An Immunocytochemical Study for Lysosomal Cathepsins B and D Related to the Intracellular Degradation of Titanium at the Bone‐Titanium Interface

Abstract

The morphological relationship between titanium and lysosomal proteinases, cathepsins B and D, at the bone-titanium interface using titanium-coated plastic implants placed for 28 days in the tibiae of 6-week-old rats was immunocytochemically investigated by the colloidal immunogold-silver method. Under light microscopy the titanium layer appeared to make direct contact with the bone and one or a few layers of slender cells were interposed between the bone and titanium. Ultrastructurally, the titanium came in contact with the bone or the slender cell layer through a 20 to 40 nm thin amorphous zone. The slender cells at the bone-titanium interface consisted of two types; one was an osteoblast type with glycogen granules which was found along the newly-formed bone facing titanium layer. The other was a fibroblast type which came in contact with the titanium layer and occasionally endocytosed the detached titanium fragments. In addition, some of the slender cells also showed degenerative changes. Immunocytochemically, cathepsins B and/or D were sometimes colocalized in some phagolysosomes with titanium fragments. These findings suggested that the fibroblast types at the bone-titanium interface may act as scavengers to remove both cell debris and titanium by means of some endocytotic ability, and lysosomal cathepsins also developed in response to the endocytosed titanium. The osteoblast type also appears to show a high degree of osteogenic activity around the titanium-coated plastic implants.

Chronological Changes in the Ultrastructure of Titanium‐Bone Interfaces: Analysis by Light Microscopy, Transmission Electron Microscopy, and Micro‐Computed Tomography

“…This experimental method is considered to be a superior technique. However, the number of reports using this technique is even smaller, and there are variabilities in the properties of thin titanium film among reports 17–25 . Okamatsu and colleagues 17 coated titanium using the DC magnetron sputtering method.…”

Ultrastructure of the Interface Between Titanium and Surrounding Tissue in Rat Tibiae – A Comparison Study on Titanium‐Coated and ‐Uncoated Plastic Implants

“…Specimens were obtained 4 weeks after implant placement to obtain detailed observation of the titanium‐bone interface after achieving osseointegration, because several investigators reported the successful osseointegration 4 to 12 weeks after implant placement 18–23,25,26 …”

“…A method of coating a thin film of titanium on plastic has been used in order to examine an intact titanium‐bone interface. However, there have been only a few such reports in the past 20 years 18–23 . In addition, opinions in these reports have not necessarily been consistent regarding the existence of an amorphous layer at the titanium‐bone interface and the response of surrounding tissue.…”

The Effects of Implant Surface Characteristics on Surrounding Bone: A Comparative Study of Two Types of Surface Characteristics

“…The results have shown that rapid, strong osseointegration can be achieved with implants having surface roughness in the order of Sa=2 μm [1][2][3] . However, since the implant body is metal, tissue samples cannot readily be prepared, and, therefore, the tissue reaction at the titanium-bone interface cannot be easily evaluated 9,[13][14][15] .…”