Type III collagen is a hallmark of the fibrotic pathomechanism in Modic type 1 changes and is linked to myofibroblast differentiation

S. Dudli, I. Heggli, Guidici L, R. Schuepbach, N. Farshad-Amacker, N. Herger, A. Juengel,

M. Betz, J.M. Spirig, F. Wanivenhaus, N. Ulrich, F. Brunner, M. Farshad, O. Distler

ISSLS Virtual Annual Meeting 2021Virtual Annual MeetingMay 31 – June 4

DISCLOSURE

The authors have no disclosures.

INTRODUCTION

1 Modic et al. 1988. Radiology. 166(1);193-9. 2 Saukkonen et al. 2020. Spine. 45(19);1360-7.

Modic changes (MC)

• Vertebral bone marrow lesions • Identified on T1- / T2-weighted MRI• 3 interconvertible types (MC1, MC2, MC3)• Independent association with cLBP 1, 2

H&E stain of Modic type 1 change 1 MC1 MC2 MC3

T1w T1w T1w

Limitations: Fibrotic mechanisms in Modic changes poorly understoodAim: To identify the fibrotic mechanisms in Modic changes

MC histopathology

• Based on Modic’s original study (n=3) 1

MC1 = Vascularized fibrous tissueMC2 = Fatty marrowMC3 = Sclerosis

METHODS

Bone marrow biopsies (A) or aspirates (B) from patients undergoing lumbar spondylodesis

Histology/Immunohistochemistry

Scored (0-3) by an experienced pathologist

Statistics: Kruskal-Wallis, p-adjusted (fdr)

Jamshidi needle

A. Biopsies B. Aspirates

Bone marrow stromal cells (BMSC) isolated

Characterized with: RNA sequencing,type I collagen expression, αSMA expression,

matrix adhesion, cell contractility

MC and intra-patient control sample

RESULTS

Histology results

Ctrl MC1 MC2 p-valuen 10 8 5Age 65.2 ± 12.7 60.3 ± 10.6 66.4 ± 10.9 0.58 (Anova)Sex (m/f) 6/4 4/4 4/1 0.75 (Fisher test)

Histology ScoresModic type 1 changes

Type III Collagen CD90 fibroblasts αSMA myofibroblasts

p=0.06

Modic type 2 changes

() Type I and III Collagen

RESULTS/DISCUSSION

Areas with type III collagen

• Interstitial (IS)• Basement membrane of vascular sinusoids (VS)

IS

IS

VS

MC1: Representative type III collagen staining More pro-collagen 3 in blood serum

Provides face validity for pro-collagen 3as biomarker for MC

RESULTS/DISCUSSION

Are CD90+ bone marrow stromal cells in MC1 pro-fibrotic?

More CD90+ stromal cells in MC1 More αSMA myofibroblastst in MC1

RESULTS/DISCUSSION

Bone marrow stromal cells in MC1 are pro-fibrotic:

a. pro-fibrotic transcriptome (n=4+4)

b. increased pro-collagen I synthesis (n=6+6)

c. higher collagen gel contractility (n=7+7)

d. myofiboblast differentiation in leptin receptor (LEPRhigh) BMSC (n=5+5)

TGF-β1 - + - +

αS

MA

ex

pre

ssio

n

a. Gene Set Enrichment Analysis

c. Collagen gel contractionb. Pro-collagen I d. αSMA expression in LEPRhigh

SUMMARY POINTS

Funding:

• Type III collagen is a key mechanism of fibrosis in MC1

• Type III collagen is a potential biomarker for MC1

• Stromal cells in MC1 are pro-fibrotic and may mediate MC1 fibrosis

• Targeting fibrosis/stromal cells in MC1 should be explored as novel treatment option

MC1: type III collagen