Sensitivity of osteoblasts, fibroblasts, bone marrow cells, and dendritic cells to 5-aminolevulinic acid based photodynamic therapy.
BACKGROUND
Photodynamic therapy with 5-aminolevulinic acid (5-ALA-PDT) exerts cell type specific effects on target cells. Since chondrocytes were found to be more resistant than osteoblasts to 5-ALA-PDT, the pre-treatment of osteochondral grafts with 5-ALA-PDT may represent a means to devitalize the osseous portion while maintaining functional cartilage. The present study was designed to determine the effects of 5-ALA-PDT in vitro on cell populations residing in skeletal tissues.


METHODS
Osteoblasts, fibroblasts, bone marrow cells, and dendritic cells were incubated with 0.5 mM 5-ALA for 4 h. Protoporphyrin IX (PpIX) accumulation and after exposure to light cellular functions were assessed for up to 6 days.


RESULTS
Accumulation of PpIX reached a plateau at 0.5 mM in osteoblasts, fibroblasts, and dendritic cells, and at 2.0 mM in bone marrow cells. At 0.5 mM 5-ALA, similar responses to illumination were observed in all cells with a survival rate of less than 12% at a light dose of 20 J/cm(2). The function of osteoblasts (proliferation, levels of mRNA encoding collagen type I, alkaline phosphatase activity) and fibroblasts (proliferation, levels of mRNAs encoding collagens type I and III) was not affected, when the cells were treated with 5-ALA and light doses of < or =10 J/cm(2). Paralleling the reduction of viable cells after 5-ALA-PDT, the capacity of dendritic cells to stimulate T cells in a mixed leukocyte reaction decreased to 4+/-2% at 20 J/cm(2).


CONCLUSIONS
The investigated cell types were sensitive to 5-ALA-PDT and the residual cell debris did not elicit an allogenic response. These findings, together with the resistance of chondrocytes to 5-ALA-PDT, encourage the further investigation of this protocol in the pretreatment of osteochondral allografts.
Egli
Rainer J
RJ
University of Berne, Group for Bone Biology and Orthopedic Research, Department Clinical Research, Murtenstrasse 35, 3010 Berne, Switzerland. rainer.egli@ndos.ox.ac.uk
Schober
Martin
M
Hempfing
Axel
A
Ganz
Reinhold
R
Hofstetter
Willy
W
Leunig
Michael
M
D000469:Alkaline Phosphatase / Q000378:metabolism; D000622:Aminolevulinic Acid / Q000494:pharmacology*; D000818:Animals; D001854:Bone Marrow Cells / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D003713:Dendritic Cells / Q000187:drug effects*; D005347:Fibroblasts / Q000187:drug effects*; D007959:Lymphocyte Culture Test, Mixed; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000187:drug effects*; D010778:Photochemotherapy; D011524:Protoporphyrins / Q000378:metabolism
D011524:Protoporphyrins; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX; D000469:Alkaline Phosphatase