Standardized 3D bioprinting of soft tissue models with human primary cells

Cells grown in 3D are more physiologically relevant than cells cultured in 2D. To use 3D models in substance testing and regenerative medicine, reproducibility and standardization are important. Bioprinting offers not only automated standardizable processes but also the production of complex tissue-like structures in an additive manner. We developed an all-in-one bioprinting solution to produce soft tissue models. The holistic approach included (1) a bioprinter in a sterile environment, (2) a light-induced bioink polymerization unit, (3) a user-friendly software, (4) the capability to print in standard labware for high-throughput screening, (5) cell-compatible inkjet-based printheads, (6) a cell-compatible ready-to-use BioInk, and (7) standard operating procedures. In a proof-of-concept study, skin as a reference soft tissue model was printed. To produce dermal equivalents, primary human dermal fibroblasts were printed in alternating layers with BioInk and cultured for up to 7 weeks. During long-term cultures, the models were remodeled and fully populated with viable and spreaded fibroblasts. Primary human dermal keratinocytes were seeded on top of dermal equivalents, and epidermis-like structures were formed as verified with hematoxylin and eosin staining and immunostaining. However, a fully stratified epidermis was not achieved. Nevertheless, this is one of the first reports of an integrative bioprinting strategy for industrial routine application

Haematocrit is invalid for estimating red cell volume: a prospective study in male volunteers

BACKGROUND: Although haematocrit and haemoglobin value are concentrations, they are commonly used to guide clinical decisions involving red cell and plasma volumes. A study challenging this convention systematically co-determined and compared these measures. MATERIALS AND METHODS: Using a non-radioactive double-tracer technique to assess blood volume components, measurements were taken once in 46 healthy male endurance athletes. The best predictors of blood composition were derived from the first 36 athletes by automated stepwise forward selection of non-invasive metric parameters (age, weight, height, body surface area and body mass index) and the resulting formulae validated in the remaining ten volunteers. Haematocrit, haemoglobin concentration, red cell volume and plasma volume were measured again 4 weeks later in eight randomly selected volunteers. RESULTS: Red cell volume (2,282±283 mL) did not correlate with either haematocrit (0.42±0.02) or haemoglobin concentration (14.2±0.8, P>0.05, resp.), but was predictable from body surface area (red cell volume [mL]=1,547 × body surface area [m2]-723; r=.88, P<0.01). A similar accuracy was unobtainable using any potential predictor for plasma or blood volume, haematocrit or haemoglobin concentration. Red cell volume showed high intra-individual stability when measured again after 4 weeks, whereas plasma volume oscillated in both directions by up to 22%. DISCUSSION: Only red cell volume shows sufficiently stable intra- and interindividual values to be an accurate, objective indicator of normality in blood composition. The measurement technique is feasible in the outpatient setting and this parameter provides effective, robust, and readily available diagnostic information that might be useful in numerous clinical situations. Its clinical significance does, however, remain to be demonstrated

RhEPO improves time to exhaustion by non-hematopoietic factors in humans

PURPOSE Erythropoietin (EPO) controls red cell volume (RCV) and plasma volume (PV). Therefore, injecting recombinant human EPO (rhEPO) increases RCV and most likely reduces PV. RhEPO-induced endurance improvements are explained by an increase in blood oxygen (O2) transport capacity, which increases maximum O2 uptake ([Formula: see text]O2max). However, it is debatable whether increased RCV or [Formula: see text]O2max are the main reasons for the prolongation of the time to exhaustion (t lim) at submaximal intensity. We hypothesized that high rhEPO doses in particular contracts PV such that the improvement in t lim is not as strong as at lower doses while [Formula: see text]O2max increases in a dose-dependent manner. METHODS We investigated the effects of different doses of rhEPO given during 4 weeks [placebo (P), low (L), medium (M), and high (H) dosage] on RCV, PV, [Formula: see text]O2max and t lim in 40 subjects. RESULTS While RCV increased in a dose-dependent manner, PV decreased independent of the rhEPO dose. The improvements in t lim (P +21.4 ± 23.8 %; L +16.7 ± 29.8 %; M +44.8 ± 62.7 %; H +69.7 ± 73.4 %) depended on the applied doses (R (2) = 0.89) and clearly exceeded the dose-independent [Formula: see text]O2max increases (P -1.7 ± 3.2 %; L +2.6 ± 6.8 %; M +5.7 ± 5.1 %; H +5.6 ± 4.3 %) after 4 weeks of rhEPO administration. Furthermore, the absolute t lim was not related (R (2) ≈ 0) to RCV or to [Formula: see text]O2max. CONCLUSIONS We conclude that a contraction in PV does not negatively affect t lim and that rhEPO improves t lim by additional, non-hematopoietic factors