Periodic Reporting for period 1 - STENIPATH (Stem and niche cell dynamics in normal and pathological conditions)
Berichtszeitraum: 2022-09-01 bis 2025-02-28
Understanding the dynamics of stem and niche cells in tissue and organ development, growth, and regeneration. Our primary aim is to understand how pathologies (viral infection, tumors), impact stem cell function at distal sites, which could lead to new insights and therapeutic strategies for chronic conditions. The project emerges from two key observations related to stem cell biology. First, we noted that pathological agents can significantly alter the properties and functions of stem/niche cells located far from the primary site of pathology. This led us to identify a novel quiescent cells state that we call G-PATH, and distinct from the well-known G0 phase.
The project has four major aims: 1) Investigate how systemic factors from pathologies influence the quiescent and activated states of MuSCs and other stem cells in different tissues. 2) Assess how pathologies affect the balance between symmetric (self-renewing) and asymmetric (differentiating) cell divisions in MuSCs. 3) Examine the role of stem / niche cell interactions in regulating MuSC behavior during regeneration and in response to pathologies. 4) Identify key regulators that govern the distinct behaviors of cranial and limb muscle stem cells and explore their roles in development and disease resistance.
The project employs a multi-faceted approach combining genetically modified mouse models, advanced imaging techniques, and multi-omics analyses to study stem cell behavior under normal and pathological conditions. The expected impact is to identify new mechanisms underlying tissue degeneration and chronic disease progression. The findings could lead to the development of targeted therapies that mitigate the adverse effects of systemic inflammation and pathological conditions on stem cells, thereby improving tissue regeneration and overall health outcomes.
The project has four major aims: 1) Investigate how systemic factors from pathologies influence the quiescent and activated states of MuSCs and other stem cells in different tissues. 2) Assess how pathologies affect the balance between symmetric (self-renewing) and asymmetric (differentiating) cell divisions in MuSCs. 3) Examine the role of stem / niche cell interactions in regulating MuSC behavior during regeneration and in response to pathologies. 4) Identify key regulators that govern the distinct behaviors of cranial and limb muscle stem cells and explore their roles in development and disease resistance.
The project employs a multi-faceted approach combining genetically modified mouse models, advanced imaging techniques, and multi-omics analyses to study stem cell behavior under normal and pathological conditions. The expected impact is to identify new mechanisms underlying tissue degeneration and chronic disease progression. The findings could lead to the development of targeted therapies that mitigate the adverse effects of systemic inflammation and pathological conditions on stem cells, thereby improving tissue regeneration and overall health outcomes.
1) Aims 1&3: Distal pathologies alter the quiescent and activated states of tissue-specific stem cells. Cellular quiescence is protective with low metabolic activity and reduced transcription. However, it is unclear how distal pathologies impact these cells. We examined two mouse models: influenza-viral lung infection and subcutaneous tumors, and their effects on limb muscle and mesenchymal stromal cells. Quiescent markers and cell cycle markers are blocked, cell size reduced, and metabolic activity diminished, delaying mitosis. Muscle regeneration is compromised, with elevated TNFa levels. Injection of TNFa alone mimicked the perturbed state. Neural stem cells showed similar perturbations (collab. Farinas lab). Chronic pathologies may thus impair tissue stem cell functions. Manuscript in preparation.
2) Aim 3: Adult MuSCs self-renew or differentiate via symmetric (SCD) and asymmetric (ACD) divisions. We analyzed MuSC divisions using Pax7 (stem) and Myogenin (differentiated) markers. Developed three imaging pipelines: ex vivo assays for live tracking, cross-transplantation to assess dynamics, and intravital imaging. MuSCs in Duchenne Muscular Dystrophy (mdx) mice show impaired SCDs and migration. Cross-grafting experiment revealed stem cell-intrinsic fate decisions but migration behavior depended on stem cell-fiber interactions. Manuscript in preparation.
3) Aim 4: Cancer cachexia, marked by decreased calorie intake and metabolic activity, affects skeletal muscle, leading to severe tissue loss. The mechanisms affecting muscle stem cells (MuSCs) during cachexia are unclear. Using the Lewis lung carcinoma (LLC1) mouse model, we examined the phenotype of MuSCs in different muscles at the level of morphology, metabolism, and autophagy. Our preliminary results point to differences in several of these parameters and these experiments are ongoing.
4) Aim 4: Mouse 3D gastruloids allow studying early development and cell fates. We developed a novel protocol that generate morphological structures preceding cranial muscle development. Observed markers (Mesp1, Tbx1, Isl1, Tcf21) indicate head skeletal muscle progenitors are present in our modified gastruloid protocol. Validation and detailed experiments are ongoing.
2) Aim 3: Adult MuSCs self-renew or differentiate via symmetric (SCD) and asymmetric (ACD) divisions. We analyzed MuSC divisions using Pax7 (stem) and Myogenin (differentiated) markers. Developed three imaging pipelines: ex vivo assays for live tracking, cross-transplantation to assess dynamics, and intravital imaging. MuSCs in Duchenne Muscular Dystrophy (mdx) mice show impaired SCDs and migration. Cross-grafting experiment revealed stem cell-intrinsic fate decisions but migration behavior depended on stem cell-fiber interactions. Manuscript in preparation.
3) Aim 4: Cancer cachexia, marked by decreased calorie intake and metabolic activity, affects skeletal muscle, leading to severe tissue loss. The mechanisms affecting muscle stem cells (MuSCs) during cachexia are unclear. Using the Lewis lung carcinoma (LLC1) mouse model, we examined the phenotype of MuSCs in different muscles at the level of morphology, metabolism, and autophagy. Our preliminary results point to differences in several of these parameters and these experiments are ongoing.
4) Aim 4: Mouse 3D gastruloids allow studying early development and cell fates. We developed a novel protocol that generate morphological structures preceding cranial muscle development. Observed markers (Mesp1, Tbx1, Isl1, Tcf21) indicate head skeletal muscle progenitors are present in our modified gastruloid protocol. Validation and detailed experiments are ongoing.
This research will make significant contributions to our understanding of stem cell biology and pathology. By elucidating how systemic factors from pathologies alter stem cell function at distal sites, we aim to uncover new mechanisms underlying tissue degeneration and chronic disease progression. The findings could lead to the development of targeted therapies that mitigate the adverse effects of systemic inflammation and pathological conditions on stem cells, thereby improving tissue regeneration and overall health outcomes. The project's impact extends beyond basic science to potential clinical applications. By exploring the differential responses of stem cells in various tissues to systemic pathologies, the research could pave the way for personalized medicine approaches that tailor treatments based on an individual's unique stem cell and tissue characteristics. Additionally, the insights gained from this study could inform the development of novel therapeutic strategies for muscle-related diseases, such as Duchenne muscular dystrophy, and other conditions involving chronic inflammation and tissue wasting. This project sets the stage for a comprehensive exploration of how pathologies influence stem cell function and tissue regeneration. The integration of advanced technologies and interdisciplinary approaches underscores the project's potential to drive innovation.