Figure 5.

Pro-migratory activity is introduced during second stage of ultrasound-induced heating. Aliquots of neutralized soluble collagen (0.8 mg ml⁻¹) were exposed to 8.8-MHz ultrasound (7.9 W cm⁻²) or sham-exposed at 3 different, sequential locations for 5 min each, for a total exposure of l5 min. Additionally, the rate of collagen polymerization was varied by setting the water bath temperature to 37, 25, 18, or 13 °C, so that the second stage of ultrasound-induced heating coincided with the first (37 °C, red), second (25 °C, green), or third (18 °C, blue) exposure location. Collagen polymerization did not occur within the 15-min exposure period when the temperature was set to 13 °C. All samples were allowed to polymerize fully post-exposure before FN-null MEFs (4.7 × 10⁴ cells cm⁻²) were seeded on gel surfaces. After 24 h, phase contrast images were captured at each of the 3 exposure locations. White outlines indicate cell-free areas on the collagen gel surface. Images represent 1 of at least 3 independent experiments. Scale bar = 500 μm.