Hutchinson-Gilford progeria syndrome (HGPS) is a rare, fatal, and premature aging disorder caused by progerin, a truncated form of lamin A that disrupts nuclear architecture, induces systemic inflammation, and accelerates senescence. While the farnesyltransferase inhibitor lonafarnib extends the lifespan by limiting progerin farnesylation, it does not address the chronic inflammation or the senescence-associated secretory phenotype (SASP), which worsens disease progression. In this study, we investigated the combined effects of baricitinib (BAR), a JAK1/2 inhibitor, and lonafarnib (FTI) in a LmnaG609G/G609G mouse model of HGPS. BAR + FTI therapy synergistically extended the lifespan by 25%, surpassing the effects of either monotherapy. Treated mice showed improved health, as evidenced by reduced kyphosis, better fur quality, decreased incidence of cataracts, and less severe dysgnathia. Histological analyses indicated reduced fibrosis in the dermal, hepatic, and muscular tissues, restored cellularity and thickness in the aortic media, and improved muscle fiber integrity. Mechanistically, BAR decreased the SASP and inflammatory markers (e.g., IL-6 and PAI-1), complementing the progerin-targeting effects of FTI. This preclinical study demonstrates the synergistic potential of BAR + FTI therapy in addressing HGPS systemic and tissue-specific pathologies, offering a promising strategy for enhancing both lifespan and health.

Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) and Spastic Paraplegia Type 7 (SPG7) are paradigmatic spastic ataxias (SPAX) with suggested white matter (WM) involvement. Aim of this work was to thoroughly disentangle the degree of WM involvement in these conditions, evaluating both macrostructure and microstructure via the analysis of diffusion MRI (dMRI) data. In this multi-center prospective study, ARSACS and SPG7 patients and Healthy Controls (HC) were enrolled, all undergoing a standardized dMRI protocol and a clinimetrics evaluation including the Scale for the Assessment and Rating of Ataxia (SARA). Differences in terms of WM volume or global microstructural WM metrics were probed, as well as the possible occurrence of a spatially defined microstructural WM involvement via voxel-wise analyses, and its correlation with patients' clinical status. Data of 37 ARSACS (M/F = 21/16; 33.4 ± 12.4 years), 37 SPG7 (M/F = 24/13; 55.7 ± 10.7 years), and 29 HC (M/F = 13/16; 42.1 ± 17.2 years) were analyzed. While in SPG7, only a mild mean microstructural damage was found compared to HC, ARSACS patients present a severe WM involvement, with a reduced global volume (p < 0.001), an alteration of all microstructural metrics (all with p < 0.001), without a spatially defined pattern of damage but with a prominent involvement of commissural fibers. Finally, in ARSACS, a correlation between microstructural damage and SARA scores was found (p = 0.004). In ARSACS, but not SPG7 patients, we observed a complex and multi-faced involvement of brain WM, with a clinically meaningful widespread loss of axonal and dendritic integrity, secondary demyelination and, overall, a reduction in cellularity and volume. The term “ptosis” is derived from the Greek word falling and refers to drooping of a body part. Blepharoptosis is upper eyelid drooping with the eyes in the primary position of gaze. The shape of one's eyes along with the position of the eyelids, shape, and position of the eyebrow determines one's identity. Hence, drooping of the eyelids may produce a functional or a cosmetic deficit. Ptosis can occur in all age groups and is the result of various factors. One must remember that when a patient presents with complaints of drooping, it is a mere symptom and not the diagnosis. A thorough evaluation is of utmost importance to determine the cause. Ptosis can classify as true ptosis or pseudoptosis. True ptosis is further classified based on the age of presentation into congenital ptosis and acquired ptosis. Acquired adult ptosis is further classified based upon the etiological factors as: 1. Aponeurotic ptosis. 2. Neurogenic ptosis. 3. Myogenic ptosis. 4. Mechanical ptosis. 5. Traumatic ptosis. Aponeurotic ptosis Aponeurotic ptosis is the most prevalent form of adult ptosis and usually presents in the 5th or 6th decade of life. It is also known as involutional ptosis. However, it can occur in young individuals following trauma, recent eyelid swelling, ocular surgery or prolonged use of contact lenses. The pathogenesis of aponeurotic ptosis is most often due to dehiscence or disinsertion of the levator aponeurosis. In involutional cases, true dehiscence is sometimes absent, and ptosis occurs due to stretching or thinning of the aponeurosis. Rarely the levator muscle shows fatty infiltration. Characteristic features of this type of ptosis are that patients have a good levator function with a high lid crease, affected eyelid appears lower on down gaze and a thin upper eyelid with redundant skin. Neurogenic ptosis Neurogenic ptosis results from any condition which disrupts the innervation of either the levator muscle or muller’s muscle. The varieties most commonly encountered by an ophthalmologist are 3rd cranial nerve palsy and Horner syndrome. Third cranial nerve palsy Lesions along the oculomotor nerve present with ptosis and restriction of adduction, elevation and depression movements of the eyeball. Pupillary involvement may or may not be present. Bell's phenomenon is usually poor. Pupil-involving third nerve palsy is considered a neurological as it is most often due to a posterior communicating artery aneurysm compressing the nerve. Pupil-sparing third nerve palsy is most often due to an ischemic vascular cause and usually resolves spontaneously in 3 months. Other causes include inflammation, trauma or tumors along the course of the nerve. Lesions of the superior orbital fissure, orbital apex, or cavernous sinus, present in combination with other cranial nerve palsies. Treatment is challenging as the patients have a poor or absent Bell’s phenomenon placing them at high risk of developing exposure keratopathy post-surgery. Ideally, strabismus surgery is done first to correct the deviation followed by ptosis correction via the frontalis sling technique with planned under-correction. Horner syndrome (Oculosympathetic paresis) Horner syndrome consists of mild ptosis, pupillary miosis, apparent enophthalmos, and anhidrosis. It occurs due to interruption of the sympathetic nerve supply to the muller’s muscle and dilator pupillae muscle. Pupillary anisocoria can be well demonstrated in dim illumination. Patients with Horner’s syndrome occurring during childhood also have iris heterochromia due to decreased melanin production in melanocytes which is controlled by the sympathetic pathway. The diagnosis of Horner syndrome is often made clinically. Pharmacological tests using 4% cocaine, 1% hydroxyamphetamine or 2.5% phenylephrine help confirm the diagnosis. Myogenic ptosis Myogenic ptosis arises due to an abnormality in the levator muscle itself. These patients usually present with reduced levator action along with restricted extraocular motility and facial expression. Myasthenia gravis Myasthenia gravis is an autoimmune disorder characterized by the presence of antibodies to acetylcholine receptors located at the neuromuscular endplates of voluntary muscles. This leads to decreased action of acetylcholine which results in muscle weakness and fatigue. Myasthenia may be generalized or localized to the eye (ocular myasthenia). The most common presenting feature is variable ptosis associated with diplopia. Symptoms may be unilateral or bilateral. Patients with myasthenia initially have a good levator function. Prolonged upgaze will cause a worsening of ptosis in these patients due to muscle fatigue. Cogan lid twitch sign: Rapid saccadic eye movements from downgaze to primary position results in rapid upshoot of the lid followed by a gradual drop to the primary position. Other tests which help confirm the diagnosis include ice test, serum acetylcholine receptor antibody assay, single fiber electromyography, and repetitive nerve stimulation test. Treatment of such patients involves administration of acetylcholinesterase drugs, oral steroids or immunosuppressants. In patients with severe ptosis, ptosis correction with planned under-correction may be an option. Myotonic dystrophy Myotonic dystrophy is an autosomal dominant disorder which presents with gradually progressing ptosis and external ophthalmoplegia. The pathologic process is a failure of muscle to relax after contraction. It also involves muscles of facial expression, neck, and limbs. Ocular examination in these patients also shows pupillary light-near dissociation, chromatic cataracts (Christmas tree cataract), and retinal pigmentary degeneration. Males develop a frontal pattern of balding and testicular atrophy. Chronic progressive external ophthalmoplegia (CPEO) CPEO is a mitochondrial myopathy causing bilateral symmetrical involvement of the extraocular muscles. Manifestations begin in childhood or adolescent age and progress slowly during adulthood. Bilateral symmetrical involvement is the first symptom followed by bilateral ophthalmoplegia. Due to the symmetric involvement of extraocular muscles, patients often do not complain of diplopia. As the muscles of facial expression are involved, patients develop an expressionless face (Hutchinson's face) Diagnosis is confirmed by muscle biopsy which shows ragged red fibers due to enlarged mitochondria. Kearns-Sayre syndrome: A variant of CPEO which shows retinal pigmentary degeneration, cardiac conduction defects, complete heart block, ataxia, neuropathy, endocrine dysfunction, and occurs in young adults. There is no treatment to date for CPEO. Ptosis surgery to clear the visual axis can be done in severe cases keeping in mind the high risk of exposure keratopathy. Oculopharyngeal muscular dystrophy This autosomal dominant disorder manifests in the 4 to 5 decade of life with bilateral ptosis, progressive external ophthalmoplegia, dysphagia, dysarthria, facial muscle weakness, and proximal limb weakness. Mechanical ptosis Ptosis secondary to any tumor producing an increased weight on the lids, cicatrization or scarring of the conjunctiva, and blepharochalasis. Traumatic ptosis Ptosis occurs due to direct or indirect trauma to the levator muscle. Penetrating injuries involving the levator can be repaired immediately. However, ptosis secondary to blunt trauma may resolve spontaneously over time. Ptosis which does not improve after 6 months can have surgical repair. Pseudoptosis It is not true ptosis but apparent ptosis due to abnormalities in structures other than the levator muscle. Causes include dermatochalasis, brow ptosis, hypotropia, microphthalmos, anophthalmos, phthisis bulbi, and contralateral eyelid retraction. It is very important to distinguish true ptosis from a pseudoptosis before embarking upon any surgical correction for drooping. Clinical presentation Patients usually complain of: 1. Drooping of eyelids. 2. Feeling of heaviness in the eyes. 3. Visual obscuration due to drooping. 4. Cosmetic complaints. Assessment A thorough history taking and clinical examination help determine the etiology of ptosis and plan appropriate treatment. History History taking should include the age of onset of ptosis, progression, duration, and any aggravating or relieving factors. Any associated symptoms such as diplopia, diurnal variation, pain, lid swelling, dysphagia or muscle weakness help provide a provisional diagnosis. Predisposing factors such as trauma, ocular or eyelid surgery, contact lens use, and botulinum toxin injection should be carefully ruled out. A family history of ptosis should be looked for to rule out hereditary disorders. In patients where the history is inconclusive, assessment of old photographs gives an idea about the time of onset. Any systemic illness, mental health issues, and medication history require documentation. Patients on blood thinners such as aspirin should be advised to stop medications 1 week before surgery. Clinical examination Clinical examination starts from the moment the patient walks into the doctor's clinic. It is essential to look for any facial asymmetry, frontalis overaction, chin up or head tilt posture. Ocular examination: 1. Visual acuity and refraction. 2. Cover test to look for any hypotropia and rule out any component of pseudoptosis. 3. Extraocular motility disturbance and any aberrant eyelid movements. 4. Pupillary examination to look for Horner syndrome or 3rd cranial nerve palsy. 5. Examination to look for any giant papillary conjunctivitis or symblepharon. 6. Corneal sensation and dry eye evaluation as they can predispose to post-operative keratopathy. 7. Fundus examination for features of retinal pigmentary degeneration. Specific examination of ptosis  Lid measurements should be done positioning the face in the frontal plane, negating the action of frontalis muscle with the thumb, and eyes in the primary position of gaze. The examiner should be seated at the eye level of the patient to avoid parallax error.  1. Palpebral fissure height (PFH): It is the vertical palpebral aperture height between the upper and lower eyelid margin in the pupillary plane with eyes in the primary position of gaze. Average PFH is around 10mm.  2. Marginal reflex distance 1 (MRD 1): MRD 1 is the distance between the upper lid margin and the corneal light reflex. Normal MRD 1 is 4-5mm. The difference in MRD 1 between the two eyes helps classify ptosis as mild, moderate or severe in patients presenting with unilateral ptosis. The difference in MRD 1 between two eyes: 2mm – Mild ptosis. 3mm – Moderate ptosis. 4mm – Severe ptosis . 3. Marginal reflex distance 2 (MRD 2): MRD 2 is the distance between the corneal light reflex and lower eyelid margin. Normally MRD 1 + MRD 2 = PFH.  4. Levator action: It is the amount of excursion measured with a millimeter scale when the eyelid moves from extreme downgaze to extreme upgaze with frontalis action negated. Normal levator action is greater than 15mm. It is the single most important measurement in a patient with ptosis as its value determines the choice of surgical procedure. Grading of levator action: Less than 4 mm – Poor. 5 to 9 mm – Fair. 9 to 11 mm – Good. Greater than 12 mm – Excellent. In patients with poor levator action (less than 4mm), frontalis sling surgery is the preferred procedure.  5. Margin crease distance (MCD): It is the distance between the lid margin and skin crease in downgaze. Normal MCD is 7 to 8mm in men and 8 to 10 mm in women. In congenital ptosis, MCD is usually absent or faint, whereas in aponeurotic ptosis MCD is higher than normal. During surgery, it is very important to reform the crease identical to the contralateral eye to maintain symmetry and achieve good cosmesis.  6. Bell’s phenomenon: This is another very important factor to be considered before ptosis correction. The patient is asked to close the eyes gently, and an attempt is made to open them. In patients with poor bell’s, ptosis correction should be avoided or undercorrected to avoid the risk of post-operative exposure keratopathy.  7. Assess presence of lagophthalmos and lid lag on downgaze which if present will worsen post-surgery.  8. Any brow ptosis or dermatochalasis if present should be documented. In involutional ptosis, blepharoplasty procedure is often combined with ptosis repair.  9. Hering test: In patients with unilateral ptosis, the ptotic lid is gently elevated manually, and the contralateral eyelid observed. Due to Hering's law of equal innervation, the contralateral eyelid may drop (See-saw effect). It is important to demonstrate this to the patient preoperatively and warn them about the possibility of requiring ptosis surgery in the contralateral eye. In such cases, a planned under-correction may be the treatment.  10. Phenylephrine test: It is a useful test in patients with mild ptosis or ptosis due to Horner syndrome; instill 2.5% phenylephrine drops in the superior fornix. Ptosis measurements are repeated after 10 minutes. Patients in whom the ptotic lid elevates due to stimulation of Muller's muscle are ideal candidates for posterior approach ptosis correction (conjunctival – mullerectomy surgery).  11. Tests to rule out myasthenia gravis: Fatigue test: The patient maintains fixation in upgaze for 30 seconds. In patients with myasthenia, the eyelid gradually drops down due to muscle fatigue. Ice test: An ice pack is placed over the closed ptotic eyelid for 2 minutes. Ptotic measurements are repeated after 2 minutes. Improvement in PFH by 2mm or more is considered positive for myasthenia. This is because cooling improves neuromuscular transmission.  12. Hertel exophthalmometry: A Hertel reading helps rule out any proptosis or enophthalmos and thus excludes pseudoptosis.

Pathogenic variants in the type I ryanodine receptor (RYR1) result in a wide range of muscle disorders referred to as RYR1-related myopathies (RYR1-RM). We developed the first RYR1-RM mouse model resulting from co-inheritance of two different RYR1 missense alleles (Ryr1TM/SC-ΔL mice). Ryr1TM/SC-ΔL mice exhibit a severe, early onset myopathy characterized by decreased body/muscle mass, muscle weakness, hypotrophy, reduced RYR1 expression, and unexpectedly, incomplete postnatal lethality with a plateau survival of ~50% at 12 weeks of age. Ryr1TM/SC-ΔL mice display reduced respiratory function, locomotor activity, and in vivo muscle strength. Extensor digitorum longus muscles from Ryr1TM/SC-ΔL mice exhibit decreased cross-sectional area of type IIb and type IIx fibers, as well as a reduction in number of type IIb fibers. Ex vivo functional analyses revealed reduced Ca2+ release and specific force production during electrically-evoked twitch stimulation. In spite of a ~threefold reduction in RYR1 expression in single muscle fibers from Ryr1TM/SC-ΔL mice at 4 weeks and 12 weeks of age, RYR1 Ca2+ leak was not different from that of fibers from control mice at either age. Proteomic analyses revealed alterations in protein synthesis, folding, and degradation pathways in the muscle of 4- and 12-week-old Ryr1TM/SC-ΔL mice, while proteins involved in the extracellular matrix, dystrophin-associated glycoprotein complex, and fatty acid metabolism were upregulated in Ryr1TM/SC-ΔL mice that survive to 12 weeks of age. These findings suggest that adaptations that optimize RYR1 expression/Ca2+ leak balance, sarcolemmal stability, and fatty acid biosynthesis provide Ryr1TM/SC-ΔL mice with an increased survival advantage during postnatal development.

The substitution for Arg168His (R168H) in γ-tropomyosin (TPM3 gene, Tpm3.12 isoform) is associated with congenital muscle fiber type disproportion (CFTD) and muscle weakness. It is still unclear what molecular mechanisms underlie the muscle dysfunction seen in CFTD. The aim of this work was to study the effect of the R168H mutation in Tpm3.12 on the critical conformational changes that myosin, actin, troponin, and tropomyosin undergo during the ATPase cycle. We used polarized fluorescence microscopy and ghost muscle fibers containing regulated thin filaments and myosin heads (myosin subfragment-1) modified with the 1,5-IAEDANS fluorescent probe. Analysis of the data obtained revealed that a sequential interdependent conformational-functional rearrangement of tropomyosin, actin and myosin heads takes place when modeling the ATPase cycle in the presence of wild-type tropomyosin. A multistep shift of the tropomyosin strands from the outer to the inner domain of actin occurs during the transition from weak to strong binding of myosin to actin. Each tropomyosin position determines the corresponding balance between switched-on and switched-off actin monomers and between the strongly and weakly bound myosin heads. At low Ca2+, the R168H mutation was shown to switch some extra actin monomers on and increase the persistence length of tropomyosin, demonstrating the freezing of the R168HTpm strands close to the open position and disruption of the regulatory function of troponin. Instead of reducing the formation of strong bonds between myosin heads and F-actin, troponin activated it. However, at high Ca2+, troponin decreased the amount of strongly bound myosin heads instead of promoting their formation. Abnormally high sensitivity of thin filaments to Ca2+, inhibition of muscle fiber relaxation due to the appearance of the myosin heads strongly associated with F-actin, and distinct activation of the contractile system at submaximal concentrations of Ca2+ can lead to muscle inefficiency and weakness. Modulators of troponin (tirasemtiv and epigallocatechin-3-gallate) and myosin (omecamtiv mecarbil and 2,3-butanedione monoxime) have been shown to more or less attenuate the negative effects of the tropomyosin R168H mutant. Tirasemtiv and epigallocatechin-3-gallate may be used to prevent muscle dysfunction.

Congenital myopathies are a vast group of genetic muscle diseases. Among the causes are mutations in the MYH2 gene resulting in truncated type IIa myosin heavy chains (MyHCs). The precise cellular and molecular mechanisms by which these mutations induce skeletal muscle symptoms remain obscure. Hence, in the present study, we aimed to explore whether such genetic defects would alter the presence as well as the post-translational modifications of MyHCs and the functionality of myosin molecules. For this, we dissected muscle fibers from four myopathic patients with MYH2 truncating mutations and from five human healthy controls. We then assessed 1) MyHCs presence/post-translational modifications using LC/MS; 2) relaxed myosin conformation and concomitant ATP consumption with a loaded Mant-ATP chase setup; 3) myosin activation with an unloaded in vitro motility assay; and 4) cellular force production with a myofiber mechanical setup. Interestingly, the type IIa MyHC with one additional acetylated lysine (Lys35-Ac) was present in the patients. This was accompanied by 1) a higher ATP demand of myosin heads in the disordered-relaxed conformation; 2) faster actomyosin kinetics; and 3) reduced muscle fiber force. Overall, our findings indicate that MYH2 truncating mutations impact myosin presence/functionality in human adult mature myofibers by disrupting the ATPase activity and actomyosin complex. These are likely important molecular pathological disturbances leading to the myopathic phenotype in patients.