Acellular human heart matrix: A critical step toward whole heart grafts.

The best definitive treatment option for end-stage heart failure currently is transplantation, which is limited by donor availability and immunorejection. Generating an autologous bioartificial heart could overcome these limitations. Here, we have decellularized a human heart, preserving its 3-dimensional architecture and vascularity, and recellularized the decellularized extracellular matrix (dECM). We decellularized 39 human hearts with sodium-dodecyl-sulfate for 4-8 days. Cell removal and architectural integrity were determined anatomically, functionally, and histologically. To assess cytocompatibility, we cultured human cardiac-progenitor cells (hCPC), bone-marrow mesenchymal cells (hMSCs), human endothelial cells (HUVECs), and H9c1 and HL-1 cardiomyocytes in vitro on dECM ventricles up to 21 days. Cell survival, gene expression, organization and/or electrical coupling were analyzed and compared to conventional 2-dimensional cultures. Decellularization removed cells but preserved the 3-dimensional cardiac macro and microstructure and the native vascular network in a perfusable state. Cell survival was observed on dECM for 21 days. hCPCs and hMSCs expressed cardiocyte genes but did not adopt cardiocyte morphology or organization; HUVECs formed a lining of endocardium and vasculature; differentiated cardiomyocytes organized into nascent muscle bundles and displayed mature calcium dynamics and electrical coupling in recellularized dECM. In summary, decellularization of human hearts provides a biocompatible scaffold that retains 3-dimensional architecture and vascularity and that can be recellularized with parenchymal and vascular cells. dECM promotes cardiocyte gene expression in stem cells and organizes existing cardiomyocytes into nascent muscle showing electrical coupling. These findings represent a first step toward manufacturing human heart grafts or matrix components for treating cardiovascular disease.

Localization of discoidin domain receptors in rat kidney.

BACKGROUND/AIM: The discoidin domain receptors (DDRs) DDR1 and DDR2 are cardinal members of a receptor tyrosine kinase subfamily, activated by collagens. They are candidate effectors in tissue injury and fibrosis. We investigated the DDR expression in normal and remnant rat kidneys. METHODS: The DDR expression in kidney and other tissues was examined by indirect immunofluorescence, immunoblotting, and ribonuclease protection assays. The expression patterns in remnant and control kidneys were compared at 2-, 4-, and 8-week time points, following induction of injury. RESULTS: DDR1 is expressed in basolateral membranes of select nephron segments, from the connecting tubule to the renal papilla. DDR2 is expressed in apical membranes of select nephron segments, from the loop of Henle to the macula densa. The DDR1 protein expression is upregulated within the glomeruli of remnant kidneys. The distribution of DDR2 in remnant kidneys is similar to that in controls. The DDR mRNA levels in remnant and control kidneys were not significantly different, at any time point. CONCLUSIONS: The DDR1 localization in the rat kidney is consistent with roles in cell-matrix interactions. Upregulation within glomeruli of remnant kidneys suggests the possibility of additional roles in kidney injury. The DDR2 localization in adult rat kidneys is inconsistent with roles in cell-matrix interactions.

Deletion mapping in Alport syndrome and Alport syndrome-diffuse leiomyomatosis reveals potential mechanisms of visceral smooth muscle overgrowth.

Diffuse leiomyomatosis is associated with the inherited kidney disease Alport syndrome, and characterized by visceral smooth muscle overgrowth within the respiratory, gastrointestinal and female reproductive tracts. Although partial deletions of the type IV collagen genes COL4A5 and COL4A6, paired head-to-head on chromosome Xq22, are known to cause diffuse leiomyomatosis, loss of function for type IV collagen does not explain smooth muscle overgrowth. To further clarify pathogenic mechanisms, we have characterized novel deletions in patients with Alport syndrome-diffuse leiomyomatosis or Alport syndrome alone. A 27.6-kb deletion, in a female with Alport syndrome-diffuse leiomyomatosis, is marked by the most proximal, i.e. most 5', COL4A5 breakpoint described to date. By comparing this deletion to others described here and previously, we have defined a minimal overlap region, only 4.2 kb in length and containing the COL4A5-COL4A6 proximal promoters, loss of which contributes to smooth muscle overgrowth. A novel deletion in a male with Alport syndrome alone is>1.4 Mb in length, encompassing COL4A5 and COL4A6 entirely, as well as neighboring genes. We postulate that loss of the 4.2-kb region in diffuse leiomyomatosis causes misregulation of neighboring genes, contributing to smooth muscle overgrowth. Deletion of the neighboring genes themselves may afford protection from this condition.