Regional Differences And Physiologic Behaviors In Peripapillary Scleral Fibroblasts

PURPOSE. The purpose of this study was to describe the cellular architecture of normal human peripapillary sclera (PPS) and evaluate surface topography's role in fibroblast behavior.METHODS. PPS cryosections from nonglaucomatous eyes were labelled for nuclei, fibrillar actin (FA), and alpha smooth muscle actin (alpha SMA) and imaged. Collagen fibrils were imaged using second harmonic generation. Nuclear density and aspect ratio of the internal PPS (iPPS), outer PPS (oPPS), and peripheral sclera were determined. FA and alpha SMA fibril alignment with collagen extracellular matrix (ECM) was determined. PPS fibroblasts were cultured on smooth or patterned membranes under mechanical strain and in the presence of TGF beta 1 and 2.RESULTS. The iPPS (7.1 +/- 2.0 x 10(-4), P < 0.0001) and oPPS (5.3 +/- 1.4 x 10(-4), P = 0.0013) had greater nuclei density (nuclei/mu m(2)) than peripheral sclera (2.5 +/- 0.8 x 10(-4)). The iPPS (2.0 +/- 0.3, P = 0.002) but not oPPS (2.4 +/- 0.4, P = 0.45) nuclei had smaller aspect ratios than peripheral (2.7 +/- 0.5) nuclei. FA was present throughout the scleral stroma and was more aligned with oPPS collagen (9.6 +/- 1.9 degrees) than in the peripheral sclera (15.9 +/- 3.9 degrees, P = 0.002). The aSMA fibers in the peripheral sclera were less aligned with collagen fibrils (26.4 +/- 4.8 degrees) than were FA (15.9 +/- 3.9 degrees, P = 0.0002). PPS fibroblasts cultured on smooth membranes shifted to an orientation perpendicular to the direction of cyclic uniaxial strain (1 Hz, 5% strain, 42.2 +/- 7.1 degrees versus 62.0 +/- 8.5 degrees, P < 0.0001), whereas aligned fibroblasts on patterned membranes were resistant to strain-induced reorientation (5.9 +/- 1.4 degrees versus 10 +/- 3.3 degrees, P = 0.21). Resistance to re-orientation was reduced by TGF beta treatment (10 +/- 3.3 degrees without TGF beta 1 compared to 23.1 +/- 4.5 degrees with TGF beta 1, P < 0.0001).CONCLUSIONS. Regions of the posterior sclera differ in cellular density and nuclear morphology. Topography alters the cellular response to mechanical strain.