Bones May Mend Faster Without Bone Marrow

Researchers at Yale University (New Haven, CT, USA) postulated that parathyroid hormone (PTH, a bone anabolic hormone) enhances the formation of new bone that forms after marrow ablation. The researchers subjected the left femur of rats to mechanical marrow ablation, and the right femur to a sham operation, and injected the animals daily with PTH or vehicle for 1, 2, or 3 weeks in a first experiment, and then with PTH, parathyroid hormone-related peptide (PTHrP), or vehicle for 3 weeks in a second experiment. Both femurs from each rat were subjected to soft X-ray, computerized tomography (CT), and histological analysis, and the concentration of serum osteocalcin was determined. The femurs were also subjected to biomechanical testing.

The results showed that after two weeks, X-rays of the rats showed that new bone had begun to form in the bone marrow cavity. PTH increased trabecular density in the left femur, but failed to induce bone formation in the medullary region of the right unoperated femoral shafts. The newly formed bone endowed left femoral shafts with improved biomechanical properties when compared to those of right femurs and left femurs from control, sham-operated, and vehicle-treated rats. In the rats treated with PTH, new bone continued to grow in the cavity into the third week and the marrow did not return. The study was published in the February 2008 issue of Tissue Engineering (part A).

"Our results reveal that the newly formed bone that follows marrow ablation is responsive to PTH, expand the role of PTH in bone, and might open new avenues of investigations to the field of regenerative medicine and tissue engineering,” concluded lead author Agnes Vignery, D.D.S., Ph.D., and colleagues of the department of orthopedics and rehabilitation. "Local bone marrow removal in conjunction with pharmacologic intervention with an anabolic agent might provide a technique for rapid preferential site-directed bone growth in areas of high bone loss.”


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