Bernard Halloran

Research Interests

Bone aging and mechanical or physical loading of bone. 

Research Summary

      My research interests are in aging and how bone senses and responds to physical loading.  The aging process is complex.  One aspect of this process involves cell aging or cell senescence.  We have shown that the cells in bone which are derived from two stem cell populations age and undergo changes that promote bone loss.  This culminates in age-related osteoporosis and an increased propensity to fracture.  We are now working with these populations, as well as embryonic stem cells, to see if we can alter their function and restore bone lost during aging. 

    We also study how bone senses and responds to physical or mechanical loading as occurs during normal daily activity.  If we decrease weight bearing on our skeleton such as occurs during spaceflight or disuse we lose bone.  In contrast, if we load our skeleton such as occurs during strenuous exercise, we increase our bone mass.  Using animal models, we have shown that these changes involve osteocytes in the bone and loss of cellular responsiveness to growth factors such as insulin-like growth factor I.  We are now studying the molecular  mechanisms responsible for these changes.

Selected Publications

Wronski, T.J., Li, M., Shen, Y., Miller, S.C., Bowman, B.M., Kostenuik, P., Halloran, B.P., Lack of an effect of space flight on bone mass and bone formation in group housed rats, J. Appl. Physiol., 85(1):279-285, 1998.

Dehority, W., Halloran, B.P., Bikle, D.D., Curren, T., Kostenuik, P.J., Wronski, T., Shen, Y., Rabkin, B., Bouraoui, A., Morey-Holton, E.R., Bone and hormonal changes induced by skeletal unloading in the mature male rat, Am. J. Physiol., 276:E62-69, 1999.

Kostenuik, P.J., Harris, J., Halloran, B.P., Turner, R., Morey-Holton, E., Bikle, D.D., Skeletal unloading causes resistance of osteoprogenitor cells to parathyroid hormone and insulin-like growth factor-I. J. Bone Min. Res., 14:21-31, 1999.

Rabkin, B.A., Szivek, J.A., Schonfeld, J.E., Halloran, B.P., Long-term measurement of bone strain in vivo: the rat tibia. J. Biomed. Materials Res. 58:277-281, 2001.

Nauman, E.A., Satcher, R.L., Keaveny, T.M., Halloran, B.P., Bikle, D.D., Osteoblasts respond to pulsatile fluid flow with short-term increases in PGE2 but no change in mineralization. J. Appl. Physiol. 90:1849-1854, 2001.

Halloran, B.P., Ferguson, V.L., Simske, S.J., Burghardt, A., Venton, L.L., Majumdar, S., Changes in bone structure and mass with advancing age in the male C57BL/6 mouse. J. Bone Min. Res. 17(6):1044-1050, 2002.

 Cao, J, Kurimoto, P, Boudignon, B and Halloran, B, Aging impairs IGF-I receptor activation and induces resistance to IGF-I.  J Bone Min Res, 21:1271, 2007.

Boudignon, B, Orwoll, B, Kurimoto, P, Bikle, D and Halloran, B, IGF-I stimulates recovery of bone lost after a period of skeletal unloading. J Appl Physiol, 103:125, 2007.

Wang, Y, Boudignon, B, Burghardt, A, Majumdar, S, Halloran, B, Clemens, T, Bikle, D, IGF-I receptor is required for the anabolic actions of PTH on bone. J Bone Min Res, 22:1329, 2007