3D printed body parts are not as far off as you may think.
This spring researchers at Northwestern University Feinberg School of Medicine announced they used 3D printing to create a prosthetic ovary, and successfully transplanted the organ into mice. These mice were then able to bear live young. It’s a significant milestone, potentially paving the way to restoring reproductive health in pediatric cancer patients and women who have lost fertility, among other applications.
Research like this also highlights challenges, and opportunities, in 3D printing body parts, particularly when it comes to women’s health. In an emailed Q&A, researchers Monica Laronda, Ramille Shah and Alexandra Rutz discuss the details and implications of their work, including the type of 3D printer and ink needed for biological material, and challenges in printing and implanting body parts, particularly ovaries (which they say are “challenging to engineer”).
The ovary is a very dynamic organ and is challenging to engineer
Chicago Inno: How did you start on this line of work, and what inspired the research on 3D printed ovaries?
Monica M. Laronda: Our motivation for creating an artificial ovary starts with the need to restore hormone function and the option of fertility in young girls or women who have insufficient ovarian function. For example, this can occur in children who undergo chemotherapy or radiation treatments to eradicate their cancer. Teresa Woodruff, my mentor and a senior author on this work, began the Oncofertility Consortium to bring awareness to and address these issues of treatment-causing infertility. Girls who have not undergone puberty, are not able to stimulate and reserve eggs prior to treatment, like some adult women may choose to do. There is also a chance that some girls do not undergo normal puberty, due to the effects of their treatment on their ovaries. Ovarian tissue slices that contain the bank of immature cells have been transplanted back into patients by groups such as Donnez & Dolmans in Brussels, Andersen in Copenhagen and Silber in St. Louis. The risk with using this tissue is that we and others have shown that the tissue can contain cancer cells, especially from patients with metastatic disease. We want to create a method for restoring their ovarian function, in a way that could be safe and standardized with their own cells. We sought to create a scaffold that would provide the necessary support of ovarian cell aggregates and be handled during surgery.
Ramille N. Shah: 3D printing allows us to create biomaterial scaffolds with precise control over pore architecture and material and cell deposition so that tissue engineers can create more sophisticated artificial microenvironments for cells (or in this case, follicles) that optimize cell viability and function. The Shah Tissue Engineering and Additive Manufacturing (TEAM) lab focuses on developing new functional biomaterial inks and structures that are both cell compatible and 3D printable for complex tissue engineering applications. We joined forces with Teresa Woodruff and Monica Laronda to see if we can create optimal biomimetic environments for culturing follicles towards creating a functional artificial ovary that can restore hormone function and fertility in women who have insufficient ovarian function.
You’re using a 3D printer to create scaffolding made out of biological material to support hormone producing cells and immature egg cells, called oocytes. What kind of 3D printer do you use, and how did you come up with the material that it prints?
Alexandra Rutz: We use an extrusion-based 3D printer, the Bioplotter, manufactured by Envisiontec. We chose gelatin as our material for this work as well as other tissues we are exploring in the Shah Lab because it is derived from collagen, which is the most abundant protein in tissues and organs. Collagen is responsible for giving tissues and organs structure, and therefore, it makes sense to use such a material as a scaffold. Cells can respond to gelatin in that they can adhere and remodel the material, allowing cells to replace the scaffold with their own synthesized tissue. Furthermore, gelatin is relatively cheap and already has several FDA-approved uses, which can facilitate the translation of our 3D printable gelatin devices for clinical use.
Once the scaffolding is implanted in the body, does normal ovarian function return quickly?
Monica M. Laronda: How quickly normal ovarian function resumes depends a lot on the state of the patient or patient model, and the type of follicles that the ovarian bioprosthesis contains. In some cases, where the ovarian tissue is transplanted, the patient is primed with hormones to trigger normal cyclicity and this could be done with our transplant as well.
What are some of the challenges and opportunities of 3D printing body parts, particularly ovaries?
Monica M. Laronda: In our model, we are 3D printing the scaffold for the ovary in a way that supports the ovarian follicles. The follicles are spherical functional units that require the surrounding connections of the hormone-producing, hormone-responsive cells to the developing egg cell, the oocyte. There is a specific developmental process that happens beginning with the follicle reserve (or bank of potential egg cells) toward the release or ovulation of a fertilizable egg. This process involves a back and forth of hormones released from the hypothalamus and pituitary with the ovary that triggers the growth and expansion of follicles to almost 25x their original size in mice and approximately 400-600x their original size in humans. The ovary is a very dynamic organ and is challenging to engineer.
Alexandra Rutz:: One of the major challenges in 3D printing body parts is knowing how to print a structure with the right spatial, biochemical, and mechanical cues that induce specific cellular behavior (i.e. proliferation, differentiation, migration, desired matrix synthesis and remodeling, vessel formation, etc). The field has been challenged by the limited number of materials that are both cell compatible and 3D printable, and that possess the ability to be tuned with regard to their biological and mechanical properties without compromising printability. The Shah TEAM lab has developed new tunable 3D ink platforms that has expanded the 3D printable biomaterial toolbox. With this technology, we now have the opportunity to investigate different parameters of the printed structures that can significantly affect the functional outcome. Another major challenge for 3D printing tissues and organs, including the ovary, is scale-up. Large, thick tissues have high metabolic demands and require perfused vasculature. If we don’t have pre-embedded vasculature for these large, multi-centimeter tissues, the tissue will necrose and the implant will fail.
You’ve so far successfully done this in mice, and next you’re moving onto testing in pigs. How soon do you anticipate this will be an option for humans? Are there any biological nuances in humans that would make this more difficult, compared to animals?
Monica M. Laronda: We are now expanding this research into pigs as part of the Fertility and Hormone Preservation and Restoration Program at the Stanley Manne Research Institute at Lurie Children’s Hospital. Piglets have commonly been used as a model for pediatric surgery and transplants due to the similarities in anatomy, physiology and immunology between pigs and humans. The pig female reproductive tract is more similar to human than that of a mouse; however, there are still major differences, including the fact that pigs have litters and humans generally have 1 or 2 children at a time. Pigs are still a great model for analyzing hormone restoration, initiation of puberty and establishment of a cyclical hormone cycle as well as the ability to mature fertilizable eggs with our ovarian bioprosthesis.
Being able to print and embed ovaries opens a myriad of possibilities for women’s health, from restoring fertility in women cancer survivors to providing a sex-reassignment solution for trans women. Who do you believe this innovation will have the most impact on, and what opportunity you most excited about?
Monica M. Laronda: I think that a successful ovarian bioprosthesis would benefit a wide array of patients, including those with disorders of sex development and others in the sex and gender minority groups. I think it would specifically benefit the significant number of pediatric cancer patients, as approximately 85% of them will survive their cancer. There is an increased risk for these patients to display hormone insufficiencies and difficulties getting pregnant. In some cases the hormone insufficiencies result in the inability to undergo puberty or cause menopause at a young age. Because sex hormones play a critical role in brain, muscle, bone, cardiovascular health, especially during puberty, I am most excited about learning more about these effects on our patients and the possibility of restoring these ovarian hormones for whole-body health.
Are there other topics in women’s health that you believe could be impacted by new tech, such as 3D printing?
Monica M. Laronda: There are many women who suffer from uterine, fallopian tube and cervical diseases that could benefit from a restorative implant. But women are also more affected by kidney disease, for example, and could benefit from a kidney transplant.
Ramille N. Shah: The Shah TEAM lab is currently developing 3D printable structures for a variety of other organ and tissue targets such as liver, kidney, cardiac, and breast tissue, which can be used for disease modeling and toxicity screening (when made on smaller scales), and hopefully one day as future artificial functional implants (either partial or whole organ structures).