Abstract

Recent evidence suggests that bone metabolism may be influenced by the innervation of skeletal tissues. Innervation of skeletal tissues might directly influence bone volume by the release or secretion of osteogenic growth factors in the form of neuropeptides. These neuropeptides could act locally on osteoblasts to increase bone formation and/or mineralization. Since calcitonin gene-related peptide (CGRP) and Substance P (SP) are the most abundant neuropeptides present in sensory nerves in bone, the current studies were intended to test the hypothesis that these two neuropeptides may have direct effects on osteoblast growth, differentiation, and mineralization. Replicate cultures of murine calvarial osteoblasts were grown with and without CGRP and/or SP, across a range of physiologic to pharmacologic doses. Cell growth was assessed by changes in cell layer protein. Differentiation was assessed by changes in cellular alkaline phosphatase levels, and mineralization was measured by alizarin red staining. Although we did not observe effects of CGRP or SP on cell growth, we did observe effects on differentiation—a 48 hour exposure to CGRP induced a dose-dependent increase in alkaline phosphatase levels in the calvarial osteoblasts (p<0.001). Alkaline phosphatase activity was also increased in a dose-dependent manner following treatment with SP (r =0.979 , p<0.001). The murine cell line MC3T3-E1 was used to determine the effect of CGRP and SP on osteoblastic mineralization. After 7–21 days of continuous treatment with CGRP and SP in mineralization media, cells were fixed and mineralization was assessed by staining with alizarin red. The results of those studies showed that both CGRP and SP increased the rate and the extent of mineralization (p<0.001) and the effects of both neuropeptides together were greater than either alone (p<0.001). The effects of CGRP, SP, and the combination of peptides on osteoblast gene expression, as assessed by RT-PCR, have further revealed that exposure to CGRP and/or SP increased the mRNA levels for the Cox 2 protein, suggesting a possible role for prostaglandins as determinants of the osteogenic action(s) of CGRP and SP. Together, these findings are consistent with the hypothesis that neuropeptides released from neurons in bone may be involved in the local regulation of bone volume, by effects on osteoblast growth, differentiation, and mineralization.

LLU Discipline

Anatomy

Department

Basic Sciences

School

School of Medicine

First Advisor

Linkhart, Thomas A.

Second Advisor

Farley, John

Third Advisor

Nava, Pedro

Fourth Advisor

Wright, Kenneth R.

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

2011

Date (Title Page)

9-2011

Language

English

Library of Congress/MESH Subject Headings

Osteoblasts; Cell Differentiation; Nerve Growth Factors; Neuropeptides; Receptors - Neurokinin-1; Interleukins; Growth Inhibitors; Bone Morphogenetic Proteins; Calcification - Physiologic;

Subject - Local

Calcitonin Gene-related Peptide; Substance P; Osteoblast Growth and Differentiation; Cellular Alkaline Phosphatase Levels; Osteoblast Mineralization

Type

Dissertation

Page Count

113

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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