX-DEPENDENT MANNER Published 17 February 2015 Presented 10 March 2015

2.  Neural stem and progenitor cell (NSPC) fate is strongly influenced by mechanotransduction: the mechanism of converting physical stimuli to chemical/electrical response BACKGROUND: MECHANOTRANSDUCTION

3.  Substrate stiffness  Softer substrates (<1 kPa): Neuronal differentiation  Stiffer substrates (>1 kPA): Astrocyte generation  Folding and cell sheet movement  Observed In vivo during CNS development  Mechanical stretching  In vitro modeling of traumatic brain injury via equibiaxial stretch  Gradual mechanical stretching enhances neurite elongation and maturation of neurons derived from adult rat hippocampal NSPCs  But how does mechanical stretching influence NSPC differentiation?  This paper investigates… SOME WELL-STUDIED MECHANICAL CUES ON NSPC’S

7. “PDGFR-α recognizes oligodendrocytes at an earlier stage of differentiation than O4, so the percentage of cells identified with this marker is higher than that recognized by the more mature marker O4 “ ( From mouse cortical NSPCs)

9.  Results after applying static stretch at the onset of differentiation and maintained for several days:  No direct effect on differentiation of mNSPCs into neurons or astrocytes  However oligodendrocyte differentiation was greatly affected  From mouse cortical NSPCs  2.6-fold reduction in 04-positive oligodendrocytes  3.2-fold reduction in in earlier stage oligodendrocytes detected by PDGFR-α  From rat hippocampal NSPCs  2.6-fold reduction in 04-positive oligodendrocytes STATIC STRETCH DECREASES OLIGODENDROCYTE DIFFERENTIATION

10. LAMININ, BUT NOT FIBRONECTIN, PLAYS A ROLE IN STRETCH-MEDIATED OLIGODENDROCYTE DIFFERENTIATION Laminin Coated Membranes

11. α6 integrin is expressed by E12 mouse NSPCs

12. ANOTHER CONTROL: SUBSTRATE STIFFNESS

13. SUBSTRATE STIFFNESS VS STRETCH Neuron Differentiation (With Other Markers

15.  Previous studies on substrate stiffness and oligodendrocyte generation  conflicting results…  Explanation: different stiffness  Why 10% Strain?  Previously applied in vitro to model trauma  Measured in models of surrogate brain material in human skulls subjected to rotational forces used to predict strain fields in vivo DISCUSSION NOTES

16.  “Specific ECMs clearly impact the response of NSPCs to mechanical stresses. Thus, these warrant attention when designing biomaterial scaffolds for NSPC transplantation into the CNS. Scaffolds in the tissue will also transmit mechanical forces, which our data suggest will affect differentiation of the embedded cells. For this reason, materials for CNS applications should be designed with consideration of the mechanical environment that takes into account stiffness of the material, the mechanical stresses transplanted cells may encounter, and the ECM or integrin ligating component of the material.” VALUE FOR OUR LAB