# In Vivo Model of Human Enthesis Regeneration

> **NIH NIH K76** · THOMAS JEFFERSON UNIVERSITY · 2020 · $239,967

## Abstract

Tendinopathies are ubiquitous and age-related. The natural history of tendinosis includes age-related tissue
degeneration of the tendon mid-substance, or of the enthesis – the tendon-bone interface – often resulting in
acute pain, loss of function and chronic disability. The primary reason for poor outcomes after surgical repair is
failure of the endogenous cells to recreate fibrocartilage at the tendon-bone interface. Our prior studies of
aged and young human tendon have revealed tenocytes develop a fibrochondrocyte and mineralized
fibrochondrocyte phenotype depending on relative intracellular levels of Rac1 and RhoA GTPase activity,
which are determined by the cell microenvironment. We have characterized this effect of RhoA/Rac1 GTPase
activity on the human tenocyte phenotype, and have discovered an essential role of combined Rac1 in-activity
and RhoA over-activity in development of the fibrochondrocyte phenotype.
The goal of this proposal is to create a fibrocartilage construct fit for eventual clinical translation. First we will
create a human tenocyte-engrafted electrospun nanofiber scaffold and culture it under conditions of hypoxia or
normoxia, under tension or compression in a bioreactor. Biochemical, immunohistochemical and kinematic
assays will be used to evaluate time and oxygen-dependent changes in human tenocyte phenotype on the
scaffolds, via expression of selected markers, assessment of tissue organization and mechanical strength.
Human tenocytes will then be treated with RhoA/Rac1 agents to produce Rac-1 in-activity and RhoA over-
activity and cultured as above.
The final objective of this proposal is to create an in vivo rabbit model for enthesis regeneration. First we will
perform proof-of-concept studies: enthesis defects will be created in the Achilles tendon of rabbits and
observed for healing at week 6 and 12 after defect creation, harvested and analyzed as above. Using the
same enthesis defect model, tenocyte-engrafted scaffolds with stable Rac1 in-activity and RhoA over-activity
will then be used to repair the enthesis defects, harvested at week 6 and 12, and analyzed as described above
to evaluate maintenance of the enthesis phenotype as well as construct integrity during physiologic loading in
vivo.
Our aging patient population is in dire need of an innovative, consistent therapy for tendinosis. Our proposed
interdisciplinary approach using cell biology, biochemical, tissue engineering and translational techniques will
create a novel enthesis construct, fit to undergo clinical testing, with the goal of decreasing pain and restoring
function in the elderly.

## Key facts

- **NIH application ID:** 9999993
- **Project number:** 5K76AG057021-02
- **Recipient organization:** THOMAS JEFFERSON UNIVERSITY
- **Principal Investigator:** Rowena McBeath
- **Activity code:** K76 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $239,967
- **Award type:** 5
- **Project period:** 2019-09-01 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9999993

## Citation

> US National Institutes of Health, RePORTER application 9999993, In Vivo Model of Human Enthesis Regeneration (5K76AG057021-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9999993. Licensed CC0.

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