Pluripotency gene expression and growth control in cultures of peripheral blood monocytes during their conversion into programmable cells of monocytic origin (PCMO): evidence for a regulatory role of autocrine activin and TGF-β

Corneal Recovery Following Rabbit Peripheral Blood Mononuclear Cell-Amniotic Membrane Transplantation with Antivascular Endothelial Growth Factor in Limbal Stem Cell Deficiency Rabbits

Background: Limbal stem cell deficiency (LSCD) is a refractory ocular surface disorder characterized by progressive corneal epithelial degeneration, conjunctivalization, and neovascularization, potentially leading to blindness. There are currently no effective therapeutic options for patients experiencing routine symptomatic treatment failure. Transplantation of amniotic membrane (AM) with adherent stem cells (but not bare AM transplantation alone) has shown promise in preclinical studies for ocular surface restoration. A major limitation, however, is finding a reliable stem cell source. Stem cells can be isolated from the peripheral blood mononuclear cell (PBMC) population, and these PBMC-derived stem cells have numerous advantages over allogeneic and other autologous stem cell types for therapeutic application, including relative ease of acquisition, nonimmunogenicity, and the absence of ethical issues associated with embryonic stem cells. Experiment: We examined the efficacy of autologous PBMC-AM sheet cultures combined with postoperative antiangiogenesis treatment for corneal restoration in LSCD model rabbits. Rabbit PBMCs (rPBMCs) were isolated, labeled with EdU for in vivo tracing, and then cultured on AMs in conditioned medium before transplantation. Rabbits were transplanted with bare AMs (group 1), rPBMC-AM sheets (group 2), or rPBMC-AM sheets plus postoperative treatment with the vascular endothelial growth factor antagonist bevacizumab (group 3). Corneal opacity and neovascularization were monitored by slit-lamp imaging for 8 weeks and corneas were examined histologically at 1 and 2 months. Results: Corneal opacity decreased in all three groups over 8 weeks, but was significantly lower in group 2 and even lower in group 3. Corneal neovascularization was significantly higher in group 1 throughout the observation period, and significantly lower in group 3 than group 1 and 2 by 8 weeks post-transplant. At 4 weeks, the corneal surface completed epithelialization (although thinner than normal) in group 3 but still patchy in groups 1 and 2. By 8 weeks, the epithelium in group 3 was complete and smooth, resembling a normal epithelium. Integrin β1 as a progenitor marker was also generally higher in groups 2 and 3. Conclusions: Autologous rPBMC-AM sheets with post-transplant topical bevacizumab can effectively facilitate corneal epithelium recovery in a LSCD model, suggesting clinical utility for LSCD-related ocular surface diseases. Impact statement Limbal stem cell deficiency (LSCD) increases corneal opacity and vascularization, resulting in severe visual impairment or even blindness. Traditional surgical limbal transplant is currently the main treatment option for LSCD, but carries the risks of rejection and immunosuppressant side effects. Autologous stem cell-based therapy is a promising alternative approach, but a reliable stem cell source is a major limitation. We report that transplantation of autologous rabbit peripheral blood mononuclear cell-amniotic membrane sheets plus antivascular endothelial growth factor restored avascular transparent cornea in a rabbit LSCD model. These results demonstrate a potentially effective approach for ocular surface reconstruction in bilateral LSCD.

In vitro efficacy of liver microenvironment in bone marrow mesenchymal stem cell differentiation

Bone marrow-derived mesenchymal stem cells (BM-MSCs) represent an interesting alternative to liver or hepatocyte transplantation to treat liver injuries. Many studies have reported that MSCs can treat several diseases, including liver damage, just by injection into the bloodstream, without evidence of differentiation. The improvements were attributed to the organotrophic factors, low immunogenicity, immunomodulatory, and anti-inflammatory effects of MSCs, rather than their differentiation. The aim of the present study was to answer the question of whether the presence of BM-MSCs in the hepatic microenvironment will lead to their differentiation to functional hepatocyte-like cells. The hepatic microenvironment was mimicked in vitro by culture for 21 d with liver extract. The resulted cells expressed marker genes of the hepatic lineage including AFP, CK18, and Hnf4a. Functionally, they were able to detoxify ammonia into urea, to store glycogen as observed by PAS staining, and to synthesize glucose from pyruvate/lactate mixture. Phenotypically, the expression of MSC surface markers CD90 and CD105 decreased by differentiation. This evidenced differentiation into hepatocyte-like cells was accompanied by a downregulation of the stem cell marker genes sox2 and Nanog and the cell cycle regulatory genes ANAPC2, CDC2, Cyclin A1, and ABL1. The present results suggest a clear differentiation of BM-MSCs into functional hepatocyte-like cells by the extracted liver microenvironment. This differentiation is confirmed by a decrease in the stemness and mitotic activities. Tracking transplanted BM-MSCs and proving their in vivo differentiation remains to be elucidated.

Transfection of Peripheral Blood Monocytes with SOX2 Enhances Multipotency, Proliferation, and Redifferentiation into Neohepatocytes and Insulin-Producing Cells

Following a several-day incubation in medium containing IL-3 and M-CSF to generate a more plastic intermediate "reprogrammed multipotent cells of monocytic origin (RMCMO)," peripheral blood mononuclear cells (PBMCs) can be efficiently converted to hepatocyte-like cells (neohepatocytes) and insulin-producing cells. However, continuous efforts are devoted to enhancing the proliferative capacity of these multipotent cells while maintaining or further increasing their redifferentiation potential. In the present work, PBMCs were transfected with one pluripotency gene (SOX2) and the resulting RMCMO compared to standard RMCMO with respect to cell viability, proliferative activity, and redifferentiation potential. Ectopic SOX2 expression increased the number of viable RMCMO, activated cell cycle genes, and enhanced proliferation as shown by quantitative RT-PCR and Ki67 immunofluorescent staining, respectively. Redifferentiation of RMCMO derived from SOX2-transfected PBMCs to neohepatocytes was more complete in comparison to control cells as revealed by higher urea and glucose secretion, increased activity of cytochrome P450 isoforms, and a phase II enzyme, while the same was true for insulin-producing cells as assessed by the expression of INS, PDX1, and GLUT2 and glucose-stimulated insulin secretion. Our results indicate that SOX2 transfection increases both multipotency and proliferation of RMCMO, eventually allowing production of neohepatocytes and insulin-producing cells of higher quality and quantity for transplantation purposes.

Inhibitory Antibodies against Activin A and TGF-β Reduce Self-Supported, but Not Soluble Factors-Induced Growth of Human Pulmonary Arterial Vascular Smooth Muscle Cells in Pulmonary Arterial Hypertension

Increased growth and proliferation of distal pulmonary artery vascular smooth muscle cells (PAVSMC) is an important pathological component of pulmonary arterial hypertension (PAH). Transforming Growth Factor-β (TGF-β) superfamily plays a critical role in PAH, but relative impacts of self-secreted Activin A, Gremlin1, and TGF-β on PAH PAVSMC growth and proliferation are not studied. Here we report that hyper-proliferative human PAH PAVSMC have elevated secretion of TGF-β1 and, to a lesser extent, Activin A, but not Gremlin 1, and significantly reduced Ser^465/467-Smad2 and Ser^423/425-Smad3 phosphorylation compared to controls. Media, conditioned by PAH PAVSMC, markedly increased Ser^465/467-Smad2, Ser^423/425-Smad3, and Ser^463/465-Smad1/5 phosphorylation, up-regulated Akt, ERK1/2, and p38 MAPK, and induced significant proliferation of non-diseased PAVSMC. Inhibitory anti-Activin A antibody reduced PAH PAVSMC growth without affecting canonical (Smads) or non-canonical (Akt, ERK1/2, p38 MAPK) effectors. Inhibitory anti-TGF-β antibody significantly reduced P-Smad3, P-ERK1/2 and proliferation of PAH PAVSMC, while anti-Gremlin 1 had no anti-proliferative effect. PDGF-BB diminished inhibitory effects of anti-Activin A and anti-TGF-β antibodies. None of the antibodies affected growth and proliferation of non-diseased PAVSMC induced by PAH PAVSMC-secreted factors. Together, these data demonstrate that human PAH PAVSMC have secretory, proliferative phenotype that could be targeted by anti-Activin A and anti-TGF-β antibodies; potential cross-talk with PDGF-BB should be considered while developing therapeutic interventions.

Programmable cells of monocytic origin as a source of osteochondroprogenitors: Effect of growth factors on osteogenic differentiation

We have demonstrated previously that peripheral blood monocytes can be converted in vitro to a multipotent stem cell-like cell termed programmable cell of monocytic origin (PCMO) and subsequently into cells with chondrocyte-like phenotype. Here, we investigated whether PCMO could also be differentiated into osteoblast-like cells using growth factors with known osteoinductive potency. Following stimulation with BMP-2, BMP-7, IGF-1 or TGF-β1 for 7 and 14 days, PCMOs were analyzed for mRNA expression of collagen types I and V, alkaline phosphatase, osteocalcin, runt-related transcription factor-2 (Runx2) and Osterix (Osx) by quantitative RT-PCR (qPCR) and the levels of collagen I in culture supernatants by ELISA. The expression of osteoblastic markers was evident, albeit at a different extent in cultures of PCMOs after treatment with the above-mentioned growth factors. Culture supernatants from PCMOs stimulated for 6-10 days with BMP-2, BMP-7, IGF-1 or TGF-β1 contained high levels of collagen type I, together with earlier data indicating synthesis and proper secretion. The findings suggest that PCMOs can transform into cells that are phenotypically similar to osteoblasts and identify these cells as osteochondroprogenitors. The possibility of differentiating PCMOs from peripheral blood in sizable quantities could be a novel way to obtain autologous bone-like substitutes without donor-site morbidity.

Peripheral Blood Monocytes as Adult Stem Cells: Molecular Characterization and Improvements in Culture Conditions to Enhance Stem Cell Features and Proliferative Potential

Adult stem or programmable cells hold great promise in diseases in which damaged or nonfunctional cells need to be replaced. We have recently demonstrated that peripheral blood monocytes can be differentiated in vitro into cells resembling specialized cell types like hepatocytes and pancreatic beta cells. During phenotypic conversion, the monocytes downregulate monocyte/macrophage differentiation markers, being indicative of partial dedifferentiation, and are partially reprogrammed to acquire a state of plasticity along with expression of various markers of pluripotency and resumption of mitosis. Upregulation of stem cell markers and mitotic activity in the cultures was shown to be controlled by autocrine production/secretion of activin A and transforming growth factor-beta (TGF-β). These reprogrammed monocyte derivatives were termed "programmable cells of monocytic origin" (PCMO). Current efforts focus on establishing culture conditions that increase both the plasticity and proliferation potential of PCMO in order to be able to generate large amounts of blood-derived cells suitable for both autologous and allogeneic therapies.