Axonal growth control

In comparison with biologically derived materials, synthetic polymers have several advantages and disadvantages. Since they do not need to be extracted from animal tissue they pose a lower risk of contamination and immunological reaction. Their physical and chemical properties can be better controlled and manipulated. On the other hand, synthetic materials usually do not activate specific cellular receptors and therefore do not by themselves elicit the desired cellular responses such as axonal growth or cell migration. Some materials may even be rejected or encapsulated in scar tissue. 

Fig. 10. Effect of ablation of the Cxi neurons on axon growth from the Til neurons in the grasshopper embryo. (A) Operated leg in which the Cxi neurons had been killed at the onset of Til neuron axonogenesis and the embryo allowed to develop further in culture medium. Asterisk indicates debris of Cxi cells. The Til axons possess multiple abnormal branches (arrowheads). (B) Contralateral control limb for (A) The Til axons take a normal pathway to the CNS. (C) Operated limb bud. The Til axons project straight ahead (arrowhead) towards efferent axons from the CNS, rather than turning posteriorly towards the Cxi cell site. (D) Contralateral control limb bud for (C), showing a normal Ti 1 trajectory. Camera lucida drawings from anti-HRP immunohistochemistry preparations. Scale bar = 100 /tm (reproduced with permission from Nature 304, (1983) Macmillan Magazines Limited).

Hefftier CD, Lumsden AGS, O Leary DDM (1990) Target control of collateral extension and directional axon growth in the mammalian brain. Science 247 217-247. 

---