Courtesy of Cornell University

March 29, 2023

Weill Cornell Researchers Develop Effective Breast Reconstruction Process Using 3D Printing

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Dr. Jason Spector, plastic and reconstructive surgery, and his lab at Weill Cornell Medicine published a study on March 8 that described a breast reconstruction technique utilizing a 3D-printed scaffold. The newly developed process aims to achieve softer, more natural and higher quality reconstructed nipples for breast cancer patients after mastectomies. 

Lead author Xue Dong, a postdoctoral student in surgery working in Spector’s lab —  the Laboratory of Bioregenerative Medicine and Surgery — explained that during breast reconstruction, surgeons typically perform flap surgery, in which they use flaps of skin and suture them together to shape a nipple. Alternatively, surgeons may perform nipple-sparing mastectomy instead of breast reconstruction, in which the nipples are preserved during removal of the breast.

After the surgery, the patient’s body carries out its own form of repair, undergoing wound healing and skin contraction in order to form scar tissue. The newly formed scar tissue in the nipple area pulls adjacent tissue together, shrinking the nipple.  

Dong also added that fibroblasts — cells involved in wound healing and formation of connective tissue — make the tissue around the nipple even smaller. Ultimately, these processes result in the loss of projection in the reconstructed nipple. 

To counteract this, surgeons provide interior support to the nipple. One option is to place stiff material inside, such as cartilage taken from other parts of the patient’s body or synthetic substances, during breast reconstruction. Surgeons can also inject soft tissue filler three to six months after the surgery to expand reconstructed nipples. 

However, Dong explained these solutions to maintaining nipple projection and shape have several issues. 

“A lot of the stiff materials used for interior support are actually not biodegradable,” Dong said. “Which means there might be wound healing issues like extrusion because of the stiffness of the materials. And the nipples are going to stay stiff over time, making the patient feel uncomfortable.” 

Fillers do not provide much more benefit, as they often break down and disappear in a short amount of time. 

These surgery procedures are also not effective enough, as reconstructed nipples lose more than 50 percent of their projection over a one-to-two-year period. 

According to Dong, Spector’s lab studies the field of tissue engineering. Having practiced medicine for more than 15 years, Spector had seen many patients deal with nipple reconstruction problems or projection loss over time. He decided to direct his focus specifically to the breast reconstruction process, in hopes of creating a new method that addresses these concerns. 

Spector and his team performed biomechanical testing on the reconstructed nipples and determined that material and scaffold design played a significant role in the success of breast reconstruction. 

For example, the team studied control groups of patients using scaffolds that consisted only of the outer shell of the nipple and compared them to experimental groups of patients using scaffolds with a strong interior lattice. They concluded that different densities of the scaffold interior lattice caused changes in the stiffness and degradation rate of the scaffold. 

The lab 3D printed a scaffold into the shape of a nipple using a biodegradable material known as Poly-4-Hydroxybutyrate or P4HB. The research team collaborated with Tepha, Inc., a company that creates P4HB for use in surgical meshes and medical devices. 

The 3D printed scaffold was then used to reconstruct the nipple and covered with flaps of skin. During the first three to six months after the surgery, the scaffold maintains its shape and resists skin contraction that typically shrinks the nipple. 

The scaffold then begins to degrade, allowing the body to replace it with local tissue nearby through the healing process. Once the wound is fully healed and the scaffold has degraded, less skin contraction occurs, allowing for the reconstructed nipple to be softer, like a real nipple. 

The scaffold also allows for long-term nipple projection. Xue states that after six to 12 months, the reconstructed nipples retained more than 80 percent of their diameter and projection compared to control groups. They also confirmed that the P4HB of the scaffold was eventually replaced by healthy soft tissue. 

Dong said that based on their results, the lab’s newly developed breast reconstruction method will provide breast cancer patients with optimal reconstructed nipples. Additionally, The Spector lab’s new method addresses patient concerns in other areas, such as aesthetics and safety.

“Our method will be able to provide a reconstructive nipple with a good projection for the long term,” Dong said. “As for safety, you do not have to worry about residual material left in the body, as opposed to synthetic material like silicone, where there are concerns that some people might still feel uncomfortable living with.”

The lab is continuing to further develop their scaffold design in a way that allows them to control the degradation rate of the scaffold. Ideally, the scaffold should break down slowly during the first three to six months after surgery and then increase its degradation rate afterwards. 

The team has been constructing scaffold designs with different diameters, interior lattice densities and shape, experimenting with a combination of P4HB and other materials that could aid in wound healing and regulation of the inflammatory response. In addition, Dr. Spector and his team are planning clinical studies to observe how the reconstructed nipple projection is maintained over time in patients.  

“When we implant a scaffold in the human body, we want to cause a proper inflammatory response that is not too severe or too mild,” Dong explained. “Otherwise, the body won’t be able to produce the local tissues to support the shape of the nipples.”

The research team hopes to continue to improve the 3D printed P4HB scaffold to develop it into a strong candidate in the nipple reconstruction field.