Response to di-functionalized hyaluronic acid with orthogonal chemistry grafting at independent modification sites in rodent models of neural differentiation and spinal cord injury.

Hyaluronic acid (HA) with one reactive moiety grafted to the backbone is a commonly used matrix in tissue engineering. The addition of a second orthogonal moiety to the backbone allows for greater control in bioactive signal tethering and gelation. In this study, thiol and azide functional groups were grafted to the HA backbone at separate modification sites. NMR, FT-IR, colorimetric assay, and radio-TLC activity were used to confirm and quantify thiol and azide grafting to the HA backbone. Various ratios of di-functional HA (dif HA) and methacrylate HA (mHA) were used to encapsulate mouse embryonic stem cells in order to examine the neural differentiation of the cells. Greater neural maturation was observed in hydrogels containing a higher percentage of dif HA compared to mHA over a six day neural differentiation time course. This formulation was then tested in a contusion spinal cord injury model for biological effect and was found to reduce the ED1+ area in the spinal cord compared to control and allow for host axon extension into the matrix filled lesion area. These results indicate that dif HA is supportive of neural differentiation and can reduce inflammation without additional bioactive signal tethering. dif HA is a promising matrix base for the central nervous system, which should be further developed.

Overexpression of a profilin (GhPFN2) promotes the progression of developmental phases in cotton fibers.

Cotton fiber development at the stages of elongation and secondary wall synthesis determines the traits of fiber length and strength. To date, the mechanisms controlling the progression of these two phases remain elusive. In this work, the function of a fiber-preferential actin-binding protein (GhPFN2) was characterized by cytological and molecular studies on the fibers of transgenic green-colored cotton (Gossypium hirsutum) through three successive generations. Overexpression of GhPFN2 caused pre-terminated cell elongation, resulting in a marked decrease in the length of mature fibers. Cytoskeleton staining and quantitative assay revealed that thicker and more abundant F-actin bundles formed during the elongation stage in GhPFN2-overexpressing fibers. Accompanying this alteration, the developmental reorientation of transverse microtubules to the oblique direction was advanced by 2 d at the period of transition from elongation to secondary wall deposition. Birefringence and reverse transcription-PCR analyses showed that earlier onset of secondary wall synthesis occurred in parallel. These data demonstrate that formation of the higher actin structure plays a determinant role in the progression of developmental phases in cotton fibers, and that GhPFN2 acts as a critical modulator in this process. Such a function of the actin cytoskeleton in cell phase conversion may be common to other secondary wall-containing plant cells.