Effects of acute 5-fluorouracil chemotherapy and insulin-like growth factor-I pretreatment on growth plate cartilage and metaphyseal bone in rats C.J. Xian, a, * G.S. Howarth, b J.C. Cool, a and B.K. Foster a a Department of Orthopaedic Surgery, University of Adelaide Department of Paediatrics, North Adelaide, SA, Australia b Child Health Research Institute, Women’s and Children’s Hospital, North Adelaide, SA, Australia Received 14 December 2003; revised 22 April 2004; accepted 30 April 2004 Abstract With the intensified use of chemotherapy and improved survival rates for childhood malignancies, it has become increasingly apparent that some children or adult survivors show poor bone growth and develop osteoporosis. As a step to investigate underlying mechanisms, this project examined short-term effects in rats of chemotherapy agent 5-fluorouracil (5-FU) on cell proliferation, apoptosis, and bone formation at tibial growth plate cartilage and its adjacent bone-forming region metaphysis. In addition, since insulin-like growth factor (IGF-I) is important for bone growth, we examined whether IGF-I pretreatment would potentially protect growth plate cartilage and bone cells from chemotherapy damage. Two days after a single high dose of 5-FU injection, proliferation of growth plate chondrocytes and metaphyseal osteoblasts/preosteoblasts was dramatically suppressed, and apoptosis was induced among osteoblasts and preosteoblasts. As a result, there was a reduction in the chondrocyte number and zonal height at the proliferative zone and a decline in the number of osteoblasts and preosteoblasts on the metaphyseal trabecular bone surface. At day 2, no obvious deleterious effects were observed on the height of the growth plate hypertrophic zone and the bone volume fraction of the metaphyseal primary spongiosa trabeculae. At day 10, while cell proliferation and growth plate structure returned to normal, there were slight decreases in trabecular bone volume, body length increase, and tibial length. While pretreatment with 1-week IGF-I systemic infusion did not attenuate the suppressive effect of 5-FU on proliferation in both growth plate and metaphysis, it significantly diminished apoptotic induction in metaphysis. These results indicate that growth plate cartilage chondrocytes and metaphyseal bone cells are sensitive to chemotherapy drug 5-FU and that IGF-I pretreatment has some anti-apoptotic protective effects on metaphyseal bone osteoblasts and preosteoblasts. Crown Copyright D 2004 Published by Elsevier Inc. All rights reserved. Keywords: Chemotherapy; IGF-I; Bone growth; Growth plate; Side effects Introduction Longitudinal bone growth is achieved through endochon- dral ossification, a process occurring at the growth plate whereby a cartilaginous template is made and then replaced by bone. It is initiated when progenitor cells at the growth plate resting zone are activated to become chondrocytes and are stimulated to proliferate at the proliferative zone and then proceed through maturation, hypertrophy, and apopto- sis stages at the hypertrophic zone of the growth plate [19]. Concomitantly, chondrocytes produce a matrix that under- goes mineralisation at the lower hypertrophic zone, which is invaded by blood vessels from the adjacent bone-forming region metaphysis. Vascularisation of the calcified cartilage brings in two cell types that replace the cartilage matrix with bone: bone/cartilage resorbing cells (osteoclasts) that re- model the mineralised cartilage, and bone-matrix synthesiz- ing cells (osteoblasts) that deposit bone matrix on the remodelled cartilage core. Osteoblasts and their precursors preosteoblasts are recruited from progenitor cells of bone marrow stroma [2], and along the osteoblastic lineage of differentiation, osteoprogenitor cells first transform to tran- sitional preosteoblasts located between the metaphyseal trabeculae and the bone marrow. 8756-3282/$ - see front matter. Crown Copyright D 2004 Published by Elsevier Inc. All rights reserved. doi:10.1016/j.bone.2004.04.027 * Corresponding author. Departmentof Orthopaedic Surgery, Women’s and Children’s Hospital, 72 King William Road, North Adelaide, SA 5006, Australia. Fax: +61-8-8161-7057. E-mail address: cory.xian@adelaide.edu.au (C.J. Xian). www.elsevier.com/locate/bone Bone 35 (2004) 739 – 749