Biology subjects

Connell, L.

Publications and source records attributed to Connell, L..

4 recordsLinked to original sources

bioRxiv2026

Long-term Musculoskeletal and Marrow Sparing with Proton FLASH in Juvenile Mice: Implications for Pediatric Osteosarcoma

PurposeOsteosarcoma is the most common primary bone malignancy in children and adolescents. Radiotherapy is limited by intrinsic radioresistance and the risk of severe long-term musculoskeletal toxicities. FLASH radiotherapy, delivered at ultra-high dose rates (>40 Gy/s), has demonstrated normal tissue sparing in preclinical models, but its effects on the developing skeleton and marrow remain poorly defined. This study evaluated the chronic normal tissue effects of proton FLASH in juvenile mice, modeling the pediatric context. Methods and MaterialsJuvenile C57BL/6 mice (3-4 weeks old) were randomized to receive 11 Gy FLASH ({approx}200 Gy/s) or conventional proton irradiation (0.2 Gy/s average), or sham treatment to the left hind leg using a synchrotron-based proton beamline. Mice were followed for 10 weeks post-treatment. Bone toxicity was assessed with microCT (bone mineral density, bone volume fractions, trabecular indices) and histology. Bone marrow cellularity was quantified on H&E-stained sections, and muscle fibrosis was assessed using Massons trichrome. ResultsFLASH-treated mice exhibited significant preservation of bone microarchitecture compared with conventional treated mice, with higher bone mineral density and bone volume fractions (p < 0.05). Trabecular numbers were maintained, while structure model index indicates a mechanically favorable trabecular structures in the FLASH group. Bone marrow cellularity was preserved in FLASH mice (5.3% reduction vs. sham) compared with conventional (11.3 % reduction, p < 0.05). Muscle fibrosis was significantly lower in FLASH group (fibrosis positivity 2.6 % vs. 3.0% for FLASH vs. conventional CONV, p < 0.05). No severe immobility or weight loss was observed across groups. ConclusionsProton FLASH significantly reduces long-term bone, marrow, and muscle toxicities in juvenile mice. These findings provide the first demonstration of musculoskeletal sparing in a synchrotron proton FLASH platform and highlight its translational potential for pediatric osteosarcoma.

cancer biology↗

bioRxiv2025

FLASH radiotherapy spares lymphocytes in tumor-draining lymph nodes and increases infiltration of immune cells in tumors

Radiotherapy (RT) delivered at conventional dose rates (CONV) can both stimulate antitumor immune responses and inhibit these immune responses by depleting circulating lymphocytes. Given the observed normal tissue sparing associated with ultra-high dose rate (FLASH) RT, we hypothesized that FLASH RT may protect lymphocytes while increasing the immunogenicity of cancer cells. We irradiated cancer cell lines in vitro with FLASH RT or CONV RT and assessed immunogenic mRNA and protein expression. Both HPV-positive cell lines MEER and TC-1 showed upregulation of Calr, Hmgb1, and cGAS-STING family members after FLASH RT but not after CONV RT in vitro. To assess changes in lymphocyte populations, we irradiated murine mEER tumors in syngeneic C57BL/6 mice with 27 Gy in 3 fractions of FLASH RT or CONV RT. In mice bearing FLASH irradiated tumors, tumor-draining lymph nodes contained greater numbers of CD8+ T cells (FLASH 1.7x104 vs 0.8x104 CONV; P<0.001) and CD4+ T cells (FLASH 2.3x104 vs CONV 1.2x104; P<0.001) after irradiation. FLASH RT was associated with increased numbers of activated CD44+CD62LloCD8+ and CD4+ lymphocytes. In irradiated tumors, FLASH RT was associated with increased CD8+ tumor-infiltrating lymphocytes, increased PD1 expression on these lymphocytes and increased PDL1 expression on macrophages. Compared with CONV RT, FLASH RT spared activated T cells in tumor-draining lymph nodes and in tumors but increased checkpoint inhibitor expression in tumors. These results suggest that FLASH RT may enhance antitumor immune responses by maintaining the immunogenic effects of RT while preserving lymphocyte numbers, which may be augmented with immune checkpoint blockade. SignificanceRadiation-induced lymphopenia is associated with poorer survival outcomes. New treatment approaches, like FLASH radiation therapy (FLASH RT), which reduce lymphopenia and enhance the antitumor response, could potentially lead to better outcomes for cancer patients.

cancer biology↗

bioRxiv2024

Discordance in acute gastrointestinal toxicity between synchrotron-based proton and linac-based electron ultra-high dose rate irradiation

PurposeProton FLASH has been investigated using cyclotron and synchrocyclotron beamlines but not synchrotron beamlines. We evaluated the impact of dose rate (ultra-high [UHDR] vs. conventional [CONV]) and beam configuration (shoot-through [ST] vs. spread-out-Bragg-peak [SOBP]) on acute radiation-induced gastrointestinal toxicity (RIGIT) in mice. We also compared RIGIT between synchrotron-based protons and linac-based electrons with matched mean dose rates. Methods and MaterialsWe administered abdominal irradiation (12-14 Gy single fraction) to female C57BL/6J mice with an 87 MeV synchrotron-based proton beamline (2 cm diameter field size as a lateral beam). Dose rates were 0.2 Gy/s (S-T pCONV), 0.3 Gy/s (SOBP pCONV), 150 Gy/s (S-T pFLASH), and 230 Gy/s (SOBP pFLASH). RIGIT was assessed by the jejunal regenerating crypt assay and survival. We also compared responses to proton [pFLASH and pCONV] with responses to electron CONV (eCONV, 0.4 Gy/s) and electron FLASH (eFLASH, 188-205 Gy/s). ResultsThe number of regenerating jejunal crypts at each matched dose was lowest for pFLASH (similar between S-T and SOBP), greater and similar between pCONV (S-T and SOBP) and eCONV, and greatest for eFLASH. Correspondingly, mice that received pFLASH SOBP had the lowest survival rates (50% at 50 days), followed by pFLASH S-T (80%), and pCONV SOBP (90%), but 100% of mice receiving pCONV S-T survived (log-rank P = 0.047 for the four groups). ConclusionsOur findings are consistent with an increase in RIGIT after synchrotron-based pFLASH versus pCONV. This negative proton-specific FLASH effect versus linac-based electron irradiation underscores the importance of understanding the physical and biological factors that will allow safe and effective clinical translation.

cancer biology↗

bioRxiv2022

The development of intracytoplasmic membranes in alphaproteobacteria involves the conserved mitochondrial crista-developing Mic60 protein

Mitochondrial cristae expand the surface area of respiratory membranes and ultimately allow for the evolutionary scaling of respiration with cell volume across eukaryotes. The discovery of Mic60 homologs among alphaproteobacteria, the closest extant relatives of mitochondria, suggested that cristae might have evolved from bacterial intracytoplasmic membranes (ICMs). Here, we investigated the predicted structure and function of alphaproteobacterial Mic60, and a protein encoded by an adjacent gene Orf52, in two distantly related purple alphaproteobacteria, Rhodobacter sphaeroides and Rhodopseudomonas palustris. In addition, we assessed the potential physical interactors of Mic60 and Orf52 in R. sphaeroides. We show that the three -helices of mitochondrial Mic60s mitofilin domain, as well as its adjacent membrane-binding amphipathic helix, are present in alphaproteobacterial Mic60. The disruption of Mic60 and Orf52 caused photoheterotrophic growth defects, which are most severe under low light conditions, and both their disruption and overexpression led to enlarged ICMs in both studied alphaproteobacteria. We also found that alphaproteobacterial Mic60 physically interacts with BamA, the homolog of Sam50, one of the main physical interactors of eukaryotic Mic60. This interaction, responsible for making contact sites at mitochondrial envelopes, has been conserved in modern alphaproteobacteria despite more than a billion years of evolutionary divergence. Our results suggest a role for Mic60 in photosynthetic ICM development and contact site formation at alphaproteobacterial envelopes. Overall, we provide support for the hypothesis that mitochondrial cristae evolved from alphaproteobacterial ICMs, and therefore have improved our understanding of the nature of the mitochondrial ancestor.

evolutionary biology↗