Human umbilical cord-derived mesenchymal stem cell transplantation improves the long COVID.

No effective treatments can ameliorate symptoms of long COVID patients. Our study assessed the safety and efficacy of human umbilical cord-derived mesenchymal stem cells (UC-MSCs) in the treatment of long COVID patients. Ten long COVID patients were enrolled and received intravenous infusions of UC-MSCs on Days 0, 7, and 14. Adverse events and clinical symptoms were recorded, and chest-high-resolution CT (HRCT) images and laboratory parameters were analyzed. During UC-MSCs treatment and follow-up, we did not observe serious adverse events, the symptoms of long COVID patients were significantly relieved in a short time, especially sleep difficulty, depression or anxiety, memory issues, and so forth, and the lung lesions were also repaired. The routine laboratory parameters did not exhibit any significant abnormalities following UC-MSCs transplantation (UMSCT). The proportion of regulatory T cells gradually increased, but it was not statistically significant until 12 months. The proportion of naive B cells was elevated, while memory B cells, class-switched B-cells, and nonswitched B-cells decreased at 1 month after infusion. Additionally, we observed a transient elevation in circulating interleukin (IL)-6 after UMSCT, while tumor necrosis factor (TNF)-α, IL-17A, and IL-10 showed no significant changes. The levels of circulating immunoglobulin (Ig) M increased significantly at month 2, while IgA increased significantly at month 6. Furthermore, the SARS-CoV-2 IgG levels remained consistently high in all patients at Month 6, and there was no significant decrease during the subsequent 12-month follow-up. UMSCT was safe and tolerable in long COVID patients. It showed potential in alleviating long COVID symptoms and improving interstitial lung lesions.

The therapeutic effect of anti-CD19 antibody on DHEA-induced PCOS mice.

Immune dysregulation has been summarized as a critical factor in the occurrence and development of Polycystic ovary syndrome (PCOS), but potential mediators and mechanisms remain unclear. Our previous study showed that CD19+ B cells were involved in the pathogenesis of dehydroepiandrosterone (DHEA)-induced PCOS mice. Here, we studied the therapeutic potential of anti-CD19 antibody (aCD19 Ab) on DHEA-induced PCOS mice. The results showed that aCD19 Ab treatment improved ovarian pathological structure and function of PCOS mice, manifested by an increased number of corpus luteum, a decreased number of cystic follicles and atretic follicles, and regular estrus cycles. The aCD19 Ab treatment reduced the proportion of splenic CD21+ CD23low marginal zone B cells as well as the level of serum IgM and decreased the percentage of peripheral blood and splenic neutrophils. In particular, aCD19 Ab treatment reduced the apoptosis of granulosa cells and macrophage infiltration in ovarian secondary follicles of PCOS mice, as well as the expression of TNF-α in ovarian tissue and serum TNF-α levels. Moreover, we confirmed that TNF-α induced the apoptosis of human ovarian granulosa tumor cell line cells in vitro. Thus, our work demonstrates that aCD19 Ab treatment improves ovarian pathological phenotype and function by reducing local and systemic inflammation in PCOS mice, which may provide a novel insight into PCOS therapy.

Human umbilical cord mesenchymal stem cells for psoriasis: a phase 1/2a, single-arm study.

Psoriasis is a common, chronic immune-mediated systemic disease that had no effective and durable treatment. Mesenchymal stem cells (MSCs) have immunomodulatory properties. Therefore, we performed a phase 1/2a, single-arm clinical trial to evaluate the safety and efficacy of human umbilical cord-derived MSCs (UMSCs) in the treatment of psoriasis and to preliminarily explore the possible mechanisms. Seventeen patients with psoriasis were enrolled and received UMSC infusions. Adverse events, laboratory parameters, PASI, and PGA were analyzed. We did not observe obvious side effects during the treatment and 6-month follow-up. A total of 47.1% (8/17) of the psoriasis patients had at least 40% improvement in the PASI score, and 17.6% (3/17) had no sign of disease or minimal disease based on the PGA score. And the efficiency was 25% (2/8) for males and 66.7% (6/9) for females. After UMSC transplantation (UMSCT), the frequencies of Tregs and CD4+ memory T cells were significantly increased, and the frequencies of T helper (Th) 17 and CD4+ naive T cells were significantly decreased in peripheral blood (PB) of psoriasis patients. And all responders showed significant increases in Tregs and CD4+ memory T cells, and significant decreases in Th17 cells and serum IL-17 level after UMSCT. And baseline level of Tregs in responders were significantly lower than those in nonresponders. In conclusion, allogeneic UMSCT is safe and partially effective in psoriasis patients, and level of Tregs may be used as a potent biomarker to predict the clinical efficacy of UMSCT. Trial registration Clinical Trials NCT03765957.

Metformin abrogates pathological TNF-α-producing B cells through mTOR-dependent metabolic reprogramming in polycystic ovary syndrome.

B cells contribute to the pathogenesis of polycystic ovary syndrome (PCOS). Clinically, metformin is used to treat PCOS, but it is unclear whether metformin exerts its therapeutic effect by regulating B cells. Here, we showed that the expression level of tumor necrosis factor-alpha (TNF-α) in peripheral blood B cells from PCOS patients was increased. Metformin used in vitro and in vivo was able to reduce the production of TNF-α in B cells from PCOS patients. Administration of metformin improved mouse PCOS phenotypes induced by dehydroepiandrosterone (DHEA) and also inhibited TNF-α expression in splenic B cells. Furthermore, metformin induced metabolic reprogramming of B cells in PCOS patients, including the alteration in mitochondrial morphology, the decrease in mitochondrial membrane potential, Reactive Oxygen Species (ROS) production and glucose uptake. In DHEA-induced mouse PCOS model, metformin altered metabolic intermediates in splenic B cells. Moreover, the inhibition of TNF-α expression and metabolic reprogramming in B cells of PCOS patients and mouse model by metformin were associated with decreased mTOR phosphorylation. Together, TNF-α-producing B cells are involved in the pathogenesis of PCOS, and metformin inhibits mTOR phosphorylation and affects metabolic reprogramming, thereby inhibiting TNF-α expression in B cells, which may be a new mechanism of metformin in the treatment of PCOS.

SPARC promotes insulin secretion through down-regulation of RGS4 protein in pancreatic ß cells.

SPARC-deficient mice have been shown to exhibit impaired glucose tolerance and insulin secretion, but the underlying mechanism remains unknown. Here, we showed that SPARC enhanced the promoting effect of Muscarinic receptor agonist oxotremorine-M on insulin secretion in cultured mouse islets. Overexpression of SPARC down-regulated RGS4, a negative regulator of ß-cell M3 muscarinic receptors. Conversely, knockdown of SPARC up-regulated RGS4 in Min6 cells. RGS4 was up-regulated in islets from sparc -/- mice, which correlated with decreased glucose-stimulated insulin secretion (GSIS). Furthermore, inhibition of RGS4 restored GSIS in the islets from sparc -/- mice, and knockdown of RGS4 partially decreased the promoting effect of SPARC on oxotremorine-M-stimulated insulin secretion. Phosphoinositide 3-kinase (PI3K) inhibitor LY-294002 abolished SPARC-induced down-regulation of RGS4. Taken together, our data revealed that SPARC promoted GSIS by inhibiting RGS4 in pancreatic ß cells.

Suicide Gene Therapy Against Malignant Gliomas by the Local Delivery of Genetically Engineered Umbilical Cord Mesenchymal Stem Cells as Cellular Vehicles.

BACKGROUND: Glioblastoma (GBM) is a malignant tumor that is difficult to eliminate, and new therapies are thus strongly desired. Mesenchymal stem cells (MSCs) have the ability to locate to injured tissues, inflammation sites and tumors and are thus good candidates for carrying antitumor genes for the treatment of tumors. Treating GBM with MSCs that have been transduced with the herpes simplex virus thymidine kinase (HSV-TK) gene has brought significant advances because MSCs can exert a bystander effect on tumor cells upon treatment with the prodrug ganciclovir (GCV). OBJECTIVE: In this study, we aimed to determine whether HSV-TK-expressing umbilical cord mesenchymal stem cells (MSCTKs) together with prodrug GCV treatment could exert a bystander killing effect on GBM. METHODS AND RESULTS: Compared with MSCTK: U87 ratio at 1:10,1:100 and 1:100, GCV concentration at 2.5µM or 250µM, when MSCTKs were cocultured with U87 cells at a ratio of 1:1, 25 µM GCV exerted a more stable killing effect. Higher amounts of MSCTKs cocultured with U87 cells were correlated with a better bystander effect exerted by the MSCTK/GCV system. We built U87-driven subcutaneous tumor models and brain intracranial tumor models to evaluate the efficiency of the MSCTK/GCV system on subcutaneous and intracranial tumors and found that MSCTK/GCV was effective in both models. The ratio of MSCTKs and tumor cells played a critical role in this therapeutic effect, with a higher MSCTK/U87 ratio exerting a better effect. CONCLUSION: This research suggested that the MSCTK/GCV system exerts a strong bystander effect on GBM tumor cells, and this system may be a promising assistant method for GBM postoperative therapy.

[Optimization of chromosome flaking technique for mesenchymal stem cells].

OBJECTIVE: To optimize the condition for chromosome flaking of mesenchymal stem cells to ensure the cytogenetic quality control of expanding production and clinical application. METHODS: Chromosomal flaking methods were optimized from current chromosome preparation techniques from the aspects of MSCs cell culture concentration, colchicine treatment time and low permeability time. RESULTS: By repeated pre-experiments, the optimal MSCS chromosome flaking condition of MSCs was determined as cell culture concentration of (1-2)× 106 cells per T25 cell culture bottle, and the colchicines processing time was determined as 2 hours and 10 minutes, and the low permeability was 1 hour. CONCLUSION: The optimized chromosome flaking condition can fulfill the requirement of cytogenetic quality control for MSCs.

Effects of human umbilical cord blood CD34+ cell transplantation in neonatal hypoxic-ischemia rat model.

Perinatal brain injury can cause death in the neonatal period and lifelong neurodevelopmental deficits. Stem cell transplantation had been proved to be effective approach to ameliorate neurological deficits after brain damage. In this study we examine the effect of human umbilical cord blood CD34+ cells on model of neonatal rat hypoxic-ischemic brain damage and compared the neuroprotection of transplantation of CD34+ cells to mononuclear cells from which CD34+ cells isolated on neonatal hypoxic-ischemia rat model. Seven-day-old Sprague-Dawley rats were subjected to hypoxic-ischemic (HI) injury, CD34+ cells (1.5 × 104 cells) or mononuclear cells (1.0 × 106 cells) were transplanted into mice by tail vein on the 7 day after HI. The transplantation of CD34+ cells significantly improved motor function of rat, and reduced cerebral atrophy, inhibited the expression of glial fibrillary acidic protein (GFAP) and apoptosis-related genes: TNF-α, TNFR1, TNFR2, CD40, Fas, and decreased the activation of Nuclear factor kappa B (NF-κB) in damaged brain. CD34+ cells treatment increased the expression of DCX and lectin in ipsilateral brain. Moreover, the transplantation of CD34+ cells and MNCs which were obtained from the same amount of human umbilical cord blood had similar effects on HI. Our data demonstrated that transplantation of human umbilical cord blood CD34+ cells can ameliorate the neural functional defect and reduce apoptosis and promote nerve and vascular regeneration in rat brain after HI injury and the effects of transplantation of CD34+ cells were comparable to that of MNCs in neonatal hypoxic-ischemia rat model.

[Therapeutic potential of BMSCs for premature ovarian failure in mice].

OBJECTIVE: To explore the therapeutic effects of bone marrow-derived mesenchymal stem cells (BMSCs) on premature ovarian failure (POF) in mice induced by cyclophosphamide (CTX) and the possible mechanisms.
 Methods: Mouse BMSCs were identified through detection of cell surface markers by flow cytometry. The model of mouse POF was induced by intraperitoneal injection of CTX at a dose of 50 mg/kg, once daily for 15 days. BMSCs were transplanted into POF mice at 2×106 cells/mouse by tail veil. The ovarian tissues were collected for HE staining at 7 days after transplantation to observe the changes of ovarian structure and real-time PCR was performed to detect the folliculogenesis gene expression.
 Results: BMSCs showed positive expression of CD29 and CD90 while low expression for endothelial and hematopoietic cell markers CD31 and CD34. The numbers of primodial follicle, primary follicle, secondary follicle and antral follicle were significantly decreased, but the numbers of atretic follicle were significantly increased in CTX induced-POF mice (P<0.05). BMSCs transplantation effectively repaired the structure of damaged ovary. The significant reduction of atretic follicle and significant increase of antral follicle and secondary follicle were observed in ovaries of BMSCs-treated mouse(P<0.05). BMSCs-transplanted mouse ovaries showed the increased mRNA expression levels of Nano3, Nobox, and Lhx8 (P<0.05).
 Conclusion: BMSCs could effectively repair ovarian structure and promote follicle development in CTX-induced POF mouse.

Lipopolysaccharide preconditioning increased the level of regulatory B cells in the spleen after acute ischaemia/reperfusion in mice.

BACKGROUND: The inflammatory reaction of the spleen is an important component in the pathophysiology of cerebral ischaemia (CI). Regulatory B cells (Bregs) derived from the spleen can inhibit the expansion of inflammation and reduce the damage caused by CI. AIM: The aim of the present study was to explore changes in spleen function and Bregs production due to lipopolysaccharide preconditioning (LPS PC) in ischaemia/reperfusion (I/R) and to uncover potential protective effect of LPS PC on stroke. METHODS: Focal cerebral I/R mice were induced by middle cerebral artery occlusion (MCAO). Infarct size and inflammatory cell infiltration in brain tissue, athletic ability, and immune status were analysed by immunostaining, behavioural analyses, and flow cytometry, respectively. RESULTS: The volume of the cerebral infarct was significantly decreased in I/R mice with LPS PC (LPS + I/R) compared to I/R mice, and neuronal apoptosis was ameliorated by LPS PC. After preconditioning with LPS, locomotor activity, forelimb strength, motor endurance, motor coordination, and short-term memory were improved to varying degrees. Moreover, blood-brain barrier (BBB) dysfunction was reversed, and CD11b+, major histocompatibility complex-II positive (MHC-II+), and Gr-1+ cell infiltration in the brains of LPS + I/R mice was also significantly reduced. B cell-activating factor (BAFF), tumour necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1ß), and IL-6 in the brain and spleen in the LPS + I/R group decreased to different degrees, while the levels of transforming growth factor-ß (TGF-ß) and IL-10 increased. LPS PC alleviated atrophy of the spleen following I/R. In addition, the number of CD8+ T cells, macrophages, TNF+ cells, NF-κB+ cells, and neutrophils in the spleen was reduced, while the number of proliferating cells and CD19+-IL10+ Bregs was significantly increased. The number of follicular B (FO B) cells and marginal zone B (MZ B) cells in the spleens of LPS + I/R mice was also increased. CONCLUSIONS: I/R mice preconditioned with LPS showed significantly reduced pathological damage, motor dysfunction, cognitive dysfunction, and inflammatory responses. LPS PC may initiate anti-inflammatory protective mechanism in the spleen after stroke, may increase the number of anti-inflammatory cells, such as Bregs, in the spleen, and may play a protective role in stroke.

[Angiogenic ability of 3 different tissues-derived mesenchymal stem cells on endothelial progenitor cells].

OBJECTIVE: To compare the ability between bone marrow-derived mesenchymal stem cells (MSCs) (BM-MSCs) and adipose-derived MSCs (AD-MSCs) or umbilical cord-derived MSCs (UC-MSCs) on promotion of vessels formation and vessels stabilization relevant to the functions of EPCs.
 Methods: In vitro, co-culture blood vessel test was performed to compare the angiogenic ability between BM-MSCs, AD-MSCs or UC-MSCs. In vivo, angiogenic assay dependent on basement membrane matrix Matrigel and immunohistochemistry were performed to compare the ability of vessels formation functions between BM-MSCs and AD-MSCs or UC-MSCs.
 Results: The lengths and dots of vascular structures formed by EPCs on AD-MSCs layer are greater than those by EPCs on BM-MSCs layer and UC-MSCs layer in angiogenic assay in vitro. The stability of the capillary-like structures formed by EPCs with AD-MSCs on Matrigel was more stable than that by the BM-MSCs, UC-MSCs or EPCs. AD-MSCs and EPCs could form abundant functional vessels with blood perfusion in Matrigelin vivo; UC-MSCs and EPCs could form a few functional vessels with blood perfusion in Matrigelin vivo; BM-MSCs and EPCs could form broken vessels with hemocytes leakage in Matrigel in vivo.
 Conclusion: AD-MSCs have the stronger ability to promote the angiogenesis and stabilize the vessels compared with BM-MSCs or UC-MSCs ex vivo and in vivo.

Decreased phosphorylation of PDGFR-ß impairs the angiogenic potential of expanded endothelial progenitor cells via the inhibition of PI3K/Akt signaling.

Human umbilical cord blood-derived endothelial progenitor cells (EPCs) have been proven to contribute to post-natal angiogenesis, and have been applied in various models of ischemia. However, to date, to the best of our knowledge, there is no available data on the angiogenic properties of EPCs during the process of in vitro expansion. In this study, we expanded EPCs to obtain cells at different passages, and analyzed their cellular properties and angiogenic ability. In the process of expansion, no changes were observed in cell cobblestone-like morphology, apoptotic rate and telomere length. However, the cell proliferative ability was significantly decreased. Additionally, the expression of CD144, CD90 and KDR was significantly downregulated in the later-passage cells. Vascular formation assay in vitro revealed that EPCs at passage 4 and 6 formed more integrated and organized capillary-like networks. In a murine model of hind limb ischemia, the transplantation of EPCs at passage 4 and 6 more effectively promoted perfusion recovery in the limbs on days 7 and 14, and promoted limb salvage and histological recovery. Furthermore, the phosphorylation levels of platelet­derived growth factor receptor-ß (PDGFR-ß) were found to be significantly decreased with the in vitro expansion process, accompanied by the decreased activation of the PI3K/Akt signaling pathway. When PDGFR inhibitor was used to treat the EPCs, the differences in the angiogenic potential and migratory ability among the EPCs at different passages were no longer observed; no significant differences were also observed in the levels of phosphorylated PI3K/Akt between the EPCs at different passages following treatment with the inhibitor. On the whole, our findings indicate that the levels of phosphorylated PDGFR-ß are decreased in EPCs with the in vitro expansion process, which impairs their angiogenic potential by inhibiting PI3K/Akt signaling. Our findings may aid in the more effective selection of EPCs of different passages for the clinical therapy of ischemic disease.

Spontaneous immortalization of mouse liver sinusoidal endothelial cells.

The spontaneous immortalization of cells in vitro is a rare event requiring genomic instability, such as alterations in chromosomes and mutations in genes. In the present study, we report a spontaneously immortalized liver sinusoidal endothelial cell (LSEC) line generated from mouse liver. These immortalized LSECs showed typical LSEC characteristics with the structure of transcellular fenestrations, the expression of von Willebrand factor (VWF) and the ability to uptake DiI-acetylated-low density lipoprotein (DiI-Ac-LDL). However, these immortalized LSECs lost the ability to form capillary-like structures, and showed clonal and multilayer growth without contact inhibition. Moreover, their proliferation rate increased with the increase in the number of passages. In addition, these cells obained the expression of CD31 and desmin, and showed an upregulation of p53 protein expression; however, their karyotype was normal, and they could not form colonies in soft agar or tumors in SCID mice. In conclusion, in the present study, we successfully established a spontaneously immortalized LSEC line.

SPARC deficiency affects bone marrow stromal function, resulting in impaired B lymphopoiesis.

It has been demonstrated that B cells were decreased in the BM of SPARC-null mice, accompanied by a lack of immune response to LPS. However, the effect of SPARC deficiency on B lymphopoiesis remains unclear. Herein, we investigated the role of SPARC in the regulation of B lymphopoiesis, as well as the underlying molecular mechanisms. In present study, we found that the size of B-lineage progenitors (pro-B and pre-B plus immature B cells) and primitive hematopoietic cells (LSK and LTC cells) were reduced, whereas multipotent progenitors (CFU-S12) were increased in BM of SPARC-null mice. When SPARC-null BM cells were transplanted into lethally irradiated WT mice, the B cell population in recipients was restored to a level equivalent to that generated by WT BM cells, suggesting that the changes of the BM microenvironment in SPARC-null mice affect B lymphopoiesis. Furthermore, we found that SPARC-null BMSCs did not support the differentiation of WT BM cells into the B cell population in vitro, and conditioned medium derived from SPARC-null BMSCs inhibited B cell differentiation. However, the addition of rmSPARC to the coculture system did not restore the impaired B lymphopoiesis. In summary, our findings suggest that SPARC plays a crucial role in the regulation of early B lymphopoiesis.

Co-transplantation of mesenchymal stromal cells and cord blood cells in treatment of diabetes.

BACKGROUND AIMS: Stem cells provide a promising source for treatment of type 1 diabetes, but the treatment strategy and mechanism remain unclear. The aims of this study were to investigate whether co-transplantation of umbilical cord-derived mesenchymal stromal cells (UC-MSCs) and cord blood mononuclear cells (CB-MNCs) could reverse hyperglycemia in type 1 diabetic mice and to determine the appropriate ratio for co-transplantation. The treatment mechanism was also studied. METHODS: A simple and efficient isolation method was developed to generate qualified UC-MSCs. UC-MSCs and CB-MNCs were then transplanted into type 1 diabetic mice at different ratios (UC-MSCs to CB-MNCs = 1:1, 1:4, 1:10) to observe the change in blood glucose concentration. Histology, immunohistochemistry, and human Alu polymerase chain reaction assay were performed to evaluate for the presence of donor-derived cells and the repair of endogenous islets. We also induced UC-MSCs into islet-like cells under specific culture conditions to determine their differentiate potential in vitro. RESULTS: Co-transplantation of UC-MSCs and CB-MNCs at a ratio of 1:4 effectively reversed hyperglycemia in diabetic mice. The detection of human Alu sequence indicated that the engraftment of donor-derived cells had homed into the recipient's pancreas and kidney. Although neither human insulin nor human nuclei antigen was detected in the regenerated pancreas, UC-MSCs could differentiate into insulin-secreted cells in vitro. CONCLUSIONS: Co-transplantation of UC-MSCs and CB-MNCs at a ratio of 1:4 could efficiently reverse hyperglycemia and repair pancreatic tissue.

SPARC fusion protein induces cellular adhesive signaling.

Secreted protein, acidic and rich in cysteine (SPARC) has been described as a counteradhesive matricellular protein with a diversity of biological functions associated with morphogenesis, remodeling, cellular migration, and proliferation. We have produced mouse SPARC with a FLAG-tag at the N-terminus of SPARC (Flag-SPARC, FSP) in a Bac-to-Bac baculoviral expression system. After affinity purification, this procedure yields SPARC of high purity, with an electrophoretic mobility of ∼44 kDa under reducing conditions, and ∼38-39 kDa under non-reducing conditions. Unexpectedly, FSP adsorbed to plastic supported cell attachment and spreading, in a calcium-dependent manner. The adhesive activity of native FSP was inhibited by prior incubation with anti-SPARC IgG. Cell adhesion to FSP induced the formation of filopodia and lamellipodia but not focal adhesions that were prominent on cells that were attached to fibronectin. In addition, FSP induced the tyrosine phosphorylation of FAK and paxillin in attached epithelial cells. Erk1/2 and Rac were also activated in cells attached to FSP, but at a lower level in comparison to cells on fibronectin. This study provides new insight into the biological functions of SPARC, a matricellular protein with important roles in cell-extracellualr matrix interactions.

SPARC promotes the development of erythroid progenitors.

Secreted protein acidic and rich in cysteine (SPARC) is a well-recognized regulator that affects cell proliferation, differentiation, and survival. Here, we investigated the impact of SPARC on erythropoiesis. Erythropoiesis in bone marrow (BM) from SPARC(-/-) mice was analyzed by flow cytometry and colony-forming assays. The mechanisms that affected erythropoiesis were investigated by BM transplantation experiments. CD34(+) cells from umbilical cord blood were isolated by MiniMACS, and the effect of SPARC on human erythropoiesis was assessed by colony-formation assay and erythroid differentiation culture. The hemoglobin level in peripheral blood (PB) was lower in SPARC(-/-) mice. Neither red blood cell count in PB nor the percentage of Ter119(+) erythrocytes in BM showed significant difference between SPARC(-/-) and WT mice. However, the ability of SPARC(-/-) bone marrow cells (BMCs) to form erythroid burst-forming units (BFU-E), as well as spleen colony-forming units (CFU-S8), was significantly decreased. The addition of exogenous SPARC could promote the formation of BFU-E from SPARC(-/-) BMCs in vitro. And the impaired ability of SPARC(-/-) BMCs to form BFU-E could be restored by transplanted into WT BM microenvironment, whereas the BFU-E formation of WT BMCs was impaired after transplanted into SPARC(-/-) recipients. Furthermore, exogenous SPARC promoted umbilical cord blood CD34(+) cells to form erythroid colonies and the hemoglobinization of erythroid, but did not affect the expression levels of glycophorin A and CD71. In conclusion, our results indicate that SPARC promotes the development of erythroid progenitors, but does not affect terminal erythroid differentiation.

Characterization and comparison of embryonic stem cell-derived KDR+ cells with endothelial cells.

Growing interest in utilizing endothelial cells (ECs) for therapeutic purposes has led to the exploration of human embryonic stem cells (hESCs) as a potential source for endothelial progenitors. In this study, ECs were induced from hESC lines and their biological characteristics were analyzed and compared with both cord blood endothelial progenitor cells (CBEPCs) and human umbilical vein endothelial cells (HUVECs) in vitro. The results showed that isolated embryonic KDR+ cells (EC-KDR+) display characteristics that were similar to CBEPCs and HUVECs. EC-KDR+, CBEPCs and HUVECs all expressed CD31 and CD144, incorporated DiI-Ac-LDL, bound UEA1 lectin, and were able to form tube-like structures on Matrigel. Compared with CBEPCs and HUVECs, the expression level of endothelial progenitor cell markers such as CD133 and KDR in EC-KDR+ was significantly higher, while the mature endothelial marker vWF was lowly expressed in EC-KDR+. In summary, the study showed that EC-KDR+ are primitive endothelial-like progenitors and might be a potential source for therapeutic vascular regeneration and tissue engineering.

Effects of an endothelial cell-conditioned medium on the hematopoietic and endothelial differentiation of embryonic stem cells.

We have examined the effect of mouse bone marrow endothelial cell-conditioned medium (mEC-CM) on hematopoietic and endothelial differentiation of mouse embryonic stem cells (mESCs). mEC-CM can efficiently promote the differentiation of mESCs into Flk(+) cells and hematopoietic colony-forming cells. mEC-CM proved to be as potent as a cytokine cocktail comprised of VEGF, bFGF, IGF and EGF. After inducing mESCs with mEC-CM, cobblestone-like cells were mechanically selected and identified which had the ability to incorporate DiI-Ac-LDL. DiI-Ac-LDL-positive cells were endothelial-like cells due to their expression of CD31 and Flk1, ability to bind to UEA1 and capacity to form capillary-like tube structures on matrigel. In conclusion, mEC-CM can efficiently promote the differentiation of mESCs into endothelial cells and hematopoietic colony-forming cells. The differentiated endothelial-like cells can be isolated by using DiI-Ac-LDL labeling and mechanical selection.