Suppression of the immune system as a critical step for bone formation from allogeneic osteoprogenitors implanted in rats.

The surface marker profile of mesenchymal stromal cells (MSCs) suggests that they can escape detection by the immune system of an allogeneic host. This could be an optimal strategy for bone regeneration applications, where off-the-shelf cells could be implanted to heal bone defects. However, it is unknown how pre-differentiation of MSCs to an osteogenic lineage, a means of improving bone formation, affects their immunogenicity. Using immunohistological techniques in a rat ectopic implantation model, we demonstrate that allogeneic osteoprogenitors mount a T cell- and B cell-mediated immune response resulting in an absence of in vivo bone formation. Suppression of the host immune response with daily administration of an immunosuppressant, FK506, is effective in preventing the immune attack on the allogeneic osteoprogenitors. In the immunosuppressed environment, the allogeneic osteoprogenitors are capable of generating bone in amounts similar to those of syngeneic cells. However, using osteoprogenitors from one of the allogeneic donors led to newly deposited bone that was attacked by the host immune system, despite the continued administration of the immunosuppressant. This suggests that, although using an immunosuppressant can potentially suppress the immune attack on the allogeneic cells, optimizing the dose of the immunosuppressant may be crucial to ensure bone formation within the allogeneic environment. Overall, allografts comprising osteoprogenitors derived from allogeneic MSCs have the potential to be used in bone regeneration applications.

[Initial immunoreaction study on PVA/n-HA + PA66 biological composite material after being implanted into animal body].

OBJECTIVE: To observe immunoreaction to PVA/n-HA+ PA66 biological composite material after being implanted into animal body. METHODS: PVA/n-HA+PA66 composite materials were implanted into mouse subcutaneous tissue. Histologial examination was performed at 2, 4, 6 weeks, the amount of CD3, CD4+, CD8+ in blood and IL-1, IL-6, TNF-alpha in spleen cells was measured at the same time. RESULTS: The amount of CD3, CD4+, CD8+ in mouse blood and IL-1, IL-6, TNF-alpha in mouse spleen cells were not different with the control groups at 2, 4, 6 weeks (P > 0.05). The fibrous tissue and some blood vessels were found growing into the porous materials, which resulted in composite materials intergration of proliferative structure. The reject reaction was not found. CONCLUSION: PVA/n-HA+PA66 biological composite material does not cause immune rejection after being implanted into animal body, verifying its good biocompatibility.

Genetics and experimental models of crystal-induced arthritis. Lessons learned from mice and men: is it crystal clear?

PURPOSE OF REVIEW: We examine the major genes in mice and humans involved in the pathogenesis of monosodium urate, calcium pyrophosphate dihydrate and hydroxyapatite crystal-induced arthritis. RECENT FINDINGS: Several genetic causes of renal disease associated with hyperuricemia and gout provide insight into genes involved in renal urate handling. Mutations or polymorphisms in exons 4 and 5 and intron 4 of urate transporter 1 may be independent genetic markers of hyperuricemia and gout. Genetic analysis supports the role of ANKH mutations in calcium pyrophosphate dihydrate-induced arthritis. ANKH gain-of-function mutations were confirmed by functional studies; however, the crystals formed in ATD5 cells were basic calcium phosphate, not calcium pyrophosphate dihydrate, underlying the significance of chondrocyte differentiation state and the factors regulating normal and pathological mineralization. Animal models have implicated a general model of crystal-induced inflammation involving innate immunity through the NALP3 (Natch domain, leucine-rich repeat, and PYD-containing protein 3) inflammasome signaling through the interleukin-1 receptor and its signaling protein myeloid differentiation primary response protein 88. SUMMARY: Genetic analysis has elucidated genes responsible for crystal formation and animal models have unveiled mechanisms in the development of crystal-induced arthritis. Future studies will hasten understanding of the pathology of crystal-induced arthritis and provide new therapies.

[Experimental studies on the effect of ceramic materials on cellular and humoral immunity]. / Eksperymental'ni doslidzhennia vplyvu keramichnogo materialu na reaktsiï klitynnogo ta gumoral'nogo imunitetu.

It has been established in an experimental setting in laboratory animals through testing a number of reactions such as active skin anaphylaxis reaction, mast cell degranulation reaction, specific leucocyte lysis reaction, delayed hypersensitivity reaction, and graft-versus-host reaction that ceramic preparations hydroxilapatite M and osteogel-7 have no sensitizing effects; osteogel-7 is not endowed with immunomodulating activity, which fact suggests to us its immunological inertness.

Superoxide anion production and phagocytosis of crystals by cultured endothelial cells.

OBJECTIVE: To show that cultured human umbilical vein endothelial cells (HUVEC) are capable of phagocytizing inflammation-causing crystals and of generating superoxide anion (SOA) during phagocytosis. METHODS: The superoxide dismutase-inhibitable reduction of nitroblue tetrazolium (NBT) dye was used as a measure of SOA production. Phagocytosis was quantified by light microscopy and confirmed by transmission electron microscopy. Cytochrome C was also studied but was found to undergo spontaneous reduction by monosodium urate (MSU) without cells. RESULTS: Crystals of MSU, calcium oxalate, hydroxyapatite, and calcium pyrophosphate dihydrate (CPPD) were phagocytized and, except for the CPPD crystals, induced NBT reduction. Cholesterol and cholesterol monohydrate were neither phagocytized nor did they induce NBT reduction. CONCLUSIONS: Endothelial cells may be a significant source of oxygen radicals in crystal-associated and other arthritides.

Biocompatibility of hydroxyapatite-coated hip prostheses.

In three patients a mechanically well-fixed Mathys Ceros 80 (Ha) hydroxyapatite-coated acetabular component was revised 2, 5 and 13 months after total hip replacement due to component malposition. In each case there was a thin cellular connective tissue membrane between hydroxyapatite and bone, the main cell type being fibroblast with only occasional giant cells. Immunohistological analysis revealed some MHC locus II antigen positive cells that were identified as monocytes. No interleukin-2 receptor positive cells were found. Under clinical cyclic loading conditions there does not seem to be chemical fixation or bony ingrowth into the hydroxyapatite coated prosthesis component. In human lymphocyte cultures, hydroxyapatite (Interpore 200, particle diameters 15-40 microns) did not cause an increase in lymphocyte DNA synthesis as assessed by the 3H-thymidine incorporation method on culture days 1, 3 and 5. As analysed with lymphocyte activation markers, the hydroxyapatite-dependent expression of MHC locus II antigen was modest and differed significantly (P less than 0.05) from that in culture medium only on day 3. Hydroxyapatite induced only a slight interleukin-2 receptor expression that did not differ from culture medium on days 1, 3 and 5. CD4 and CD8 positive lymphocytes as well as monocytes were not seen attached to hydroxyapatite particles during the culture days. Our findings suggest that hydroxyapatite is an immunologically inert implant material.

[Antigenicity of alumina ceramic and calcium phosphate ceramics--genetic control of the immune response].

Antigenicity of alumina ceramic, hydroxyapatite ceramic and tricalcium phosphate ceramic was studied by induction of footpad swelling in C57BL/6 mice immunized by ceramics with Freund's complete adjuvant. Significant footpad swelling was observed in mice immunized with tricalcium phosphate ceramic at 2 and 4 weeks after immunization. Antigenic specificity was demonstrated between tricalcium phosphate ceramic and fetal bovine serum in crisscross. Time course of the reaction suggested that delayed-type hypersensitivity played an important role in footpad swelling. These results indicate that tricalcium phosphate ceramic has antigenicity to C57BL/6 mice. Antigenicity of alumina ceramic and hydroxyapatite ceramic was not demonstrated in this study. A positive footpad reaction to tricalcium phosphate ceramic was shown in C57BL/10 (H-2b) and C57BL/10 X BR (H-2k), but was not observed in C57BL/10 X D2(H-2d). These results suggest that this response to tricalcium phosphate ceramic was under control by a gene located within the major histocompatibility complex.

Inflammatory responses to intradermal crystals in healthy volunteers and patients with rheumatic diseases.

The inflammatory response to intradermal injections of urate, pyrophosphate and hydroxyapatite crystals in human forearm skin is described. Patients with rheumatoid arthritis responded normally to urate crystals, and patients with osteoarthritis or pyrophosphate arthropathy responded normally to hydroxyapatite and pyrophosphate crystals respectively. These results suggest that variation in host response to crystals cannot explain the different patterns of crystal-induced disease seen in man. The model, however, is recommended as a safe, simple ethical and reproducible test of inflammation in human subjects.

Fibril-mediated adherence of Actinomyces viscosus to saliva-treated hydroxyapatite.

Fibril-mediated adherence of Actinomyces viscosus strain T14V cells to saliva-treated hydroxyapatite was studied. Fibrils were purified by ammonium sulfate precipitation and differential centrifugation from the crude supernatant of whole cells that were sheared by one passage through a French pressure cell. Purified fibrils and crude supernatant inhibited strain T14V adherence to saliva-treated hydroxyapatite to similar extents. However, anti-strain T14V serum and antifibril specific antibody completely abolished strain T14V adherence. The blocking immunoglobulin could be adsorbed from anti-T14V serum by strain T14V whole cells, by purified fibrils, and, to a lesser extent, by cell walls. It was concluded that fibrils mediate adherence of strain T14V cells to saliva-treated hydroxyapatite. In addition, fibril preparations were shown to contain more than 95% protein and to be antigenically homogeneous by immunodiffusion and Laurell rocket immunoelectrophoresis. Purified fibril preparations showed serological identity with the virulence-associated 1 antigen of Lancefield-extracted T14V cells, whereas crude supernatants contained both virulence-associated 1 and virulence-associated 2 antigens, as shown by rocket immunoelectrophoresis.