van Lent PL, van den Bersselaar L, van den Hoek AE, van de Ende M, Dijkstra CD, van Rooijen N, van de Putte LB, van den Berg WB.
Reversible depletion of synovial lining cells after intra-articular treatment with liposome-encapsulated dichloromethylene diphosphonate.
Rheumatol. Int. 1993;13(1):21–30.
[toggle_content title=”Abstract”]We studied the depletion and repopulation of synovial lining cells in mice. A single intra-articular injection of liposomes encapsulating the drug dichloromethylene diphosphonate (CL2MDP) in the mouse knee joint caused selective elimination of synovial lining cells. Depletion of cells occurred within a few days as evidenced by light microscopic, electron microscopic and immunohistochemical studies. Maximal depletion was seen on day 7. Repopulation was observed in the following weeks, starting at the bone side of the joint. Until day 30, full recovery (60% recovery) was not observed in the lining lying adjacent to the dermis. Side effects on cartilage metabolism, such as inhibition of proteoglycan synthesis or degradation of proteoglycans from the matrix was minor but significant, 1 and 2 days after liposome treatment but thereafter full recovery was observed. Selective elimination of lining cells from the joint enabled us to study the in vivo role of these cells in the onset and subsequent pathology of experimental arthritis. An immune-complex-mediated experimental arthritis elicited in lining cell depleted joints that had received CL2MDP-liposomes 7 days earlier prevented inflammation as compared to controls.[/toggle_content] [toggle_content title=”Clodronate Liposome Parameters”] [custom_table]
Clodronate Concentration Total Lipid Concentration Lipid Composition Lipid Mole % Liposome Type Control Liposomes Control Free Clodronate
12.5 mg/ml 21.5 mg/ml EPC/Chol 77/23 MLV PBS 75 µg/6 µl
[/custom_table] [/toggle_content] [toggle_content title=”Animals and Dosing”] [custom_table]
Animal Description Clodronate Dose Dosing Method/Site Target Phagocytes Systemic Dosing? Systemic Results
C57BL/6 mice, male, 8-12 w, 25-30 g 75 µg/6 µl intra-articular/knee MOMA-1+, MOMA-2+synovial , F4/80+NLDC-145+ phagocytes no N/A
[/custom_table] [/toggle_content] [toggle_content title=”Notes”]
  1. No liposome prep method was cited.
  2. This concentration of encapsulated clodronate is atypically high although a typical encapsulation efficiency of 1% was reported.
  3. The authors report centrifuging at 100,000xg during the washing process so they may have collected more of the smaller liposomes which are not usually spun down during a 10,000xg centrifugation step.
[/toggle_content] [toggle_content title=”Results”]
  1. When when a single dose of clodronate liposomes, control liposomes, clodronate, or clodronate + control liposoomes was injected into normal mouse knee joints followed by histological examination on days 1, 3 and 7 revealed that
    • Free clodronate had no effect on the synovial lining cells nor did it elicit inflammatory cells into the synovium.
    • Control fluorescent liposomes and clodronate liposomes elicited some inflammatory cells into the synovial fluids which had disappeared by day 7.
    • Control fluorescent liposomes localized to the synovial lining and remained visible at least until day 7; no further time points investigated.
    • Clodronate liposomes caused enlargement and gradual depletion of synovial lining cells which reached a maximum at day 7, although the fibroblast-like cells just under the lining were unchanged.
  2. Continued observation of clodronate liposome treated animals showed
    • Synovial lining cells had begun to repopulate by day 9 on the femoral side of the synovium; complete repopulation at this site was accomplished by day 15.
    • Recovery of the dermal side of the lining began on day 20 and was only about 60% complete at day 30.
    • Only MOMA-2+ and F4/80+ cells were found in the synovial lining.
  3. Co-culturing of synovial macrophages and fibroblasts followed by treatment with clodronate liposomes confirmed that only the macrophages were affected.
  4. Proteoglycan synthesis was inhibited and degradation increased (collagen metabolism) on days 1-3 but returned to baseline by day 4.
  5. Control liposomes solicited PMN at a similar level to clodronate liposomes, but the control liposomes did not affect collagen metabolism.
  6. Immune-complex induced arthritis was initiated on day 7, but no joint swelling was measured in clodronate-liposome treated knees.