A newly developed synthetic tissue can repair injuries and restore normal erectile function in pigs, according to a study published January 4 in the journal Matter. The artificial tunica albuginea, which is similar to a fibrous sheath of tissue necessary to maintain erections, might help repair penile injuries in humans as well, the study states.
How was artificial tunica albuginea developed?
The researchers developed a method of preparing hydrogels with parallel way fibres. Hydrogels are three-dimensional network structures capable of imbibing large amounts of water and do not dissolve due to chemical or physical cross-links.
The study authors prepared an artificial tunica albuginea with a bionic double-layer structure. Artificial tunica albuginea has bionic mechanical properties and biocompatibility, and can be used to prepare tissue analogues in the future, the study says.
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The mammalian tunica albuginea has a double-layer orthogonal structure that is composed of stacked parallel wavy collagen fibres, which, during an erection, undergo sequential straightening and stretching to mediate the soft-to-firm transition, according to the study.
The researchers, inspired by the delicate-strain adaptive structure of natural tunica albuginea, proposed an artificial tunica albuginea composed of a strain-stiffening hydrogel. This hydrogel consists of aligned yet crimped fibres.
Why was polyvinyl alcohol chosen to develop the artificial tissue?
The study authors produced the delicate structure by stretching an isotropic polyvinyl alcohol gel. Then, they performed covalent cross-linking of the gel. Polyvinyl alcohol has a curled fibre structure similar to that of the tissue present in natural tunica albuginea.
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The reason the researchers chose polyvinyl alcohol is that the treatment of patients with damaged tunica albuginea by making patches from other tissues in the patient's body can cause the immune system to reject the tissue, and result in complications. Moreover, it is difficult for the patches to replace the natural tissue of tunica albuginea perfectly, because the microstructures of these tissues are different from natural tunica albuginea.
What were the characteristics of artificial tunica albuginea?
Some of the mechanical features of natural tunica albuginea, which its artificial counterpart possesses, are excellent fatigue resistance to sustain cyclic bursts, high toughness, and rapid strain stiffening over small intervals of deformation.
According to the study, artificial tunica albuginea holds great promise for penile injury repair.
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The researchers tested the artificial tunica albuginea in miniature pigs with penile injuries, and observed that patches made from the artificial tissue restored erectile function in a way such that it was similar to that of normal penile tissue. This suggests that the patch made using polyvinyl alcohol successfully replaced the functions of natural tunica albuginea.
On analysing the effect of the artificial tunica albuginea patches after one month, the researchers found that the artificial tissue developed fibrous tissues comparable to that in normal tissue, and achieved a normal erection after the penis was infected with saline.