Biomedical subjects

B Weyand

Publications and source records attributed to B Weyand.

5 recordsLinked to original sources

PubMed2003

[Skin tissue engineering].

Cultivated epithelial autografts as multilayered, thin sheets represent a common standard in clinically applied tissue engineering substitutes, outnumbering all experimental alternatives. However, the unsatisfying short- and long-term results concerning mechanical stability and scarring require alternatives. The cultivation and transplantation of cultured autologous keratinocytes as a single cell suspension in a fibrin matrix, combined with allogenic skin grafting, has been investigated extensively in athymic nude mice. Wounds can be reliably reepithelialized after a cultivation period of only 14 days. Moreover, the successful combination of keratinocyte fibrin suspension and acellular dermis in an attempt to regenerate full thickness skin defects in a pig model has been demonstrated. The usefulness of subconfluently cultured keratinocytes-which can be harvested very early and are easy to handle-is enhanced by cotransplantation with decellularized dermis.

Animals↗

PubMed2003

Skin tissue engineering.

The coverage of extensive wounds with viable autologous keratinocytes remains the only option of treatment if autologous donor skin is not obtainable. There is evidence that proliferating keratinocytes, as suspended cells or as a single layer, are adequate for wound closure. Understanding keratinocyte-matrix interactions not only allows us to influence keratinocyte outgrowth, adhesion, and migration, but may also guide us to modify matrix molecules for enhancing keratinocyte take. Further approaches may include the generation of genetically manipulated keratinocytes, which allow the use of an off-the-shelf epidermal replacement. As surgeons, our goal is to help burn patients with the best quality of skin in the shortest time possible. As tissue engineers, we have not achieved the goal of a universal skin product. By continually reviewing the options and using them, we can at least use the proper material in the adequate situation. Because of the limited resources, the need for comparisons of clinical effectiveness and cost are ever more important. As anatomy and physiology of engineered skin substitutes improve, they will become more similar to native skin autografts. Improvement of skin substitutes will result from inclusion of additional cell types (eg, melanocytes) and from modifications of culture media and scaffolds. Skin-substitute materials may be able to stimulate regeneration rather than repair, and tissue-engineered skin may match the quality of split-skin autografts, our present gold standard.

Animals↗

PubMed1999

A quantitative analysis of the effect of insulin-like growth factor-1 infusion during mandibular distraction osteogenesis in rabbits.

AIM: To quantify, by histomorphometry, the effects of local insulin-like growth factor-1 (IGF-1) during mandibular distraction at various rates. METHODOLOGY: Mature rabbits underwent bilateral mandibular corticotomy and distraction lengthening. Recombinant IGF-1 was administered to two groups of rabbits via osmotic infusion pumps. Distraction regimes were as follows: Group A, 1 mm/day for 15 days; Group B, as for A plus IGF-1; Group C, 3 mm/day for 5 days; Group D, as for C plus IGF-1; and Group E, sham-operated controls. After a 28-day consolidation period, rabbits were sacrificed and bone deposition quantified using DEXA scanning, three-point bending, histological examination and sampled for histomorphometric analysis. RESULTS: DEXA scanning and three-point bending failed to detect any effect of distraction rate or of IGF-1 infusion. Histological and histomorphometric analysis suggested 1 mm/day to be the ideal distraction rate, as this was associated with greater osteoblastic activity and consistent bony union. However, IGF-1 infusion significantly enhanced osteoblastic activity at both distraction rates and resulted in bony union when distraction was performed at 3 mm/day. CONCLUSIONS: Distraction osteogenesis at a rate of 1 mm/day provides greater osteogenic stimulus than 3 mm/day. Exogenous IGF-1 has a positive influence on osteoblastic activity during distraction. Its effect is probably minimised by high levels of endogenous IGF-1.

Animals↗

PubMed1998

The basolateral Ca2+-dependent K+ channel in rat colonic crypt cells.

Previous studies have indicated that a 16-pS K+ channel (KCca) in the basolateral membrane is responsible for the acetylcholine-induced whole-cell K+ conductance in these cells. In the present study we have examined this channel in excised inside-out patches of the basolateral membrane. Over a wide voltage range this channel showed inward rectification. The Ca2+ sensitivity was very marked, with a Hill coefficient of three and with half-maximal activation at 330 nmol/l. After several minutes most channels showed a slow run-down. Channel activity could be refreshed by addition of ATP (1 mmol/l) to the bath solution. The non-metabolizable derivative 5'-adenylylimidodiphosphate (AMP-PNP) had no such effect. In contrast, it inhibited channel activity by some 50%. ATP and its derivatives had no effect on the Ca2+ sensitivity. Channels activated by ATP were subsequently studied in the presence of alkaline (10 kU/l) or acidic (1 kU/l) phosphatase. Both phosphatases reduced channel activity significantly. These data suggest that the 16-pS K+ channel is directly controlled by cytosolic Ca2+. This regulatory step is probably distal to an activation produced by protein-kinase-C-dependent phosphorylation. As is the case for several other K+ channels, high concentrations of non-metabolizable ATP analogues inhibit this channel.

Acid Phosphatase↗

PubMed1998

Hypertonic cell shrinkage reduces the K+ conductance of rat colonic crypts.

It has previously been shown in studies of a renal epithelial cell line that nonselective cation (NSC) channels are activated by exposure to hypertonic solution. We have also found such channels in excised patches of colonic crypt cells. They require high Ca2+ activities on the cytosolic side and a low ATP concentration for their activation and have not been recorded from cell-attached patches of colonic crypts. We examine here whether this type of channel is activated by hypertonic cell shrinkage. Bath osmolality was increased by addition of 25, 50 or 100 mmol/l mannitol. Cell-attached and whole-cell patch recordings were obtained from rat base and mid-crypt cells. In whole-cell recordings we found that addition of 50 or 100 mmol/l mannitol depolarized these cells significantly from -78+/-2.0 to -66+/-3.8 mV (n=22) and from -78+/-1. 3 to -56+/-2.6 mV (n=61), respectively, and reduced the whole-cell conductance from 20+/-8.0 to 14+/-6.6 nS (n=7) and from 20+/-3.0 to 9.8+/-1.6 nS (n=19), respectively. In cell-attached patches K+ channels with a single-channel conductance of approximately 16 pS were found in most recordings. The activity of these channels (NxPo, N=number, Po=open channel probability) was reduced from 2.08+/-0.37 to 0.98+/-0.23 (n=15) by the addition of 50 mmol/l mannitol and from 1.75+/-0.26 to 0.77+/-0.20 (n=12) by 100 mmol/l mannitol. No NSC channel activity was apparent in any of these recordings. Previously we have shown that the 16-pS K+ channel is controlled by cytosolic Ca2+ ([Ca2+]i). Therefore we measured [Ca2+]i by the fura-2 method and found that hypertonic solution reduced [Ca2+]i significantly (n=16). These data indicate that exposure of rat colonic crypts to hypertonic solutions does not activate NSC channels; [Ca2+]i falls in hypertonic solution leading to a reduction in the value of K+ channel NxPo, a reduced whole-cell conductance and depolarization of mid-crypt cells. These processes probably assist volume regulation inasmuch as they reduce KCl losses from the cell.

Animals↗