Challenging applicability of ISO 10993-5 for calcium phosphate biomaterials evaluation: Towards more accurate in vitro cytotoxicity assessment.

Research on biomaterials typically starts with cytocompatibility evaluation, using the ISO 10993-5 standard as a reference that relies on extract tests to determine whether the material is safe (cell metabolic activity should exceed 70 %). However, the generalized approach within the standard may not accurately reflect the material's behavior in direct contact with cells, raising concerns about its effectiveness. Calcium phosphates (CaPs) are a group of materials that, despite being highly biocompatible and promoting bone formation, still exhibit inconsistencies in basic cytotoxicity evaluations. Hence, in order to test the cytocompatibility dependence on different experimental setups and material-cell interactions, we used amorphous calcium phosphate, α-tricalcium phosphate, hydroxyapatite, and octacalcium phosphate (0.1 mg/mL to 5 mg/mL) with core cell lines of bone microenvironment: mesenchymal stem cells, osteoblast-like and endothelial cells. All materials have been characterized for their physicochemical properties before and after cellular contact and once in vitro assays were finalized, groups identified as 'cytotoxic' were further analyzed using a modified Annexin V apoptosis assay to accurately determine cell death. The obtained results showed that indirect contact following ISO standards had no sensitivity of tested cells to the materials, but direct contact tests at physiological concentrations revealed decreased metabolic activity and viability. In summary, our findings offer valuable guidelines for handling biomaterials, especially in powder form, to better evaluate their biological properties and avoid false negatives commonly associated with the traditional standard approach.

Modeling Pkd1 gene-targeted strategies for correction of polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) causes renal cysts and leads to end-stage renal disease in midlife due mainly to PKD1 gene mutations. Virtually no studies have explored gene therapeutic strategies for long-term effective treatment of PKD. Toward this aim, the severely cystic Pkd1-null mouse model was targeted with a series of transgene transfers using genomic Pkd1 under its regulatory elements (Pkd1wt), a kidney-targeted Pkd1 gene (SBPkd1), or Pkd1Minigene. The introduced Pkd1wt gene constructs with ∼8-fold overexpression display similar endogenous cellular profiles and full complementation of Pkd1-/- phenotype and establish the referral Pkd1 genomic length for proper regulation. SBPkd1 transgene transfer expressing 0.6- or 7-fold Pkd1 endogenous levels is sufficient to correct glomerular and proximal tubular cysts and to markedly postpone cysts in other tubular segments as well, showing that the small SB elements appreciably overlap with Pkd1 promoter/5' UTR regulation. Renal-targeted Pkd1Minigene at high copy numbers conveys an expression level similar to that of the endogenous Pkd1 gene, with widespread and homogeneous weak Pkd1 cellular signal, partially rescuing all cystic tubular segments. These transgene transfers determine that Pkd1 intragenic sequences regulate not only expression levels but also spatiotemporal patterns. Importantly, our study demonstrates that Pkd1 re-expression from hybrid therapeutic constructs can ameliorate, with considerably extended lifespan, or eliminate PKD.

Exploring the Formation Kinetics of Octacalcium Phosphate from Alpha-Tricalcium Phosphate: Synthesis Scale-Up, Determination of Transient Phases, Their Morphology and Biocompatibility.

Even with decades of research studies behind octacalcium phosphate (OCP), determination of OCP phase formation has proved to be a cumbersome challenge. Even though obtaining a large quantity of OCP is important for potential clinical uses, it still remains a hindrance to obtain high yields of pure OCP. Taking that into consideration, the purpose of this study was to scale-up OCP synthesis for the first time and to use a multi-technique approach to follow the phase transformation pathway at multiple time points. In the present study, OCP has been synthesized from α-tricalcium phosphate (α-TCP), and subsequently scaled-up tenfold and hundredfold (100 mg → 10 g). The hydrolysis mechanism has been followed and described by using XRD and FTIR spectroscopy, as well as Raman and SEM. Gradual transformation into the OCP phase transpired through dicalcium phosphate dihydrate (brushite, DCPD, up to ~36%) as an intermediary phase. Furthermore, the obtained transitional phases and final OCP phases (across all scale-up levels) were tested with human bone marrow-derived mesenchymal stem cells (hBMSCs), in order to see how different phase mixtures affect the cell viability, and also to corroborate the safety of the scaled-up product. Twelve out of seventeen specimens showed satisfactory percentages of cell viability and confirmed the prospective use of scaled-up OCP in further in vitro studies. The present study, therefore, provides the first scale-up process of OCP synthesis, an in depth understanding of the formation pathway, and investigation of the parameters able to contribute in the OCP phase formation.

Injectable bone cement containing carboxymethyl cellulose microparticles as a silver delivery system able to reduce implant-associated infection risk.

In the challenging quest for a solution to reduce the risk of implant-associated infections in bone substitution surgery, the use of silver ions is promising regarding its broad spectrum on planktonic, sessile as well as multiresistant bacteria. In view of controlling its delivery in situ at the desired dose, we investigated its encapsulation in carboxymethyl cellulose (CMC) microparticles by spray-drying and included the latter in the formulation of a self-setting calcium phosphate bone cement. We implemented an original step-by-step methodology starting from the in vitro study of the antibacterial properties and cytotoxicity of two silver salts of different solubility in aqueous medium and then in the cement to determine the range of silver loading able to confer anti-biofilm and non-cytotoxic properties to the biomaterial. A dose-dependent efficiency of silver was demonstrated on the main species involved in bone-implant infection (S. aureus and S. epidermidis). Loading silver in microspheres instead of loading it directly inside the cement permitted to avoid undesired silver-cement interactions during setting and led to a faster release of silver, i.e. to a higher dose released within the first days combining anti-biofilm activity and preserved cytocompatibility. In addition, a combined interest of the introduction of about 10% (w/w) silver-loaded CMC microspheres in the cement formulation was demonstrated leading to a fully injectable and highly porous (77%) cement, showing a compressive strength analogous to cancellous bone. This injectable silver-loaded biomimetic composite cement formulation constitutes a versatile bone substitute material with tunable drug delivery properties, able to fight against bone implant associated infection. STATEMENT OF SIGNIFICANCE: This study is based on two innovative scientific aspects regarding the literature: i) Choice of silver ions as antibacterial agent combined with their way of incorporation: Carboxymethylcellulose has never been tested into bone cement to control its drug loading and release properties. ii) Methodology to formulate an antibacterial and injectable bone cement: original and multidisciplinary step-by-step methodology to first define, through (micro)biological tests on two silver salts with different solubilities, the targeted range of silver dose to include in carboxymethylcellulose microspheres and, then optimization of silver-loaded microparticles processing to fulfill requirements (encapsulation efficiency and size). The obtained fully injectable composite controls the early delivery of active dose of silver (from 3 h and over 2 weeks) able to fight against bone implant-associated infections.

Inflammatory Potential of Four Different Phases of Calcium Pyrophosphate Relies on NF-κB Activation and MAPK Pathways.

Background: Calcium pyrophosphate (CPP) microcrystal deposition is associated with wide clinical phenotypes, including acute and chronic arthritis, that are interleukin 1ß (IL-1ß)-driven. Two CPP microcrystals, namely monoclinic and triclinic CPP dihydrates (m- and t-CPPD), have been identified in human tissues in different proportions according to clinical features. m-CPP tetrahydrate beta (m-CPPTß) and amorphous CPP (a-CPP) phases are considered as m- and t-CPPD crystal precursors in vitro. Objectives: We aimed to decipher the inflammatory properties of the three crystalline phases and one amorphous CPP phase and the intracellular pathways involved. Methods: The four synthesized CPP phases and monosodium urate crystals (MSU, as a control) were used in vitro to stimulate the human monocytic leukemia THP-1 cell line or bone marrow-derived macrophages (BMDM) isolated from WT or NLRP3 KO mice. The gene expression of pro- and anti-inflammatory cytokines was evaluated by quantitative PCR; IL-1ß, IL-6 and IL-8 production by ELISA; and mitogen-activated protein kinase (MAPK) activation by immunoblot analysis. NF-κB activation was determined in THP-1 cells containing a reporter plasmid. In vivo, the inflammatory potential of CPP phases was assessed with the murine air pouch model via cell analysis and production of IL-1ß and CXCL1 in the exudate. The role of NF-κB was determined by a pharmacological approach, both in vivo and in vitro. Results:In vitro, IL-1ß production induced by m- and t-CPPD and m-CPPTß crystals was NLRP3 inflammasome dependent. m-CPPD crystals were the most inflammatory by inducing a faster and higher production and gene expression of IL-1ß, IL-6, and IL-8 than t-CPPD, m-CPPTß and MSU crystals. The a-CPP phase did not show an inflammatory property. Accordingly, m-CPPD crystals led to stronger activation of NF-κB, p38, extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) MAPKs. Inhibition of NF-κB completely abrogated IL-1ß and IL-8 synthesis and secretion induced by all CPP crystals. Also, inhibition of JNK and ERK1/2 MAPKs decreased both IL-1ß secretion and NF-κB activation induced by CPP crystals. In vivo, IL-1ß and CXCL1 production and neutrophil infiltration induced by m-CPPD crystals were greatly decreased by NF-κB inhibitor treatment. Conclusion: Our results suggest that the inflammatory potential of different CPP crystals relies on their ability to activate the MAPK-dependent NF-κB pathway. Studies are ongoing to investigate the underlying mechanisms.

Composition and properties of silver-containing calcium carbonate-calcium phosphate bone cement.

The introduction of silver, either in the liquid phase (as silver nitrate solution: Ag(L)) or in the solid phase (as silver phosphate salt: Ag(S)) of calcium carbonate-calcium phosphate (CaCO3-CaP) bone cement, its influence on the composition of the set cement (C-Ag(L) and C-Ag(S) cements with a Ca/Ag atomic ratio equal to 10.3) and its biological properties were investigated. The fine characterisation of the chemical setting of silver-doped and reference cements was performed using FTIR spectroscopy. We showed that the formation of apatite was enhanced from the first hours of maturation of C-Ag(L) cement in comparison with the reference cement, whereas a longer period of maturation (about 10 h) was required to observe this increase for C-Ag(S) cement, although in both cases, silver was present in the set cements mainly as silver phosphate. The role of silver nitrate on the setting chemical reaction is discussed and a chemical scheme is proposed. Antibacterial activity tests (S. aureus and S. epidermidis) and in vitro cytotoxicity tests (human bone marrow stromal cells (HBMSC)) showed that silver-loaded CaCO3-CaP cements had antibacterial properties (anti-adhesion and anti-biofilm formation) without a toxic effect on HBMSC cells, making C-Ag(S) cement a promising candidate for the prevention of bone implant-associated infections.

Strontium-loaded mineral bone cements as sustained release systems: Compositions, release properties, and effects on human osteoprogenitor cells.

This study aims to evaluate in vitro the release properties and biological behavior of original compositions of strontium (Sr)-loaded bone mineral cements. Strontium was introduced into vaterite CaCO3 -dicalcium phosphate dihydrate cement via two routes: as SrCO3 in the solid phase (SrS cements), and as SrCl2 dissolved in the liquid phase (SrL cements), leading to different cement compositions after setting. Complementary analytical techniques implemented to thoroughly investigate the release/dissolution mechanism of Sr-loaded cements at pH 7.4 and 37°C during 3 weeks revealed a sustained release of Sr and a centripetal dissolution of the more soluble phase (vaterite) limited by a diffusion process. In all cases, the initial burst of the Ca and Sr release (highest for the SrL cements) that occurred over 48 h did not have a significant effect on the expression of bone markers (alkaline phosphatase, osteocalcin), the levels of which remained overexpressed after 15 days of culture with human osteoprogenitor (HOP) cells. At the same time, proliferation of HOP cells was significantly higher on SrS cements. Interestingly, this study shows that we can optimize the sustained release of Sr(2+) , the cement biodegradation and biological activity by controlling the route of introduction of strontium in the cement paste.

Significant persistent ductus arteriosus in infants less or equal to 6 kg: percutaneous closure or surgery?

BACKGROUND: Percutaneous closure of large persistent ductus arteriosus using the Amplatzer duct occluder is an alternative to surgery. However, this device is not recommended in infants weighing less than 6 kg. AIM: To evaluate the safety and effectiveness of this procedure in low-body-weight infants. METHODS: We reviewed retrospectively data for infants weighing less or equal to 6 kg who underwent percutaneous closure of significant persistent ductus arteriosus using the Amplatzer duct occluder in France between 1998 and 2007. RESULTS: Data for 58 patients (mean weight: 5 kg, range: 3.4-6; mean age: 5.5 months, range: 2.1-15.3) were reviewed. Mean angiographic persistent ductus arteriosus minimal diameter was 3.7 mm (range: 1-7.5). Implantation of the Amplatzer duct occluder was successful in 89.7% of cases. In six (10.3%) patients, the device was not implanted because it would have led to significant aortic obstruction. One procedure-related death occurred in a 4 kg infant (1.7%). Major and minor complications occurred in 6.9 and 31.0% of patients, respectively. Persistent ductus arteriosus diameter greater than 3.7 mm, type C (tubular shape) and diameter/patient weight ratio greater than 0.91 were significantly associated with an unsuccessful procedure and/or major complications. During a median 10-month follow-up, no late device embolization occurred. CONCLUSIONS: Although percutaneous closure of significant persistent ductus arteriosus with the Amplatzer duct occluder is effective in low-body-weight infants, the level and severity of complications indicate surgery as first-line treatment, at least until further studies are done to assess the safety and effectiveness of the new Amplatzer duct occluder II in low-body-weight infants.

Experimental off-pump transventricular pulmonary valve replacement using a self-expandable valved stent: A new approach for pulmonary incompetence after repaired tetralogy of Fallot?

OBJECTIVE: Off-pump valve replacement using self-expandable stents is an emerging technique for pulmonary valve disease. However, significant limitations are the lack of easily available valve substitute to be inserted within the stent and, in the setting of repaired tetralogy of Fallot, the existence of huge pulmonary trunk. We report the first experimental results of a transventricular approach using a decellularized porcine xenograft mounted in a self-expandable stent. METHODS: Pulmonary valve replacement was realized in 15 lambs by direct access of the infundibulum through a left thoracotomy, combined with pulmonary artery banding. Animals were followed by transthoracic echocardiography and, after control hemodynamic study, were electively killed either at day 7, month 1, or month 4 after implantation. RESULTS: Implantation succeeded in all lambs. Two animals died after implantation (1 pneumothorax and 1 endocarditis). Doppler echocardiographic follow-up did not show any significant transvalvular gradient and showed only mild pulmonary regurgitation. The hemodynamic control before termination revealed a systolic pulmonary valve gradient of 18.5 +/- 12.4 mm Hg at 1 week (n = 4), 13.5 +/- 10.6 mm Hg at 1 month (n = 4), and 4.3 +/- 4.9 mm Hg at 4 months (n = 5). Gross examination demonstrated the presence of connective tissue between the valved stent and pulmonary wall, which increased with time. CONCLUSION: Fifteen lambs underwent successful deployment of a self-expandable valved stent in the pulmonary position using a transventricular approach. This technique combined with pulmonary artery banding could be a therapeutic option for pulmonary insufficiency after repair of tetralogy of Fallot with a transannular patch.

TEVAR in patients with late complications of aortic coarctation repair.

PURPOSE: To review the use of thoracic endovascular aortic repair (TEVAR) for late pseudoaneurysm formation after surgical repair of aortic coarctation. METHODS: From May 2001 to May 2005, 8 patients (5 men; mean age 47.6 years, range 18-73) with a history of aortic coarctation repairs 17 to 40 years prior were referred to our institution for an anastomotic thoracic pseudoaneurysm. TEVAR was performed successfully in 7 patients; 1 died of suspected aneurysm rupture before the scheduled procedure. A carotid-subclavian bypass was performed in 3 patients. RESULTS: All the procedures were immediately successful. No type I endoleaks were seen on the final control angiogram, but 2 of the patients with carotid-subclavian bypasses required additional left subclavian artery embolization due to type II endoleak. One of these patients died before embolotherapy on the 5th postoperative day from presumed aneurysm rupture (14% 30-day mortality rate). Over a follow-up period ranging from 15 to 72 months (mean 37), all the false aneurysms have remained thrombosed and the mean diameter has decreased from 44 to 23 mm. No endograft-related complications have occurred, and no further interventions have so far been necessary. CONCLUSION: TEVAR is a feasible alternative treatment for patients who have already undergone surgical repair of aortic coarctation. Technical issues regarding the endovascular strategy should be discussed with a multidisciplinary team to define the correct interventional plan.

Preoperative ECMO in transposition of the great arteries with persistent pulmonary hypertension.

Persistent fetal circulation in transposition of the great arteries results in severe persistent pulmonary hypertension, which increases the risk of early mortality. We report the case of a newborn with transposition of the great arteries and intact ventricular septum associated with pulmonary hypertension. After the failure of immediate balloon atrial septostomy and supportive therapy including inhaled nitric oxide, preoperative extracorporeal membrane oxygenation reversed pulmonary hypertension and ventricular insufficiency and preceded a safe, delayed, cardiac surgical procedure. Unlike the authors of the other few case reports on this subject, we recommend a preoperative stabilization period after discontinuation of extracorporeal membrane oxygenation to avoid left ventricular "deconditioning" and postoperative deterioration related to recurrent persistent pulmonary hypertension.

Transcatheter closure of aortocaval fistula with the amplatzer duct occluder.

PURPOSE: To report percutaneous closure of aortocaval fistulas with the Amplatzer Duct Occluder. CASE REPORTS: An aortocaval fistula was diagnosed after surgical repair of an abdominal aortic aneurysm in a 73-year-old man. A 3-year-old girl was treated for a congenital aortocaval fistula in another case. An 8 x 6-mm Amplatzer Duct Occluder was introduced via a 6-F introducer in each case, successfully occluding the fistulous track. Both patients are well and without any echocardiographic evidence of a shunt at 6 months. CONCLUSIONS: In selected patients, transcatheter closure of aortocaval fistula with the Amplatzer Duct Occluder could be an alternative to open surgery. Further evaluation is necessary.

Transcatheter occlusion of moderate to large patent arterial ducts, having a diameter above 2.5 mm, with the Amplatzer Duct Occluder. Comparisons with the Rashkind, buttoned devices, and coils in 116 consecutive patients.

AIM: To report results of transcatheter occlusion of moderate to large patent arterial ducts, having a minimum diameter above 2.5 mm, with the Amplatzer duct occluder, and to compare these with results achieved using Rashkind or Sideris devices and Cook detachable coils. DESIGN AND SETTING: Retrospective study conducted on intention-to-treat data from a tertiary referral centre. PATIENTS: Since 1989, 116 consecutive patients, 77 females and 39 males, underwent percutaneous closure with several devices. We used the Rashkind double umbrella in 23 patients, the Sideris buttoned device in 39 patients, coils in 17 patients, and the Amplatzer duct occluder in 37 patients. The median age of the patients was 37 months, and the median weight 13 kg. The mean minimum diameter of the duct was 3.8 +/- 1.22 mm, with a median of 3.5 mm, and range from 2.5 to 10 mm. RESULTS: Implantation succeeded in all but 9 of the children (92%). The time of fluoroscopy was shorter, and full occlusion was better as judged on angiography, in patients closed using the Amplatzer device, despite closure of larger ducts, than in patients closed using other devices (p < 0.0001, p = 0.0003, and p = 0.0015 for the Rashkind, Sideris, and coils, respectively). Complications included embolisation in 2 patients, and haemolysis in 3 patients. In 12 patients, a second device was inserted because of residual shunting noted during follow-up. Complete occlusion was achieved earlier after implantation (p = 0.0002), and the rate of complete occlusion was better in patients receiving an Amplatzer device (97%, p = 0.024) than in patients undergoing closure with other devices. CONCLUSION: Transcatheter closure of moderate to large patent arterial ducts using the Amplatzer duct occluder is an effective and safe procedure, providing better results than those achieved using other occluders.

Transcatheter closure of traumatic ventricular septal defect: an alternative to surgery.

The incidence of ventricular septal defect (VSD) occurs in up to 4.5% of penetrating cardiac trauma. We report a patient with persistent VSD who underwent surgical repair with significant left-to-right shunt and signs of heart failure. We performed a successful transcatheter closure of the VSD with an Amplatzer septal occluder (AGA Medical Corporation; Golden Valley, MN).

Pulmonary arterial occlusive disease following chemotherapy and bone marrow transplantation for leukaemia.

UNLABELLED: Cancer treatment is not known to cause obstructive lesions in the pulmonary artery. We report the case of an 8-year-old girl in whom apparent primary pulmonary hypertension developed shortly after chemotherapy and bone marrow transplantation for myelomonocytic leukaemia (LAME 91 protocol). Cardiac catheterisation showed, at baseline, severe precapillary pulmonary hypertension (mean pulmonary arterial pressure 49 mm Hg) with an increase in pulmonary vascular resistance (23.3 U/m(2)). Prostacyclin infusion demonstrated a 49% reduction and diltiazem infusion a 30% reduction in pulmonary vascular resistance without significant modification of systemic vascular resistance or cardiac output. Significant improvement in functional status was obtained with oral diltiazem. Follow-up cardiac catheterisation 3 months later showed a maintained haemodynamic improvement. CONCLUSION: pulmonary arterial occlusive disease should be added to the list of complications likely to occur after cancer chemotherapy. In addition, our report demonstrates that the pulmonary vasodilator response of vasodilating agents should be tested in such patients.

Aortic arch reconstruction with pulmonary autograft patch aortoplasty.

OBJECTIVE: The optimal technique for aortic arch reconstruction through median sternotomy is still under debate. We have introduced the technique of pulmonary autograft patch aortoplasty as a reliable alternative. METHODS: The outcomes of 51 infants who underwent neonatal repair of interrupted aortic arch (n = 28) or coarctation associated with ventricular septal defect (n = 23) since 1992 were analyzed. The patients were reviewed in three groups according to the aortic arch reconstruction technique: group I underwent direct anastomosis (n = 23), group II underwent homograft or pericardial patch aortoplasty (n = 8), and group III underwent pulmonary autograft patch aortoplasty (n = 20). The pulmonary autograft patch consisted in the anterior wall of the main pulmonary artery, between the supracommissural level and the divided ductus arteriosus. The created defect was replaced with fresh autologous pericardium. RESULTS: All patients except 1 were discharged without significant residual gradient at the level of the aortic arch. At a median delay of 7 months (range 2-51 months), 11 patients (22%) had recurrence of arch obstruction and underwent balloon angioplasty (n = 8) or surgical correction (n = 3). One patient who had undergone direct anastomosis required reoperation for bronchial compression. At a median follow-up of 29 months, the actuarial freedoms from recurrent arch obstruction were 81% for direct anastomosis, 28% for homograft or pericardial patch aortoplasty, and 100% for pulmonary autograft aortoplasty (P =.03 for group III vs group I and P <.0001 for group III vs group II). CONCLUSIONS: The aortic arch repair associated with pulmonary autograft patch augmentation resulted in superior midterm outcomes and therefore constitutes a reliable alternative to the direct anastomosis technique. It allowed complete relief of anatomic afterload and diminished the anastomotic tension, thus reducing the risk of restenosis and tracheobronchial compression. We observed a significantly higher rate of recurrence after patch aortoplasty with other materials.