Insights into the Health of the Quadriceps from the Articularis Genu of Patients with Osteoarthritis
Location
LSUHSC Center for Advanced Learning and Simulation (CALS)
Document Type
Presentation
Start Date
22-6-2024 10:30 AM
End Date
22-6-2024 11:25 AM
Publication Date
2024-06-22
Description
Introduction: Knee osteoarthritis (kOA) disability involves cartilage degeneration, painful inflammation, and stiffening fibrosis of the joint as a whole, resulting in debilitation of the articular musculature, such as the quadriceps femoris (QF). The vastus medialis oblique (VMO) of the QF is particularly sensitive to severe kOA and functional limitations. Another joint muscle, the articularis genu (AG), runs continuous to the vastus intermedius into the knee and can be sampled as part of the residual tissue excised during total knee arthroplasty (TKA). For this reason, the AG can be used to evaluate features of kOA-attributable myopenia relative to, for example, the muscle-derived paracrine secretome in synovial fluid (SF). Such a link could help develop SF analytics pre-TKA to inform individualized peri-operative strategies for muscular conditioning or rehabilitation. However, the AG must first be solidly confirmed as a surrogate for the disease status of the QF. Previous studies indicate similarities in myofiber type distribution and size between the AG and vastus lateralis relative to kOA-induced deficits in range of motion. This comparative study expands on the structural and gene expression changes related to the size, distribution, and specification of myofibers and endomysial fibrosis in AG and VMO sets of end-stage kOA patients. Methods: Sets of AG and VMO were collected from 19 kOA patients during TKA. Equivalent portions from each muscle were fixed or cryopreserved for histology or RNA isolation, respectively. Fixed muscles were processed for serial paraffin sectioning and stained by picrosirius (PS) technique for collagen or indirect co-immunofluorescence(IIF) labeling of myosin heavy chain (MHC) 7, 2A, and 2X, corresponding to myofiber type (T) 1 (slow), 2a (fast), and 2a/x hybrids (super-fast/inefficient). Three 200x photomicrographs were captured per sample by confocal(Olympus) using excitation at 592nm for PS and 488, 592, and 633nm for myofiber IIF. Slidebook™ (3i) software assisted morphometry of collagen and myofiber tags was used to segment and measure fibrosis or myofiber types and cross-sectional area (CSA). Samples were homogenized, RNA isolated, and cDNA synthesized (Superscript IV; Thermo) for qPCR array (Biorad) with a Lightcycler 480 (Roche) to measure gene expression related to T1 (Myh7, Mef2c) T2a (Myh2, Pgc1α), and T2x (Myh1) myofibers; hypertrophy (Igf1); atrophy (Trim63, Fbxo32); and fibrosis (Ctgf, Tgfβ1). Prism 10.1.2 (GraphPad) was used for correlation analyses using Spearman’s rho (R) with α=0.05. Results: The AG and VMO displayed high association in the distribution of T1 or T2a (R=0.70; p=0.001) and T2a/x (R=0.89; p<0.0001) isoforms, validated by moderate correlations in genes driving specification and transition of T1: Myh7 (R=0.86, p<0.0001) and Mef2c (R=0.50; p=0.070) T2a: Myh2 (R=0.53, p=.042); and T2a/x: Myh1 (R=0.52, p=0.048), all of which displayed an expression trend relative to fiber type percentages in both muscles. The size of T2a fibers was consistent between the muscles (R=0.78, p=<0.0001) and significantly smaller than the CSA of T1 fibers. Higher Igf1 values corresponded to larger CSA of T1 and T2a fibers and were associated between muscles (R=0.74; p=0.002). Conversely high expression of Trim63 indicated severity of atrophy and correlated between the muscles (R=0.79, p=0.0003). Lastly, the severity of endomysial fibrosis was moderately comparable between muscles (R=0.51, p=0.030), in agreement with the number of Tgfβ1 transcripts (R=0.56, p=0.031). Discussion: This comparative study unveils a novel finding-AG myopenia from kOA mirrors measures that indicate disuse of the VMO. These include the presence of typically rare T2a/x hybrid myofibers, compensatory hypertrophy, preferential atrophy of fast twitch fibers, and abnormal thickening of the endomysium with fibrous deposits. This discovery paves the way for future assessment of structural changes in the otherwise discarded parts AG in relation to the levels of muscle-derived drivers of disuse-mediated myopenia of the QF in SF. Significance/Clinical relevance: Establishing the AG as a surrogate for the QF status in kOA marks a significant advancement in developing objective and individualized assessment tools for the condition of the articular musculature before TKA that will impact peri-operative physical therapy and further improve surgical outcomes.
Recommended Citation
Martin, Davis, "Insights into the Health of the Quadriceps from the Articularis Genu of Patients with Osteoarthritis" (2024). Dept. of Orthopaedics: Robert D. D’Ambrosia Lectureship & Research Day. 11.
https://digitalscholar.lsuhsc.edu/ortho_rd/2024/presentation2/11
Insights into the Health of the Quadriceps from the Articularis Genu of Patients with Osteoarthritis
LSUHSC Center for Advanced Learning and Simulation (CALS)
Introduction: Knee osteoarthritis (kOA) disability involves cartilage degeneration, painful inflammation, and stiffening fibrosis of the joint as a whole, resulting in debilitation of the articular musculature, such as the quadriceps femoris (QF). The vastus medialis oblique (VMO) of the QF is particularly sensitive to severe kOA and functional limitations. Another joint muscle, the articularis genu (AG), runs continuous to the vastus intermedius into the knee and can be sampled as part of the residual tissue excised during total knee arthroplasty (TKA). For this reason, the AG can be used to evaluate features of kOA-attributable myopenia relative to, for example, the muscle-derived paracrine secretome in synovial fluid (SF). Such a link could help develop SF analytics pre-TKA to inform individualized peri-operative strategies for muscular conditioning or rehabilitation. However, the AG must first be solidly confirmed as a surrogate for the disease status of the QF. Previous studies indicate similarities in myofiber type distribution and size between the AG and vastus lateralis relative to kOA-induced deficits in range of motion. This comparative study expands on the structural and gene expression changes related to the size, distribution, and specification of myofibers and endomysial fibrosis in AG and VMO sets of end-stage kOA patients. Methods: Sets of AG and VMO were collected from 19 kOA patients during TKA. Equivalent portions from each muscle were fixed or cryopreserved for histology or RNA isolation, respectively. Fixed muscles were processed for serial paraffin sectioning and stained by picrosirius (PS) technique for collagen or indirect co-immunofluorescence(IIF) labeling of myosin heavy chain (MHC) 7, 2A, and 2X, corresponding to myofiber type (T) 1 (slow), 2a (fast), and 2a/x hybrids (super-fast/inefficient). Three 200x photomicrographs were captured per sample by confocal(Olympus) using excitation at 592nm for PS and 488, 592, and 633nm for myofiber IIF. Slidebook™ (3i) software assisted morphometry of collagen and myofiber tags was used to segment and measure fibrosis or myofiber types and cross-sectional area (CSA). Samples were homogenized, RNA isolated, and cDNA synthesized (Superscript IV; Thermo) for qPCR array (Biorad) with a Lightcycler 480 (Roche) to measure gene expression related to T1 (Myh7, Mef2c) T2a (Myh2, Pgc1α), and T2x (Myh1) myofibers; hypertrophy (Igf1); atrophy (Trim63, Fbxo32); and fibrosis (Ctgf, Tgfβ1). Prism 10.1.2 (GraphPad) was used for correlation analyses using Spearman’s rho (R) with α=0.05. Results: The AG and VMO displayed high association in the distribution of T1 or T2a (R=0.70; p=0.001) and T2a/x (R=0.89; p<0.0001) isoforms, validated by moderate correlations in genes driving specification and transition of T1: Myh7 (R=0.86, p<0.0001) and Mef2c (R=0.50; p=0.070) T2a: Myh2 (R=0.53, p=.042); and T2a/x: Myh1 (R=0.52, p=0.048), all of which displayed an expression trend relative to fiber type percentages in both muscles. The size of T2a fibers was consistent between the muscles (R=0.78, p=<0.0001) and significantly smaller than the CSA of T1 fibers. Higher Igf1 values corresponded to larger CSA of T1 and T2a fibers and were associated between muscles (R=0.74; p=0.002). Conversely high expression of Trim63 indicated severity of atrophy and correlated between the muscles (R=0.79, p=0.0003). Lastly, the severity of endomysial fibrosis was moderately comparable between muscles (R=0.51, p=0.030), in agreement with the number of Tgfβ1 transcripts (R=0.56, p=0.031). Discussion: This comparative study unveils a novel finding-AG myopenia from kOA mirrors measures that indicate disuse of the VMO. These include the presence of typically rare T2a/x hybrid myofibers, compensatory hypertrophy, preferential atrophy of fast twitch fibers, and abnormal thickening of the endomysium with fibrous deposits. This discovery paves the way for future assessment of structural changes in the otherwise discarded parts AG in relation to the levels of muscle-derived drivers of disuse-mediated myopenia of the QF in SF. Significance/Clinical relevance: Establishing the AG as a surrogate for the QF status in kOA marks a significant advancement in developing objective and individualized assessment tools for the condition of the articular musculature before TKA that will impact peri-operative physical therapy and further improve surgical outcomes.