The use of donor-derived veto cells in hematopoietic stem cell transplantation

The induction of immune tolerance by specific agents, as opposed to general immune suppression, is a most desirable goal in transplantation biology. One approach to attain this goal is afforded by the use of donor-derived cells endowed with veto activity, which is the ability of a cell to specifically suppress only T cells directed against its antigens. A megadose of purified veto CD34+ hematopoietic stem cells is already used in patients to allow hematopoietic stem cells transplantation (HSCT) across major genetic barriers, while avoiding severe graft versus host disease (GVHD). However, allowing engraftment of such T cell-depleted HSCT under safer reduced intensity conditioning (RIC) protocols still remains a challenge. Therefore, combining megadose of CD34+ HSCT with other GVHD-depleted veto cells could enable facilitation of engraftment of HSCT under RIC without the adverse complication of GVHD. This approach might provide a safer modality for enabling engraftment of HSCT, enabling its application in elderly patients who cannot tolerate intensive protocols and to a variety of patients with non-malignant disorders, associated with longer life expectancy, in whom the use of a high risk conditioning cannot be considered

Embryonic Porcine Skin Precursors Can Successfully Develop into Integrated Skin without Teratoma Formation Posttransplantation in Nude Mouse Model

How to improve the wound healing quality of severe burn patients is still a challenge due to lack of skin appendages and rete ridges, no matter how much progress has been made in the fields of either stem cell or tissue engineering. We thus systematically studied the growth potential and differentiation capacity of porcine embryonic skin precursors. Implantation of embryonic skin precursors (PESPs) of different gestational ages in nude mice can generate the integrity skin, including epidermis, dermis and skin appendages, such as sweat gland, hair follicle, sebaceous gland, etc.. PESPs of embryonic day 42 possess the maximal growth potential, while, the safe window time of PESPs transplantation for prevention of teratoma risk is E56 or later. In conclusion, PESPs can form the 3 dimensional structures of skin with all necessary skin appendages. Our data strongly indicate that porcine embryonic skin precursors harvested from E56 of minipig may provide new hope for high-quality healing of extensive burns and traumas

Lung Cell Transplantation for Pulmonary Fibrosis

Idiopathic pulmonary fibrosis is a major cause of death with few treatment options. Here, we demonstrate the therapeutic efficacy for lung fibrosis of adult lung cell transplantation using a single-cell suspension of the entire lung in two distinct mouse systems: bleomycin treatment and mice lacking telomeric repeat-binding factor 1 expression in alveolar type 2 (AT2) cells (SPC-Cre TRF1fl/fl), spontaneously developing fibrosis. In both models, the progression of fibrosis was associated with reduced levels of host lung progenitors, enabling engraftment of donor progenitors without any additional conditioning, in contrast to our previous studies. Two months after transplantation, engrafted progenitors expanded to form numerous donor-derived patches comprising AT1 and AT2 alveolar cells, as well as donor-derived mesenchymal and endothelial cells. This lung chimerism was associated with attenuation of fibrosis, as demonstrated histologically, biochemically, by computed tomography imaging, and by lung function measurements. Our study provides a strong rationale for the treatment of lung fibrosis using lung cell transplantation

Estimating Cell Depth from Somatic Mutations

The depth of a cell of a multicellular organism is the number of cell divisions it underwent since the zygote, and knowing this basic cell property would help address fundamental problems in several areas of biology. At present, the depths of the vast majority of human and mouse cell types are unknown. Here, we show a method for estimating the depth of a cell by analyzing somatic mutations in its microsatellites, and provide to our knowledge for the first time reliable depth estimates for several cells types in mice. According to our estimates, the average depth of oocytes is 29, consistent with previous estimates. The average depth of B cells ranges from 34 to 79, linearly related to the mouse age, suggesting a rate of one cell division per day. In contrast, various types of adult stem cells underwent on average fewer cell divisions, supporting the notion that adult stem cells are relatively quiescent. Our method for depth estimation opens a window for revealing tissue turnover rates in animals, including humans, which has important implications for our knowledge of the body under physiological and pathological conditions

Natural and cryptic peptides dominate the immunopeptidome of atypical teratoid rhabdoid tumors

BACKGROUND: Atypical teratoid/rhabdoid tumors (AT/RT) are highly aggressive CNS tumors of infancy and early childhood. Hallmark is the surprisingly simple genome with inactivating mutations or deletions in the SMARCB1 gene as the oncogenic driver. Nevertheless, AT/RTs are infiltrated by immune cells and even clonally expanded T cells. However, it is unclear which epitopes T cells might recognize on AT/RT cells. METHODS: Here, we report a comprehensive mass spectrometry (MS)-based analysis of naturally presented human leukocyte antigen (HLA) class I and class II ligands on 23 AT/RTs. MS data were validated by matching with a human proteome dataset and exclusion of peptides that are part of the human benignome. Cryptic peptide ligands were identified using Peptide-PRISM. RESULTS: Comparative HLA ligandome analysis of the HLA ligandome revealed 55 class I and 139 class II tumor-exclusive peptides. No peptide originated from the SMARCB1 region. In addition, 61 HLA class I tumor-exclusive peptide sequences derived from non-canonically translated proteins. Combination of peptides from natural and cryptic class I and class II origin gave optimal representation of tumor cell compartments. Substantial overlap existed with the cryptic immunopeptidome of glioblastomas, but no concordance was found with extracranial tumors. More than 80% of AT/RT exclusive peptides were able to successfully prime CD8(+) T cells, whereas naturally occurring memory responses in AT/RT patients could only be detected for class II epitopes. Interestingly, >50% of AT/RT exclusive class II ligands were also recognized by T cells from glioblastoma patients but not from healthy donors. CONCLUSIONS: These findings highlight that AT/RTs, potentially paradigmatic for other pediatric tumors with a low mutational load, present a variety of highly immunogenic HLA class I and class II peptides from canonical as well as non-canonical protein sources. Inclusion of such cryptic peptides into therapeutic vaccines would enable an optimized mapping of the tumor cell surface, thereby reducing the likelihood of immune evasion

Embryonic Pig Pancreatic Tissue Transplantation for the Treatment of Diabetes

BACKGROUND: Transplantation of embryonic pig pancreatic tissue as a source of insulin has been suggested for the cure of diabetes. However, previous limited clinical trials failed in their attempts to treat diabetic patients by transplantation of advanced gestational age porcine embryonic pancreas. In the present study we examined growth potential, functionality, and immunogenicity of pig embryonic pancreatic tissue harvested at different gestational ages. METHODS AND FINDINGS: Implantation of embryonic pig pancreatic tissues of different gestational ages in SCID mice reveals that embryonic day 42 (E42) pig pancreas can enable a massive growth of pig islets for prolonged periods and restore normoglycemia in diabetic mice. Furthermore, both direct and indirect T cell rejection responses to the xenogeneic tissue demonstrated that E42 tissue, in comparison to E56 or later embryonic tissues, exhibits markedly reduced immunogenicity. Finally, fully immunocompetent diabetic mice grafted with the E42 pig pancreatic tissue and treated with an immunosuppression protocol comprising CTLA4-Ig and anti–CD40 ligand (anti-CD40L) attained normal blood glucose levels, eliminating the need for insulin. CONCLUSIONS: These results emphasize the importance of selecting embryonic tissue of the correct gestational age for optimal growth and function and for reduced immunogenicity, and provide a proof of principle for the therapeutic potential of E42 embryonic pig pancreatic tissue transplantation in diabetes

Reconstruction of Cell Lineage Trees in Mice

The cell lineage tree of a multicellular organism represents its history of cell divisions from the very first cell, the zygote. A new method for high-resolution reconstruction of parts of such cell lineage trees was recently developed based on phylogenetic analysis of somatic mutations accumulated during normal development of an organism. In this study we apply this method in mice to reconstruct the lineage trees of distinct cell types. We address for the first time basic questions in developmental biology of higher organisms, namely what is the correlation between the lineage relation among cells and their (1) function, (2) physical proximity and (3) anatomical proximity. We analyzed B-cells, kidney-, mesenchymal- and hematopoietic-stem cells, as well as satellite cells, which are adult skeletal muscle stem cells isolated from their niche on the muscle fibers (myofibers) from various skeletal muscles. Our results demonstrate that all analyzed cell types are intermingled in the lineage tree, indicating that none of these cell types are single exclusive clones. We also show a significant correlation between the physical proximity of satellite cells within muscles and their lineage. Furthermore, we show that satellite cells obtained from a single myofiber are significantly clustered in the lineage tree, reflecting their common developmental origin. Lineage analysis based on somatic mutations enables performing high resolution reconstruction of lineage trees in mice and humans, which can provide fundamental insights to many aspects of their development and tissue maintenance