No abstract

. Tubular cell-enriched subpopulation of primary renal cells improves survival and augments kidney function in rodent model of chronic kidney disease. Am J Physiol Renal Physiol 299: F1026 -F1039, 2010. First published September 8, 2010 doi:10.1152/ajprenal.00221.2010.-Established chronic kidney disease (CKD) may be identified by severely impaired renal filtration that ultimately leads to the need for dialysis or kidney transplant. Dialysis addresses only some of the sequelae of CKD, and a significant gap persists between patients needing transplant and available organs, providing impetus for development of new CKD treatment modalities. Some postulate that CKD develops from a progressive imbalance between tissue damage and the kidney's intrinsic repair and regeneration processes. In this study we evaluated the effect of kidney cells, delivered orthotopically by intraparenchymal injection to rodents 4 -7 wk after CKD was established by two-step 5/6 renal mass reduction (NX), on the regeneration of kidney function and architecture as assessed by physiological, tissue, and molecular markers. A proof of concept for the model, cell delivery, and systemic effect was demonstrated with a heterogeneous population of renal cells (UNFX) that contained cells from all major compartments of the kidney. Tubular cells are known contributors to kidney regeneration in situ following acute injury. Initially tested as a control, a tubular cellenriched subpopulation of UNFX (B2) surprisingly outperformed UNFX. Two independent studies (3 and 6 mo in duration) with B2 confirmed that B2 significantly extended survival and improved renal filtration (serum creatinine and blood urea nitrogen). The specificity of B2 effects was verified by direct comparison to cell-free vehicle controls and an equivalent dose of non-B2 cells. Quantitative histological evaluation of kidneys at 6 mo after treatment confirmed that B2 treatment reduced severity of kidney tissue pathology. Treatmentassociated reduction of transforming growth factor (TGF)-␤1, plasminogen activator inhibitor (PAI)-1, and fibronectin (FN) provided evidence that B2 cells attenuated canonical pathways of profibrotic extracellular matrix production. regeneration; stabilization CHRONIC KIDNEY DISEASE (CKD) affects more than 19 million people in the U.S. and frequently develops as a consequence of chronic obesity, diabetes, and/or hypertension (42). Patients in stage 4 -5 CKD receive dialysis and a complex drug regimen, and the number of kidneys available for transplant is vastly insufficient to meet the need (30). New treatments that delay or reduce dialysis dependence are needed to fill this void.Kidney tissue is composed of Ͼ20 specialized cell types structurally organized into morphologically and functionally distinct compartments that act in concert to filter blood, produce urine, and regulate endocrine function and acid-base and electrolyte balance. Cell-cell interactions are critical to kidney function and are at least partially dependent on spatial and architectural relations...

Heart valve replacements fabricated from glutaraldehyde (Glut)-crosslinked heterograft materials, porcine aortic valves or bovine pericardium, have been widely used in cardiac surgery to treat heart valve disease. However, these bioprosthetic heart valves often fail in long-term clinical implants due to pathologic calcification of the bioprosthetic leaflets, and for stentless porcine aortic valve bioprostheses, bioprosthetic aortic wall calcification also typically occurs. Previous use of the epoxide-based crosslinker, Triglycidyl amine (TGA), on cardiac bioprosthetic valve materials demonstrated superior biocompatibility, mechanics, and calcification resistance for porcine aortic valve cusps (but not porcine aortic wall) and bovine pericardium, versus Glut-prepared controls. However, TGA preparation did not completely prevent long-term calcification of cusps or pericardium. Herein we report further mechanistic investigations of an added therapeutic component to this system, 2-Mercaptoethylidene-1,1-bisphosphonic acid (MABP), a custom synthesized thiol bisphosphonate, which has previously been shown in a preliminary report to prevent bioprosthetic heterograft biomaterial calcification when used in combination with initial TGA crosslinking for 7 days. In the present studies we have further investigated the effectiveness of MABP in experiments that examined: 1) The use of MABP after optimal TGA crosslinking, in order to avoid any competitive interference of MABP-reactions with TGA during crosslinking; 2) Furthermore, recognizing the importance of alkaline phosphatase in the formation of dystrophic calcific nodules, we have investigated the hypothesis that the mechanism by which MABP primarily functions is through the reduction of alkaline phosphatase activity. Results from cell-free model systems, cell culture studies, and rat subcutaneous implants, show that materials functionalized with MABP after TGA crosslinking have reduced alkaline phosphatase activity, and in vivo have no significant calcification in long term implant studies. It is concluded that bioprosthetic heart valves prepared in this fashion are compelling alternatives for Glut-prepared bioprostheses.

Soft tissues such as blood vessel, lung, ureter, skin, etc., possess mechanical behavior characterized by a "J"-shaped curve on a stress-strain diagram with a low-stiffness highly elastic zone giving rise to a high-stiffness zone. This mechanical behavior may be adaptive and protective against aneurysm formation in tissues whose primary loading is pressure-based. "J"-shaped behavior arises from the synergistic interplay of two main structural proteins: collagen and elastin. An innovative electrospinning technique has been utilized to form tubular scaffold composites with structural features reminiscent of the corrugated laminae seen in blood vessels. In doing so, tubular scaffolds have been fabricated with complex "J"-shaped behavior through the use of elastic polyurethane and reinforcing poly-glycolic acid (PGA) woven mesh. In these studies, corrugated laminae were formed on the 175 μm and 1.5 mm scale. Initial moduli were 0.5±0.17 MPa (mean±standard deviation) giving rise to stiffer moduli of 36.09±6.72 MPa at a strain of 1.31±0.15. Burst pressures were physiologically relevant at 3095±1016 mmHg. The toughness of these prototypes was 6.3±1.9 MJ/m(3). The ability to employ different materials and different formation parameters utilizing this technique promises the ability to match complex stress-strain behaviors in soft tissues with a high degree of fidelity.

Three-dimensional collagen gel contraction is the standard assay utilized for functionally quantifying a variety of cell types, in particular smooth muscle cells (SMCs) and myofibroblasts. Here, we have developed a method to effectively reduce the three-dimensional parameters of the standard collagen gel into a single, linear measurement. Cell/collagen suspensions that are cast into glass capillary tubes provide several advantages over the well plate format, such as eliminating the need for digital imaging equipment and software to quantify the amount of cellular contraction. In addition, capillary tube gels require significantly fewer cells and far less reagents than standard methods.