25th anniversary article: Engineering hydrogels for biofabrication

With advances in tissue engineering, the possibility of regenerating injured tissue or failing organs has become a realistic prospect for the first time in medical history. Tissue engineering - the combination of bioactive materials with cells to generate engineered constructs that functionally replace lost and/or damaged tissue - is a major strategy to achieve this goal. One facet of tissue engineering is biofabrication, where three-dimensional tissue-like structures composed of biomaterials and cells in a single manufacturing procedure are generated. Cell-laden hydrogels are commonly used in biofabrication and are termed "bioinks". Hydrogels are particularly attractive for biofabrication as they recapitulate several features of the natural extracellular matrix and allow cell encapsulation in a highly hydrated mechanically supportive three-dimensional environment. Additionally, they allow for efficient and homogeneous cell seeding, can provide biologically-relevant chemical and physical signals, and can be formed in various shapes and biomechanical characteristics. However, despite the progress made in modifying hydrogels for enhanced bioactivation, cell survival and tissue formation, little attention has so far been paid to optimize hydrogels for the physico-chemical demands of the biofabrication process. The resulting lack of hydrogel bioinks have been identified as one major hurdle for a more rapid progress of the field. In this review we summarize and focus on the deposition process, the parameters and demands of hydrogels in biofabrication, with special attention to robotic dispensing as an approach that generates constructs of clinically relevant dimensions. We aim to highlight this current lack of effectual hydrogels within biofabrication and initiate new ideas and developments in the design and tailoring of hydrogels. The successful development of a "printable" hydrogel that supports cell adhesion, migration, and differentiation will significantly advance this exciting and promising approach for tissue engineering.

Biofabrication of multi-material anatomically shaped tissue constructs

Additive manufacturing in the field of regenerative medicine aims to fabricate organized tissue-equivalents. However, the control over shape and composition of biofabricated constructs is still a challenge and needs to be improved. The current research aims to improve shape, by converging a number of biocompatible, quality construction materials into a single three-dimensional fiber deposition process. To demonstrate this, several models of complex anatomically shaped constructs were fabricated by combined deposition of poly(vinyl alcohol), poly(ε-caprolactone), gelatin methacrylamide/gellan gum and alginate hydrogel. Sacrificial components were co-deposited as temporary support for overhang geometries and were removed after fabrication by immersion in aqueous solutions. Embedding of chondrocytes in the gelatin methacrylamide/gellan component demonstrated that the fabrication and the sacrificing procedure did not affect cell viability. Further, it was shown that anatomically shaped constructs can be successfully fabricated, yielding advanced porous thermoplastic polymer scaffolds, layered porous hydrogel constructs, as well as reinforced cell-laden hydrogel structures. In conclusion, anatomically shaped tissue constructs of clinically relevant sizes can be generated when employing multiple building and sacrificial materials in a single biofabrication session. The current techniques offer improved control over both internal and external construct architecture underscoring its potential to generate customized implants for human tissue regeneration.

An investigation into utilising gestational body mass index as a screening tool for adverse birth outcomes and maternal morbidities in a group of pregnant women in Khayelitsha

OBJECTIVE

The aim of this study was to investigate the ability of the gestational body mass index (BMI) method to screen for adverse birth outcomes and maternal morbidities.

DESIGN

This was a substudy of a randomised controlled trial, the Philani Mentor Mothers' study.

SETTING AND SUBJECTS

The Philani Mentor Mothers' study took place in a peri-urban settlement, Khayelitsha, between 2009 and 2010. Pregnant women living in the area in 2009-2010 were recruited for the study.

OUTCOME MEASURES

Maternal anthropometry (height and weight) and gestational weeks were obtained at baseline to calculate the gestational BMI, which is maternal BMI adjusted for gestational age. Participants were classified into four gestational BMI categories: underweight, normal, overweight and obese. Birth outcomes and maternal morbidities were obtained from clinic cards after the births.

RESULTS

Pregnant women were recruited into the study (n = 1 058). Significant differences were found between the different gestational BMI categories and the following birth outcomes: maternal (p-value = 0.019), infant hospital stay (p-value = 0.03), infants staying for over 24 hours in hospital (p-value = 0.001), delivery mode (p-value = 0.001), birthweight (p-value = 0.006), birth length (p-value = 0.007), birth head circumference (p-value = 0.007) and pregnancy-induced hypertension (p-value = 0.001).

CONCLUSION

To the best of our knowledge, this is the first study that has used the gestational BMI method in a peri-urban South African pregnant population. Based on the findings that this method is able to identify unfavourable birth outcomes, it is recommended that it is implemented as a pilot study in selected rural, peri-urban and urban primary health clinics, and that its ease and effectiveness as a screening tool is evaluated. Appropriate medical and nutritional advice can then be given to pregnant women to improve both their own and their infants' birth-related outcomes and maternal morbidities.

[Tissue printing; the potential application of 3D printing in medicine]

Complex structures based on a digital blueprint can be created using a 3D printer. As this blueprint can be created using patient imaging data, there are many potential patient-specific applications of 3D printing in medicine. Individually printed metal implants and synthetic devices are currently being used on a limited scale in clinical practice. Researchers in the field of regenerative medicine are now going a step further by printing a combination of cells, growth factors and biomaterials. This process is known as 'bioprinting'. It can be used to copy the complex organization of natural tissue required to repair or replace damaged tissues or organs. The technique needs to be optimized, however, and more knowledge is required regarding the development of printed living constructs into functional tissues before 'tissue from the printer' can be clinically applied.

Non-Hodgkin's lymphoma of the synovium discovered in total knee arthroplasty: a case report

Background

Musculoskeletal involvement occurs in 25% of patients with non-Hodgkin’s lymphoma (NHL). Primary lymphoma in the joint is rare. It can present as a bone lesion or as atypical soft tissue proliferation. NHL has an increased incidence in patients with autoimmune rheumatic diseases.

Case presentation

We present a case in which non-Hodgkin’s lymphoma was found coincidentally in the synovium during knee joint replacement surgery in a 69-year old woman with rheumatoid arthritis. Pigmented, vitreous tissue was resected, which turned out to be a diffuse large B-cell lymphoma after histological examination. The coincidental intraoperative finding of intra-articular non-Hodgkin’s lymphoma was reported twice before, presenting as synovial proliferation in elbow and shoulder surgery. In a few other cases non-Hodgkin’s lymphoma presented most often in the knee, as a bone lesion or, when soft tissue was involved, as arthritis.

Conclusion

Non-Hodgkin’s lymphoma should be considered in patients with autoimmune rheumatic diseases. In case of persistent arthritis, non-respondent to anti-inflammatory drugs, a biopsy might be warranted. Moreover, when arthroscopy or arthrotomy is planned, any atypical tissue should be sent for histological analysis. Early diagnosis of NHL can contribute to improved outcome of its rapidly developing treatment options.

Poor early graft function impairs long-term outcome in living donor kidney transplantation

Background

Poor early graft function (EGF) after living donor kidney transplantation (LDKT) has been found to decrease rejection-free graft survival rates. However, its influence on long-term graft survival remains inconclusive.

Methods

Data were collected on 472 adult LDKTs performed between July 1996 and February 2010. Poor EGF was defined as the occurrence of delayed or slow graft function. Slow function was defined as serum creatinine above 3.0 mg/dL at postoperative day 5 without dialysis.

Results

The incidence of slow and delayed graft function was 9.3 and 4.4%, respectively. Recipient overweight, pretransplant dialysis and warm ischemia were identified as risk factors for the occurrence of poor EGF. The rejection-free survival was worse for poor EGF as compared to immediate graft function with an adjusted hazard ratio (HR) of 6.189 (95% CI 4.075–9.399; p < 0.001). Long-term graft survival was impaired in the poor EGF group with an adjusted HR of 4.206 (95% CI 1.839–9.621; p = 0.001).

Conclusions

Poor EGF occurs in 13.7% of living donor kidney allograft recipients. Both, rejection-free and long-term graft survivals are significantly lower in patients with poor EGF as compared to patients with immediate graft function. These results underline the clinical relevance of poor EGF as phenomenon after LDKT.

Early intrauterine transfusion in severe red blood cell alloimmunization

OBJECTIVE

To determine perinatal outcome in pregnancies with early severe red blood cell (RBC) alloimmunization.

METHODS

This was a retrospective analysis of 30 patients requiring their first intrauterine transfusion (IUT) at < 22 weeks of gestation. Timing of the first IUT was based on evaluation of either the middle cerebral artery peak systolic velocity (MCA-PSV) or development of ascites.

RESULTS

Thirty-three per cent of the patients had experienced a previous intrauterine fetal death as a result of RBC alloimmunization. Of these alloimmunized pregnancies, 26 (87%) were associated with anti-D, four (13%) with anti-Kell and 12 had more than one antibody type involved. The antibody titers before the first IUT ranged from 1:128 to 1:8024. All fetuses were severely anemic before the first IUT with a median hemoglobin (Hb) level of 37 (range, 3-81) g/L. The nine hydropic fetuses had a lower Hb level compared with non-hydropic fetuses (median 15 g/L vs. 42 g/L, P = 0.016). However, 15 (71%) non-hydropic fetuses had an Hb level of < 50 g/L before the first IUT. The median gestational age at the first IUT was 20.4 (range, 16-22) weeks, and between one and nine transfusions were needed during pregnancy. Transfusion was via the intrahepatic vein (IHV) (n = 19), umbilical vein (n = 6) or umbilical artery (n = 2), or was intracardiac (n = 2) or intraperitoneal (n = 1). Overall perinatal survival rate was 80% and did not differ between hydropic and non-hydropic fetuses. Median gestation at delivery, after exclusion of six intrauterine fetal deaths, was 36.7 (range, 27.8-38.4) weeks.

CONCLUSIONS

In early severe RBC alloimmunization, fetuses can be severely anemic without hydrops, and prognosis cannot be predicted by the presence or absence of hydrops. Early IUT followed by serial transfusions is associated with a perinatal survival rate of about 80%.

A new imaging method for understanding chemical dynamics: efficient slice imaging using an in-vacuum pixel detector

The implementation of the Timepix complementary metal oxide semiconductor pixel detector in velocity map slice imaging is presented. This new detector approach eliminates the need for gating the imaging detector. In time-of-flight mode, the detector returns the impact position and the time-of-flight of charged particles with 12.5 ns resolution and a dynamic range of about 100 μs. The implementation of the Timepix detector in combination with a microchannel plate additionally allows for high spatial resolution information via center-of-mass centroiding. Here, the detector was applied to study the photodissociation of NO(2) at 452 nm. The energy resolution observed in the experiment was ΔE/E=0.05 and is limited by the experimental setup rather than by the detector assembly. All together, this new compact detector assembly is well-suited for slice imaging and is a promising tool for imaging studies in atomic and molecular physics research.

The prevalence of dietary-related complementary and alternative therapies and their perceived usefulness among cancer patients

BACKGROUND

The present study aimed to directly assess and compare the usage, benefits and side-effects of dietary-related complementary and alternative medicine (CAM) use among adult cancer patients and non-cancer adults in Norwich, UK.

METHODS

Self-administered questionnaires were completed by 98 cancer patients and 92 non-cancer adults to compare demographics, types of CAM usage with reasons, benefits, side-effects and CAM information sources. The groups were matched for gender, age, marital status, education and household income. The mean ages were 62.7 and 59.7 years, respectively, with slightly more female than male participants.

RESULTS

CAM use was high in both groups (47% in cancer and 53% in non-cancer respondents, P > 0.05). The most widely-used diet-related CAM among both groups was the large intake of fruit, vegetables and juice, multivitamins, fish oils and glucosamine. Fish oil intake was significantly higher in the non-cancer group (P < 0.05), whereas selenium and beta-carotene supplements were significantly higher in the cancer group (P < 0.01 and P = 0.02, respectively). The main reasons for using CAM were to boost the immune system and to improve quality of life (P > 0.05). Reported benefits included increased optimism and hope for the cancer group and increased optimism and pain relief for the non-cancer group.

CONCLUSIONS

Diet-related CAM is used frequently by both cancer patients and non-cancer adults, with many reported benefits and few reported side-effects. Significant differences between the groups included a higher prevalence of fish oil used by the non-cancer group, and a higher use of selenium and beta-carotene supplements in the cancer group.

Fibrinogen beta-chain tyrosine nitration is a prothrombotic risk factor

Elevated levels of circulating fibrinogen are associated with an increased risk of atherothrombotic diseases although a causative correlation between high levels of fibrinogen and cardiovascular complications has not been established. We hypothesized that a potential mechanism for an increased prothrombotic state is the post-translational modification of fibrinogen by tyrosine nitration. Mass spectrometry identified tyrosine residues 292 and 422 at the carboxyl terminus of the beta-chain as the principal sites of fibrinogen nitration in vivo. Immunoelectron microscopy confirmed the incorporation of nitrated fibrinogen molecules in fibrin fibers. The nitration of fibrinogen in vivo resulted in four distinct functional consequences: increased initial velocity of fibrin clot formation, altered fibrin clot architecture, increased fibrin clot stiffness, and reduced rate of clot lysis. The rate of fibrin clot formation and clot architecture was restored upon depletion of the tyrosine-nitrated fibrinogen molecules. An enhanced response to the knob "B" mimetic peptides Gly-His-Arg-Pro(am) and Ala-His-Arg-Pro(am) suggests that incorporation of nitrated fibrinogen molecules accelerates fibrin lateral aggregation. The data provide a novel biochemical risk factor that could explain epidemiological associations of oxidative stress and inflammation with thrombotic complications.

Frequencies and role of regulatory T cells in patients with (pre)malignant cervical neoplasia

Oncogenic human papillomavirus (HPV)-infection is crucial for developing cervical cancer and its precursor lesions [cervical intraepithelial neoplasia (CIN)]. Regulatory T cells (T(regs)) might be involved in the failure of the immune system to control the development of HPV-induced cancer. We investigated frequencies, phenotype and activity of T(regs) in patients with cervical neoplasia. CIN and cervical cancer patients showed increased CD4(+)/CD25(high) T cell frequencies in peripheral blood and CD4(+) T cell fraction. These CD4(+)/CD25(high) T cells represent T(regs) as demonstrated by their low proliferation rate, low interferon (IFN)-gamma/interleukin (IL)-10 ratio, high expression of CD45RO, GITR, CTLA-4, forkhead box P3 (FoxP3) and low CD45RA expression. Moreover, in HPV16(+) cervical cancer patients, in-vitro depletion of CD25(+) T cells resulted in increased IFN-gamma T cell responses against HPV16 E6- and E7 peptides. Thus, increased frequencies of T(regs) in cervical cancer patients may indeed suppress HPV-specific immunity. Longitudinal analysis of CD4(+)/CD25(high) T cell frequencies in patients showed a modest decline 1 year after curative surgery or chemoradiation. This study demonstrates increased frequencies and suppressive activity of T(regs) in cervical cancer. These results imply that T(regs) may suppress the immune control of cervical neoplasia and furthermore that suppression of immunity by T(regs) will be another hurdle to overcome in therapeutic immunization strategies against cervical neoplasia.

Strong artificial selection in the wild results in predicted small evolutionary change

Estimates of genetic variation and selection allow for quantitative predictions of evolutionary change, at least in controlled laboratory experiments. Natural populations are, however, different in many ways, and natural selection on heritable traits does not always result in phenotypic change. To test whether we were able to predict the evolutionary dynamics of a complex trait measured in a natural, heterogeneous environment, we performed, over an 8-year period, a two-way selection experiment on clutch size in a subdivided island population of great tits (Parus major). Despite strong artificial selection, there was no clear evidence for evolutionary change at the phenotypic level. Environmentally induced differences in clutch size among years are, however, large and can mask evolutionary changes. Indeed, genetic changes in clutch size, inferred from a statistical model, did not deviate systematically from those predicted. Although this shows that estimates of genetic variation and selection can indeed provide quantitative predictions of evolutionary change, also in the wild, it also emphasizes that demonstrating evolution in wild populations is difficult, and that the interpretation of phenotypic trends requires great care.

Hormonal versus non-hormonal contraceptives in women with diabetes mellitus type 1 and 2

BACKGROUND

Adequate contraceptive advice is important in women with diabetes mellitus type 1 and 2 to reduce the risk of maternal and infant morbidity and mortality in unplanned pregnancies. A wide variety of contraceptives are available for these women. However hormonal contraceptives might influence carbohydrate and lipid metabolism and increase micro- and macrovascular complications. So caution in selecting a contraceptive method is required.

OBJECTIVES

To investigate whether progestogen-only, combined estrogen/progestogen or non-hormonal contraceptives differ in terms of effectiveness in preventing pregnancy, in their side effects on carbohydrate and lipid metabolism and in long-term complications such as micro- and macrovascular disease, when used in women with diabetes mellitus.

SEARCH STRATEGY

The search was performed in MEDLINE, EMBASE, CENTRAL/CCTR, POPLINE, CINAHL, WorldCat, ECO, ArticleFirst, the Science Citation Index, the British Library Inside, and reference lists of relevant articles. Last search was performed in May 2005. In addition, experts in the field and pharmaceutical companies marketing contraceptives were contacted to identify published, unpublished or ongoing studies.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials that studied women with diabetes mellitus comparing: 1. hormonal versus non-hormonal contraceptives. 2. progestogen-only versus estrogen/progestogen contraceptives. 3. contraceptives containing <50 microg estrogen versus contraceptives containing > or = 50 microg estrogen. 4. contraceptives containing 'first'-, 'second'- and 'third'-generation progestogens, drospirenone and cyproterone acetate. Principal outcomes were contraceptive effectiveness, diabetes control, lipid metabolism and micro- and macrovascular complications.

DATA COLLECTION AND ANALYSIS

Two investigators evaluated the titles and abstracts from the literature search. Quality assessment was performed independently with discrepancies resolved by discussion or consulting a third reviewer. Because the trials differed in studied contraceptives, participant characteristics and methodological quality, we could not combine the data in a meta-analysis. The trials were therefore examined on an individual basis and narrative summaries were provided.

MAIN RESULTS

Three randomised controlled trials were included. Only one was of good methodological quality. It compared the influence of levonorgestrel-releasing IUD versus copper-IUD on carbohydrate metabolism in women with type 1 diabetes mellitus. No difference was found in daily insulin requirement, glycosylated hemoglobin (HbA1c) or fasting blood sugar after twelve months. The other two trials were of limited methodological quality. Both compared progestogen-only pills with different estrogen/progestogen combinations. The trials reported blood glucose levels to remain stable during treatment with most regimens. Only high-dose combined oral contraceptives were found to slightly impair glucose homeostasis. Combined oral contraceptives also appeared to have a minor adverse effect on lipid metabolism whereas progestogen-only contraceptives slightly improved lipid-metabolism. Only one study reported on micro- and macrovascular complications. No signs or symptoms of thromboembolic incidents or visual disturbances were observed. However study duration was short. Minor adverse effects were reported in one study. The trial found progestogen-only pills to cause more bleeding irregularities when compared with combined oral contraceptives. Unintended pregnancies were not observed during any of the studies.

AUTHORS' CONCLUSIONS

The three included randomised controlled trials in this systematic review provided insufficient evidence to assess whether progestogen-only and combined contraceptives differ from non-hormonal contraceptives in diabetes control, lipid metabolism and complications. Two of the three studies were of limited methodological quality, sponsored by pharmaceutical companies and described surrogate outcomes. Ideally, an adequately reported, high-quality randomised controlled trial analysing both intermediate outcomes (i.e. glucose and lipid metabolism) and true clinical endpoints (micro- and macrovascular disease) in users of combined, progestogen-only and non-hormonal contraceptives should be conducted. However, due to the low incidence of micro- and macrovascular disease and accordingly the large sample size and follow-up period needed to observe differences in risk, a randomised controlled trial might not be the ideal design.