Fiber technology for reliable repair of skeletal muscle.

Conventional soft-tissue reclosure methods-sutures and staples-require substantial organized-collagen content. Some tissues lack extensive intrinsic collagenous content. Wound disruption consequences range from newly closed abdominal wounds bursting open, to post-cesarean wombs splitting at delivery, to heart valves loosening. Although sutures do approach the theoretical limit of normal force transfer-cross-sectional area times compressive strength, a different paradigm-shear force transfer across the far greater surface attainable by fine fibers parallel to the potential disruptive force could exceed that theoretical limit. Capacity is now the product of frictional coefficient, existing tissue pressure, and contact area. Using a device comprising bundles of poly(ethylene terephthalate) fibers through tissue, we previously coupled muscles to devices and bones. Here we tested an analogous device for reclosing fascia-stripped abdominal wall muscles. In 28 rabbits, fascia-deprived rectus abdominus muscles were reclosed, using the experimental device or conventional sutures. Testing muscles from the 21 three-week survivors, (with closure devices retained-the usual clinical practice) demonstrated experimental failure strength which exceeded that of controls by 58%. Histologically, solid tissue elements did in-grow between fibers for an extensive tissue-prosthetic interface. Both histology and mechanical performance suggest the fiber technology presented herein surpasses conventional sutures in closure of collagen-deficient tissues.

Fetal tissue engineering: diaphragmatic replacement.

BACKGROUND/PURPOSE: Prosthetic repair of congenital diaphragmatic hernia has been associated with high complication rates. This study was aimed at applying fetal tissue engineering to diaphragmatic replacement. METHODS: Fetal lambs underwent harvest of skeletal muscle specimens. Once expanded in vitro, fetal myoblasts were suspended in a collagen hydrogel submitted to controlled radial tension. The construct was then placed in a bioreactor. After birth, all animals underwent creation of 2 diaphragmatic defects. One defect was repaired with the autologous-engineered construct placed in between 2 acellular supporting membranes and the other with an identical construct but without any cells. Each animal was its own control (graft, n = 10). Animals were killed at different time-points postimplantation for histologic examination. Statistical analysis was by analysis of variance (ANOVA). RESULTS: Fetal myoblasts expanded up to twice as fast as neonatal cells. Hydrogel-based radial tension enhanced construct architecture by eliciting cell organization within the scaffold. No eventration was present in 4 of 5 engineered constructs but in 0 of 5 acellular grafts (P<.05). At harvest, engineered constructs were thick and histologically resembled normal skeletal muscle, whereas acellular grafts were thin, floppy, and showed low cell density with increased fibrosis. CONCLUSIONS: Unlike acellular grafts, engineered cellular diaphragmatic constructs are anatomically and histologically similar to normal muscle. Fetal tissue engineering may be a viable alternative for diaphragmatic replacement.

Vascular anomalies: classification, diagnosis, and natural history.

In the past, patients with vascular anomalies went from one physician to another. No one seemed to understand the condition, and sometimes the child was harmed by the wrong treatment. Now interdisciplinary vascular anomalies centers are organizing. The disciplines may differ, depending on local interest and capabilities. Such teams form a critical mass for proper diagnosis, therapy, and clinical/basic research. The advances in genetics are leading the way to a molecular understanding of vascular anomalies, and someday, molecular-based, novel therapy. The Internet also has had a major impact on this field. Because of continued confusion about diagnosis and therapy, cyber-savvy parents will self-refer to specialists. Family support groups have arisen and provide commendable service to these patients.

Soft-tissue augmentation with injectable alginate and syngeneic fibroblasts.

Tissue engineering, a field that combines polymer scaffolds with isolated cell populations to create new tissue, may be applied to soft-tissue augmentation-an area in which polymers and cell populations have been injected independently. We have developed an inbred rat model in which the subcutaneous injection of a hydrogel, a form of polymer, under vacuum permits direct comparison of different materials in terms of both histologic behavior and their ability to maintain the specific shape and volume of a construct. Using this model, we compared three forms of calcium alginate, a synthetic hydrogel, over an 8-week period-standard alginate that was gelled following injection into animals (alginate post-gel), standard alginate that was gelled before injection into animals (alginate pre-gel) and alginate-RGD, to which the cell adhesion tripeptide RGD was linked covalently (RGD post-gel). Parallel groups that included cultured syngeneic fibroblasts suspended within each of these three gels were also evaluated (alginate post-gel plus cells, alginate pre-gel plus cells, and RGD post-gel plus cells). The study used 54 inbred Lewis rats (n = 9 for each of the six groups). Construct geometry was optimally maintained in the alginate post-gel group in which 58 percent of the original volume was preserved at 8 weeks and increased to 88 percent at 8 weeks when syngeneic fibroblasts were included within the gel. Volume was not as well preserved in the RGD post-gel group (25 percent of original volume at 8 weeks), but again increased when syngeneic fibroblasts were included (41 percent of original volume at 8 weeks). Maintenance of volume was poorest in the alginate pre-gel group (31 percent of original volume at 8 weeks) and failed to be augmented by the addition of fibroblasts (19 percent of original volume at 8 weeks). Histologically, the gel remained a uniform sheet surrounded by a fibrous capsule in the alginate post-gel groups. In the alginate pre-gel and RGD post-gel groups, there was significant ingrowth of a fibrovascular stroma into the gel with fragmentation of the construct. In constructs in which syngeneic fibroblasts were included, cells were visualized throughout the gel but did not extend processes or appear to contribute to new tissue formation. Material compression testing indicated that the alginate and RGD post-gel constructs became stiffer over a 12-week period, particularly in the cell-containing groups. Our results suggest that calcium alginate could be a suitable agent for soft-tissue augmentation when gelled subcutaneously following injection. The addition of syngeneic fibroblasts enhanced the ability of the gel to maintain the volume of a construct; this seems to be mediated by increased gel stiffness rather than by de novo tissue formation. Our animal model, in combination with material testing data, permits rigorous comparison of different materials used for soft-tissue augmentation.