Collagen type VI regulates TGFß bioavailability in skeletal muscle.

Collagen VI-related disorders (COL6-RDs) are a group of rare muscular dystrophies caused by pathogenic variants in collagen VI genes (COL6A1, COL6A2, and COL6A3). Collagen type VI is a heterotrimeric, microfibrillar component of the muscle extracellular matrix (ECM), predominantly secreted by resident fibroadipogenic precursor cells in skeletal muscle. The absence or mislocalizatoion of collagen VI in the ECM underlies the non-cell autonomous dysfunction and dystrophic changes in skeletal muscle with an as of yet elusive direct mechanistic link between the ECM and myofiber dysfunction. Here, we conduct a comprehensive natural history and outcome study in a novel mouse model of COL6-RDs (Col6a2-/- mice) using standardized (Treat-NMD) functional, histological, and physiologic parameter. Notably, we identify a conspicuous dysregulation of the TGFß pathway early in the disease process and propose that the collagen VI deficient matrix is not capable of regulating the dynamic TGFß bioavailability at baseline and also in response to muscle injury. Thus, we propose a new mechanism for pathogenesis of the disease that links the ECM regulation of TGFß with downstream skeletal muscle abnormalities, paving the way for developing and validating therapeutics that target this pathway.

Association of Initial Maximal Motor Ability With Long-term Functional Outcome in Patients With COL6-Related Dystrophies.

OBJECTIVE: To accurately categorize the phenotypes of individuals with collagen VI-related dystrophies (COL6-RDs) during the first years of life to predict long-term motor function and pulmonary function, to provide phenotype-specific anticipatory care, and to improve clinical trial readiness. METHODS: This retrospective, multicenter, international study analyzed the relationship of long-term motor and pulmonary function with the initial maximal motor ability achieved in individuals with COL6-RD. RESULTS: We studied 119 patients with COL6-RD from Spain (n = 54) and the United States (n = 65). The early maximal motor milestones of ability to rise from the floor unassisted and ability to climb 4 steps without holding onto a railing demonstrated reliability in distinguishing between 3 COL6-RD phenotypic subgroups: (1) Ullrich congenital muscular dystrophy, (2) intermediate COL6-RD, and (3) Bethlem myopathy. Long-term motor function and pulmonary function are strongly correlated with the maximal motor ability achieved during the first years of life. Maximal motor capacity can predict other disease-relevant events such as the age at loss of ambulation and the need for the initiation of nocturnal noninvasive ventilation. CONCLUSION: This work proposes a prospective phenotypic classification for COL6-RDs that will enable an accurate prediction of a patient's COL6-RD phenotype during the first years of life. The ability to establish a patient's COL6-RD phenotypic classification early will enable a more accurate prognosis of future motor and pulmonary function, thus improving anticipatory clinical care, and it will be instrumental in aiding the design of future clinical trials by allowing early stratification of trial cohorts.

Innocuous pressure sensation requires A-type afferents but not functional ΡΙΕΖΟ2 channels in humans.

The sensation of pressure allows us to feel sustained compression and body strain. While our understanding of cutaneous touch has grown significantly in recent years, how deep tissue sensations are detected remains less clear. Here, we use quantitative sensory evaluations of patients with rare sensory disorders, as well as nerve blocks in typical individuals, to probe the neural and genetic mechanisms for detecting non-painful pressure. We show that the ability to perceive innocuous pressures is lost when myelinated fiber function is experimentally blocked in healthy volunteers and that two patients lacking Aß fibers are strikingly unable to feel innocuous pressures at all. We find that seven individuals with inherited mutations in the mechanoreceptor PIEZO2 gene, who have major deficits in touch and proprioception, are nearly as good at sensing pressure as healthy control subjects. Together, these data support a role for Aß afferents in pressure sensation and suggest the existence of an unknown molecular pathway for its detection.

PIEZO2 in sensory neurons and urothelial cells coordinates urination.

Henry Miller stated that "to relieve a full bladder is one of the great human joys". Urination is critically important in health and ailments of the lower urinary tract cause high pathological burden. Although there have been advances in understanding the central circuitry in the brain that facilitates urination1-3, there is a lack of in-depth mechanistic insight into the process. In addition to central control, micturition reflexes that govern urination are all initiated by peripheral mechanical stimuli such as bladder stretch and urethral flow4. The mechanotransduction molecules and cell types that function as the primary stretch and pressure detectors in the urinary tract mostly remain unknown. Here we identify expression of the mechanosensitive ion channel PIEZO2 in lower urinary tract tissues, where it is required for low-threshold bladder-stretch sensing and urethral micturition reflexes. We show that PIEZO2 acts as a sensor in both the bladder urothelium and innervating sensory neurons. Humans and mice lacking functional PIEZO2 have impaired bladder control, and humans lacking functional PIEZO2 report deficient bladder-filling sensation. This study identifies PIEZO2 as a key mechanosensor in urinary function. These findings set the foundation for future work to identify the interactions between urothelial cells and sensory neurons that control urination.

Dominant collagen XII mutations cause a distal myopathy.

OBJECTIVE: To characterize the natural history and clinical features of myopathies caused by mono-allelic, dominantly acting pathogenic variants in COL12A1. METHODS: Patients with dominant COL12A1-related myopathies were characterized by history and clinical examination, muscle imaging, and genetic analysis. Pathogenicity of the variants was assessed by immunostaining patient-derived dermal fibroblast cultures for collagen XII. RESULTS: Four independent families with childhood-onset weakness due to novel, dominantly acting pathogenic variants in COL12A1 were identified. Adult patients exhibited distal-predominant weakness. Three families carried dominantly acting glycine missense variants, and one family had a heterozygous, intragenic, in-frame deletion of exon 52 of COL12A1. All pathogenic variants resulted in increased intracellular retention of collagen XII in patient-derived fibroblasts as well as loss of extracellular, fibrillar collagen XII deposition. Since haploinsufficiency for COL12A1 is largely clinically asymptomatic, we designed and evaluated small interfering RNAs (siRNAs) that specifically target the mutant allele containing the exon 52 deletion. Immunostaining of the patient fibroblasts treated with the siRNA showed a near complete correction of collagen XII staining patterns. INTERPRETATION: This study characterizes a distal myopathy phenotype in adults with dominant COL12A1 pathogenic variants, further defining the phenotypic spectrum and natural history of COL12A1-related myopathies. This work also provides proof of concept of a precision medicine treatment approach by proposing and validating allele-specific knockdown using siRNAs specifically designed to target a patient's dominant COL12A1 disease allele.

3D Printing of Elastic Membranes for Fluidic Pumping and Demonstration of Reciprocation Inserts on the Microfluidic Disc.

While 3D printing is increasingly used in most fields of engineering, its utilization for microfluidics has thus far been limited. To demonstrate future applications of 3D printing for microfluidic structures, we investigate the fluidic characteristics of material jetted surfaces. We also demonstrate the manufacture of dual-material microfluidic inserts that feature rigid and elastic elements. The fabricated parts are inserted on a microfluidic CD, enhancing design freedom and prototyping capability of over molded parts. Furthermore, printed elastic membranes are tested for fatigue during elastic-pneumatic pumping and rigid and elastic surfaces are characterized with regards to hydrophilicity and surface topography. Finally, different printed disc inserts are demonstrated for moving liquid towards the center of rotation, the mixing of liquids, and controlling burst events through channels width.