CD34 positive cells isolated from traumatized human skeletal muscle require the CD34 protein for multi-potential differentiation

PTTG1 promotes CD34+CD45+ cells to repair the pulmonary vascular barrier via activating the VEGF-bFGF/PI3K/AKT/eNOS signaling pathway in rats with phosgene-induced acute lung injury

Accidental exposure to phosgene can cause acute lung injury (ALI), characterized by uncontrolled inflammation and impaired lung blood-gas barrier. CD34⁺CD45⁺ cells with high pituitary tumor transforming gene 1 (PTTG1) expression were identified around rat pulmonary vessels through single-cell RNA sequencing, and have been shown to attenuate P-ALI by promoting lung vascular barrier repair. As a transcription factor closely related to angiogenesis, whether PTTG1 plays a role in CD34⁺CD45⁺ cell repairing the pulmonary vascular barrier in rats with P-ALI remains unclear. This study provided compelling evidence that CD34⁺CD45⁺ cells possess endothelial differentiation potential. Rats with P-ALI were intratracheally administered with CD34⁺CD45⁺ cells transfected with or without PTTG1-overexpressing and sh-PTTG1 lentivirus. It was found that CD34⁺CD45⁺ cells reduced the pulmonary vascular permeability and mitigated the lung inflammation, which could be reversed by knocking down PTTG1. Although PTTG1 overexpression enhanced the ability of CD34⁺CD45⁺ cells to attenuate P-ALI, no significant difference was found. PTTG1 was found to regulate the endothelial differentiation of CD34⁺CD45⁺ cells. In addition, knocking down of PTTG1 significantly reduced the protein levels of VEGF and bFGF, as well as their receptors, which in turn inhibited the activation of the PI3K/AKT/eNOS signaling pathway in CD34⁺CD45⁺ cells. Moreover, LY294002 (PI3K inhibitor) treatment inhibited the endothelial differentiation of CD34⁺CD45⁺ cells, while SC79 (AKT activator) yielded the opposite effect. These findings suggest that PTTG1 can promote the endothelial differentiation of CD34⁺CD45⁺ cells by activating the VEGF-bFGF/PI3K/AKT/eNOS signaling pathway, leading to the repair of the pulmonary vascular barrier in rats with P-ALI.

Prognostic Significance of Integrin Subunit Alpha 2 (ITGA2) and Role of Mechanical Cues in Resistance to Gemcitabine in Pancreatic Ductal Adenocarcinoma (PDAC)

INTRODUCTION

PDAC is an extremely aggressive tumor with a poor prognosis and remarkable therapeutic resistance. The dense extracellular matrix (ECM) which characterizes PDAC progression is considered a fundamental determinant of chemoresistance, with major contributions from mechanical factors. This study combined biomechanical and pharmacological approaches to evaluate the role of the cell-adhesion molecule ITGA2, a key regulator of ECM, in PDAC resistance to gemcitabine.

METHODS

The prognostic value of ITGA2 was analysed in publicly available databases and tissue-microarrays of two cohorts of radically resected and metastatic patients treated with gemcitabine. PANC-1 and its gemcitabine-resistant clone (PANC-1R) were analysed by RNA-sequencing and label-free proteomics. The role of ITGA2 in migration, proliferation, and apoptosis was investigated using hydrogel-coated wells, siRNA-mediated knockdown and overexpression, while collagen-embedded spheroids assessed invasion and ECM remodeling.

RESULTS

High ITGA2 expression correlated with shorter progression-free and overall survival, supporting its impact on prognosis and the lack of efficacy of gemcitabine treatment. These findings were corroborated by transcriptomic and proteomic analyses showing that ITGA2 was upregulated in the PANC-1R clone. The aggressive behavior of these cells was significantly reduced by ITGA2 silencing both in vitro and in vivo, while PANC-1 cells growing under conditions resembling PDAC stiffness acquired resistance to gemcitabine, associated to increased ITGA2 expression. Collagen-embedded spheroids of PANC-1R showed a significant matrix remodeling and spreading potential via increased expression of CXCR4 and MMP2. Additionally, overexpression of ITGA2 in MiaPaCa-2 cells triggered gemcitabine resistance and increased proliferation, both in vitro and in vivo, associated to upregulation of phospho-AKT.

CONCLUSIONS

ITGA2 emerged as a new prognostic factor, highlighting the relevance of stroma mechanical properties as potential therapeutic targets to counteract gemcitabine resistance in PDAC.

Enhancing Interrogation of Skeletal Muscle Samples for Informative Quantitative Data

Careful quantitative analysis of histological preparations of muscle samples is crucial to accurate investigation of myopathies in man and of interpretation of data from animals subjected to experimental or potentially therapeutic treatments. Protocols for measuring cell numbers are subject to problems arising from biases associated with preparative and analytical techniques. Prominent among these is the effect of polarized structure of skeletal muscle on sampling bias. It is also common in this tissue to collect data as ratios to convenient reference dominators, the fundamental bases of which are ill-defined, or unrecognized or not accurately assessable. Use of such 'floating' denominators raises a barrier to estimation of the absolute values that assume practical importance in medical research, where accurate comparison between different scenarios in different species is essential to the aim of translating preclinical research findings in animal models to clinical utility in Homo sapiens.This review identifies some of the underappreciated problems with current morphometric practice, some of which are exacerbated in skeletal muscle, and evaluates the extent of their intrusiveness into the of building an objective, accurate, picture of the structure of the muscle sample. It also contains recommendations for eliminating or at least minimizing these problems. Principal among these, would be the use of stereological procedures to avoid the substantial counting biases arising from inter-procedure differences in object size and section thickness.Attention is also drawn to the distortions of interpretation arising from use of undefined or inappropriate denominators.