Despite its limited ability to repair, articular cartilage harbors an endogenous population of progenitor cells (ACPCs), that to date, received limited attention in biomaterials and tissue engineering applications. Harnessing the potential of these cells in 3D hydrogels can open new avenues for biomaterial-based regenerative therapies, especially with advanced biofabrication technologies (e.g. bioprinting). This study highlights the potential of ACPCs to generate neo-cartilage in a gelatin-based hydrogel and bioink. The ACPC-laden hydrogel is a suitable substrate for chondrogenesis and data shows it has a bias in directing cells towards a superficial zone phenotype. For the first time, ACPC-hydrogels are evaluated both as alternative for and in combination with chondrocytes and MSCs, using co-cultures and bioprinting for cartilage regeneration in vitro. This study provides important cues on ACPCs, indicating they represent a promising cell source for the next generation of cartilage constructs with increased biomimicry.
Polyamines are essential for the growth of eukaryotic cells and can be dysregulated in tumors. Here we describe a strategy to deplete polyamines through host–guest encapsulation using a peptide-pillar[5]arene conjugate (P1P5A, P1 = RGDSK(N
3
)EEEE) as a supramolecular trap. The RGD in the peptide sequence allows the molecule to bind to integrin α
v
β
3
-overexpressing tumor cells. The negative charged glutamic acid residues enhance the inclusion affinities between the pillar[5]arene and cationic polyamines via electrostatic interactions and facilitate the solubility of the conjugate in aqueous media. The trap P1P5A efficiently encapsulates polyamines with association constants of 10
5
–10
6
M
−1
. We show that P1P5A has a wide spectrum of antitumor activities, and induces apoptosis via affecting the polyamine biosynthetic pathway. Experiments in vivo show that P1P5A effectively inhibits the growth of breast adenocarcinoma xenografts in female nude mice. This work reveals an approach for suppressing tumor growth by using supramolecular macrocycles to trap polyamines in tumor cells.
Rationale:
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare disease, manifested by syncope or sudden death in children or young adults under stress conditions. Mutations in the Ca
2+
release channel/ryanodine receptor (RyR2) gene account for about 60% of the identified mutations. Recently, we found and described a mutation in RyR2 N-terminal domain, RyR2
R420Q
.
Objective:
To determine the arrhythmogenic mechanisms of this mutation.
Methods and Results:
Ventricular tachycardias under stress conditions were observed in both CPVT patients and KI mice. During action potential recording (by patch-clamp in KI mouse cardiomyocytes and by microelectrodes in mutant hiPSC-CM) we observed an increased occurrence of delayed after-depolarizations (DADs) under isoproterenol stimulation, associated with increased Ca
2+
waves during confocal Ca
2+
recording in both mouse and human RyR2
R420Q
cardiomyocytes. In addition, Ca
2+
-induced Ca
2+
-release, as well as a rough indicator of fractional Ca
2+
release, were higher and Ca
2+
sparks longer in the RyR2
R420Q
expressing cells. At the ultrastructural nanodomain level, we observed smaller RyR2 clusters and widened junctional sarcoplasmic reticulum (jSR) measured by g-STED super-resolution and electronic microscopy, respectively. The increase in jSR width might be due to the impairment of RyR2
R420Q
binding to junctophilin-2, as there were less junctophilin-2 co-immunoprecipitated with RyR2
R420Q
. At the single current level, the RyR2R420Q channel dwells longer in the open state at low [Ca
2+
]
i
, but there is predominance of a subconductance state. The latter might be correlated with an enhanced interaction between the N-terminus and the core solenoid, a RyR2 inter-domain association that has not been previously implicated in the pathogenesis of arrhythmias and sudden cardiac death.
Conclusions:
The RyR2
R420Q
CPVT mutation modifies the interdomain interaction of the channel and weaken its association with junctophillin-2. These defects may underlie both nanoscale disarrangement of the dyad and channel dysfunction.
Most cancer chemotherapy regimens rely on the use of two or more chemotherapeutic agents. A supramolecular approach that may allow co-delivery of two drugs is described here.
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