Medical and economic impacts of managing corneas from older donors at the tissue bank-a single-center retrospective study spanning over 12 years.

Aim: To evaluate the impact of corneas from donors over 80 years of age on the activity of the North of France Tissue Bank and to determine the potential cost implications for banks using corneas from older donors.

Methods: We analyzed data from a single-center retrospective cohort study of 6,023 corneas preserved at the Lille Tissue Bank between 2012 and 2023. Donors, unrestricted by age, were divided into two groups: younger (≤ 80 years) and older (> 80 years).

Retrospective study of COVID-19 seroprevalence among tissue donors at the onset of the outbreak before implementation of strict lockdown measures in France.

Background The COVID-19 pandemic has altered organ and tissue donations as well as transplantation practices. SARS-CoV-2 serological tests could help in the selection of donors. We assessed COVID-19 seroprevalence in a population of tissue donors, at the onset of the outbreak in France, before systematic screening of donors for SARS-CoV-2 RNA.

How to improve donor skin availability: Pragmatic procedures to minimize the discard rate of cryopreserved allografts in skin banking.

Background: Microbial contamination of human skin allografts is a frequent cause of allograft discard. Our purpose was to evaluate the discard rate of skin bank contaminated allografts and specific procedures used to reduce allograft contamination without affecting safety.

Methods: We conducted at the Lille Tissue Bank a retrospective study of all deceased donors (n = 104) harvested from January 2018 to December 2018.

Benefits of cryopreserved human amniotic membranes in association with conventional treatments in the management of full-thickness burns.

The use of split-thickness skin autografts (STSA) with dermal substitutes is the gold standard treatment for third-degree burn patients. In this article, we tested whether cryopreserved amniotic membranes could be beneficial to the current treatments for full-thickness burns. Swines were subjected to standardised full-thickness burn injuries, and then were randomly assigned to treatments: (a) STSA alone; (b) STSA associated with the dermal substitute, Matriderm; (c) STSA plus human amniotic membrane (HAM); and (d) STSA associated with Matriderm plus HAM.

Expression of the 49 human ATP binding cassette (ABC) genes in pluripotent embryonic stem cells and in early- and late-stage multipotent mesenchymal stem cells: possible role of ABC plasma membrane transporters in maintaining human stem cell pluripotency.

The 49-member human ATP binding cassette (ABC) gene family encodes 44 membrane transporters for lipids, ions, peptides or xenobiotics, four translation factors without transport activity, as they lack transmembrane domains, and one pseudogene. To understand the roles of ABC genes in pluripotency and multipotency, we performed a sensitive qRT-PCR analysis of their expression in embryonic stem cells (hESCs), bone marrow-derived mesenchymal stem cells (hMSCs) and hESC-derived hMSCs (hES-MSCs). We confirm that hES-MSCs represent an intermediate developmental stage between hESCs and hMSCs.

Comparison of Gene Expression in Human Embryonic Stem Cells, hESC-Derived Mesenchymal Stem Cells and Human Mesenchymal Stem Cells.

We present a strategy to identify developmental/differentiation and plasma membrane marker genes of the most primitive human Mesenchymal Stem Cells (hMSCs). Using sensitive and quantitative TaqMan Low Density Arrays (TLDA) methodology, we compared the expression of 381 genes in human Embryonic Stem Cells (hESCs), hESC-derived MSCs (hES-MSCs), and hMSCs. Analysis of differentiation genes indicated that hES-MSCs express the sarcomeric muscle lineage in addition to the classical mesenchymal lineages, suggesting they are more primitive than hMSCs.

Optimization of physiological xenofree molecularly defined media and matrices to maintain human embryonic stem cell pluripotency.

We describe in this chapter the development of a xenofree molecularly defined medium, SBX, associated with xenofree matrices, to maintain human embryonic stem cell (hESC) pluripotency as determined by phenotypic, functional and TLDA studies. This simple, inexpensive, and more physiological culture condition has been chosen because (1) it is xenofree and molecularly defined; it is devoid of albumin, which is a carrier of undefined molecules; (2) it maintains pluripotency, but very significantly reduces differentiation gene expression during hESC self-renewal, as compared to the widely used culture conditions tested so far; and (3) it can be further improved by replacing high concentrations of expensive additives by physiological concentrations of new factors. Xenofree molecularly defined media and matrices represent valuable tools for elucidating still unknown functions of numerous embryonic genes using more physiological culture conditions.

[bFGF-stimulated MEF-conditioned medium is capable of maintaining human embryonic stem cells].

4 ng/ml bFGF is indispensable for hESC cultured on mouse embryonic fibroblasts (MEF), withdrawal of bFGF drives the hESC to differentiate. In order to exploit effect of bFGF on MEF, we collected a series of MEF conditioned medium (bFGF-MCM) by co-culturing MEF with increasing bFGF concentrations: 0.03, 0.

Use of xenofree matrices and molecularly-defined media to control human embryonic stem cell pluripotency: effect of low physiological TGF-beta concentrations.

To monitor human embryonic stem cell (hESC) self-renewal without differentiation, we used quantitative RT-PCR to study a selection of hESC genes, including markers for self-renewal, commitment/differentiation, and members of the TGF-beta superfamily and DAN gene family. Indeed, low commitment/differentiation gene expression, together with a significant self-renewal gene expres sion, provides a better pluripotency index than self-renewal genes alone. We demonstrate that matrices derived from human mesenchymal stem cells (hMSCs) can advantageously replace murine embryonic fibroblasts (MEF) or hMSC feeders.

Simultaneous differentiation of endothelial and trophoblastic cells derived from human embryonic stem cells.

Here we present a simple two-step in vitro model of vascularized trophoblastic tissue derived from human embryonic stem (hES) cells. The first step is the formation of cystic embryoid bodies (EBs) in suspension in a semisolid methyl cellulose medium, within which an endothelial platelet/endothelial cell adhesion molecule-1 (PECAM-1(+)) cell network develops. In a second step, deposition of these EBs on the bottom of nontreated, polystyrene tissue culture plates, leads by centrifugal outgrowth of the EB to the emergence of an adherent cell layer, with which a PECAM-1(+) network is associated.

A sub-population of high proliferative potential-quiescent human mesenchymal stem cells is under the reversible control of interferon alpha/beta.

Type I interferon (IFN) is shown to control the reversible quiescence of a primitive human bone marrow mesenchymal stem cell (MSC) subpopulation. A 24 h pre-treatment of Stro1+/GlycoA- or CD45-/GlycoA- subpopulations with a monoclonal antibody (mAb) against the IFNAR1 chain of the human type I IFN receptor (64G12), or with a polyclonal anti-IFNalpha antibody, resulted in a marked increase in the number of very large colonies (CFU-F >3000 cells) obtained in the presence of low, but necessary, concentrations of bFGF. Over a 2-month culture period, this short activation promoted a faster and greater amplification of mesenchymal progenitors for adipocytes and osteoblasts.

[Human embryonic stem cells: practical problems and scientific potentialities].

Human embryonic stem cells (hESCs) are derived from pre-implantation embryos given to research with the informed consent of the parents. These cells cannot give rise to a human being: they are not totipotent. They have an unlimited self-renewal capacity and they can generate the three embryonic germ layers, their respective derivatives and the extra-embryonic tissues: they are pluripotent.

Long-term expansion of human functional epidermal precursor cells: promotion of extensive amplification by low TGF-beta1 concentrations.

We have previously introduced the concept of high proliferative potential-quiescent (HPP-Q) cells to refer to primitive human hematopoietic progenitors, on which transforming growth factor-beta1 (TGF-beta1) exerts a pleiotropic effect. TGF-beta1 confers to these slow-dividing cells a mitogenic receptor(low) phenotype and maintains immature properties by preventing differentiation and apoptosis. However, the effect of TGF-beta1 on long-term expansion has not yet been clearly demonstrated.

Control of hematopoietic stem/progenitor cell fate by transforming growth factor-beta.

A major obstacle to the use of adult somatic stem cells for cell therapy is our current inability to fully exploit stem cell self-renewal properties. The challenge is to obtain defined culture systems where cycling of primitive stem/progenitor cells is stimulated, while their differentiation and senescence are prevented. The cytokine transforming growth factor-beta1 (TGF-beta1) appears as a potential regulator of hematopoietic stem/ progenitor cell self-renewal, as it participates in the control of cell proliferation, survival/apoptosis, and cell immaturity/differentiation.

Specific dose-response effects of TGF-beta1 on developmentally distinct hematopoietic stem/progenitor cells from human umbilical cord blood.

Introduction: Transforming Growth Factor-beta1 is known to maintain primitive human hematopoietic stem/progenitor cells in a quiescent state. However, its specific role in the control of distinct progenitor cell types needs to be further elucidated. In this study, we have investigated the dose-response effect of TGF-beta1 on progenitors ranging from primitive high proliferative potential (HPP)-Mix, -GM or -BFU-E to later BFU-E, CFU-G or CFU-M.

Fibrinogen cooperates with cytokines to induce interleukin-6 receptor mRNA expression in human hematopoietic CD34+ progenitors.

We have previously demonstrated that purified human fibrinogen (Fg), a major plasma component removed during serum preparation, shows mitogenic properties towards lymphoma cells and normal human hematopoietic progenitors. Indeed, adding Fg with IL-3 to a serum-containing medium stimulates growth of human CD34+ progenitors. In this report, we show in serum-free medium, that this stimulating effect only occurs in the presence of IL-6.

The high proliferative potential-quiescent (HPP-Q) cell assay allows an optimized evaluation of gene transfer efficiency into primitive hematopoietic stem/progenitor cells.

Various protocols have been described to optimize gene transfer into hematopoietic cells. However, most of these methods do not specify whether they are associated with an improved transduction of the more primitive stem/progenitor cells, the best candidates for long-term engraftment. The majority of these primitive cells remains in quiescence because of the negative control of TGF-beta1, effective on these cells at low concentrations (10 pg/ml).

Transforming growth factor-beta: pleiotropic role in the regulation of hematopoiesis.

Hematopoiesis is a remarkable cell-renewal process that leads to the continuous generation of large numbers of multiple mature cell types, starting from a relatively small stem cell compartment. A highly complex but efficient regulatory network is necessary to tightly control this production and to maintain the hematopoietic tissue in homeostasis. During the last 3 decades, constantly growing numbers of molecules involved in this regulation have been identified.

p21(cip1) mRNA is controlled by endogenous transforming growth factor-beta1 in quiescent human hematopoietic stem/progenitor cells.

Transforming growth factor-beta1 (TGF-beta1) has been described as an efficient growth inhibitor that maintains the CD34(+) hematopoietic progenitor cells in quiescence. The concept of high proliferative potential-quiescent cells or HPP-Q cells has been introduced as a working model to study the effect of TGF-beta1 in maintaining the reversible quiescence of the more primitive hematopoietic stem cell compartment. HPP-Q cells are primitive quiescent stem/progenitor cells on which TGF-beta1 has downmodulated the cytokine receptors.

Release from quiescence of primitive human hematopoietic stem/progenitor cells by blocking their cell-surface TGF-beta type II receptor in a short-term in vitro assay.

Genetic alterations of the signaling cascade of transforming growth factor-beta (TGF-beta) are often associated with neoplastic transformation of primitive cells. This demonstrates the key role for this pleiotropic factor in the control of quiescence and cell proliferation in vivo. In the high proliferative potential-quiescent cell (HPP-Q) in vitro assay, the use of TGF-beta1 blocking antibodies (anti-TGF-beta1) allows the detection within two to three weeks of primitive hematopoietic cells called HPP-Q, which otherwise would not grow.

TGF-(beta)1 maintains hematopoietic immaturity by a reversible negative control of cell cycle and induces CD34 antigen up-modulation.

Somatic stem cells are largely quiescent in spite of their considerable proliferative potential. Transforming growth factor-(beta)1 (TGF-(beta)1) appears to be a good candidate for controlling this quiescence. Indeed, various mutations in the TGF-beta signalling pathway are responsible for neoplasic proliferation of primitive stem/progenitor cells in human tissues of various origins.

High proliferative potential-quiescent cells: a working model to study primitive quiescent hematopoietic cells.

Human adult hematopoietic stem cells are mostly quiescent or slow cycling. We have previously demonstrated that blocking of transforming growth factor-beta1 (TGF-beta1) is able to activate, in the presence of cytokines, primitive quiescent hematopoietic multipotent progenitors which could not grow in a two week semi-solid culture assay (short term culture). We have also shown that anti-TGF-beta1 can up-modulate c-KIT, the receptor of the stem cell factor (steel factor).

Mitogenic effect of fibrinogen on hematopoietic cells: involvement of two distinct specific receptors, MFR and ICAM-1.

In addition to its well-known functions in blood clotting and cell adhesion, fibrinogen has been reported to be a mitogen for lymphoid cell lines and for human hematopoietic progenitors. Two specific receptors, the mitogenic fibrinogen receptor (MFR) and intercellular adhesion molecule-1 (ICAM-1/CD54), have been identified as possible candidates for the mediation of the mitogenic effect of fibrinogen. However, it has been questioned whether the MFR and ICAM-1 are truly distinct molecules.