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Mouse rib cage stained to show cartilage (blue) and bone (red). In adult mice, surgically removed sections of either portion can fully regenerate. (Credit: Francesca Mariani)

bones

Humans and mice can regenerate missing rib

Mammals can’t regenerate lost limbs like salamanders can, but they can repair large sections of their ribs.

Using CT imaging, researchers monitored the healing of a human rib that had been partially removed by a surgeon. The eight centimeters of missing bone and one centimeter of missing cartilage did partially repair after six months.

To better understand this repair process, they surgically removed sections of rib cartilage—ranging from three to five millimeters—from mice.

When they removed both rib cartilage and its surrounding sheath of tissue—called the “perichondrium,” the missing sections failed to repair even after nine months. However, when they removed rib cartilage but left its perichondrium, the missing sections entirely repaired within one to two months.

They also found that a perichondrium retains the ability to produce cartilage even when disconnected from the rib and displaced into nearby muscle tissue—further suggesting that the perichondrium contains progenitor or stem cells.

Rib cell therapy?

“We believe that the development of this model in the mouse is important for making progress in the field of skeletal repair, where an acute clinical need is present for ameliorating skeletal injury, chronic osteoarthritis, and the severe problems associated with reconstructive surgery,” says team leader Francesca Mariani, assistant professor of cell and neurobiology and principal investigator in the Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at University of Southern California.

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“At the early stages in our understanding, the mouse provides us with an exceptional ability to make progress, and we are excited about the potential for using cells derived from the rib perichondrium or using rib perichondrium-like cells for regenerative therapy.”

The lab received support for this study and future work from the NIH, the Merck Investigator Studies Program, and the USC Regenerative Medicine Initiative Award.

As Mariani explains, “These grants will allow us to address several key questions: Which cells are involved in mediating the repair? How big of a piece of rib can we take out and still see repair? And can we use cells from the rib to get repair in another part of the skeleton? By answering these questions, we are accelerating the discovery of new regenerative therapies for the patients who need them the most.”

The results of the study appear in the Journal of Bone and Mineral Research.

Funding came from an Oral and Maxillofacial Surgery Foundation Research Award; the Baxter Medical Scholar Research Fellowship; USC undergraduate fellowships; the Provost, Dean Joan M. Schaeffer, and Rose Hills fellowships; a California Institute of Regenerative Medicine (CIRM) training fellowship; CIRM BRIDGES fellowships through California State University, Fullerton, and Pasadena City College; and the James H. Zumberge Research and Innovation Fund.

Additional coauthors contributed from USC and Children’s Hospital Los Angeles.

Source: USC

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