Donor-derived hepatocytes in human hematopoietic cell transplant recipients: evidence of fusion
Reconstitution of hepatocytes by hematopoietic stem cells—a phenomenon which occurs in rodents under highly selective conditions—results from infrequent fusion between incoming myelomonocytes and host hepatocytes, with subsequent proliferation. Human hematopoietic stem cell transplant recipients have been little studied, with some support for transdifferentiation (direct differentiation). We studied routinely obtained autopsy liver tissue of four female hematopoietic cell transplant recipients with male donors, using a highly specific conjoint immunohistochemistry in situ hybridization light microscopic technique. Hepatocyte nuclei were identified by cytokeratin (Cam5.2) staining and evaluated for X and Y chromosome content. Over 1.6 million hepatocytes were assessed for rare instances of donor origin, revealing a Y chromosome in 67. Mixed tetraploids (XXXY) and their nuclear truncation products (XXY, XY, Y) were directly demonstrated, with no detection of the male tetraploids (XXYY) that may result from transdifferentiation with subsequent tetraploidization, nor their unique truncation products (XYY, YY), implicating fusion as the mechanism. To determine whether it is the sole mechanism, we modeled the chromosome distribution based on the same probability of detection of each X chromosome, deriving parameters of sensitivity and female tetraploidy by best fit. We then hypothesized that the distribution of Y chromosome–containing cells could be predicted by a similar model. After modification to account for “clumpy” Y chromosomes, the observed results were in accord with the predicted results (p = 0.6). These results suggest that all the Y-containing cells, including apparent XY cells, derive from mixed tetraploids, consistent with fusion as the sole mechanism.
KeywordsLiver regeneration Stem cells Progenitor cells In situ hybridization Hematopoietic stem cell transplant
We thank Dr. Ted A. Gooley for statistics advice.
DM conceived and designed the study; analyzed the data; and wrote, edited, and reviewed the manuscript. RKP acquired the data and edited and reviewed the manuscript. Both authors read and approved the final manuscript.
This work was supported in part by grants from the National Institutes of Health CA18029, CA15074, and HL36444.
Compliance with ethical standards
The study was performed under a protocol approved by the Institutional Review Board of the Fred Hutchinson Cancer Research Center.
Conflict of interest
The authors declare that they have no conflict of interest.
- 7.Resaz R, Emionite L, Vanni C, Astigiano S, Puppo M, Lavieri R, Segalerba D, Pezzolo A, Bosco MC, Oberto A, Eva C, Chou JY, Varesio L, Barbieri O, Eva A (2011) Treatment of newborn G6pc−/− mice with bone marrow-derived myelomonocytes induces liver repair. J Hepatol 55:1263–1271. https://doi.org/10.1016/j.jhep.2011.02.033 CrossRefPubMedGoogle Scholar
- 17.Wu T, Cieply K, Nalesnik MA, Randhawa PS, Sonzogni A, Bellamy C, Abu-Elmagd K, Michalopolous GK, Jaffe R, Kormos RL, Gridelli B, Fung JJ, Demetris AJ (2003) Minimal evidence of transdifferentiation from recipient bone marrow to parenchymal cells in regenerating and long-surviving human allografts. Am J Transplant 3:1173–1181CrossRefGoogle Scholar
- 19.Myerson D, Parkin RK, Benirschke K, Tschetter CN, Hyde SR (2006) The pathogenesis of villitis of unknown etiology: analysis with a new conjoint immunohistochemistry-in situ hybridization procedure to identify specific maternal and fetal cells. Pediatr Dev Pathol 9:257–265. https://doi.org/10.2350/08-05-0103.1 CrossRefPubMedGoogle Scholar
- 36.Johansson CB, Youssef S, Koleckar K, Holbrook C, Doyonnas R, Corbel SY, Steinman L, Rossi FMV, Blau HM (2008) Extensive fusion of haematopoietic cells with Purkinje neurons in response to chronic inflammation. Nat Cell Biol 10:575–583. https://doi.org/10.1038/ncb1720 CrossRefPubMedPubMedCentralGoogle Scholar