Local leptin production in osteoarthritis subchondral osteoblasts may be responsible for their abnormal phenotypic expressionReportar como inadecuado




Local leptin production in osteoarthritis subchondral osteoblasts may be responsible for their abnormal phenotypic expression - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Arthritis Research and Therapy

, 12:R20

First Online: 08 February 2010Received: 09 September 2009Revised: 08 January 2010Accepted: 08 February 2010

Abstract

IntroductionLeptin is a peptide hormone with a role in bone metabolism and rheumatic diseases. The subchondral bone tissue plays a prominent role in the pathophysiology of osteoarthritis OA, related to abnormal osteoblast Ob differentiation. Although leptin promotes the differentiation of Ob under normal conditions, a role for leptin in OA Ob has not been demonstrated. Here we determined if endogenous leptin produced by OA Ob could be responsible for the expression of the abnormal phenotypic biomarkers observed in OA Ob.

MethodsWe prepared primary normal and OA Ob from subchondral bone of tibial plateaus removed for knee surgery of OA patients or at autopsy. We determined the production of leptin and of the long, biologically active, leptin receptors OB-Rb using reverse transcriptase-polymerase chain reaction, ELISA and Western blot analysis. We determined the effect of leptin on cell proliferation by BrdU incorporation and 3-4,5-Dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide MTT assays, and we determined by Western blot analysis phospho 42-44 MAPK p42-44 Erk1-2 and phospho p38 levels. We then determined the effect of the addition of exogenous leptin, leptin receptor antagonists, inhibitors of leptin signaling or siRNA techniques on the phenotypic features of OA Ob. Phenotypic features of Ob were determined by measuring alkaline phosphatase activity ALP, osteocalcin release OC, collagen type 1 production CICP and of Transforming Growth Factor-β1 TGF-β1.

ResultsLeptin expression was increased approximately five-fold and protein levels approximately two-fold in OA Ob compared to normal. Leptin stimulated its own expression and the expression of OB-Rb in OA Ob. Leptin dose-dependently stimulated cell proliferation of OA Ob and also increased phosphorylated p42-44 Erk1-2 and p38 levels. Inactivating antibodies against leptin reduced ALP, OC, CICP and TGF-β1 levels in OA Ob. Tyrphostin AG490 and piceatannol Pce, inhibitors of leptin signaling, reproduced this effect. Inhibition of endogenous leptin levels using siRNA for leptin or inhibiting leptin signaling using siRNA for OB-Rb expression both reduced ALP and OC about 60%. Exogenous leptin addition stimulated ALP, yet this failed to further increase OC or CICP.

ConclusionsThese results suggest that abnormal production of leptin by OA Ob could be responsible, in part, for the elevated levels of ALP, OC, collagen type 1 and TGF-β1 observed in these cells compared to normal. Leptin also stimulated cell proliferation, and Erk 1-2 and p38 signaling. Taken together, these data suggest leptin could contribute to abnormal osteoblast function in OA.

AbbreviationsALPalkaline phosphatise

BMDbone mineral density

BMIbody mass index

BSAbovive serum albumin

CICPcollagen type 1 carboxyl terminal peptide

CNScentral nervous system

IGF-1insulin-like growth factor 1

MTT3-4,5-Dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide

OAosteoarthritis

Obosteoblasts

OB-Rbleptin receptor long form

OCosteocalcin

OPGosteoprotegerin

PCRpolymerase chain reaction

PNPPpara-nitrophenyl phosphate

PVDFPolyvinylidene Fluoride

TGF-β1transforming growth factor beta-1.

Electronic supplementary materialThe online version of this article doi:10.1186-ar2925 contains supplementary material, which is available to authorized users.

Marie-Solange Mutabaruka, Mohamed Aoulad Aissa contributed equally to this work.

Download fulltext PDF



Autor: Marie-Solange Mutabaruka - Mohamed Aoulad Aissa - Aline Delalandre - Martin Lavigne - Daniel Lajeunesse

Fuente: https://link.springer.com/



DESCARGAR PDF




Documentos relacionados