Toward cell therapy for vascular calcification: osteoclast-mediated demineralization of calcified elastin.
BACKGROUND
Elastin-oriented vascular calcification is a clinically significant feature, which involves formation of ectopic bone-like structures. Taking advantage of the similarities between arterial calcification and bone regulation, our hypothesis was that therapeutic approaches for limitation of vascular calcification could be developed using site-specific delivery of autologous osteoclasts. In the present paper, we tested the hypothesis that bone-marrow-derived osteoclasts have the ability to demineralize calcified elastin, without significant alterations in elastin integrity.


METHODS
Active, multinucleated osteoclasts were obtained by in vitro maturation of rat bone-marrow-derived progenitor cells in the presence of vitamin D(3) and retinoic acid. Cell phenotype was validated by staining for tartrate-resistant acid phosphatase, formation of resorption pits on hydroxyapatite-coated disks, and RT-PCR for identification of cathepsin K gene expression. Calcified aortic elastin was seeded with osteoclasts and calcium, and phosphorous levels were monitored in gels and culture media to detect demineralization of elastin. Soluble elastin peptides were also monitored in culture media for elastin degradation. For in vivo experiments, pure aortic elastin was coimplanted with allogenic osteoclasts subdermally into rats, and the degree of elastin calcification and degradation was evaluated using mineral analysis and desmosine quantitation.


RESULTS
Bone-marrow-derived osteoclasts reduced mineral content of calcified elastin in vitro by 80%. Moreover, in vivo implantation of allogenic osteoclasts in the vicinity of calcifying elastin limited elastin mineralization by almost 50%, in the absence of detectable elastin degradation.


CONCLUSIONS
Osteoclasts have the ability to demineralize calcified elastin, without significant alterations in elastin integrity.
Simpson
Chartrisa LaShan
CL
Department of Bioengineering, Clemson University, Clemson, SC, 29634, USA.
Lindley
Suzanne
S
Eisenberg
Carol
C
Basalyga
Dina M
DM
Starcher
Barry C
BC
Simionescu
Dan T
DT
Vyavahare
Narendra R
NR
D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology*; D002114:Calcinosis / Q000378:metabolism* / Q000473:pathology; D056657:Cathepsin K; D002403:Cathepsins / Q000235:genetics / Q000378:metabolism; D017690:Cell Transplantation; D002478:Cells, Cultured; D002762:Cholecalciferol / Q000494:pharmacology; D004195:Disease Models, Animal; D004338:Drug Combinations; D004549:Elastin / Q000737:chemistry / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D010010:Osteoclasts / Q000378:metabolism* / Q000637:transplantation; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014212:Tretinoin / Q000494:pharmacology
D004338:Drug Combinations; D012333:RNA, Messenger; D002762:Cholecalciferol; D014212:Tretinoin; D004549:Elastin; D002403:Cathepsins; D056657:Cathepsin K; C534133:Ctsk protein, rat