In vivo genome-wide expression study on human circulating B cells suggests a novel ESR1 and MAPK3 network for postmenopausal osteoporosis.
BACKGROUND
Osteoporosis is characterized by low BMD. Studies have shown that B cells may participate in osteoclastogenesis through expression of osteoclast-related factors, such as RANKL, transforming growth factor beta (TGFB), and osteoprotegerin (OPG). However, the in vivo significance of B cells in human bone metabolism and osteoporosis is still largely unknown, particularly at the systematic gene expression level.


METHODS
In this study, Affymetrix HG-U133A GeneChip arrays were used to identify genes differentially expressed in B cells between 10 low and 10 high BMD postmenopausal women. Significance of differential expression was tested by t-test and adjusted for multiple testing with the Benjamini and Hochberg (BH) procedure (adjusted p </= 0.05).


RESULTS
Twenty-nine genes were downregulated in the low versus high BMD group. These genes were further analyzed using Ingenuity Pathways Analysis (Ingenuity Systems). A network involving estrogen receptor 1 (ESR1) and mitogen activated protein kinase 3 (MAPK3) was identified. Real-time RT-PCR confirmed differential expression of eight genes, including ESR1, MAPK3, methyl CpG binding protein 2 (MECP2), proline-serine-threonine phosphatase interacting protein 1 (PSTPIP1), Scr-like-adaptor (SLA), serine/threonine kinase 11 (STK11), WNK lysine-deficient protein kinase 1 (WNK1), and zinc finger protein 446 (ZNF446).


CONCLUSIONS
This is the first in vivo genome-wide expression study on human B cells in relation to osteoporosis. Our results highlight the significance of B cells in the etiology of osteoporosis and suggest a novel mechanism for postmenopausal osteoporosis (i.e., that downregulation of ESR1 and MAPK3 in B cells regulates secretion of factors, leading to increased osteoclastogenesis or decreased osteoblastogenesis).
Xiao
Peng
P
Osteoporosis Research Center and Department of Biomedical Sciences, Creighton University, Omaha, Nebraska, USA.
Chen
Yuan
Y
Jiang
Hui
H
Liu
Yao-Zhong
YZ
Pan
Feng
F
Yang
Tie-Lin
TL
Tang
Zi-Hui
ZH
Larsen
Jennifer A
JA
Lappe
Joan M
JM
Recker
Robert R
RR
Deng
Hong-Wen
HW
D001402:B-Lymphocytes / Q000378:metabolism*; D015519:Bone Density; D047628:Estrogen Receptor alpha / Q000235:genetics*; D005260:Female; D015894:Genome, Human; D006801:Humans; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics*; D010024:Osteoporosis / Q000235:genetics*; D017698:Postmenopause; D020133:Reverse Transcriptase Polymerase Chain Reaction
C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D048052:Mitogen-Activated Protein Kinase 3