Altered Expression of Wnt Signaling Pathway Components in Osteogenesis of Mesenchymal Stem Cells in Osteoarthritis Patients.
BACKGROUND
Osteoarthritis (OA) is characterized by altered homeostasis of joint cartilage and bone, whose functional properties rely on chondrocytes and osteoblasts, belonging to mesenchymal stem cells (MSCs). WNT signaling acts as a hub integrating and crosstalking with other signaling pathways leading to the regulation of MSC functions. The aim of this study was to evaluate the existence of a differential signaling between Healthy and OA-MSCs during osteogenesis.


METHODS
MSCs of seven OA patients and six healthy controls were isolated, characterised and expanded. During in vitro osteogenesis, cells were recovered at days 1, 10 and 21. RNA and protein content was obtained. Expression of WNT pathway genes was evaluated using RT-qPCR. Functional studies were also performed to study the MSC osteogenic commitment and functional and post-traslational status of β-catenin and several receptor tyrosine kinases.


RESULTS
Several genes were downregulated in OA-MSCs during osteogenesis in vitro. These included soluble Wnts, inhibitors, receptors, co-receptors, several kinases and transcription factors. Basal levels of β-catenin were higher in OA-MSCs, but calcium deposition and expression of osteogenic genes was similar between Healthy and OA-MSCs. Interestingly an increased phosphorylation of p44/42 MAPK (ERK1/2) signaling node was present in OA-MSCs.


CONCLUSIONS
Our results point to the existence in OA-MSCs of alterations in expression of Wnt pathway components during in vitro osteogenesis that are partially compensated by post-translational mechanisms modulating the function of other pathways. We also point the relevance of other signaling pathways in OA pathophysiology suggesting their role in the maintenance of joint homeostasis through modulation of MSC osteogenic potential.
Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), UGC Reumatología, Hospital Clínico San Carlos, 4ª Planta, Ala Norte, C/ Profesor Martín Lagos s/n, 28040, Madrid, Spain.
Pilar
P
Tornero-Esteban
Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), UGC Reumatología, Hospital Clínico San Carlos, 4ª Planta, Ala Norte, C/ Profesor Martín Lagos s/n, 28040, Madrid, Spain.
Ascensión
A
Peralta-Sastre
Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), UGC Reumatología, Hospital Clínico San Carlos, 4ª Planta, Ala Norte, C/ Profesor Martín Lagos s/n, 28040, Madrid, Spain.
Eva
E
Herranz
Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), UGC Reumatología, Hospital Clínico San Carlos, 4ª Planta, Ala Norte, C/ Profesor Martín Lagos s/n, 28040, Madrid, Spain.
Luis
L
Rodríguez-Rodríguez
Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), UGC Reumatología, Hospital Clínico San Carlos, 4ª Planta, Ala Norte, C/ Profesor Martín Lagos s/n, 28040, Madrid, Spain.
Arkaitz
A
Mucientes
Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), UGC Reumatología, Hospital Clínico San Carlos, 4ª Planta, Ala Norte, C/ Profesor Martín Lagos s/n, 28040, Madrid, Spain.
Lydia
L
Abásolo
Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), UGC Traumatología, Hospital Clínico San Carlos, 6ª Planta, Ala Norte, C/ Profesor Martín Lagos s/n, 28040, Madrid, Spain.
Fernando
F
Marco
Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), UGC Reumatología, Hospital Clínico San Carlos, 4ª Planta, Ala Norte, C/ Profesor Martín Lagos s/n, 28040, Madrid, Spain.
Benjamín
B
Fernández-Gutiérrez
Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), UGC Reumatología, Hospital Clínico San Carlos, 4ª Planta, Ala Norte, C/ Profesor Martín Lagos s/n, 28040, Madrid, Spain.
José Ramón
JR
Lamas
D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000032:analysis; D001853:Bone Marrow / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D019070:Cell Lineage; D002478:Cells, Cultured; D020219:Chondrogenesis; D015536:Down-Regulation; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000378:metabolism*; D008875:Middle Aged; D010003:Osteoarthritis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D060888:Real-Time Polymerase Chain Reaction; D011956:Receptors, Cell Surface / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000378:metabolism
D015703:Antigens, CD; C495270:CTNNB1 protein, human; D011956:Receptors, Cell Surface; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin; D011494:Protein Kinases; D002118:Calcium