Fas-L promotes the stem cell potency of adipose-derived mesenchymal cells.

Fas-L is a TNF family member known to trigger cell death. It has recently become evident that Fas-L can transduce also non-apoptotic signals. Mesenchymal stem cells (MSCs) are multipotent cells that are derived from various adult tissues. Although MSCs from different tissues display common properties they also display tissue-specific characteristics. Previous works have demonstrated massive apoptosis following Fas-L treatment of bone marrow-derived MSCs both in vitro and following their administration in vivo. We therefore set to examine Fas-L-induced responses in adipose-derived stem cells (ASCs). Human ASCs were isolated from lipoaspirates and their reactivity to Fas-L treatment was examined. ASCs responded to Fas-L by simultaneous apoptosis and proliferation, which yielded a net doubling of cell quantities and a phenotypic shift, including reduced expression of CD105 and increased expression of CD73, in association with increased bone differentiation potential. Treatment of freshly isolated ASCs led to an increase in large colony forming unit fibroblasts, likely produced by early stem cell progenitor cells. Fas-L-induced apoptosis and proliferation signaling were found to be independent as caspase inhibition attenuated Fas-L-induced apoptosis without impacting proliferation, whereas inhibition of PI3K and MEK, but not of JNK, attenuated Fas-L-dependent proliferation, but not apoptosis. Thus, Fas-L signaling in ASCs leads to their expansion and phenotypic shift toward a more potent stem cell state. We speculate that these reactions ensure the survival of ASC progenitor cells encountering Fas-L-enriched environments during tissue damage and inflammation and may also enhance ASC survival following their administration in vivo.

Potent in vitro and in vivo effects of polyclonal anti-human-myeloma globulins.

INTRODUCTION: Multiple myeloma is still incurable in most cases. Polyclonal anti T lymphocyte globulins (ATG) have been reported to kill human myeloma cells in vitro and in mouse models. METHODS: Anti-human-myeloma globulins (AMG) were produced by immunizing rabbits with human myeloma cell lines RPMI-8226 (AMG-8226) or KMS-12-BM (AMG-12-BM). Cytotoxicity of the polyclonal antibodies was analyzed in vitro and in a xenograft NOD-SCID mouse model. RESULTS: Both AMG had stronger cytotoxicity against myeloma cells compared to ATG. In primary T cells, AMG-8226 showed greater complement-dependent cytotoxicity (CDC) than ATG, whereas complement-independent cytotoxicity did not differ. Effects on non-hematopoietic cell lines were also similar. Competitive blocking assays revealed fourfold more antibodies against CD38 in AMG-8226 compared to ATG. Low concentrations of AMG-8226 and ATG increased ADCC. At higher concentrations, ATG inhibited ADCC more potently than AMG-8226. Combinations of ATG and AMG-8226 with melphalan or bortezomib showed additive to synergistic cytotoxicity on myeloma cells. The cytotoxic effects of AMG and ATG were confirmed in the xenograft NOD-SCID mouse model. CONCLUSION: Our data show more potent antimyeloma effects of AMG compared to ATG. These results lay the ground for the development of polyclonal antibodies for the treatment of multiple myeloma.

Cultured Mesenchymal Stem Cells Stimulate an Immune Response by Providing Immune Cells with Toll-Like Receptor 2 Ligand.

Mesenchymal stem cells (MSCs) serve as supporting and regulatory cells, by providing tissues with multiple factors and are also known for their immunosuppressive capabilities. Our laboratory had previously shown that MSCs expressed toll-like receptor (TLR) 2 and are activated by its ligand Pam3Cys. TLR2 is an important component of the innate immune system, as it recognizes bacterial lipopeptides, thus priming a pro-inflammatory immune response. This study showed that Pam3Cys attached extensively to cells of both wild-type and TLR2 deficient cultured MSCs, thus, independently of TLR2. The TLR2 independent binding occurred through the adsorption of the palmitoyl moieties of Pam3Cys. It was further showed that Pam3Cys was transferred from cultured MSCs to immune cells. Moreover, Pam3Cys provided to the immune cells induced a pro-inflammatory response in vitro and in vivo. Overall, it is demonstrated herein that a TLR2 ligand bound to MSCs also through a TLR2 independent mechanism. Furthermore, the ligand incorporated by MSCs is subsequently released to stimulate an immune response both in vitro and in vivo. It is thus suggested that during bacterial infection, stromal cells may retain a reservoir of the TLR2 ligands, in a long-term manner, and release them slowly to maintain an immune response.

Relative genomic stability of adipose tissue derived mesenchymal stem cells: analysis of ploidy, H19 long non-coding RNA and p53 activity.

INTRODUCTION: Mesenchymal stem cells (MSCs) are multipotent and have been derived from various tissues. Although MSCs share many basic features, they often display subtle tissue specific differences. We previously demonstrated that bone marrow (BM) MSCs frequently become polyploid in culture. This tendency was mediated by a reduction in the expression of H19 long non-coding RNA during the transition from a diploid to a polyploid state. METHODS: MSCs were derived from both BM and adipose tissue of mice and expanded under normoxic and hypoxic culture conditions. Cells were stained by propidium iodide and their ploidy was evaluated by FACS. Gene expression of independent MSC preparations was compared by quantitative real time PCR and protein expression levels by Western blot analysis. p53 silencing in MSCs was performed by a specific small hairpin RNA (shRNA). RESULTS: We set to examine whether genomic instability is common to MSCs originating from different tissues. It is demonstrated that adipose derived MSCs (ASCs) tend to remain diploid during culture while a vast majority of BM MSCs become polyploid. The diploid phenotype of ASCs is correlated with reduced H19 expression compared to BM MSCs. Under hypoxic conditions (3% oxygen) both ASCs and BM MSCs demonstrate increased RNA expression of H19 and Vascular endothelial growth factor A. Importantly, ASC gene expression is significantly less variable than BM MSCs under both oxygen conditions, indicating to their superior homogeneity. Gene expression analysis revealed that p53 target genes, often induced by DNA damage, are up-regulated in ASCs under basal conditions. However, p53 activation following treatment with DNA damaging agents was strongly elevated in BM MSCs compared to ASCs. We found that p53 is involved in maintaining the stable diploid state of ASCs as p53 shRNA induced ploidy changes in ASCs but not in BM MSCs. CONCLUSIONS: The increased genomic stability of murine ASCs together with their lower H19 expression and relative homogeneity suggest a tissue specific higher stability of ASCs compared to BM MSCs, possibly due to higher activity of p53. The tissue specific differences between MSCs from a different tissue source may have important consequences on the use of various MSCs both in vitro and in vivo.

Cell isolation induces fate changes of bone marrow mesenchymal cells leading to loss or alternatively to acquisition of new differentiation potentials.

Mesenchymal stromal cell populations include a fraction, termed mesenchymal stem cells, exhibiting multipotency. Other cells within this population possess a lesser differentiation range. This was assumed to be due to a mesenchymal cellular cascade topped by a multipotent cell, which gives rise to progeny with diminishing differentiation potentials. Here, we show that mesenchymal cells, a priori exhibiting a limited differentiation potential, may gain new capacities and become multipotent following single-cell isolation. These fate changes were accompanied by upregulation of differentiation promoting genes, many of which also became H4K20me1 methylated. Early events in the process included TGFß and Wnt modulation, and downregulation of hypoxia signaling. Indeed, hypoxic conditions inhibited the observed cell changes. Overall, cell isolation from neighboring partners caused major molecular changes and particularly, a newly established epigenetic state, ultimately leading to the acquisition of new differentiation potentials and an altered cell fate.

Divergent levels of LBP and TGFß1 in murine MSCs lead to heterogenic response to TLR and proinflammatory cytokine activation.

The outstanding heterogeneity of stem cell populations is a major obstacle on the way to their clinical application. It is therefore paramount to identify the molecular mechanisms that underlay this heterogeneity. Individually derived bone marrow mesenchymal stromal cells (MSCs) preparations, studied here, diverged markedly in various properties, despite of being all tripotent in their differentiation potential. Microarray analysis showed that MSC diversity is evident also in highly variable gene expression patterns. Differentially expressed genes were significantly enriched in toll-like receptors (TLRs) and differentiation pathways. Marked differences were observed in LPS binding protein (LBP) and transforming growth factor (TGF)ß1 expression. These differences correlated with MSC functionality. Therefore, the possible contribution of these molecules to MSC diversity was examined. In the TLR signaling pathway, LBP levels predicted the ability of specific MSCs to secrete interleukin (IL)-6 in response to LPS. A relatively higher expression of TGFß1 endowed MSCs with a capacity to respond to IL-1ß by reduced osteogenic differentiation. This study thus demonstrates major diversity within MSC isolates, which appears early on following derivation and persists following long-term culture. MSC heterogeneity results from highly variable transcriptome. Differential expression of LBP and TGFß1, along with other genes, in different MSC preparations, produces the variable responses to external stimuli.

Resistance of hematopoietic progenitors to Fas-mediated apoptosis is actively sustained by NFκB with a characteristic transcriptional signature.

Umbilical cord blood (UCB) is a good source of hematopoietic progenitors with increasing implementation in the clinical transplant setting. This study evaluates the molecular mechanisms of progenitor resistance to apoptosis triggered by Fas cross-linking. CD34(+) and lineage-negative progenitors survive short-term ex vivo incubation and are not induced into apoptosis by Fas cross-linking. Furthermore, brief exposure of UCB cells to Fas-ligand for 24-48 h does not impair quantitative severe combine immune deficiency (SCID) reconstitution activity and appears to foster myelomonocyte reconstitution. The transcriptome of Fas receptor-positive CD34(+) cells that survived an apoptotic challenge showed significant transcriptional upregulation of caspase-8, mucosa-associated lymphoid tissue lymphoma translocation gene-1 (MALT1), HtrA2, and GSK3ß in addition to higher levels of c-FLICE inhibitory protein (FLIP), Bcl-2, and cytosolic inhibitor of apoptosis protein (cIAP) in all Fas-positive cells. Most prominent is the transcriptional upregulation of several key components the NFκB1 pathway including the membrane receptors TGF-ß, interleukin-1 (IL-1), and TCR, the associated factor TNF receptor-associated factor-6 (TRAF6), and the converting enzymes TGF-ß-activated kinase-1 (TAK1), double-stranded RNA-activated protein kinase (PKR), and α-catalytic subunit of IκB kinase (IKKα), that promote activation and nuclear translocation of this transcription factor. These data indicate that hematopoietic progenitors are not insensitive to apoptosis but are actively shielded from the extrinsic and intrinsic apoptotic pathways. This may occur through inherent transcriptional upregulation of the entire NFκB pathway in the presence of competent apoptotic signaling.

The origin of human mesenchymal stromal cells dictates their reparative properties.

BACKGROUND: Human mesenchymal stromal cells (hMSCs) from adipose cardiac tissue have attracted considerable interest in regard to cell-based therapies. We aimed to test the hypothesis that hMSCs from the heart and epicardial fat would be better cells for infarct repair. METHODS AND RESULTS: We isolated and grew hMSCs from patients with ischemic heart disease from 4 locations: epicardial fat, pericardial fat, subcutaneous fat, and the right atrium. Significantly, hMSCs from the right atrium and epicardial fat secreted the highest amounts of trophic and inflammatory cytokines, while hMSCs from pericardial and subcutaneous fat secreted the lowest. Relative expression of inflammation- and fibrosis-related genes was considerably higher in hMSCs from the right atrium and epicardial fat than in subcutaneous fat hMSCs. To determine the functional effects of hMSCs, we allocated rats to hMSC transplantation 7 days after myocardial infarction. Atrial hMSCs induced greatest infarct vascularization as well as highest inflammation score 27 days after transplantation. Surprisingly, cardiac dysfunction was worst after transplantation of hMSCs from atrium and epicardial fat and minimal after transplantation of hMSCs from subcutaneous fat. These findings were confirmed by using hMSC transplantation in immunocompromised mice after myocardial infarction. Notably, there was a correlation between tumor necrosis factor-α secretion from hMSCs and posttransplantation left ventricular remodeling and dysfunction. CONCLUSIONS: Because of their proinflammatory properties, hMSCs from the right atrium and epicardial fat of cardiac patients could impair heart function after myocardial infarction. Our findings might be relevant to autologous mesenchymal stromal cell therapy and development and progression of ischemic heart disease.

Polyploidization of murine mesenchymal cells is associated with suppression of the long noncoding RNA H19 and reduced tumorigenicity.

Mesenchymal stromal cells (MSC) are used extensively in clinical trials; however, the possibility that MSCs have a potential for malignant transformation was raised. We examined the genomic stability versus the tumor-forming capacity of multiple mouse MSCs. Murine MSCs have been shown to be less stable and more prone to malignant transformation than their human counterparts. A large series of independently isolated MSC populations exhibited low tumorigenic potential under syngeneic conditions, which increased in immunocompromised animals. Unexpectedly, higher ploidy correlated with reduced tumor-forming capacity. Furthermore, in both cultured MSCs and primary hepatocytes, polyploidization was associated with a dramatic decrease in the expression of the long noncoding RNA H19. Direct knockdown of H19 expression in diploid cells resulted in acquisition of polyploid cell traits. Moreover, artificial tetraploidization of diploid cancer cells led to a reduction of H19 levels, as well as to an attenuation of the tumorigenic potential. Polyploidy might therefore serve as a protective mechanism aimed at reducing malignant transformation through the involvement of the H19 regulatory long noncoding RNA.

Stable changes in mesenchymal stromal cells from multiple myeloma patients revealed through their responses to Toll-like receptor ligands and epidermal growth factor.

In human multiple myeloma (MM), the tumor cells exhibit strict dependence on bone marrow (BM) stromal elements. It has been suggested that, in turn, MM cells modify multipotent stromal cells (MSCs), diverting them to support the myeloma. We investigated MM-derived MSCs by comparing their toll-like receptor (TLR) responses to those of MSCs derived from healthy controls. We now report that MM-derived MSCs manifested intact proliferation responses and IL-6 secretion and their adipose and osteogenic differentiation responses to TLR ligands were also similar to those of healthy controls, ranging from augmentation to inhibition. However, MM-derived MSCs were found to be defective in IL-8 secretion and ERK1/2 phosphorylation following TLR-2 activation. Moreover, MM-derived MSCs failed to respond to EGF by elevation of ERK1/2 phosphorylation. The persistence of these changes in extensively cultured MM-derived MSCs, suggests that these cells are stably, if not irreversibly modified.

Mitochondria as a sequestration site for incomplete TCRß peptides: the TCRß transmembrane domain is a sufficient mitochondrial targeting signal.

The existence of incomplete T cell receptor (TCR) mRNA forms, including germline transcripts and products of unfruitful TCR rearrangements, has long been known. However, it is unclear whether these molecules are functional. We have previously shown that T cells also contain truncated TCRß peptides that lack the N-terminal part and contain C-terminus sequences. These partial forms of TCRß, target the mitochondrion and induce apoptosis, exhibiting a novel mode of TCR mediated cell death. Here we aimed at analyzing the minimal TCR sequences that direct the peptide to the mitochondrion. It is shown that truncated TCRß, targets mitochondria and induces mitochondrial perinuclear clustering, in both monkey COS-7 and human 293 cells. These phenomena are mediated by the C-terminus of the molecule. Whereas the positively charged amino acids flanking the transmembrane domain (TMD) of TCRß are beneficial for this process, they are not essential. Indeed, the isolated TMD of TCRß serves as a sufficient mitochondrial targeting sequence. These results indicate that any given partial form of TCRß, that contains the TMD, is bound to be sequestered by the mitochondrion. This may assure that incomplete TCR forms would not interfere with correct TCR complex formation.

The origins of mesenchymal stromal cell heterogeneity.

Cultured mesenchymal stromal cell (MSC) populations are best characterized by the capacity of some cells within this population to differentiate into mesodermal derivatives such as osteoblasts, chondrocytes and adipocytes. However, this progenitor property is not shared by all cells within the MSC population. Furthermore, MSCs exhibit variability in their phenotypes, including proliferation capacity, expression of cell surface markers and ability to secrete cytokines. These facts raise three major questions: (1) Does the in vitro observed variability reflect the existence of MSC subsets in vivo? (2) What is the molecular basis of the in vitro observed heterogeneity? and (3) What is the biological significance of this variability? This review considers the possibility that the variable nature of MSC populations contributes to the capacity of adult mammalian tissues to adapt to varying microenvironmental demands.

Mammalian cell dedifferentiation as a possible outcome of stress.

Differentiation cascades are arranged hierarchically; stem cells positioned at the top of the hierarchy generate committed progenitors that, in turn, proliferate and further differentiate stepwise into mature progeny. This rigid, irreversible structure ensures the phenotypic stability of adult tissues. However, such rigidity may be problematic under conditions of tissue damage when reconstitution is required. Although it may seem unlikely that the restrictions on changes in cell phenotypes would be lifted to enable tissue reconstitution, it is nevertheless possible that mammalian tissues are endowed with sufficient flexibility to enable their adaptation to extreme conditions.

The hemopoietic stem cell niche versus the microenvironment of the multiple myeloma-tumor initiating cell.

Multiple myeloma cells are reminiscent of hemopoietic stem cells in their strict dependence upon the bone marrow microenvironment. However, from all other points of view, multiple myeloma cells differ markedly from stem cells. The cells possess a mature phenotype and secrete antibodies, and have thus made the whole journey to maturity, while maintaining a tumor phenotype. Not much credence was given to the possibility that the bulk of plasma-like multiple myeloma tumor cells is generated from tumor-initiating cells. Although interleukin-6 is a major contributor to the formation of the tumor's microenvironment in multiple myeloma, it is not a major factor within hemopoietic stem cell niches. The bone marrow niche for myeloma cells includes the activity of inflammatory cytokines released through osteoclastogenesis. These permit maintenance of myeloma cells within the bone marrow. In contrast, osteoclastogenesis constitutes a signal that drives hemopoietic stem cells away from their bone marrow niches. The properties of the bone marrow microenvironment, which supports myeloma cell maintenance and proliferation, is therefore markedly different from the characteristics of the hemopoietic stem cell niche. Thus, multiple myeloma presents an example of a hemopoietic tumor microenvironment that does not resemble the corresponding stem cell renewal niche.

Mesenchymal stromal cells revert multiple myeloma cells to less differentiated phenotype by the combined activities of adhesive interactions and interleukin-6.

Multiple myeloma is characterized by the malignant growth of immunoglobulin producing plasma cells, predominantly in the bone marrow. The effects of primary human mesenchymal stromal cells on the differentiation phenotype of multiple myeloma cells were studied by co-culture experiments. The incubation of multiple myeloma cells with bone marrow-derived mesenchymal stromal cells resulted in significant reduction of the expression of the predominant plasma cell differentiation markers CD38 and CD138, and cell surface immunoglobulin light chain. While the down-regulation of CD138 by stromal cells was completely dependent on their adhesive interactions with the multiple myeloma cells, interleukin-6 induced specific down-regulation of CD38. Mesenchymal stromal cells or their conditioned media inhibited the growth of multiple myeloma cell line, thereby reducing the overall amounts of secreted light chains. Analysis of primary multiple myeloma bone marrow samples reveled that the expression of CD38 on multiple myeloma cells was not affected by adhesive interactions. The ex vivo propagation of primary multiple myeloma cells resulted in significant increase in their differentiation markers. Overall, the data indicate that the bone marrow-derived mesenchymal stromal cells revert multiple myeloma cells to less differentiated phenotype by the combined activities of adhesive interactions and interleukin-6.

p53 plays a role in mesenchymal differentiation programs, in a cell fate dependent manner.

BACKGROUND: The tumor suppressor p53 is an important regulator that controls various cellular networks, including cell differentiation. Interestingly, some studies suggest that p53 facilitates cell differentiation, whereas others claim that it suppresses differentiation. Therefore, it is critical to evaluate whether this inconsistency represents an authentic differential p53 activity manifested in the various differentiation programs. METHODOLOGY/PRINCIPAL FINDINGS: To clarify this important issue, we conducted a comparative study of several mesenchymal differentiation programs. The effects of p53 knockdown or enhanced activity were analyzed in mouse and human mesenchymal cells, representing various stages of several differentiation programs. We found that p53 down-regulated the expression of master differentiation-inducing transcription factors, thereby inhibiting osteogenic, adipogenic and smooth muscle differentiation of multiple mesenchymal cell types. In contrast, p53 is essential for skeletal muscle differentiation and osteogenic re-programming of skeletal muscle committed cells. CONCLUSIONS: These comparative studies suggest that, depending on the specific cell type and the specific differentiation program, p53 may exert a positive or a negative effect, and thus can be referred as a "guardian of differentiation" at large.

Increased regulatory versus effector T cell development is associated with thymus atrophy in mouse models of multiple myeloma.

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) play a central role in cancer tolerance. However, mechanisms leading to their accumulation in cancer remain unknown. Although the thymus is the main site of Treg development, thymic contribution to Treg expansion in cancer has not been directly examined. Herein, we used two murine models of multiple myeloma (MM), 5T2 MM and 5T33 MM, to examine Treg accumulation in peripheral lymphoid organs, including spleen, lymph nodes, bone marrow, and blood, and to explore thymic Treg development during malignancy. We found that peripheral ratios of suppressive-functional Tregs increased in both models of MM-inflicted mice. We found that thymic ratios of Treg development in MM increased, in strong association with thymus atrophy and altered developmental processes in the thymus. The CD4(+)CD8(+) double-positive population, normally the largest thymocyte subset, is significantly decreased, whereas the CD4(-)CD8(-) double-negative population is increased. Administration of thymocytes from MM-inflicted mice compared with control thymocytes resulted in increased progression of the disease, and this effect was shown to be mediated by Tregs in the thymus of MM-inflicted mice. Our data suggest that increased ratios of Treg development in the thymus may contribute to disease progression in MM-inflicted mice.

The myelopoietic supportive capacity of mesenchymal stromal cells is uncoupled from multipotency and is influenced by lineage determination and interference with glycosylation.

Cultured bone marrow stromal cells create an in vitro milieu supportive of long-term hemopoiesis and serve as a source for multipotent mesenchymal progenitor cells defined by their ability to differentiate into a variety of mesodermal derivatives. This study aims to examine whether the capacity to support myelopoiesis is coupled with the multipotency. Our results show that the myelopoietic supportive ability of stromal cells, whether from the bone marrow or from embryo origin, is not linked with multipotency; cell populations that possess multipotent capacity may or may not support myelopoiesis, whereas others, lacking multipotency, may possess full myelopoietic supportive ability. However, upon differentiation, the ability of multipotent mesenchymal progenitors to support myelopoiesis is varied. Osteogenic differentiation did not affect myelopoietic supportive capacity, whereas adipogenesis resulted in reduced ability to support the maintenance of myeloid progenitor cells. These differences were accompanied by a divergence in glycosylation patterns, as measured by binding to lectin microarrays; osteogenic differentiation was associated with an increased level of antennarity of N-linked glycans, whereas adipogenic differentiation caused a decrease in antennarity. Inhibition of glycosylation prior to seeding the stroma with bone marrow cells resulted in reduced capacity of the stromal cells to support the formation of cobblestone areas. Our data show that myelopoietic support is unrelated to the multipotent phenotype of cultured mesenchymal progenitors but is dependent on the choice of differentiation pathway and upon correct glycosylation of the stromal cells.

Targeting the bone marrow with activin A-overexpressing embryonic multipotent stromal cells specifically modifies B lymphopoiesis.

In vitro and in vivo studies implicate a series of cytokines in regulation of lymphohematopoiesis. However, direct indications for a local role of most of these cytokines within the bone marrow is lacking. In the present study, we aimed to test the contribution of a specific cytokine, activin A, a member of the transforming growth factor-beta (TGF-beta) family, to lymphohematopoiesis in mouse bone marrow. We show that mouse embryonic fibroblasts (MEFs) are indistinguishable from multipotent stromal cells (MSCs). Such MEFs overexpressing activin A, supported in vitro myelopoiesis in long-term bone marrow cultures as effectively as control MEFs. In contrast, activin A-overexpressing MEFs interfered with the in vitro generation of B lineage cells in such cultures. Thus, excessive expression in vitro of activin A, by supportive stromal cells, causes preferential maturation of myeloid rather than lymphoid cells. Moreover, the activin A-overexpressing MEFs caused an increased incidence in vivo of relatively immature B lineage cells; upon transplantation through the spleen route, MEFs engrafted the bone marrow specifically. Activin A-overexpressing MEFs accumulated in the bone marrow compartment and slowed down the progression of B cell precursors along the differentiation pathway, while sparing the myeloid population. The assay system described in this paper provides a means to assess the contribution of a wide range of molecules to hematopoiesis without perturbing the constitution of other organs.

Activin betaA in term placenta and its correlation with placental inflammation in parturients having epidural or systemic meperidine analgesia: a randomized study.

STUDY OBJECTIVE: To investigate the immunohistochemical localization of betaA subunit of activin A in human term placenta, as a marker for placental infection/inflammation and elevated temperature, in parturients laboring during two analgesic regimens. DESIGN: Prospective, randomized controlled study. SETTING: Delivery room. PATIENTS: 56 healthy, ASA physical status I and II primiparous women in labor. INTERVENTIONS: Parturients were assigned to receive patient-controlled epidural analgesia (PCEA) with 0.2% ropivacaine or patient-controlled intravenous analgesia PCA with meperidine. MEASUREMENTS: Histologic and immunohistochemical placental evaluation for white blood cell infiltration and activin betaA staining were made. Maternal temperature elevation above 37.6 degrees C and leukocytosis above 15,000/microL were recorded. MAIN RESULTS: Temperature was not significantly increased in parturients receiving PCEA over those who received (PCA) with meperidine (31% vs 11%, respectively; P = 0.1). There was also no association between temperature elevation during epidural analgesia and increased white blood cell count (>15,000/microL) or presence of polymorphonuclear and/or lymphocyte aggregation in the placenta. Immunohistochemical staining with antisera against the betaA subunit of activin was present mainly in the placental cytotrophoblast, syncytiotrophoblast, and vascular endothelium, and was not associated with an increase in maternal temperature. No significant difference was noted between the two analgesic techniques with regard to maternal temperature elevation. Intrapartum temperature elevation was not associated with histologic signs of placental inflammation or with expression of activin betaA in the placenta. CONCLUSION: Other mechanisms may be involved in the etiology of temperature elevation during labor.