Rashmi Malpe

Abstract

Among the many bone growth factors, this study focused on the IGF and BMP systems because of some of their unique functions, namely, IGFs function both as local and systemic agents and BMPs are capable of inducing de novo bone formation at non-skeletal sites. There is varied osteoblast differentiation in and load bearing on the skeletal system which led to the first study whose hypothesis was that these skeletal site dependent differences are associated with site-specific differences in IGF system components' production. Results from their quantitation in the CM of normal HBC derived from calvaria, mandibles, ribs, vertebrae, and marrow stroma showed that mandibular cells produced the most IGF-II and IGFBP-4, vertebral cells IGFBP-3, and calvarial cells IGFBP-5. IGF-I levels were almost undetectable and on a molar basis, IGFBPs were produced more than IGFs. Based on evidence that IGF-II is the most abundant mitogen produced by HBCs and exerts significant biological effects on osteoblasts and the evidence that inhibitory IGFBP-4 is one of the two most abundant IGFBPs produced by HBCs and is regulated by several osteoregulatory agents, the hypothesis for the second study that endogenously produced IGF-II is an important determinant of osteoblast cell proliferation and osteoblast-produced IGFBP-4 acts by modulating locally produced IGF activity was proposed. Using antisense technology, blocking IGF-II production in human osteosarcoma cells resulted in decreased cell proliferation at 2.5µM concentration while IGFBP-4 production blockage resulted in increased cell proliferation. One of the agents that modulates the production of IGF system components is BMP-7/0P-1. To evaluate if OP-1 effects are mediated via OP-1- specific receptors in HBCs, binding studies were carried out with [125I]-OP-1. OP-1 specifically bound HBCs in a time- and temperature-dependent manner, unlabeled OP-1, BMP-2 and TGF-ß displaced the binding (the former two more than the latter), TE85 cells have at least two binding sites, 30,000 (Kd, 2.5 x 10-10M) and 60,000 (Kd, 1 x 10-9M), respectively, and affinity crosslinking revealed three binding sites (Mr, 34, 65 and >205kDa), thus indicating the presence of BMP-specific receptors for OP-1 effects' mediation in HBCs. The potential role of OP-1 receptors in mediating OP-1 effects remains to be elucidated.

LLU Discipline

Biochemistry

Department

Biochemistry

School

Graduate School

First Advisor

Subburaman Mohan

Second Advisor

John R. Farley

Third Advisor

Raymond G. Hall

Fourth Advisor

E. Clifford Herrmann

Fifth Advisor

Donna D. Strong

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

1999

Date (Title Page)

6-1999

Language

English

Library of Congress/MESH Subject Headings

Growth Substances; Growth Inhibitors; Insulin-Like Growth Factor I; Insulin-Like Growth Factor II; Somatomedins; Insulin-Like Growth-Factor Binding Proteins; Bone Morphogenetic Proteins; Osteoblasts; Bone Development

Type

Dissertation

Page Count

xii; 197

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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