Osteoblast response against Mycobacterium tuberculosis infection
Kaur Khushpreet * , PC Karakousis # , Verma Indu*
* Dept. of Biochemistry, Postgraduate Institute of Medical Education and Research, Chandigarh-160012
# Center for Tuberculosis Research, John Hopkins University school of Medicine, Baltimore, MD 21287
Tuberculous osteomyelitis is widely characterized by bone loss and bone destruction caused by Mycobacterium tuberculosis (M.tb). It is difficult to treat and usually requires longer anti-tubercular treatment (ATT) due to bone complexity. The pathogenesis of disease has not yet established. Thus the present study aimed to investigate whether Mtb invades osteoblast and further how it affects the osteogenesis process resulting into bone loss as seen in patients suffering from bone tuberculosis. The MC3T3 pre-osteoblast like cells were infected with M.tb H37Rv-lux. Invasion and intracellular multiplication of M.tb H37Rv-lux was measured in terms of relative luminescence units (RLU). Osteoblast proliferation and differentiation markers were studied at 3d, 7d, 14d and 21day post infection using various osteogenesis markers like osteoblast cell proliferation, ALP activity via pNPP substrate solution, collagen deposition using sirius red and calcium mineralization using alizarin red staining. It was found that mycobacteria not only invades but also actively multiplies within the osteoblasts upto 21days post infection. Further, significant inhibition of the expression of key markers of osteoblast growth and division such as alkaline phosphatase, collagen and calcium mineralization suggested the role of M.tb infection in disrupting bone homeostasis resulting into bone loss. These results suggests that osteoblast provides a suitable microenvironment for the growth and survival of M.tb. Invasion and multiplication of intracellular bacteria seems to be associated with reduced activity of osteoblast through various coordinated signals that accounts for bone loss as seen in tuberculous osteomyelitis cases. A better understanding of the underlying mechanism may improve the ongoing ATT treatment or lead to the development of therapeutic agents for treatment of disease.