Question

Silicone breast implants have been the subject of considerable controversy. Several women who received silicone breast implants were later diagnosed with various negative tissue responses.

Discuss the typical tissue responses with a focus on negative response and discuss methods of reducing negative tissue response focussing on implant material

Answer 1

Negative tissue response:

Light microscopy was used to study connective tissue capsules formed around different silicone breast implants. It has been found that due to the activity of microfibroblasts to minimize the volume of foreign bodies, the capsule gradually shrinks; its inner surface deforms and develops an undulating appearance with a multitude of outgrowths or protrusions inside. With the passage of time, silicone migrates to the capsule tissue and outside where it is absorbed by phagocytes. The inerter to a living organism the implant material is, the less it will stimulate a macrophage response. The task of designing new implants is to search for maximally bioinert materials that are strong enough to be compressed by the capsule and be fragmented and, moreover, elastically similar to normal breast tissue.

Local morphological reaction patterns on breast implants can be of high significance as possible starting point for controversely discussed systemic immune response triggered by silicon or silicone.

under a scanning electron microscope and light-microscopically using antibodies to the macrophage antigen CD68, vimentin, muscle actin, and the proliferation antigen MIB1, and were then correlated with anamnestic data (implanted type of prosthesis, indication for im- or explantation). According to our examinations, the in-vivo durability of the prostheses' shells is considerably decreasing with the expansion of their surfaces. Regardless of the type of the prostheses' surface regularly a chronic-proliferating inflammation pattern could be identified in the periprosthetic capsulectomy specimens starting with a synovial metaplasia of proliferating CD-68-negative and vimentin-positive mesenchymal cells in the area surrounding the implants and ending by its transformation into a stage of dense hyaline collagenous fibrous tissue after an advanced implantation period (> 2 years). By this, the texturing of the prosthesis surface modifies only the course, but not the quality of the chronically fibrosing inflammation. Bleeding of prosthesis as well as the incorporation of the polyurethane-foam coating of different prosthesis types into the periprosthetic breast capsule lead to a significant lymphoplasmacytic infiltration, partly with participation of local vessels as defined in a "silicone vasculitis". Morphological signs of an at least local immune response are detectable in 8.3% of the examined fibrotic capsules even without a morphologically identifiable foreign-body embedding. They can be possibly referred to- as well as the complete absence of hyaline collagenous fibrous tissue in 30% of the cases-a yet not causally clarified, inter-individually different susceptibility of the implant bearers. Only the systematic registration of the above-mentioned morphological reaction patterns in a "prosthesis-passport" together with the additional clinical observation of the patients can ensure in future the realistic estimation of potential health risks caused by silicone breast implants.

Reducing negative response:

A variety of biomaterial implantable devices has been developed. Of particular significance to pharmaceutical sciences is the progress made on the development of drug/implantable device combination products. However, the clinical application of these devices is still a critical issue due to the host response, which results from both the tissue trauma during implantation and the presence of the device in the body. Accordingly, the in vivo functionality and durability of any implantable device can be compromised by the body response to the foreign material. Numerous strategies to overcome negative body reactions have been reported. The aim of this review is to outline some key issues of biomaterial/tissue interactions such as foreign body response and biocompatibility and biocompatibility assessment. In addition, general approaches used to overcome the in vivo instability of implantable devices are presented, including (a) biocompatible material coatings, (b) steroidal and nonsteroidal anti-inflammatory drugs, and (c) angiogenic drugs. In particular, strategies to overcome host response to glucose biosensors are summarized.