Vascular constructs

FIGURE 8.22 Chemical structure of biodegradable poly(ester amide)s with potential interest as vascular constructs for therapeutic uses. 

Tubular PGA fiber scaffolds, seeded with chondrocytes and implanted into sternohyoid muscle for 4 weeks, have been used, with a silicon tube as stent (removed after 2 months). Six of 10 animals, implanted with vascularization, survived more than 6 months, whereas all the animals in the control group (without vascularization) died within 2 months after reconstruction, due to mucus impaction. Six months after implantation, vascularized constructs retained structures and features of cartUage-like tissue and developed a continuous cihated columnar epithehum layer, suggesting the importance of the prevascularization for the development of a suitable airway graft [126]. A copolymer of L-lactide and e-caprolactone sponge tube reinforced by PGA was implanted into sheep. A silicone stent (7 cm in length) was placed perioperatively to prevent graft collapse. After 9 months, only stent had positive outcomes, even if a complete and spontaneous reconnection of the native trachea was not observed [127]. 

Narita, Y, K. Hata, H. Kagami et al. 2004. Novel pulse dupUcating hioreactor system for tissue-engineered vascular construct. Tissue Eng 10(7-8) 1224-33. 

Sehktar, D., R. M. Nerem, and Z. S. Gabs. 2001. The role of matrix metaUoproteinase-2 in the remodehng of cell-seeded vascular constructs subjected to cyclic strain. Ann Biomed Eng 29 11) 923-M. 

Matsumura G, Miyagawa-Tomita S, Shin Oka T, Ikada Y, and Kurosawa H. First evidence that bone marrow cells contribute to the construction of tissue-engineered vascular autografts in vivo. Circulation, 2003, 108, 1729-1734. 

Halichlorine 11 is a structurally unique alkaloid that was isolated from the sponge Halichondria okadai and found to act as an inhibitor of the induction of vascular cell adhesion molecule (VCAM-1), a potential target in the development of drugs for the treatment of several vascular diseases. The strategies employed for the construction of its spiroquinolizidine unit are summarized in Scheme 106. 

Other limitations of mouse/rat models are that tumour growth is different in the animal model compared to the situation in man.Tumour growth is more rapid in the rat/mouse model which has an effect on vascularization and intra-tumoural pressure for example. These factors can, as discussed in Section 8.4, have great impact on tumour penetration and uptake of the MAb-based drug-targeting constructs. 

Biomedical Applications—CNTs allow cells to grow on and over them without adherence to the nanotubes and without toxic reaction. Potential applications range from their use within coatings and composites to be used within the body, for prosthetics, and in the construction of vascular stents and neuron growth and regulation. 

By comparison, erectile dsyfunction (ED) is an example of how social dissatisfaction can be transformed into medical dysfunction and then remedied by a pill. On the one hand, it is certainly true that, in some cases, ED is the consequence of organic causes, including peripheral vascular diseases, hypertension, drug-side effects, hormonal imbalance, and diabetes. The MMAS suggests, for example, that 10 per cent of American males have complete inability to achieve erection of the penis (Feldman et al. 1994). But ED is primarily a socially constructed condition based on a socially constructed male "problem." As one commentator has explained, " [T]he more anxiety a corporation can produce, the larger its market. In other words, worrying about ED may in fact cause ED" (Loe 2004). 

---