Duygu Uckan-Cetinkaya

Pericytes: Properties, Functions and Applications in Tissue Engineering

Mesenchymal stem cells (MSCs) are one of the most studied adult stem cells and in recent years. They have become attractive agents/cell source for cellular therapy and regenerative medicine applications. During investigations about their origin, researchers hypothesized that perivascular regions are the common anatomical regions where MSCs come from and perivascular cells like pericytes (PCs) (Rouget cells, mural cells) are in vivo counterparts of MSCs. Beside capillaries and microvessels as their most common locations, PCs are also found in large vessels (arteries and veins). They can be isolated from several tissues and organs particularly from retina and brain. There are different approaches about their isolation, characterization and culture but there has been no common protocol yet because of the lack of defined PC-specific marker. They make special contact with endothelial cells in the basement membrane and have very important functions in several tissues and organs. They participate in vascular development, stabilization, maturation, and remodeling, blood pressure control, endothelial cell proliferation and differentiation, contractility of vascular smooth muscle cells, wound healing, vasculogenesis and angiogenesis, long-term maintenance of hematopoietic stem cells in bone marrow niche. Their multipotential differentiation capacity and participation in many events in the body make PCs preferred cells in tissue engineering applications including 3D blood–brain barrier models, skeletal muscle constructs, bone tissue engineering and tissue-engineered vascular grafts.

A novel mutation in a family with DNA ligase IV deficiency syndrome

DNA ligase IV deficiency syndrome (LIG4 syndrome) is a rare autosomal recessive disorder characterized by microcephaly, growth retardation, low birth weight, dysmorphic facial findings, immunodeficiency, pancytopenia, and radiosensitivity due to impaired repair of DNA double‐strand breaks by non‐homologous end‐joining. Herein, we report two siblings with LIG4 syndrome with a novel mutation. One of the siblings, who had normocellular marrow, had autologous reconstitution after initial non‐myeloablative conditioning and underwent successful second hematopoietic stem cell transplantation after conditioning with busulfan, cyclophosphamide, and anti‐thymocyte globulin. Our findings indicate that transplantation with myeloablative conditioning can be used successfully in LIG4 syndrome patients. Pediatr Blood Cancer 2009;53:482–484.

A New Chapter for Mesenchymal Stem Cells: Decellularized Extracellular Matrices

From orthopedic to neurological disorders, stem cells are used as platforms to understand disease mechanisms and considered as novel and promising treatment options, especially when the valid therapeutic approaches are unavailable or ineffective. There are different stem cell types in the literature, however the spindle-shaped, colony forming and multilineage-differentiating cells, also known as mesenchymal stem cells (MSC) are very popular, as MSC can be isolated from different tissues with minimal ethical concerns and without tumor formations, which make them easily accessible and widely used in vitro and in vivo studies. In the literature, MSC have been shown to have therapeutic effects and orchestrate the healing process via their mobilization, migration, differentiation capacities, immunomodulation properties and/or secretion of bioactive factors. Nowadays, MSC derived extracellular matrices (ECM), which are part of the secreted/produced bioactive molecules from MSC; draw attention of researchers due to their key roles in cell biology. Several groups have isolated ECM from in vitro cultured MSC using different methods of decellularization techniques for tissue-engineering approaches. According to current knowledge, decellularized ECM (dECM) influence growth, adhesion, differentiation, migration, apoptosis, proliferation, and phenotype of cells, covering almost all cellular events. In this comprehensive review we focused on MSC and the isolation methods and effects of MSC derived dECM (MSC-dECM).

Angiopoietins in the bone marrow microenvironment of acute lymphoblastic leukemia.

Objective: Angiogenesis have implications in leukemia biology. Angiopoietin 1 (Ang 1) is an angiogenic cytokine which is essential in survival and proliferation of endothelial cells. Angiopoietin 2 (Ang 2) promotes dissociation of pericytes and increases vascular permeability and stromal derived factor 1 alpha (SDF 1α) which is a key player in stem cell traffic in the bone marrow (BM), has stimulating effects on angiogenesis as well. Here, we investigated the role of the leukemic BM microenvironment and specifically, the role of SDF 1α-CXCR4 and Ang 1/Ang 2–Tie 2 axes. Methods: Here, Ang 1, Ang 2, and SDF 1α levels were measured in the BM plasma and in supernatants of mesenchymal stem/stromal cells (MSCs) of patients with ALL and compared with those of healthy controls. Results: The results showed that at diagnosis, BM plasma levels of Ang 1 and SDF 1α were significantly low and Ang 2 was high when compared to control values. Remission induction was associated with an increase in Ang 1/Ang 2 ratio and SDF levels in BM plasma. Discussion: The results suggest that BM microenvironment and leukemic cell–stroma interaction influences the secretion of Ang 1, 2 and SDF 1α, thus, may affect both angiogenesis, homing and mobilization of leukemic blasts.

Successful hematopoietic stem cell transplantation in a child with congenital erythropoietic porphyria due to a mutation in GATA-1.

To the editor, Congenital erythropoietic porphyria (CEP) is a rare genetic disease that is characterized by a severe cutaneous photosensitivity causing unrecoverable deformities, chronic hemolytic anemia requiring blood transfusion program, and fatal systemic complications (1). Most cases are autosomal recessive and caused by mutations in UROS gene (2). GATA-1, which is well known for its role in transient myeloproliferative disease and acute megakaryoblastic leukemia associated with Down syndrome, is also a regulator of UROS gene (3). CEP caused by mutation in GATA-1 gene is inherited in an X-linked manner (3). Pierro et al. have described two patients suffering from CEP due to a mutation in GATA-1 gene (4). Here, we describe the hematopoietic stem cell transplantation (HSCT) course in the five-yr-old Turkish boy mentioned in that manuscript who was transplanted from his HLA identical healthy brother. Informed consent was taken from the family before HSCT. Pretransplant physical examination revealed multiple scars on his face and hands, mild hypertrichosis, brown discoloration of the teeth, and splenomegaly (Fig. 1a,b). His hemoglobin was 8.5 g/dL, leukocyte count 6100/mm3, platelet count 61 000/mm3, and ferritin 101 ng/dL. Conditioning regimen consisted of iv busulphan (Bu) 3.2 mg/kg/day for four days and cyclophosphamide (Cy) 50 mg/kg/day for four days. Cyclosporin A (CsA) and short-term methotrexate were administered for graft-versus-host disease (GvHD) prophylaxis. Low molecular weight heparin and ursodeoxycholic acid were administered for the prophylaxis of veno-occlusive disease. He received 5.6 9 10/kg nucleated bone marrow cells and 7.0 9 10/kg CD34 (+) stem cells. On day 0, he developed febrile neutropenia and was treated with empirical antibiotics of piperacillin/tazobactam and amikacin. On day +3, he developed watery diarrhea of 500 cc/day with occult blood positivity on stool. On day +6, the diarrhea persisted and methylprednisolone treatment at a dosage of 2 mg/kg/day was started for possible hyperacute gastrointestinal GvHD. Later on, the analysis of stool showed positivity for rotavirus antigen and he was also treated with oral immunoglobulin. On day +17, the diarrhea resolved and methylprednisolone was slowly tapered. Neutrophil engraftment was achieved on day +21. On day +31, watery and bloody diarrhea started again. Colonoscopic examination was compatible with pancolitis and histopathology revealed acute GvHD. The serology and PCR of Epstein–Barr virus (EBV) and cytomegalovirus (CMV) were all negative in blood and biopsy samples. He was treated with methylprednisolone, octreotide, and budesonide. On day +37, mesenchymal stem cells (1 9 10/ kg) were administered intravenously. Platelet engraftment was achieved on day +38 and diarrhea resolved on day +42. He had a generalized tonic clonic seizure and hallucinations on day +58. Cranial MRI was compatible with posterior reversible encephalopathy syndrome (PRES). Plasma level of CsA at onset of PRES was in therapeutical range. His blood pressure was mildly elevated. He had neither metabolic disturbances nor electrolyte imbalance at onset of PRES. He did not show any sign of infections or autoimmune diseases. After ruling out other causes, PRES was attributed to CsA toxicity. Seizures were treated with phenytoin and levetiracetam, and blood pressure was also regulated. CsA was discontinued and replaced with tacrolimus and mycophenolate mofetil (MMF) after PRES. Hallucinations and seizures resolved within one wk. He was discharged from hospital on day +79. Methylprednisolone was discontinued

Hematopoietic Stem Cell Transplantation in Pediatric Diseases

Since the first successful hematopoietic stem cell transplantation (HSCT) in 1968, HSCT is currently a well-accepted treatment option for not only hematological diseases but also for immunodeficiency syndromes, solid tumors, and metabolic, rheumatological, and neurological disorders. Stem cell therapies are mainly classified as hematopoietic and mesenchymal stem cell therapies. Similar to adults, the main field of hematopoietic stem cell therapy in pediatric age group is hematopoietic stem cell transplantation (HSCT). The conditioning and the graft-versus-host disease (GVHD) prophylactic regimens have improved in the recent years associated with advancement in understanding of transplant biology; and these regimens are increasingly being tailored according to underlying disease, donor type, and stem cell source. The improvements in the supportive care of these patients including those for infectious complications and sinusoidal obstruction syndromes (SOS) have decreased the related morbidities and mortalities. Furthermore, our knowledge about the regenerative potential of hematopoietic stem cells is expanding.