Biopsy specimen identification by detection of sex chromosomes: application of in situ hybridisation

Liver chimerism after allogeneic blood stem cell transplantation

Blood stem cells can mature into elements of many different lineages. We investigated the presence and nature of donor-derived (chimeric) cells within the liver after allogeneic stem cell transplantation.

METHODS

Liver biopsy autopsy specimens were examined from nine female patients who had undergone allogeneic bone marrow (n = 6) or peripheral stem cell (n = 3) transplantation from a male donor. To identify the male origin of cells within the liver, in-situ hybridization for Y-chromosomes was performed in conjunction with CD45 staining to identify leucocytes.

RESULTS

Hematopoietic stem cell engraftment was confirmed in all nine recipients. Histologic examination of the liver tissue sections revealed 5.6-fold more Y-chromosome-positive than CD45-positive staining cells (P < .02), indicative of considerable nonleucocytic chimerism. This was particularly observed in patients who had developed graft-versus-host disease.

CONCLUSIONS

Donor-derived cells can be found in liver tissue specimens after allogeneic stem cell transplantation. A considerable fraction of chimeric (donor-derived) cells appeared to be of nonlymphohematopoietic origin. This finding supports the theory of blood stem cells developing into liver cells of mesenchymal origin.

Hepatitis C virus genotype testing in paraffin wax embedded liver biopsies for specimen identification

Despite advances in medical technology, careful specimen identification is still a fundamental principle of laboratory testing. If pathological samples are mixed up, especially in the case of extremely small biopsy samples, large amounts of time and energy may be wasted in correctly identifying the specimens. Recently, two liver biopsy specimens were mixed up in this department, and a new pathological technology was used to resolve the issue. Liver biopsy was performed on two patients with hepatitis C virus (HCV) infection. During sample transfer or tissue processing, the biopsy specimens were mixed up. Because the ABO blood group of the two patients was identical (type AB), the specimens were subsequently identified by analysing the HCV genotypes. RNA extracted from the paraffin wax embedded liver specimens was examined by a polymerase chain reaction based HCV genotype assay. This enabled the correct identification of the specimens, and each patient received the appropriate treatment on the basis of the accurate diagnosis.

Extensive chimerism in liver transplants: vascular endothelium, bile duct epithelium, and hepatocytes

The transplanted liver has been shown to be particularly capable of inducing tolerance. An explanation may be the presence of chimerism. Cells of donor origin have been found in recipient tissues after transplantation of any solid organ. Evidence for the presence of cells of recipient origin within the transplanted liver is very limited. We investigated whether nonlymphoid cells of recipient origin can be found within human liver allografts. Five male patients who received a liver transplant from a female donor and 11 patients who received an HLA-I mismatched liver transplant were studied. We confirmed our observations with two different techniques in combination with double-staining techniques. To identify male cells in female liver transplants, we used in situ hybridization for sex chromosomes. To identify specific HLA class I antigens of recipient origin, we used immunohistochemistry with HLA class I-specific antibodies. Double staining was performed to discriminate different cell lineages and inflammatory cells. Endothelial cells of recipient origin were found in 14 of 16 donor livers. Bile duct epithelial cells of recipient origin were found in 5 of 16 cases. Hepatocytes of recipient origin were seen in only 1 of the 5 studied sex-mismatched donor livers. Our study provides evidence that cells of recipient origin can replace biliary epithelial cells, endothelial cells, and hepatocytes within the human liver allograft. This is consistent with the concept that circulating pluripotent progenitor cells exist, capable of differentiating into endothelial cells, epithelial cells, and hepatocytes.

Endothelial cell chimerism after renal transplantation and vascular rejection

BACKGROUND

The blood vessels of a transplanted organ are the interface between donor and recipient. The endothelium in the blood vessels is thought to be the major target for graft rejection. Endothelial cells of a transplanted organ are believed to remain of donor origin after transplantation. We aimed to verify this concept.

METHODS

We studied biopsy samples from 12 renal transplants for the presence of endothelial cells of recipient origin. We used three different techniques: immunohistochemistry for MHC class-I antigens, immunohistochemistry for ABO-blood-group antigens, and in-situ hybridisation for X and Y chromosomes. After we had confirmed that these techniques did identify endothelial cells of recipient origin, tests were done in a second group of 26 patients to find out whether endothelial chimerism correlated with graft rejection.

FINDINGS

We found a strong correlation between the percentage of recipient endothelial cells in the peritubular capillaries and the type of graft rejection (r = 0.71, p < 0.0001). These cells were found mainly in grafts of patients who had had rejection, especially among patients with vascular rejection. In grafts of patients without rejection only sporadically recipient endothelial cells were detectable.

INTERPRETATION

Our data show that endothelial cells of the recipient can replace those of the donor. This replacement is associated with graft rejection. We postulate that endothelium that is damaged by vascular rejection is repaired by endothelial cells of the recipient.

Non-isotopic in situ hybridization to detect chick Sox gene mRNA in plastic-embedded tissue

In situ hybridization techniques have rapidly become widely used by the molecular biologist for the localization of specific nucleic acid sequences in individual cells or tissues. We describe the demonstration of Sox gene mRNA in chick tissue that has been embedded in the plastic methyl methacrylate to permit the preparation of sections for high-resolution light microscopy. Polymerization of the plastic was induced by using either N,N-dimethylaniline or N,N-3,5-tetramethylaniline. The in situ hybridization technique used was non-isotopic and used a digoxigenin-labelled probe detected with an antibody bound to alkaline phosphatase, which was then localized using X-phosphate-Nitro BT as a substrate-chromogen mix. Various pretreatments of the tissue sections were investigated, including the use of proteinase K, and heat-mediated techniques using a microwave oven and a pressure cooker. The best results were produced using pressure cooking on tissue in which the plastic had been chemically polymerized with N,N-3,5-tetramethylaniline. For the demonstration of Sox 11, this combination had a critical influence on the staining results, but for Sox 21 all protocols used produced good staining.