Scientists in China have developed a new method for regrowing bone after Steroid-Induced Osteonecrosis of the Femoral Head (SONFH), in work that uses a 3D-printed scaffold inspired by coral to overcome inflammation that typically inhibits effective bone repair.
In a recent paper published in Bone Research, the medical team revealed their new solution to one of the leading causes of non-traumatic osteonecrosis, a debilitating condition.
The new work marks a major breakthrough in healing a bone condition long responsible for severe pain and mobility issues.
SONFH in Bone Explained
Glucocorticoid therapy is a common course of treatment in patients who are experiencing stronger-than-desired immune responses. These can take the form of asthma, lupus, arthritis, or other inflammatory conditions, and by suppressing the immune system, the symptoms of these conditions can be alleviated. Additionally, transplant patients require immunosuppression drugs to ensure that their body does not reject the new organ.
However, these treatments can often come at a cost: between 9% and 40% of patients on prolonged or high-dose glucocorticoid therapy experience progressive wearing of the femoral head, known as SONFH.
Currently, core decompression is the standard treatment at the early stages, but this is hampered by inflammation, which impedes bone healing. At later stages, the joint may eventually collapse, creating a major challenge for physicians.
“Current treatments mainly provide structural support but do not address the pathological immune microenvironment that prevents bone regeneration,” explained co-author Dr. Yan Xiong. “Our coral-inspired immunoreprogramming strategy provides a new approach for targeting this microenvironment and promoting bone repair.”
Immune Freezing
The immune cells responsible for organizing tissue repair, macrophages, are at the core of the problem. These cells can take two important states: In the M1 state, they encourage inflammation to defend the body against invaders and destroy defective cells. Their other primary state is M2, which guides tissue repair in the body. The issue is that these macrophages become locked in an immune freeze in which, instead of coordinating essential repairs, they create inflammation.
When a patient’s body enters this “immune freeze,” it degrades blood vessel repair and bone regeneration. Existing surgical interventions fail to alleviate the condition and resume bone repair. To overcome this, the medical research team needed a way to stop the inflammation from choking off repairs—and so they turned to the porous texture of coral as a novel means of providing relief from that dangerous pressure.
3D Printed Bone
For their bone-regrowth scaffold, the team combined two essential elements: multi-walled carbon nanotubes (MWCNTs) and Nano-hydroxyapatite (nHA). NHA is already in use as a synthetic substitute for bone or tooth enamel, composed of calcium phosphate. MWCNTs are commonly used to interface with macrophages to intentionally trigger inflammation, suppress the immune system, or deliver antigens to improve vaccine efficacy.
The team’s unique design has primary functions. Its nHA acts as the scaffold, forming a biomimetic mineral matrix for the bone-forming cells to attach to, grow, and differentiate. To facilitate this growth, the MWCNT component shifts macrophages to an M2 state.
To test their solution, the team implanted the scaffold in the femoral joints of seven rabbits and measured bone growth against a control group of seven unaltered rabbits. After four weeks, the researchers found that the scaffold successfully shifted the macrophages from M1 to M2 states while promoting the growth of blood vessels and bone cells.
“The coral-inspired immunoreprogramming technique proposed in this study provides a new strategy for targeting the regulation of the pathological microenvironment in SONFH,” Dr. Meng Tian concluded. “Although further studies are needed before clinical application, our findings provide a foundation for developing regenerative therapies that improve bone repair by restoring a pro-regenerative immune environment.”
The paper, “Coral-inspired Immunoreprogramming Scaffold Reverses the “Immune-freeze” Microenvironment to Promote Bone Regeneration in Steroid-induced Osteonecrosis of the Femoral Head,” appeared in Bone Research on June 30, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org.