An international team of researchers from China, Japan, and the US has taken an important step in the 3D printing of organs, an intriguing but extremely challenging aspect of biomedical engineering. The organ of choice was the penis, part of which was reconstructed in the lab using a hydrogel showing realistic functionality. The artificial organ was then implanted into rabbits and pigs with penile issues, and these animals were then able to mate and reproduce within a few weeks.
One of the crucial challenges in printing an organ from its basic tissue has to do with its vascular network. The cells that make up the organs need blood to reach them in order to bring the oxygen and nutrients they require to function and survive. When it comes to the penis, the vascular network has the specific function of generating an erection; blood becomes trapped in the corpora cavernosa, which leads the penis to become erect.
The research team was able to use a hydrogel to 3D-print models of the penis, which included the main structures: the corpora cavernosa and the corpus spongiosum with its urethral structure, as well as the tunica albuginea that covers them. This approach allowed the researchers to study possible defects and interventions in vitro, so that properties and defects in normal penile function could be studied without animals or humans.
Damages to the tunica albuginea and the corpora cavernosa can lead to medical conditions. In particular, the team wanted to create in vitro models for erectile dysfunction and Peyronie’s disease, a condition where scar tissues forms under the skin of the penis, which can lead to curved and painful erections.
The hydrogel model was used to demonstrate how blood flows into the corpora cavernosa, engorging the organ, and how the cavernous sinuses work as a valve blocking the blood flow, giving the ability to achieve and maintain an erection.
The team was also able to create a version of the model that could be transplanted into pigs and rabbits. They made a dynamic model of the corpora cavernosa, seeded with endothelial cells, the single layer of cells that lines all blood vessels. It was then implanted in rabbits and pigs with penile defects. Within a few weeks, normal erectile function was restored; it also allowed the animals to mate and reproduce.
“These findings underscore the potential clinical applications of biomimetic corpus cavernosum (BCC) for the treatment of penile injuries. Furthermore, this study advances the clinical application of 3D-printed artificial tissue organs,” the authors wrote in a paper detailing the model.
Just over half of cis men aged between 40 and 70 will have mild to moderate erectile dysfunction according to the Massachusetts Male Aging Study. The prevalence of Peyronie’s disease is significantly lower (between 1 and 13 percent). A future human-graded version of this model could be employed as a treatment for these conditions, or in gender-affirming surgery for trans men.
The study is published in Nature Biomedical Engineering.
