3D presentation of a neurotrophic factor for the regulation of neural progenitor cells

Background: Adequate cell–scaffold interactions and neurotrophin support are essential factors for neural regeneration. Aim: To provide insight into the biofunctionalization of complex 3D scaffolds with nanoscale precision, as well as the effect of spatial distribution of brain-derived neurotrophic factor (BDNF) and its prolonged stimulation in combination with enhanced cell affinity of nanofibrous scaffolds on the survival/proliferation and neurite outgrowth. Methods & materials: We developed a versatile approach using layer-by-layer self-assembly to incorporate cell adhesion and spatial representation of neurotrophic factors into complex nanofibrous scaffolds. Results: Heparin/poly-L-lysine (PLL) polyelectrolyte multilayers (PEMs) were deposited on electrospun poly-ε-caprolatone nanofibers. Well-controlled amounts of BDNF were immobilized on the PEM-modified nanofibers. In addition, longer neurite outgrowth was observed in neural progenitor cells cultured on PLL-terminating PEM scaffolds. The immobilized BDNF on PLL-terminated PEM scaffolds resulted in significantly longer neurites and higher cell numbers (p < 0.01) compared with BDNF-free and BDNF-adsorbed PLL-terminating scaffolds. Interestingly, there was no upregulation of TrkB-FL, TrkB-T1 or GAP-43 mRNAs with immobilized BDNF in day 5 cultures. Discussion & conclusion: This work reinforces the importance of the combinatorial effects of biomaterial scaffold nanostructure and spatial presentation of neurotrophins in directing neural progenitor cell fates.

Original submitted 18 January 2013; Revised submitted 3 May 2013

Estrogen is not directly required for oocyte developmental competence

Oocyte maturation and ovulation require a coordinated interaction between gonadotrophs, steroid hormones, and growth factors. The extent to which estrogen is required in this process, however, remains unclear. To better understand the role of estrogen in maintaining developmental competence of mammalian oocytes, we studied the Aromatase knockout (ArKO) mouse, which has been genetically engineered to be incapable of synthesizing endogenous estrogen. Previous studies have established that ArKO female mice are anovulatory with ovaries that progressively degenerate, developing hemorrhagic cystic follicles. In young ArKO females, however, apparently healthy follicles and oocytes have been observed. We investigated if these oocytes could be induced to ovulate, then mature, fertilize, and develop in vitro. Following a standard superovulation protocol, ArKO oocytes did not ovulate. When recovered manually from the ovary, however, ArKO oocytes successfully progressed through in vitro maturation, fertilization, and development to the blastocyst stage at the same rate as wild-type and heterozygote littermates. Therefore, it appears that estrogen is not required for the production and growth of oocytes capable of maturation and complete preimplantation development but is required for continued follicle growth and feedback regulation of ovulation.