Tachykinin expression in cartilage and function in human articular chondrocyte mechanotransduction.
OBJECTIVE
To assess whether substance P and the corresponding neurokinin 1 (NK1) receptor are expressed in human articular cartilage, and whether these molecules have a role in chondrocyte mechanotransduction.


METHODS
Transgenic studies, immunohistochemistry, Western blotting, and reverse transcriptase-polymerase chain reaction were used to assess the expression of the preprotachykinin (PPT) gene, substance P, and NK1 in developing mice, in adult human articular cartilage, and in human chondrocytes in culture. Chondrocytes obtained from PPT knockout mice and human articular chondrocytes were mechanically stimulated in the presence or absence of inhibitors of substance P signaling, and cell membrane potentials or relative levels of aggrecan messenger RNA (mRNA) were measured.


RESULTS
Replacing a region of the PPT gene transcriptional site that contains a dominant repressor of the proximal promoter activity with the constitutive minimal promoter of the human beta-globin promoter allowed expression of a marker gene in areas of chondrogenesis during mouse development and in adult chondrocytes grown in culture. Adult human articular chondrocytes expressed endogenous PPT mRNA, substance P, and the corresponding NK1 receptor in vivo and in vitro. Blockade of substance P signaling by a chemical antagonist to the NK1 receptor inhibited chondrocyte responses to mechanical stimulation.


CONCLUSIONS
Substance P is expressed in human articular cartilage and is involved in chondrocyte mechanotransduction via the NK1 receptor in an autocrine and paracrine manner. This suggests that substance P and the NK1 receptor have roles in the maintenance of articular cartilage structure and function that were previously unrecognized.
Millward-Sadler
S J
SJ
University of Edinburgh, Edinburgh, UK.
Mackenzie
A
A
Wright
M O
MO
Lee
H-S
HS
Elliot
K
K
Gerrard
L
L
Fiskerstrand
C E
CE
Salter
D M
DM
Quinn
J P
JP
D000367:Age Factors; D053674:Aggrecans; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002358:Cartilage, Articular / Q000166:cytology / Q000502:physiology*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000502:physiology*; D004558:Electric Stimulation; D004594:Electrophysiology; D016326:Extracellular Matrix Proteins; D005260:Female; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D015847:Interleukin-4 / Q000494:pharmacology; D037181:Lectins, C-Type; D040542:Mechanotransduction, Cellular / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D018345:Mice, Knockout; D011247:Pregnancy; D011401:Promoter Regions, Genetic / Q000235:genetics; D011498:Protein Precursors / Q000235:genetics; D011509:Proteoglycans / Q000235:genetics; D018040:Receptors, Neurokinin-1 / Q000235:genetics; D013373:Substance P / Q000235:genetics*; D015320:Tachykinins / Q000235:genetics; D015854:Up-Regulation / Q000502:physiology
C508320:Acan protein, mouse; D053674:Aggrecans; D000970:Antineoplastic Agents; D016326:Extracellular Matrix Proteins; D037181:Lectins, C-Type; D011498:Protein Precursors; D011509:Proteoglycans; D018040:Receptors, Neurokinin-1; D015320:Tachykinins; C044206:preprotachykinin; D015847:Interleukin-4; D013373:Substance P