Utilization of Hepatitis B viremic donors (NAT+) leads to improved kidney transplant access for older adult recipients with little to no wait time

BACKGROUND

Though the use of Hepatitis B viremic (HBV) donor kidneys may be a safe alternative to improve access to transplantation, there has not been wide acceptance of this practice. In this study, we determined the safety and effectiveness of HBV NAT (+) donor kidneys in a protocolized manner in an older adult population.

METHODS

Over a 3-year period, 16 decreased donor kidney transplants were performed with HBV NAT+ kidneys. Recipients of HBV NAT+ kidneys were treated with entecavir started pre-operatively and continued for 52 weeks.

RESULTS

HBV NAT+ kidneys were preferentially used in older (68 ± 5 vs. 64 ± 9 years; p = .01) recipients with less dialysis time (93.8% < 5 years vs. 67% <5 years; p = .03). In this cohort, 3/16 had detectable HBV PCR 1-week post-transplant, but all were negative at 9- and 12-months. Calculated estimated glomerular filtration rate (eGFR) was slightly decreased 12-months post-transplant. Post-transplant outcomes in an age-matched cohort showed no difference in rates of delayed graft function, readmission within 30 days, and graft loss or death within 6 months of transplant (p > .05).

CONCLUSION

Transplants with HBV NAT+ donor kidneys in a pre-emptive treatment protocol allow for increased safe access to transplantation in older adult recipients with little or no dialysis time.

Prevalence and feasibility of assessing the frailty phenotype among hemodialysis patients in a dialysis unit

BACKGROUND

Frailty increases risk of morbidity and mortality in hemodialysis patients. Frailty assessments could trigger risk reduction interventions if broadly adopted in clinical practice. We aimed to assess the clinical feasibility of frailty assessment among Veteran hemodialysis patients.

METHODS

Hemodialysis patients' ≥50 years were recruited from a single dialysis unit between 9/1/2021 and 3/31/2022.Patients who consented underwent a frailty phenotype assessment by clinical staff. Five criteria were assessed: unintentional weight loss, low grip strength, self-reported exhaustion, slow gait speed, and low physical activity. Participants were classified as frail (3-5 points), pre-frail (1-2 points) or non-frail (0 points). Feasibility was determined by the number of eligible participants completing the assessment.

RESULTS

Among 82 unique dialysis patients, 45 (52%) completed the assessment, 13 (16%) refused, 18 (23%) were not offered the assessment due to death, transfers, or switch to transplant or peritoneal dialysis, and 6 patients were excluded because they did not meet mobility criteria. Among assessed patients, 40(88%) patients were identified as pre-frail (46.6%) or frail (42.2%). Low grip strength was most common (90%). Those who refused were more likely to have peripheral vascular disease (p = 0.001), low albumin (p = 0.0187), low sodium (p = 0.0422), and ineligible for kidney transplant (p = 0.005).

CONCLUSIONS

Just over half of eligible hemodialysis patients completed the frailty assessment suggesting difficulty with broad clinical adoption expectations. Among those assessed, frailty and pre-frailty prevalence was high. Given patients who were not tested were clinically high risk, our reported prevalence likely underestimates true frailty prevalence. Providing frailty reduction interventions to all hemodialysis patients could have high impact for this group.

Risk Factors for CMV and BK Infections in an Elderly Veteran Population Following Kidney Transplantation: Implications for Immunosuppression Induction and Management

Cytomegalovirus (CMV) and BK Polyomavirus (BKPyV) are the most common opportunistic pathogens following kidney transplantation. We evaluated 102 patients with a median age of 63 at Edward Hines VA Hospital from November 2020 to December 2022. Our primary interest was the incidence of CMV and BKPyV infections, as well as CMV and BKPyV coinfection. Secondary interests included time to infection, rejection, and graft and patient survival. There were no statistically significant differences in patient age, donor age, race, transplant type, incidence of delayed graft function, or induction in both cohorts (any infection (N = 46) vs. those without (N = 56)). There was a 36% (37/102) incidence of CMV, a 17.6% (18/102) of BKPyV and an 8.8% (9/102) incidence of coinfection. There was a decreased incidence of CMV infection in Basiliximab induction versus antithymocyte globulin (21% and 43%). CMV risk status had no effect on the incidence of CMV infection following transplant. African American recipients had a lower incidence of BKPyV infection (12% vs. 39%), yet a higher incidence was observed in those with high cPRA (50% vs. 14%). Most CMV and/or BKPyV infections occurred within the first six months post-transplant (54%). Immunosuppression management of the elderly should continually be evaluated to reduce opportunistic infections post-transplant.

Regulation of DNA damage and transcriptional output in the vasculature through a cytoglobin-HMGB2 axis

Identifying novel regulators of vascular smooth muscle cell function is necessary to further understand cardiovascular diseases. We previously identified cytoglobin, a hemoglobin homolog, with myogenic and cytoprotective roles in the vasculature. The specific mechanism of action of cytoglobin is unclear but does not seem to be related to oxygen transport or storage like hemoglobin. Herein, transcriptomic profiling of injured carotid arteries in cytoglobin global knockout mice revealed that cytoglobin deletion accelerated the loss of contractile genes and increased DNA damage. Overall, we show that cytoglobin is actively translocated into the nucleus of vascular smooth muscle cells through a redox signal driven by NOX4. We demonstrate that nuclear cytoglobin heterodimerizes with the non-histone chromatin structural protein HMGB2. Our results are consistent with a previously unknown function by which a non-erythrocytic hemoglobin inhibits DNA damage and regulates gene programs in the vasculature by modulating the genome-wide binding of HMGB2.

Nuclear cytoglobin associates with HMGB2 and regulates DNA damage and genome-wide transcriptional output in the vasculature

Identifying novel regulators of vascular smooth muscle cell function is necessary to further understand cardiovascular diseases. We previously identified cytoglobin, a hemoglobin homolog, with myogenic and cytoprotective roles in the vasculature. The specific mechanism of action of cytoglobin is unclear but does not seem to be related to oxygen transport or storage like hemoglobin. Herein, transcriptomic profiling of injured carotid arteries in cytoglobin global knockout mice revealed that cytoglobin deletion accelerated the loss of contractile genes and increased DNA damage. Overall, we show that cytoglobin is actively translocated into the nucleus of vascular smooth muscle cells through a redox signal driven by NOX4. We demonstrate that nuclear cytoglobin heterodimerizes with the non-histone chromatin structural protein HMGB2. Our results are consistent with a previously unknown function by which a non-erythrocytic hemoglobin inhibits DNA damage and regulates gene programs in the vasculature by modulating the genome-wide binding of HMGB2.

Kidney Transplantation in an Elderly Veteran Population With Hepatitis C Virus Nucleic Acid Test-Positive Donors Results in Improved Outcomes After Prophylactic Glecaprevir/Pibrentasvir Therapy

BACKGROUND

The average age of waitlisted veterans is 64. Recent data has shown the safety and benefits of using kidneys from hepatitis C virus nucleic acid test (HCV NAT)-positive donors. However, these studies were limited to younger patients with initiation of therapy after transplant. The aim of this study was to determine the safety and efficacy of a preemptive treatment protocol in an elderly veteran population.

METHODS

This was a prospective, open-label trial with 21 deceased donor kidney transplantations (DDKTs) with HCV NAT-positive kidneys and 32 DDKTs with HCV NAT-negative transplanted between November 2020 and March 2022. The HCV NAT-positive recipients were treated with once-daily glecaprevir/pibrentasvir started preoperatively and continued for 8 weeks. Sustained virologic response (SVR)12 was determined by negative NAT Student's t test. Other endpoints included patient and graft survival as well as graft function.

RESULTS

There was no major difference between the cohorts other than the increased number of donation after circulatory death kidneys in the non-HCV recipients. Post-transplant graft and patient outcomes were equivalent between the groups. Eight of the 21 HCV NAT-positive recipients had detectable HCV viral loads 1 day after transplant, but all were undetectable by day 7 with 100% SVR12. Calculated estimated glomerular filtration rate was improved in the HCV NAT-positive cohort at week 8 (58.26 vs 47.16 mL/min; P < .05) and continued to be improved over non-HCV recipients 1 year after transplant (71.38 vs 42.15 mL/min; P < .05). Immunologic risk stratification was similar in both cohorts.

CONCLUSION

The HCV NAT-positive transplants with a preemptive treatment protocol results in improved graft function with minimal to no complications in an elderly veteran population.

Beclin-1 dependent autophagy improves renal outcomes following Unilateral Ureteral Obstruction (UUO) injury

Background

Interstitial Fibrosis and Tubular Atrophy (IFTA) is the most common cause of long-term graft failure following renal transplant. One of the hallmarks of IFTA is the development of interstitial fibrosis and loss of normal renal architecture. In this study, we evaluated the role of autophagy initiation factor Beclin-1 in protecting against post-renal injury fibrosis.

Methods

Adult male wild type (WT) C57BL/6 mice were subjected to Unilateral Ureteral Obstruction (UUO), and kidney tissue samples were harvested at 72-hour, 1- and 3-week post-injury. The UUO-injured and uninjured kidney samples were examined histologically for fibrosis, autophagy flux, inflammation as well activation of the Integrated Stress Response (ISR). We compared WT mice with mice carrying a forced expression of constitutively active mutant form of Beclin-1, Becn1F121A/F121A .

Results

In all experiments, UUO injury induces a progressive development of fibrosis and inflammation. These pathological signs were diminished in Becn1F121A/F121A mice. In WT animals, UUO caused a strong blockage of autophagy flux, indicated by continuously increases in LC3II accompanied by an over 3-fold accumulation of p62 1-week post injury. However, increases in LC3II and unaffected p62 level by UUO were observed in Becn1F121A/F121A mice, suggesting an alleviation of disrupted autophagy. Beclin-1 F121A mutation causes a significant decrease in phosphorylation of inflammatory STING signal and limited production of IL6 and IFNγ, but had little effect on TNF-α, in response to UUO. Furthermore, activation of ISR signal cascade was detected in UUO-injured in kidneys, namely the phosphorylation signals of elF2S1 and PERK in addition to the stimulated expression of ISR effector ATF4. However, Becn1F121A/F121A mice did not reveal signs of elF2S1 and PERK activation under the same condition and had a dramatically reduced ATF level at 3-week post injury.

Conclusions

The results suggest that UUO causes a insufficient, maladaptive renal autophagy, which triggered downstream activation of inflammatory STING pathway, production of cytokines, and pathological activation of ISR, eventually leading to the development of fibrosis. Enhancing autophagy via Beclin-1 improved renal outcomes with diminished fibrosis, via underlying mechanisms of differential regulation of inflammatory mediators and control of maladaptive ISR.

Disparities in living donation

PURPOSE OF REVIEW

Living organ donation provides improved access to transplantation, thereby shortening transplant wait times and allowing for more deceased organ transplants. However, disparity in access to living donation has resulted in decreased rates of living donor transplants for some populations of patients.

RECENT FINDINGS

Though there have been marked improvements in deceased donor equity, there are still challenges as it relates to gender, racial/ethnic, and socio-economic disparity. Improvements in living donation rates in Hispanic and Asian populations are tempered by challenges in African American rates of organ donation. Socio-economic disparity may drive gender disparities in organ donation resulting in disproportionate female living donors. Tailored approaches relating to language-specific interventions as well as directed educational efforts have helped mitigate disparity. Additionally, the use of apolipoprotein1 testing and modifications of glomerular filtration rate calculators may improve rates of African American donation. This review will evaluate recent data in living donor disparity as well as highlight successes in mitigating disparity.

SUMMARY

Though there are still challenges in living donor disparity, many efforts at tailoring education and access as well as modifying living donor evaluation and identifying systemic policy changes may result in improvements in living donation rates.

Emerging perspectives on cytoglobin, beyond NO dioxygenase and peroxidase

Cytoglobin is an evolutionary ancient hemoglobin with poor functional annotation. Rather than constrained to penta coordination, cytoglobin's heme iron may exist either as a penta or hexacoordinated arrangement when exposed to different intracellular environments. Two cysteine residues at the surface of the protein form an intramolecular disulfide bond that regulates iron coordination, ligand binding, and peroxidase activity. Overall, biochemical results do not support a role for cytoglobin as a direct antioxidant enzyme that scavenges hydrogen peroxide because the rate of the reaction of cytoglobin with hydrogen peroxide is several orders of magnitude slower than metal and thiol-based peroxidases. Thus, alternative substrates such as fatty acids have been suggested and regulation of nitric oxide bioavailability through nitric oxide dioxygenase and nitrite reductase activities has received experimental support. Cytoglobin is broadly expressed in connective, muscle, and nervous tissues. Rational for differential cellular distribution is poorly understood but inducibility in response to hypoxia is one of the most established features of cytoglobin expression with regulation through the transcription factor hypoxia-inducible factor (HIF). Phenotypic characterization of cytoglobin deletion in the mouse have indicated broad changes that include a heightened inflammatory response and fibrosis, increase tumor burden, cardiovascular dysfunction, and hallmarks of senescence. Some of these changes might be reversed upon inhibition of nitric oxide synthase. However, subcellular and molecular interactions have been seldom characterized. In addition, specific molecular mechanisms of action are still lacking. We speculate that cytoglobin functionality will extend beyond nitric oxide handling and will have to encompass indirect regulatory antioxidant and redox sensing functions.

Impact of the new kidney allocation system A2/A2B → B policy on access to transplantation among minority candidates

Blood group B candidates, many of whom represent ethnic minorities, have historically had diminished access to deceased donor kidney transplantation (DDKT). The new national kidney allocation system (KAS) preferentially allocates blood group A2/A2B deceased donor kidneys to B recipients to address this ethnic and blood group disparity. No study has yet examined the impact of KAS on A2 incompatible (A2i) DDKT for blood group B recipients overall or among minorities. A case-control study of adult blood group B DDKT recipients from 2013 to 2017 was performed, as reported to the Scientific Registry of Transplant Recipients. Cases were defined as recipients of A2/A2B kidneys, whereas controls were all remaining recipients of non-A2/A2B kidneys. A2i DDKT trends were compared from the pre-KAS (1/1/2013-12/3/2014) to the post-KAS period (12/4/2014-2/28/2017) using multivariable logistic regression. Post-KAS, there was a 4.9-fold increase in the likelihood of A2i DDKT, compared to the pre-KAS period (odds ratio [OR] 4.92, 95% confidence interval [CI] 3.67-6.60). However, compared to whites, there was no difference in the likelihood of A2i DDKT among minorities post-KAS. Although KAS resulted in increasing A2/A2B→B DDKT, the likelihood of A2i DDKT among minorities, relative to whites, was not improved. Further discussion regarding A2/A2B→B policy revisions aiming to improve DDKT access for minorities is warranted.

Vimentin expression is required for the development of EMT-related renal fibrosis following unilateral ureteral obstruction in mice

Most renal transplants ultimately fail secondary to chronic allograft nephropathy (CAN). Vimentin (vim) is a member of the intermediate filament family of proteins and has been shown to be important in the development of CAN. One of the pathways leading to chronic renal fibrosis after transplant is thought to be epithelial to mesenchymal transition (EMT). Even though vim expression is one of the main steps of EMT, it is unknown whether vim expression is required for EMT leading to renal fibrosis and allograft loss. To this end, the role of vim in renal fibrosis was determined via unilateral ureteral obstruction (UUO) in vim knockout mice (129 svs6 vim -/-). Following UUO, kidneys were recovered and analyzed via Western blotting, immunofluorescence, and transcriptomics. Cultured human proximal renal tubular (HK-2) cells were subjected to lentiviral-driven inhibition of vim expression and then treated with transforming growth factor (TGF)-β to undergo EMT. Immunoblotting as well as wound healing assays were used to determine development of EMT. Western blotting analyses of mice undergoing UUO reveal increased levels of vim soon after UUO. As expected, interstitial collagen deposition increased in control mice following UUO but decreased in vim -/- kidneys. Immunofluorescence analyses also revealed altered localization of β-catenin in vim -/- mice undergoing UUO without significant changes in mRNA levels. However, RNA sequencing revealed a decrease in β-catenin-dependent genes in vim -/- kidneys. Finally, vim-silenced HK-2 cell lines undergoing EMT were shown to have decreased cellular migration during wound healing. We conclude that vim inhibition decreases fibrosis following UUO by possibly altering β-catenin localization and downstream signaling.

Insights into cellular and molecular basis for urinary tract infection in autosomal-dominant polycystic kidney disease

Urinary tract infection (UTI) is a broad term referring to an infection of the kidneys, ureters, bladder, and/or urethra. Because of its prevalence, frequent recurrence, and rising resistance to antibiotics, UTI has become a challenge in clinical practice. Autosomal-dominant polycystic kidney disease (ADPKD) is the most common monogenic disorder of the kidney and is characterized by the growth of fluid-filled cysts in both kidneys. Progressive cystic enlargement, inflammation, and interstitial fibrosis result in nephron loss with subsequent decline in kidney function. ADPKD patients frequently develop UTI; however, the cellular and molecular mechanisms responsible for the high UTI incidence in ADPKD patients remain virtually unaddressed. Emerging evidence suggests that α-intercalated cells (α-ICs) of the collecting ducts function in the innate immune defense against UTI. α-ICs inhibit bacterial growth by acidifying urine and secreting neutrophil gelatinase-associated lipocalin (NGAL) that chelates siderophore-containing iron. It is necessary to determine, therefore, if ADPKD patients with recurrent UTI have a reduced number and/or impaired function of α-ICs. Identification of the underlying cellular and molecular mechanisms may lead to the development of novel strategies to reduce UTI in ADPKD.

Anti-vimentin Antibodies Present at the Time of Transplantation May Predict Early Development of Interstitial Fibrosis/Tubular Atrophy

BACKGROUND

Anti-vimentin (a cytoskeletal protein) autoantibodies in renal transplant recipients have been correlated with interstitial fibrosis/tubular atrophy (IFTA). In this study, we examine the association between pretransplantation anti-vimentin antibodies and the subsequent development of IFTA.

METHODS

Sera obtained before renal transplantation from 97 transplant recipients were analyzed for the presence of anti-vimentin antibodies via Luminex assays to determine the concentration of anti-vimentin antibodies. Results were correlated with findings of IFTA on biopsy as well as graft function and patient and graft survival.

RESULTS

In our patient population, 56 of 97 patients were diagnosed by biopsy with IFTA 2.9 (±2.1) years after renal transplantation. Patients with IFTA on biopsy had higher mean concentration of anti-vimentin antibodies when compared to patients without IFTA (32.2 μg/mL [3.97-269.12 μg/mL] vs 14.57 μg/mL [4.71-87.81 μg/mL]). The risk of developing IFTA with a concentration of anti-vimentin antibody >15 μg/mL before transplantation was 1.96 (95% CI = 1.38-2.79, P = .011). Patients with elevated anti-vimentin antibody concentrations (>15 μg/mL) at the time of transplantation also had a higher risk of developing IFTA (81.4% vs 41.2%; P < .05). In addition, graft function was worse at 1, 3, and 5 years posttransplantation in patients with elevated concentrations of pretransplantation anti-vimentin antibody. Although there were more graft losses in the IFTA groups (49.12% vs 25.64%, P = .021) and the IFTA patients loss their grafts earlier (4.3 years vs 3.6 years), there was no statistical difference in graft loss rates.

CONCLUSIONS

Pretransplantation anti-vimentin antibody concentrations >15 μg/mL may be a risk factor for IFTA.

Dual Function for Mature Vascular Smooth Muscle Cells During Arteriovenous Fistula Remodeling

BACKGROUND

The arteriovenous fistula (AVF) is the preferred form of hemodialysis access for patients with chronic kidney disease. However, AVFs are associated with significant problems including high incidence of both early and late failures, usually attributed to inadequate venous arterialization and neointimal hyperplasia, respectively. Understanding the cellular basis of venous remodeling in the setting of AVF could provide targets for improving AVF patency rates.

METHODS AND RESULTS

A novel vascular smooth muscle cell (VSMC) lineage tracing reporter mouse, Myh11-Cre/ERT2-mTmG, was used to track mature VSMCs in a clinically relevant AVF mouse model created by a jugular vein branch end to carotid artery side anastomosis. Prior to AVF surgery, differentiated medial layer VSMCs were labeled with membrane green fluorescent protein (GFP) following tamoxifen induction. Four weeks after AVF surgery, we observed medial VSMC layer thickening in the middle region of the arterialized vein branch. This thickened medial VSMC layer was solely composed of differentiated VSMCs that were GFP+/MYH11+/Ki67-. Extensive neointimal hyperplasia occurred in the AVF region proximal to the anastomosis site. Dedifferentiated VSMCs (GFP+/MYH11-) were a major cellular component of the neointima. Examination of failed human AVF samples revealed that the processes of VSMC phenotypic modulation and intimal hyperplasia, as well as medial VSMC layer thickening, also occurred in human AVFs.

CONCLUSIONS

We demonstrated a dual function for mature VSMCs in AVF remodeling, with differentiated VSMCs contributing to medial wall thickening towards venous maturation and dedifferentiated VSMCs contributing to neointimal hyperplasia. These results provide valuable insights into the mechanisms underlying venous adaptations during AVF remodeling.

Early steroid withdrawal results in improved patient and graft survival and lower risk of post-transplant cardiovascular risk profiles: A single-center 10-year experience

Long-term use of steroids results in predictable secondary effects that can lead to increased morbidity and mortality. In this study, we present 10 years worth of data of early steroid withdrawal (ESW) immunosuppression consisting of mycophenolate, sirolimus, and tacrolimus. From 2003 to 2013, 563 kidney transplant recipients were weaned off steroids prior to discharge. We compared outcomes with that of our 65 historical controls maintained on steroids. We analyzed graft and patient survival and determined the incidence of steroid-related comorbidities such as hypertension, hypercholesterolemia, diabetes, coronary artery disease, and weight gain. Patients on ESW maintenance immunosuppression had improved patient and graft survival compared to controls. (HR: 0.23; P≤.011, 0.57; P=.026). Rates of biopsy-proven acute rejection were not different among both groups (HR: 1.24; P=.610). Incidence of post-transplant diabetes were reduced but not statistically significant (OR: 0.67; P=.138). Additionally, the development of hypertension (OR: 0.86, P≤.01), hypercholesterolemia (RR: 0.82; P=.027), CAD (RR: 0.43; P=.002), and >20 lbs. weight gain (RR: 0.29; P≤.01) was significantly improved over 10 years following initiation of ESW protocols. Early steroid withdrawal in renal transplant recipients results in improved patient and graft survival as well as better rates of post-transplant comorbid conditions.

Centrifugal seeding increases seeding efficiency and cellular distribution of bone marrow stromal cells in porous biodegradable scaffolds

Bone marrow stromal cells (MSCs) are a promising cell source for a variety of tissue engineering applications, given their ready availability and ability to differentiate into multiple cell lineages. MSCs have been successfully used to create neotissue for cardiovascular, urological, and orthopedic reconstructive surgical procedures in preclinical studies. The ability to optimize seeding techniques of MSCs onto tissue engineering scaffolds and the ability to control neotissue formation in vitro will be important for the rational design of future tissue engineering applications using MSCs. In this study we investigated the effect of centrifugal force on seeding MSCs into a biodegradable polyester scaffold. MSCs were isolated and seeded onto porous scaffold sections composed of nonwoven polyglycolic acid mesh coated with poly(L-lactide-co-epsilon-caprolactone). Compared to standard static seeding techniques, centrifugal seeding increased the seeding efficiency by 38% (p < 0.007) and significantly improved cellular distribution throughout the scaffold. Overall, centrifugal seeding of MSCs enhances seeding efficiency and improves cellular penetration into scaffolds, making it a potentially useful technique for manipulating neotissue formation by MSCs for tissue engineering applications.

Development of a mouse model for evaluation of small diameter vascular grafts

BACKGROUND

It is estimated that 80,000 individuals are unable to undergo life or limb saving bypass surgery because of inadequate small caliber synthetic vascular grafts. The use of tissue engineering methods has been proposed as a potential means of creating improved vascular conduits. We have developed a severe combined immunodeficiency (SCID) mouse aortic interposition model for initial evaluation and screening of small diameter vascular conduits in vivo.

METHODS

Fifteen small diameter vascular conduits, approximately 1 mm in diameter and 10 mm in length, were implanted as infrarenal aortic interposition grafts for 1 to 35 days. Eight grafts were constructed using a decellularized ovine arterial tissue as a scaffold. Seven grafts were constructed from silastic tubing. Four grafts were composed of Polyurethane, and two were made of expanded polytetrafluroethylene. To explore noninvasive means of evaluating patency, grafts were selectively imaged using ultrasound and micro-computed tomography.

RESULTS

All grafts were patent immediately post-operatively and at time of sacrifice. All imaging modalities were able to visualize the grafts and confirm patency. All specimens were sent for histology to evaluate neotissue formation and to correlate radiographic morphology with histological morphology.

CONCLUSIONS

The use of the SCID mouse model for initial evaluation of small caliber grafts is feasible and provides a cost effective rapid screening model with the added advantage of being able to use human cells in further studies.

Construction of an autologous tissue-engineered venous conduit from bone marrow-derived vascular cells: optimization of cell harvest and seeding techniques

BACKGROUND

Currently available vascular grafts for pediatric cardiovascular operations are limited by their inability to grow. Tissue-engineering techniques can be used to create vascular grafts with the potential for repair, remodeling, and growth. This study demonstrates the feasibility of constructing an autologous tissue-engineered venous conduit from bone marrow-derived vascular cells (BMVCs) in the ovine animal model.

METHODS

Ovine mononuclear cells were isolated from the bone marrow, cultured in endothelial growth medium, and characterized with immunocytochemistry. Biodegradable tubular scaffolds were constructed from polyglycolic acid mesh coated with a copolymer of poly[epsilon-caprolactone-L-lactide]. Scaffolds were seeded at various cell concentrations and incubation times to optimize seeding conditions for the construction of an autologous venous conduit. Using optimized conditions, 6 tissue-engineered vascular grafts were implanted as inferior vena cava interposition grafts in juvenile lambs. Grafts were assessed for patency at days 1 to 30 postoperatively and explanted for histological and immunohistochemical analysis.

RESULTS

A mixed cell population of BMVCs consisting of smooth muscle cells and endothelial cells was cultured from ovine sternal bone marrow. A seeding concentration of 2 x 10(6) cells/cm2 and 7 days of postseeding incubation were optimal for creating a confluent cellular layer on the polyglycolic acid/poly[epsilon-caprolactone-L-lactide]) scaffold. Grafts were explanted up to 4 weeks postoperatively. All grafts were patent without evidence of thrombosis. Histological evaluation of the explanted grafts demonstrated neo-endothelialization. Graft wall was composed of neo-tissue made up of residual polymer matrix, mesenchymal cells, and extracellular matrix without evidence of calcification.

CONCLUSIONS

Bone marrow-derived vascular cells, containing endothelial and smooth muscle cells, can be isolated and cultured from ovine sternal bone marrow and used as a cell source for vascular tissue engineering. Our optimized techniques for BMVC harvest and seeding onto biodegradable scaffolds can be used for studying autologous tissue-engineered vascular grafts in the ovine animal model.

Liver resection for metastatic colorectal cancer in the age of neoadjuvant chemotherapy and bevacizumab

Hepatic metastases from colorectal carcinoma (CRC) were once thought to portend a uniformly grim outcome; however, improvements in chemotherapeutic and surgical approaches have led to significant advances as well as new clinical challenges. Some 60% of the 150,000 patients diagnosed with CRC each year in the United States will develop hepatic metastases. Only a fraction of these metastases are resectable at the time of presentation, but an increasing number of patients are able to undergo resection after neoadjuvant chemotherapy. Additionally, recent trials have demonstrated the efficacy of using chemotherapy with bevacizumab as first-line therapy for metastatic CRC, but how this treatment will affect surgical resection is unknown. Herein, we review the recent literature regarding neoadjuvant chemotherapy for hepatic metastases from CRC, discuss key aspects of the basic science of hepatic regeneration with regard to angiogenic mediators, and outline the key problems to be solved so that a rational strategy can be developed to treat patients with hepatic colorectal metastases in the age of neoadjuvant chemotherapy and antiangiogenic drugs.

Functions and dysfunctions of the nuclear lamin Ig-fold domain in nuclear assembly, growth, and Emery-Dreifuss muscular dystrophy

The non-alpha-helical C terminus of Xenopus lamin B3 (LB3T) inhibits the polymerization of lamin B3 in vitro and prevents the assembly of nuclei in Xenopus egg interphase extracts. To more precisely define the functions of LB3T in nuclear assembly, we have expressed subdomains of LB3T and determined their effects on nuclear assembly in Xenopus extracts. The results demonstrate that the Ig-fold motif (LB3T-Ig) is sufficient to inhibit lamin polymerization in vitro. Addition of the LB3T-Ig to egg extracts before the introduction of chromatin prevents chromatin decondensation and the assembly of the lamina, membranes, and pore complexes comprising the nuclear envelope. When added to assembled nuclei, LB3T-Ig prevents the further incorporation of lamin B3 into the endogenous lamina and blocks nuclear growth. The introduction of a point mutation in LB3T-Ig (R454W; LB3T-IgRW), known to cause Emery-Dreifuss muscular dystrophy when present in lamin A, does not inhibit lamin polymerization, chromatin decondensation, or nuclear assembly and growth. These results shed light on the specific alterations in lamin functions attributable to a known muscular dystrophy mutation and provide an experimental framework for revealing the effects of other mutations causing a wide range of laminopathies.

A role for nuclear lamins in nuclear envelope assembly

The molecular interactions responsible for nuclear envelope assembly after mitosis are not well understood. In this study, we demonstrate that a peptide consisting of the COOH-terminal domain of Xenopus lamin B3 (LB3T) prevents nuclear envelope assembly in Xenopus interphase extracts. Specifically, LB3T inhibits chromatin decondensation and blocks the formation of both the nuclear lamina-pore complex and nuclear membranes. Under these conditions, some vesicles bind to the peripheral regions of the chromatin. These "nonfusogenic" vesicles lack lamin B3 (LB3) and do not bind LB3T; however, "fusogenic" vesicles containing LB3 can bind LB3T, which blocks their association with chromatin and, subsequently, nuclear membrane assembly. LB3T also binds to chromatin in the absence of interphase extract, but only in the presence of purified LB3. Additionally, we show that LB3T inhibits normal lamin polymerization in vitro. These findings suggest that lamin polymerization is required for both chromatin decondensation and the binding of nuclear membrane precursors during the early stages of normal nuclear envelope assembly.

Review: the dynamics of the nuclear lamins during the cell cycle-- relationship between structure and function

The nuclear lamins are members of the intermediate filament (IF) family of proteins. The lamins have an essential role in maintaining nuclear integrity, as do the other IF family members in the cytoplasm. Also like cytoplasmic IFs, the organization of lamins is dynamic. The lamins are found not only at the nuclear periphery but also in the interior of the nucleus, as distinct nucleoplasmic foci and possibly as a network throughout the nucleus. Nuclear processes such as DNA replication may be organized around these structures. In this review, we discuss changes in the structure and organization of the nuclear lamins during the cell cycle and during cell differentiation. These changes are correlated with changes in nuclear structure and function. For example, the interactions of lamins with chromatin and nuclear envelope components occur very early during nuclear assembly following mitosis. During S-phase, the lamins colocalize with markers of DNA replication, and proper lamin organization must be maintained for replication to proceed. When cells differentiate, the expression pattern of lamin isotypes changes. In addition, changes in lamin organization and expression patterns accompany the nuclear alterations observed in transformed cells. These lamin structures may modulate nuclear function in each of these processes.