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Stem and progenitor cells are helping researchers understand the complex process of mammalian development and also show great promise in treating diseases that are unresponsive to standard therapies. The potential for embryonic stem cells to differentiate into any cell in the body is their great benefit but avoiding co-culture with animal cells and efficiently narrowing cell fate to a single cell type remains challenging. Adult progenitor cells have a more restricted cell fate, but have the potential for use in autologous cell therapies and avoid the ethical issues surrounding the derivation of embryonic stem cell lines. While progress is encouraging, there is much work to be done in directing cells to specific lineages before stem and progenitor cells can be commonly used in clinical settings. This review discusses current techniques used for investigation of the growth and differentiation of stem and progenitor cells, with a focus on neural cell fates.

We evaluated a biodegradable graft for reconstruction of rat vasa deferentia with long obstructed or missing segments. A total of 47 Sprague-Dawley rats underwent bilateral vasectomy and were divided into groups according to length of the vas deferens affected (0.5, 1, 1.5 cm). After 8 weeks, poly-(D,L-lactide) (PDLA) grafts were used to reconnect the vas deferens. Grafts and adjoining vasa deferentia were excised 8 and 12 weeks later and evaluated microscopically. At 8 weeks, microscopic changes included a robust inflammatory response around the grafts. All grafts were still intact but in the early stages of degradation. No microtubules, indicative of vas deferens recanalization, were identified. One specimen showed evidence of healing and neovascularization at the interface zone between the vas deferens and the graft. At 12 weeks, grafts were further degraded but still present. Microscopic evaluation showed decreased inflammation. Seven specimens showed neovascularization at the interface zone; two of these showed distinct epithelialized vas deferens microcanals at the graft edges. One specimen showed a microcanal spanning the entire 0.5-cm graft. A time period of 8 weeks is not ample enough for vas deferens regeneration in the setting of a biodegradable PDLA graft; however, early evidence of re-growth was seen at 12 weeks. A longer healing time should permit further biodegradation of the graft, as well as re-growth and possible eventual reconnection of the vas deferens, allowing passage of sperm. These findings suggest a potential role for biodegradable grafts in the reconstruction of vas deferens with long obstructed segments.

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