Understanding the Impact of Group 14 Elements on the Reactivity of [1 + 2] Cycloaddition Reaction between a Cyclic (Alkyl)(amino)carbene Analogue with a Group 14 Element and a Heavy Acetylene Molecule.

Computational exploration using the density functional theory framework (M06-2X-D3/def2-TZVP) was undertaken to investigate the [1 + 2] cycloaddition reaction between a five-membered-ring heterocyclic carbene analogue (G14-Rea; G14 = group 14 element) and a heavy acetylene molecule (G14G14-Rea). It was theoretically observed that exclusively Si-Rea, Ge-Rea, and Sn-Rea demonstrate the capacity to participate in the [1 + 2] cycloaddition reaction with the triply bonded SiSi-Rea. In addition, only three heavy acetylenes (SiSi-Rea, GeGe-Rea, and SnSn-Rea) can catalyze the [1 + 2] cycloaddition reaction with Si-Rea. Our theoretical findings elucidated that the reactivity trend observed in these [1 + 2] cycloaddition reactions primarily arise from the deformation energies of the distorted G14G14-Rea. Also, our study reveals that the bonding characteristics of their respective transition states are controlled by the singlet-singlet interaction (donor-acceptor interaction), rather than the triplet-triplet interaction (electron-sharing interaction). Additionally, our work demonstrates that the bonding behavior between G14-Rea and G14G14-Rea is predominantly determined by the filled p-π orbital of G14G14-Rea (HOMO) → the empty perpendicular p-π orbital of G14-Rea (LUMO), rather than the vacant p-π* orbital of G14G14-Rea (LUMO) ← the filled sp2 orbital of G14-Rea (HOMO).

Evaluation of models to predict prognosis in patients with advanced hepatocellular carcinoma treated with TACE combined with apatinib.

BACKGROUND: The HAP, Six-and-Twelve, Up to Seven, and ALBI scores have been substantiated as reliable prognostic markers in patients presenting with intermediate and advanced hepatocellular carcinoma (HCC) undergoing transarterial chemoembolization (TACE) treatment. Given this premise, our research aims to assess the predictive efficacy of these models in patients with intermediate and advanced HCC receiving a combination of TACE and Apatinib. Additionally, we have conducted a meticulous comparative analysis of these four scoring systems to discern their respective predictive capacities and efficacies in combined therapy. METHODS: Performing a retrospective analysis on the clinical data from 200 patients with intermediate and advanced HCC, we studied those who received TACE combined with Apatinib at the First Affiliated Hospital of the University of Science and Technology of China between June 2018 and December 2022. To identify the factors affecting survival, the study performed univariate and multivariate Cox regression analyses, with calculations of four different scores: HAP, Six-and-Twelve, Up to Seven, and ALBI. Lastly, Harrell's C-index was employed to compare the prognostic abilities of these scores. RESULTS: Cox proportional hazards model results revealed that the ALBI score, presence of portal vein tumor thrombus (PVTT, )and tumor size are independent determinants of prognostic survival. The Kaplan-Meier analyses showed significant differences in survival rates among patients classified by the HAP, Six-and-Twelve, Up to Seven, and ALBI scoring methods. Of the evaluated systems, the HAP scoring demonstrated greater prognostic precision, with a Harrell's C-index of 0.742, surpassing the alternative models (P < 0.05). In addition, an analysis of the area under the AU-ROC curve confirms the remarkable superiority of the HAP score in predicting short-term survival outcomes. CONCLUSION: Our study confirms the predictive value of HAP, Six-and-Twelve, Up to Seven, and ALBI scores in intermediate to advanced Hepatocellular Carcinoma (HCC) patients receiving combined Transarterial Chemoembolization (TACE) and Apatinib therapy. Notably, the HAP model excels in predicting outcomes for this specific HCC subgroup.

Tetrakis(N-heterocyclic Carbene)-Diboron(0): Double Single-Electron-Transfer Reactivity.

The use of 1,3,4,5-tetramethylimidazol-2-ylidene (IMe) to coordinate with diatomic B2 species afforded a tetrakis(N-heterocyclic carbene)-diboron(0) [(IMe)2B-B(IMe)2] (2). The singly bonded B2 moiety therein possesses a valence electronic configuration 1σg21πu21πg*2 with four vacant molecular orbitals (1σu*, 2σg, 1πu', 1πg'*) coordinated with IMe. Its unprecedented electronic structure is analogous to the energetically unfavorable planar hydrazine with a D2h symmetry. The two highly reactive πg* antibonding electrons enable double single-electron-transfer (SET) reactivity in small-molecule activation. Compound 2 underwent a double SET reduction with CO2 to form two carbon dioxide radical anions CO2•-, which then reduced pyridine to yield a carboxylated pyridine reductive coupling dianion [O2CNC5(H)5-C5(H)5NCO2]2- and converted compound 2 to the tetrakis(N-heterocyclic carbene)-diborene dication [(IMe)2B═B(IMe)2]2+ (32+). This is a remarkable transition-metal-free SET reduction of CO2 without ultraviolet/visible (UV/vis) light conditions.

Reactivity of the Intramolecular Vicinal Group-13/P- and B/Group-15-Based Frustrate Lewis Pairs with Sulfur Dioxide: Mechanistic Insight from DFT.

The emission of SO2 gas by industrialized societies contributes to the occurrence of acid rain in natural environments. In this study, we put forward a theoretical investigation into the capture reactions of SO2. Our analysis centers on the energy profiles of intramolecular 1,2-cyclohexylene-bridged FLP-associated molecules. We will particularly examine the reactions involving G13/P-based (with G13 denoting Group 13 element) and B/G15-based (with G15 representing Group 15 element) FLP-associated molecules. Except for Tl/P-FLP, B/N-FLP, and B/Bi-FLP, our theoretical examinations indicate that the remaining six FLP-associated molecules, namely G13'/P-FLP (G13' = B, Al, Ga, and In) and B/G15 ' -FLP (G15' = P, As, and Sb), can easily undergo SO2 capture reactions due to their energetic feasibility. Particularly, our theoretical findings suggested that 1,2-cyclohexylene-bridged Al/P-FLP, Ga/P-FLP, B/As-FLP, and B/Sb-FLP are capable of undergoing a reversible reaction and returning to the initial reactant state. Our theoretical evidence indicates that the G13-G15 bond length in the 1,2-cyclohexylene-linked G13/G15-FLP can serve as a basis for evaluating the free activation barrier associated with its reaction with SO2. Two theoretical methods, namely, the frontier molecular orbital theory and the energy decomposition analysis-natural orbitals of chemical valence approach, are utilized to investigate the electronic structure and bonding nature of the reactions under consideration. Moreover, the analyses based on the activation strain model revealed that it is the geometrical deformation energies of G13/G15-FLP, which is the key factor that greatly influences the activation barriers of such SO2 capture reactions. Further, our theoretical computations indicate that such capturing reactions of SO2 by intramolecular 1,2-cyclohexylene-linked G13/G15-based FLP-type molecules obey the Hammond postulate.

Influence of the Element and Substituent Effects on the Reactivity of Catching Reactions of Difluorocarbene by Benzene-Bridged and Group-13/Group-15-Based Frustrated Lewis Pairs.

The trapping reactions of CF2 by benzene-bridged Group-13/P-based and B/Group-15-based frustrated Lewis pairs (FLPs) have been computationally investigated based on density functional theory. Interestingly, our theoretical calculations predict that the capture of CF2 by all five Group-13/P-based FLPs is energetically feasible. However, in the B/Group-15-based FLPs, only the phosphorus-based B/P-FLP can trap CF2 from kinetic and thermodynamical viewpoints. According to the analyses of the activation strain model, it can be known that the atomic radius of the G15 element (Lewis base) of benzene-bridged B/Group-15-FLP plays an important role in controlling the reactivity of the CF2 catching reactions, whereas the atomic radius of the Group-13 center (Lewis acid) does not play a role in influencing the activation barrier of these CF2 catching reactions. Our theoretical findings based on sophisticated methods suggest that the forward bonding is the FLP-to-CF2 interaction, the LP (Group-15-donor) → vacant p-π-orbital (CF2), which was quantitatively proved to be strong in such present CF2 catching reactions. However, the back bonding is the CF2-to-FLP interaction, the empty σ-orbital (Group-13-acceptor) ← sp2-σ-orbital (CF2), which was verified to be relatively weak. Our theoretical pieces of evidence reveal that the stronger electron-donating ability of the substituents is attached to the Lewis basic center and can make the reaction barrier of the benzene-bridged Group-13/Group-15-based FLP-related compound catching CF2 smaller and more exothermic.

Diverse Reactions of o-Carborane-Fused Silylenes with C≡E (E = C, P) Triple Bonds.

The reactivities of o-carborane-fused silylenes toward molecules with C≡E (E = C, P) bonds are reported. The reactions of bis(silylene) [(LSi:)C]2B10H10 (1a, L = PhC(NtBu)2) with arylalkynes afforded bis(silylium) carborane adducts 2 and 3, showing a Si(µ-C2)Si structure with an open-cage nido-carborane backbone. In contrast, the reaction of 1a with a phosphaalkyne AdC≡P (Ad = 1-adamantyl) smoothly furnished compound 4, comprising fused CPSi rings with a C=Si double bond and Si-Si single bond, and the related formation mechanism was investigated by DFT calculations. Furthermore, when monosilylene [(LSi:)C]CHB10H10 (1b) was employed to react with AdC≡P, compound 5 was isolated. The structure of 5 features a 1,2,3-triphosphetene core. All products were characterized by NMR spectroscopy and/or X-ray crystallography.

NHC-Silyliumylidene Cation-Catalyzed Hydroboration of Isocyanates with Pinacolborane.

The low-oxidation-state silicon-catalyzed hydroboration of isocyanates with pinacolborane (HBpin) using the NHC-silyliumylidene cation catalyst [(IMe)2SiH]I (1, IMe = :C{N(Me)C(Me)}2) is described. In the catalysis, the Si lone pair electrons activate isocyanates, and the latter react with HBpin to form N-boryl formamides at room temperature. Catalyst 1 further activates N-boryl formamides at 70 °C, the intermediates of which react with HBpin to form N-boryl methylamines and (pinB)2O.

Computational insights into the reactivity for the [2+5] cycloaddition reactions of norbornene-linked group 14 element/P-based and Si/group 15 element-based frustrated Lewis pairs with benzaldehyde.

The element effects of Lewis acid (LA) and Lewis base (LB) on the potential energy surfaces of [2+5] cycloaddition reactions of norbornene-based G14/P-based (G14 = group 14 element) and Si/G15-based (G15 = group 14 element) frustrated Lewis pair (FLP)-type molecules with benzaldehyde were theoretically examined via density functional theory and several sophisticated methods. The theoretical findings indicated that among the above nine norbornene-linked G14/G15-based FLPs, only the Si/N-Rea, Si/P-Rea, and Si/As-Rea FLP-assisted compounds can readily undergo cycloaddition reactions with doubly bonded organic systems from kinetic and thermodynamic viewpoints. The energy decomposition analysis showed that the bonding interactions between the norbornene-based G14/G15-FLPs and benzaldehyde are better described in terms of the singlet-singlet model (donor-acceptor model) rather than the triplet-triplet model (electron-sharing model). In particular, natural orbitals for chemical valence findings revealed that the forward bonding is the lone pair (G15) → p-π*(C) interaction, which is a significantly strong FLP-to-benzaldehyde interaction. However, the back-bonding is the p-π*(G14) ← lone-pair orbital(O) interaction, which is a weak benzaldehyde-to-FLP interaction. The analyses based on the activation strain model showed that the larger the atomic radius of either the G14(LA) or the G15(LB) atom, the greater the G14⋯G15 separation distance in the norbornene-based G14/G15-FLP molecule, the smaller the orbital overlaps between G14/G15-FLP and Ph(H)CO, and the higher the activation barrier during its cycloaddition reaction with benzaldehyde.

The reactivity of the trapping reaction of the benzene-bridged boron/phosphorus-based frustrated Lewis pair with difluorocarbene and its group 14 analogs: A theoretical investigation.

The trapping reactions of carbene analogs G14F2 (G14 = group 14 element) by the benzene-bridged B/P-Rea frustrated Lewis pair (FLPs) molecule are studied using density functional theory (B3LYP-D3(BJ)/def2-TZVP). Our theoretical investigations predict that only the CF2 intermediate rather than other heavy carbene analogs can be trapped by the B/P-Rea FLP-type molecule. Energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV) analyses indicate that the bonding nature of the G14F2 catching reactions by the B/P-Rea FLP-type molecule is a donor-acceptor (singlet-singlet) interaction rather than an electron-sharing (triplet-triplet) interaction. Moreover, EDA-NOCV and frontier molecular orbital (FMO) theory findings strongly suggest that the lone pair (LP) (P) → vacant p-π-orbital (G14F2 ) interaction rather than the empty σ-orbital (B) ← sp2 -σ-orbital (G14F2 ) interaction plays a predominant role in establishing its bonding condition during the G14F2 trapping reaction with the B/P-Rea FLP-associated molecule. Our activation strain model findings reveal that the atomic radius of the G14 element of G14F2 plays a key role in determining the activation barrier of the G14F2 trapping reactions by the benzene-bridged B/P-Rea FLP. The valence bond state correlation diagram (VBSCD) model developed by Shaik is used to rationalize the calculated results. The VBSCD findings demonstrate that in the present trapping reactions, the singlet triplet splitting of G14F2 plays a significant role in influencing its reaction barrier and reaction enthalpy. Our theoretical results demonstrate that the relationship between the geometrical parameters of the transition states and the corresponding reaction free energy barriers agrees well with the findings based on the Hammond postulate.

Understanding the Reactivity of Combination Reactions of Intramolecular Geminal Group 13 Element/Phosphorus and Gallium/Group 15 Element Frustrated Lewis Pairs with CS2.

The reactions of CS2 captured by intramolecular geminal G13/P-based (G13 = group 13 elements) and Ga/G15-based (G15 = group 15 elements) frustrated Lewis pairs have been theoretically examined by using density functional theory (DFT) computations. With regard to the nine FLP-related compounds, our DFT calculated results reveal that only Al/P-Rea and Ga/P-Rea can kinetically and thermodynamically precede the energetically feasible combination reactions with CS2 to form the five-membered heterocyclic adducts. Our activation strain model analyses on the nine aforementioned model molecules indicate that the atomic radius of the Lewis acceptor (G13) and the Lewis donor (G15) plays a role in controlling their barrier heights to obtain good orbital overlaps among G13/P-Rea, Ga/G15-Rea, and CS2. Our theoretical observations based on the energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV) approach strongly indicate that the donor-acceptor bonding (i.e., singlet-singlet bonding) rather than the electron-sharing bonding (i.e., triplet-triplet bonding) plays a central role in determining the bonding conditions of the transition states, G13/P-TS and Ga/G15-TS. In addition, the theoretical evidence obtained by the frontier molecular orbital theory and EDA-NOCV analyses reveals that the best description for the bonding natures of the combination reactions of intramolecular geminal G13/P-Rea and Ga/G15-Rea with CS2 is the lone pair(G15) → p-π*(C) interaction rather than the p-π*(G13) ← p-π(S) interaction. Moreover, our present DFT computations concerning the calculated structures and corresponding relative energetics of the stationary points connected with the aforementioned sophisticated approaches are in accordance with the Hammond postulate.

Isolation of Silacycles from the Reactions of a Monochlorosilylene LSi(:)Cl (L = PhC(NtBu)2) with Ethynyl Lithium Salts.

The reactions of amidinate silylene chloride LSi(:)Cl (L = PhC(NtBu)2) with TMS- and Ph-ethynyl lithium salts gave rise to silacycles 1 and 4, respectively. The formation of 1 and 4 may undergo cyclo-condensations of transient ethynylsilylene intermidiates and the activation of an amidinate backbone. The distinct structures of 1 and 4 may be derived from the different electronic or steric properties of ethynyl substituents, and their formation mechanisms were investigated by density functional theory (DFT) calculations. Moreover, a sequential reaction of LSi(:)Cl with BH3·SMe2 and TMSC≡CLi as well as a reaction of LSi(:)Cl with TMSC≡CLi under O2 exclusively obtained ethynylsilanes 2 and 3, respectively, which indicated that either blocking a lone pair of a Si(II) atom or oxidizing Si(II) to Si(IV) prevents the further conversion of ethynylsilylenes to silacycle 1. All products were characterized by NMR spectroscopy and X-ray crystallography.

Deoxygenating Reduction of CO2 by [Cp*Al]4 to Form a (Al3O2C)2 Cluster Featuring Two Ketene Moieties.

Herein we report that the reaction of the low-valent aluminum(I) species [Cp*Al]4 (Cp* = pentamethylcyclopentadienyl) with CO2 exhibits complete cleavages of the C═O bonds. The deoxygenating reduction reaction of [Cp*Al]4 with CO2 at 120 °C afforded [(Cp*)3Al3O2C(CO)]2 (1), which featured two stacked (Al3O2C)2 units and two C═C═O ketene moieties. Moreover, the isoelectronic analogues of diimine and isothiocyanate with CO2 were also investigated, and the reactions of [Cp*Al]4 with Dipp*-N═C═N-Dipp* and Dipp-C═N═S [Dipp* = 2,6-bis(diphenylmethyl)-4-tert-butylphenyl; Dipp = 2,6-diisopropylphenyl] afforded dialuminylimine (2) and tetrameric [Cp*AlS]4 (3), respectively.

Theoretical Study of the Activation Reaction of a Zr+/P-Based Frustrated Lewis Pair with Carbon Dioxide.

The combination reactions of carbon dioxide with a Zr+/P-based frustrated Lewis pair (FLP) were computationally explored within the density functional theory framework [B3LYP-D3(BJ)/def2-TZVP]. Results showed that these reactions are exothermic, associated with relatively low activation barriers, and proceed concertedly involving Zr+-O and P-C chemical bond formations. Theoretical analysis revealed that the shorter the Zr+···P bond length of the Zr+/P-based FLP, the shorter the stretching O-C bond length of CO2 upon reaction, the larger the ∠OCO bending angle of CO2, the smaller the deformation energy of CO2, the lower the barrier height, and the greater the reactivity between the Zr+/P-based FLP and CO2. According to the energy decomposition analysis-natural orbitals for chemical valence, the bonding natures of their associated transition states are determined by the singlet-singlet interaction (donor-acceptor interaction), not the triplet-triplet interaction (electron-sharing interaction). Moreover, the bonding characteristics between Zr+/P-based FLPs and CO2 are established predominantly by the lone pair orbital(P) → the empty p-π* orbital (CO2) interaction, not the empty d-orbital(Zr+) ← the filled p-π orbital (CO2) interaction. With the use of the activation strain model, theoretical examinations showed that the reactivity trend of such combination reactions is mainly attributed to the deformation energies of the deformed reactants. The relationship between deformed geometrical structures and related activation energies is in good agreement with Hammond's postulate.

A Pyridine-Stabilized N-Phosphinoamidinato N-Heterocyclic Carbene-Diboravinyl Cation: Boron Analogue of Vinyl Cation.

A boron analogue of vinyl cation, pyridine-stabilized N-phosphinoamidinato N-heterocyclic carbene (NHC)-diboravinyl cation 2+ , was synthesized by displacement of bromide in diborene 1 with excess pyridine. Experimental and computational studies showed that the positive charge is mainly at the B-B skeleton with delocalization to the pyridine ligand. One of the main modes of reactivity is through the B=B double bond alongside activation of the pyridine substituent, where the Bpyridine center is the predominant nucleophilic center and the predominant electrophilic center is either the activated pyridine para position or the BNHC center, illustrating the presence of diborene cation A, borylene-borenium cation B and diborene-pyridinium cation C resonance structures in cation 2+ .

Significant Insight into the Origin of Reaction Barriers Determining Dihydrogen Activation by G13-P-P (G13 = Group 13 Element) and G15-P-Ga (G15 = Group 15 Element) Frustrated Lewis Pairs.

The heterolytic cleavage of H2 by multiply bonded phosphorus-bridged G13-P-P-Rea (G13 = B, Al, Ga, In, and Tl) and G15-P-Ga-Rea (G15 = N, P, As, Sb, and Bi) frustrated Lewis pairs (FLPs) has been theoretically investigated using density functional theory calculations. For the above nine FLP-type molecules, our theoretical findings suggest that only Al-P-P-Rea, Ga-P-P-Rea, and In-P-P-Rea can undergo the energetically feasible H2 activation reaction from kinetic and thermodynamic viewpoints. Our study based on the activation strain model (ASM) reveals that gaining a better orbital overlap between G13-P-P-Rea and G15-P-Ga-Rea molecules and H2 affected the reaction barriers through the atomic radius of G13 and G15. According to our energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV) results, the bonding of these H2 activation reactions involving G13-P-P-Rea and G15-P-Ga-Rea is dominated by the donor-acceptor interaction (singlet-singlet interaction) rather than the electron-sharing interaction (triplet-triplet interaction). Moreover, our EDA-NOCV evidence reveals that the best description for the above bonding situations is the lone pair(G15) → σ*(H2) interaction rather than the empty p-π-orbital(G13) ← σ(H2) interaction. In particular, the findings in this work based on theoretically calculated geometries and the corresponding relative free energies of the stationary points combined with the results from the above sophisticated methods nicely agree with the famous Hammond postulate.

Reactivity of dicationic N-heterocyclic chalcogen carbene analogues with methane and ethene: a theoretical investigation.

The reactions of chalcogen N-heterocyclic carbenic (NHC) dications [(Dipp2DAB)M2+, M = O, S, Se, and Te, and Dipp2DAB = 1,4-(2,6-diisopropyl)phenyl-1,4-diaza-1,3-butadiene] with methane and ethene are investigated by the density functional theory. The activation energies and reaction enthalpies are analyzed by the energy decomposition analysis (EDA) to understand the reactivity of the reactions. Calculations show that the oxide carbenic dication (Dipp2DAB)O2+ reactant has a pair of rather unbalanced O-N bonds due to the combined effects of the smallness of the central O atom and the bulkiness of the two Dipp ligands surrounding the DAB ring, suggesting the oxide reactant is much less stable than the chalcogenide ones. Because of its unique characteristics, the oxide carbenic dication distinguishes itself from the rest of the chalcogen family. The differences between oxides and chalcogenides of the chalcogen family complexes well known in inorganic chemistry are also observed in this theoretical investigation. This work further reveals that the reasons for the distinctive characteristics between oxide and chalcogenide complexes are due to the fundamental fact that the 2s and 2p atomic orbitals are more amenable to hybridization than those of higher valences, and the mixing of the former valence orbitals results in much smaller atoms than the latter.

Formation of Alkynylgermyl-Substituted Germylenes via a Catenation of Ge Atoms.

Reactions of amidinate-stabilized germylene chlorides R1Ge(:)Cl (R1 = PhC(NtBu)2) and R2Ge(:)Cl (R2 = PhC(NCy)2, Cy = cyclohexanyl) with trimethylsilylethynyl lithium salt (LLi, L = -C≡CTMS) afforded alkynylgermyl-substituted germylenes R1(:)Ge-GeL3 (1) and [R2GeL2]2Ge(:) (2), respectively. Both of them may undergo the formation of Ge-Ge single bonds with a concomitant 1,2-shift of ethynyl groups. DFT calculations determined the reaction pathways where two possible intermediates (:)GeL2 and RGe(:)L (R = R1, R2) are proposed, which were consistent with the trapping reactions of (:)GeL2 toward IAr-(:)GeL2 (3, IAr = :C{N(Ar)CH}2, Ar = 2,6-iPr2C6H3). The reaction of 1 with N3TMS gave a new aminogermylene R1(:)Ge-N(TMS)-GeL3 (4), indicating a reactive Ge-Ge bond.

Mechanistic Investigations on the Photorearrangement Reactions of M(CO)4(CS) (M = Group 6 Metal).

The mechanisms for the photoisomerization reactions are studied theoretically at the M06-2X/Def2-TZVPD level of theory, using the five-coordinated M(CO)4(CS) (M = Cr, Mo, and W) complexes as model systems. This study provides the first theoretical evidence for the mechanisms of these photorearrangements of the five coordinated metal complexes. That is, the photoisomerization process is primary the axial to basal movement of CS. The model study demonstrates that the preferred reaction route for the photorearrangement reactions is as follows: reactant → Franck-Condon region → minimum (triplet) → transition state (triplet) → triplet/singlet intersystem crossing → photoproduct. The theoretical results also show that the energy differences between the crucial points are quite small, which demonstrates that the CS group rotates easily to form the different conformations when the M(CO)4(CS) molecules have been photoirradiated. These photochemical mechanisms are consistent with the available experimental observations.

Distinguishing characteristics of stem cells derived from different anatomical regions of human degenerated intervertebral discs.

INTRODUCTION: Several types of stem cells have been successfully demonstrated to exist in the human degenerated intervertebral disc (IVD), which is composed of annulus fibrosus (AF), nucleus pulposus (NP) and cartilage endplate (CEP). However, the differences in the biological characteristics among these and bone marrow derived mesenchymal stem cells (BM-MSCs) remain unclear. MATERIALS AND METHODS: To investigate this issue, cells were harvested from human AF, NP, CEP, and bone marrow, respectively; passage 2 cells were selected using the agarose suspension culture system to obtain stem cell clones. Following expansion in vitro, stem cells from different anatomical regions were compared regarding the morphology, proliferation ability, immunophenotypic expression, and multi-lineage differentiation capacity. In addition, stem cell-alginate bead compositions were constructed for the comparison of DNA and sGAG content. RESULTS: There were subtle differences regarding cell morphology, but no significant differences in proliferation ability among the four types of stem cells. For the immunophenotypic analysis, all stem cells basically fulfilled the criteria for mesenchymal stem cells (MSCs), which have been published by the International Society for Cellular Therapy (ISCT), with a significant difference in CD105 expression. A comparison of the osteogenic capacities indicated: cartilage endplate-derived stem cells (CESCs) > annulus fibrosus-derived stem cells (AFSCs) > BM-MSCs > nucleus pulposus-derived stem cells (NPSCs). The chondrogenesis difference was similar to osteogenesis. For adipogenesis: BM-MSCs >NPSCs >CESCs >AFSCs. In the stem cell/alginate composition, the CESCs consistently showed the superior chondrogenic potential among all those cell types. CONCLUSIONS: Our data indicated that all the four types of stem cells shared some similar biological properties (regarding shape, proliferation ability and immunophenotypic expression). CESCs, which had the strongest osteogenic and chondrogenic potentials, may serve as excellent seed cells for NP/cartilage or bone tissue engineering.

Minimally invasive transforaminal interbody fusion surgery for the old fracture of the thoracolumbar junction.

STUDY DESIGN: Retrospective analysis of the clinical outcomes of 15 patients with the old thoracolumbar junction fracture treated by minimally invasive surgery (MIS) transforaminal interbody fusion surgery. OBJECTIVE: To investigate the efficacy and safety of MIS for the old fracture of the thoracolumbar junction in a pilot study. SUMMARY OF BACKGROUND DATA: MIS have demonstrated efficacy in the treatment of lumbar degenerative diseases. There is some controversy regarding the ideal management of thoracolumbar fractures, especially those without an associated neurologic deficit. Reports concerning MIS for old thoracolumbar junction fracture with chronic pain are quite rare. METHODS: A total of 15 MIS fusion, performed between October 2006 and May 2011, were examined in a retrospective study. The clinical and radiological data were collected and analyzed. Fusion levels were T10­T11 (2 patients), T11­T12 (5 patients), T12­L1 (6 patients), L1­L2 (2 patients). Clinical outcome was assessed using the visual analogue scale and the Oswestry disability index. Radiographic evaluation of the lumbar spine was performed at the second day and 12 months postoperatively. RESULTS: The average follow-up period was 26.3 months, with a minimum of 17 months. The mean operating time, intraoperative blood loss, and x-ray exposure time were 125±31 minutes, 226±45 mL, and 47±12 seconds, respectively. At last followup,the visual analogue scale for back pain and the Oswestry disability index decreased significantly postoperatively from 7.4±2.3 to 1.8±0.6 (P<0.01) and from 38.9±7.1 to 13.5±4.5 (P<0.01), respectively. The average Cobb angle was improved from 19.1­15.1 degrees in this series. No significant correction of local kyphosis was found postoperatively (P>0.05). Radiographic evaluation showed satisfactory bony union at the fixed level in all cases except for 2 patients. There were no other major complications at last follow-up. CONCLUSIONS: MIS transforaminal interbody fusion is a safe and effective procedure for old thoracolumbar junction fracture with chronic pain. Improvement of kyphosis is limited and occurrence of nonunion is relatively high.