Neuromuscular Regeneration of Volumetric Muscle Loss (VML)

Injury in response to agrin-Functionalized tissue Engineered Muscle Grafts and Rehabilatie Exercise

Problem: What is VML?

Volumetric Muscle Loss is a disruptie critifcal size injury

what are the halmarks of volumertic msucle loss

tissue loss scale ovewhelem regernation, nerve and vascular damage leads to fucnional loss, persists over patient lifetime.

What doe current treatemnts for VMLs entail?

free msuckle flao transfer

in minor injuries, what cells assist in regenerative process?

Skeletal msucle has a robust regenrtaive response involving dormanst Pac7+ cells

What three stages does a successful regenration involve?

rebuilding muscle, reconnect muscle to surrounding nerves, restore and encoruge fucntion

What stage of regernation do tissue engineered msucle grafts (TEMGs) target?

Stage 1: Rebuilding muscle

Tissue-Engineered Muslce grafts (TEMGs) are promosing for VML:

recover portions of lost tissue, promote vascularity and innervation, potentially restoire muscle function

what are the limits of tissue engineered muscle grafts?

healthy myogenic tissue recovery is challenging even with Pax7+ cells, neuromuscular junctions(NMJ) regenration remians limited

what are the needs for the deign of TEMGs?

scaffold mimicking skeletal muscle architecture and fucntion, porous to facilitate cell, vascular, and neaurl ingrowth, biodgeradable at an appropriate timescale, sufficient tensile strength for handling and implantation

TRhe aspects the paper further focused ona dressing for the TEMGs needs were:

use of the human myogenic progenitor(hMP) cell to treat VML, seeding the TEMG with Pax7+ to create an hMP-TEMG(hTEMG)

how did the authors create the scaffold to rebuild muslce?

the TEMG consist of an electro-spun fibrin hydrogel seeded with Pax7+ cells obatined from the quadriceps of a 29yr old male

rebuilding msucle:myogenic proeprties

as the cells developed, most of the cells on the fibrin fibers displayed myogenic properties for the duration of the 14-day culture period, indicating myogenic maturity

does the hTEMG regernate Muscle in Vivo?

the hTEMG was impalnted onto a surgically created VML defect on a male mouse , demspnstrated muscle recovery in untreated and hmp treated vml (VML+hMP fibers had the most msucle regrowth

do trnasplanted human cells presist?

human donor cells exist intiallyt but drop substantially over the 8-week period. Despite this, substantial tissue repair still occurs

adressing NMJ recovery

Neuromuslce junctions regenration remains limited , VML disrupts these connections inhibiting msucle activation, restoring skeletal msucle alone does not restore fucntion

neuromuscle junctions

the electrical contact points between nerves and msucel

how is NMJ recovery Facilitated? (the two methods the authors used)

conducting comparative analysis of sex-specific exercise regimens , continuous, interval and control

incorportaing agrin to imporve neuromuscular connectivity , use of argin improves acetycholine recptior )(AChR) density

Three diffrent excercise regimines meanings: continuous, intevral, control

low intensity, longer durations(male preferred), higher intesnity, shoirter duration(female preferred) , no exercise

exercise-focused rehabilitation A

The authors perfomed this study on male mice, testing continuous and interval traing in recovery outcomes, results show minimal differnce bewtween fibrotic response across groups

excercise-foucused rehabilitation B

significant increase in acetycholine recptors(AChR) cluster density for exercise groups, significant increase in nerve density for exercise groups, noticeably wrse vascular density when male perfoemd interval traning

argin-focused rehabilitation A

aregin treated bTEMGs produced slight advantage over hTEMGs alone in fast-twitch myosin heavy chain(MHC) protein, argin treatment showd significant increase in AChR cluster density, AChR cluster density w.r.t fast-twitch muscle area (MHC+) showed no signifiant increase , Qunatification of nerve density showed no advantage with argin

aregin-foucsed rehabilitation B

argin treated hTEMGs produced slight advantage over hTEMGs alone in fast-twitch myosin heavy chain (MHC) protein, argin treatment showed significant increase in AChR cluster count, AChR cluster desnity w.r.t fast-twitch msucle area (MHC+) showed no significant increase, qunatification of nerve density shows no advantage with argin

combination of argin & Exercise effects

exercise group benefited most from increase in weight, argin treatment showed significant increase in: recovered muscle weight and msucel cross-sectional area , exercise groups showed greater force production relative to non-exercise, but argin influcne was negligible

what what the impact of creating hTEMGs?

significant muscle recovery from VML

What were the results of the Sex-specific exercise regimen?

increased AChR cluster density, increased nerve density, minimal differnce in msucle weight

How did argin impact cluster density

it increased AChR cluster density

Was there any great significance in the combination of exercise and argin?

No, it was minimal