Columbia University uses technological innovation to study bone structure

(Press-News.org) A team of researchers at Columbia Engineering and Columbia University Medical Center announced today the results of the first study comparing bone structure in Chinese-American women to Caucasian women. The report, just presented at the Orthopaedic Research Society's annual meeting at Long Beach, CA, found that pre-menopausal Chinese-American women have far greater bone strength than their Caucasian counterparts, as determined by a breakthrough technological advance.

The Columbia team was led by X. Edward Guo, Professor of Biomedical Engineering at Columbia University's School of Engineering and Applied Science, and, from Columbia University Medical Center, John P. Bilezikian, Professor of Medicine and Pharmacology, Marcella Walker, Assistant Professor of Medicine, and X. Sherry Liu, Associate Research Scientist.

The team used a groundbreaking analytical technique developed at Columbia Engineering— Individual Trabeculae Segmentation (ITS) — to analyze the microstructure and strength of the trabecular, or spongy bone, one of the two types of tissue that form bone (the other is cortical, or compact bone). Trabecular bone is the most important site of osteoporosis-related fractures. Critical to the research was the use of ITS, an advanced 3-D imaging analysis technique that was conceived and developed in Dr. Guo's Bone Bioengineering Laboratory, and has a unique ability – using high-resolution computed tomography images – to quantify the plate and rod microstructure crucial to bone strength and osteoporotic fracture of bone.

The Columbia group is the first to apply ITS to clinical studies; this is the first time they have applied ITS to ethnic studies of bone health. A total of 95 women were included in the study—49 Caucasian and 46 Chinese-American. There were no significant age differences between the two groups (36±7 vs. 35±4).

"We found in this research that Chinese-American women do not have the same risk of fracture as Caucasian women due to the plate-like structure of their bone, which offers mechanical advantages over the rod-like structure found in the bones of Caucasian women," Dr. Guo explained. "If you look at a building made of walls, you can see that it is much stronger than a building made only of columns. Columbia Engineering's ITS is the only established technique that can distinguish plate vs. rod and it clearly revealed in this study the striking magnitude of the differences between the bone structure of the Chinese-American and Caucasian women."

Drs. Bilezikian and Marcella Walker led the clinical aspect of the study and quantified the microstructures in the distal radius and the tibia. "These are the two areas that the instrument can measure," Dr. Bilezikian said. "But we believe the data that come from these sites can be applied to other sites such as the hip."

Dr. Liu, who earned her PhD on ITS development in Dr. Guo's Bone Bioengineering Laboratory, noted that the most important factor when determining bone strength is the ratio of plate to rod in trabecular bone. "We found the plate to rod ratio of trabecular bone in Chinese-American women was twice that of Caucasian women (0.62 vs. 0.30). We also found the number of trabecular plates was significantly higher in Chinese-American women when compared to Caucasian women, indicating that Chinese-American women have much stronger trabecular bone than Caucasian women." Liu is currently an associate research scientist with Dr. Bilezikian in Columbia University Medical Center's Endocrinology Division.

Dr. Liu continued, "The size of the individual trabecular plates was significantly larger in the Chinese-American women versus the Caucasian women. Trabecular plates were 9% and 4% greater in thickness and 11% greater in surface area at the distal radius and tibia." The researchers also found that Chinese-American women had better cortical bone quality than Caucasian women. The study has not yet explored potential explanations for these differences.

"The advanced ITS morphological analysis developed at Columbia Engineering showcases a paradigm-shift technology in measuring bone micro-architecture," said Dr. Guo. "ITS is a must-have technology for both basic science and clinical studies of osteoporosis and we are very excited about continuing our research."

Drs. Guo and Bilezikian traveled to China this past November and are planning to return in early 2011 to work on creating Columbia-associated research centers there with the goal of extending their research to Chinese women living in both urban and rural areas of China. "The major differences between Chinese-American women and Caucasian women elucidated in this paper may eventually help us understand the mechanisms by which hormones and other factors control skeletal microstructure," Dr. Bilezikian said. "The essence of what we found here helps to account for the markedly reduced risk of a hip fracture in Chinese-American woman compared to Caucasian women."

### This study was supported by the National Institutes of Health, the National Osteoporosis Foundation, the Thomas L. Kempner and Katheryn C. Patterson Foundation, the Mary and David Hoar Fellowship Program of the New York Academy of Medicine, and Dr. Clyde Wu.

Columbia University's Fu Foundation School of Engineering and Applied Science, founded in 1864, offers programs in nine departments to both undergraduate and graduate students. With facilities specifically designed and equipped to meet the laboratory and research needs of faculty and students, Columbia Engineering is home to NSF-NIH funded centers in genomic science, molecular nanostructures, materials science, and energy, as well as one of the world's leading programs in financial engineering. These interdisciplinary centers are leading the way in their respective fields while individual groups of engineers and scientists collaborate to solve some of society's more vexing challenges. http://www.engineering.columbia.edu/

Columbia University Medical Center provides international leadership in basic, pre-clinical and clinical research, in medical and health sciences education, and in patient care. The medical center trains future leaders and includes the dedicated work of many physicians, scientists, public health professionals, dentists, and nurses at the College of Physicians and Surgeons, the Mailman School of Public Health, the College of Dental Medicine, the School of Nursing, the biomedical departments of the Graduate School of Arts and Sciences, and allied research centers and institutions. Established in 1767, Columbia's College of Physicians and Surgeons was the first institution in the country to grant the M.D. degree and is among the most selective medical schools in the country. Columbia University Medical Center is home to the largest medical research enterprise in New York City and state and one of the largest in the United States. For more information, please visit www.cumc.columbia.edu.