Preventing germinal matrix layer rupture and intraventricular hemorrhage

Research Advances of Germinal Matrix Hemorrhage: An Update Review

Germinal matrix hemorrhage (GMH) refers to bleeding that derives from the subependymal (or periventricular) germinal region of the premature brain. GMH can induce severe and irreversible damage attributing to the vulnerable structure of germinal matrix and deleterious circumstances. Molecular mechanisms remain obscure so far. In this review, we summarized the newest preclinical discoveries recent years about GMH to distill a deeper understanding of the neuropathology, and then discuss the potential diagnostic or therapeutic targets among these pathways. GMH studies mostly in recent 5 years were sorted out and the authors generalized the newest discoveries and ideas into four parts of this essay. Intrinsic fragile structure of preterm germinal matrix is the fundamental cause leading to GMH. Many molecules have been found effective in the pathophysiological courses. Some of these molecules like minocycline are suggested active to reduce the damage in animal GMH model. However, researchers are still trying to find efficient diagnostic methods and remedies that are available in preterm infants to rehabilitate or cure the sequent injury. Merits have been obtained in the last several years on molecular pathways of GMH, but more work is required to further unravel the whole pathophysiology.

A clinical scoring system to predict the development of intraventricular hemorrhage (IVH) in premature infants

OBJECTıVE: The aim of this study is to develop a scoring system for the prediction of intraventricular hemorrhage (IVH) in preterm infants in the first 7 days of life.

METHODS

A prospective, clinical study was conducted in Bahcesehir University, Medical Park Goztepe Hospital Neonatal Intensive Care Unit, with the enrollment of 144 preterm infants with gestational age between 24 and 34 weeks. All preterms were followed up for IVH after birth until the 4th week of life. The demographic characteristics and clinical risk factors were noted. Risk factors were analyzed. The score was established after logistic regression analysis, considering the impact of each variable on the occurrence of IVH within the first 7 days of life. The IVH scores were further applied prospectively to 89 preterm infants as validation cohort.

RESULTS

Low gestational age (GA), low Apgar score, and having bleeding diathesis were the most important risk factors for IVH. According to these risk factors, a scoring system was developed for IVH ranged from 0 to 5. According to the risk ratios (RR) obtained from the logistic regression model, low GA (≤ 28 gestational week), presence of bleeding diathesis within 7 days, and low Apgar score increased the risk of IVH (RR = 3.32 for GA ≤ 28 gestational week, RR = 6.7 for presence of bleeding diathesis in 7th day, RR = 3 for having low Apgar score). The score was validated successfully in 89 infants. The area under ROC curve was 0.85 for derivation cohort and 0.807 for validation cohort. The predictive ability of the IVH score for derivation and validation cohort was calculated. The negative predictive values of a score less than 4 were 96.4 and 59.1%. CONCLUSıON: Concerning IVH-related sequelae which continue to be a major public health problem, we have developed a feasible predictive model for evaluating the risk for developing IVH for preterm infants in the first 7 days of life.

Physiologic and pathophysiologic roles of interaction between C-type lectin-like receptor 2 and podoplanin: partners from in utero to adulthood

A platelet activation receptor, C-type lectin-like receptor 2 (CLEC-2), has been identified as a receptor for a platelet-activating snake venom, rhodocytin. CLEC-2 protein is highly expressed in platelets/megakaryocytes, and at lower levels in liver Kupffer cells. Recently, podoplanin has been revealed as an endogenous ligand for CLEC-2. Podoplanin is expressed in certain types of tumor cells, fibroblastic reticular cells (FRCs) in lymph nodes, kidney podocytes, and lymphatic endothelial cells, but not in vascular endothelial cells. CLEC-2 in platelets cannot have access to podoplanin under normal conditions, but they interact with each other under pathologic conditions or during developmental stages, and play various pathophysiologic roles. CLEC-2 facilitates hematogenous metastasis of podoplanin-expressing tumors. During development, the interaction between CLEC-2 and podoplanin in lymphatic endothelial cells or neuroepithelial cells facilitates blood-lymphatic vessel separation and cerebrovascular patterning and integrity, respectively. In adulthood, platelet CLEC-2 binding to FRCs is crucial for maintenance of the integrity of high endothelial venules in lymph nodes. Podoplanin-expressing FRC-like cells have recently been identified in the bone marrow, and facilitate megakaryocyte proliferation and proplatelet formation by binding to megakaryocyte CLEC-2. Podoplanin is inducibly expressed in liver monocytes and keratinocytes during Salmonella infection and wound healing, and regulates thrombus formation in the liver and controlled wound healing, respectively. By binding to unknown ligands, platelet CLEC-2 regulates the maintenance of vascular integrity during inflammation, thrombus stability under flow, and maintenance of quiescence of hematopoietic stem cells. Podoplanin is expressed in various cells, and additional roles of the CLEC-2-podoplanin interaction will be revealed in the future.

Podoplanin and CLEC-2 drive cerebrovascular patterning and integrity during development

Mice with a constitutive or platelet-specific deletion of the C-type-lectin-like receptor (CLEC-2) exhibit hemorrhaging in the brain at mid-gestation. We sought to investigate the basis of this defect, hypothesizing that it is mediated by the loss of CLEC-2 activation by its endogenous ligand, podoplanin, which is expressed on the developing neural tube. To induce deletion of podoplanin at the 2-cell stage, we generated a podoplanin(fl/fl) mouse crossed to a PGK-Cre mouse. Using 3-dimensional light-sheet microscopy, we observed cerebral vessels were tortuous and aberrantly patterned at embryonic (E) day 10.5 in podoplanin- and CLEC-2-deficient mice, preceding the formation of large hemorrhages throughout the fore-, mid-, and hindbrain by E11.5. Immunofluorescence and electron microscopy revealed defective pericyte recruitment and misconnections between the endothelium of developing blood vessels and surrounding pericytes and neuro-epithelial cells. Nestin-Cre-driven deletion of podoplanin on neural progenitors also caused widespread cerebral hemorrhaging. Hemorrhaging was also seen in the ventricles of embryos deficient in the platelet integrin subunit glycoprotein IIb or in embryos in which platelet α-granule and dense granule secretion is abolished. We propose a novel role for podoplanin on the neuro-epithelium, which interacts with CLEC-2 on platelets, mediating platelet adhesion, aggregation, and secretion to guide the maturation and integrity of the developing vasculature and prevent hemorrhage.